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Field Evaluation of Reflected Noise from a Single Noise Barrier (2018)

Chapter: Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results

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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
×
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Suggested Citation:"Appendix B - Phase 2 (Sound-Absorbing Barriers) Detailed Analysis and Results ." National Academies of Sciences, Engineering, and Medicine. 2018. Field Evaluation of Reflected Noise from a Single Noise Barrier. Washington, DC: The National Academies Press. doi: 10.17226/25297.
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Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

B-3 C H A P T E R B - 1 Introduction to Appendix B This appendix presents the details of the Phase 2 research data collection and analysis at three sound- absorbing, single-barrier locations. It does not provide background on the subject, data collection and analysis protocols, comparison to the Phase 1 results, overall findings, applications, recommendations, or suggested research. Those topics are covered in the main report and the other appendices. In Phase 1, several acoustical differences were found between areas across the highway from single, sound-reflecting barriers and equivalent areas with No Barrier present. In Phase 2, this analysis was expanded to include data at sound-absorbing barriers. The goal of Phase 2 was to compare absorptive sites with reflective sites, using similar analyses and metrics developed for Phase 1. In addition, a prototype screening tool to help estimate the effect of barrier reflections was developed further and validated, and a layperson’s guide to barrier reflections was prepared, as detailed in separate appendices. Chapter B-2 of this appendix provides a general description of the three sound-absorbing barrier locations. Chapters B-3 through B-5 describe in detail the results at each location. The results are presented first in terms of differences in the raw 5-minute broadband equivalent sound levels (Leq (5 min.)), both for the unweighted sound pressure level and the A-weighted sound levels. Then, the 5-minute periods found to be equivalent to each other in terms of source and meteorological class are identified and studied for one- third octave band sound pressure level differences at the microphone pairs. Sample one-third octave band unweighted sound pressure level spectra are also presented for comparison at the microphone pairs. Analysis of the L90 and L99 statistical exceedance descriptors is also presented for the broadband unweighted and A-weighted levels, as well as one-third octave band analysis of seven Ln statistical measures ranging from L1 to L99. Finally, results for the spectrograms are presented and discussed. As used herein, the unit of dB refers to a change in level or difference in levels, both for unweighted sound pressure levels, which are designated with the unit dBZ per the International Standards Organization, and for A-weighted sound levels, designated with the unit dBA.

B-4 C H A P T E R B - 2 Study Locations Measurements were made at the following three study locations during the week of November 15, 2016: 1. I-75, Troy, Ohio. 2. I-70, South Vienna, Ohio. 3. I-270, Grove City, Ohio. Paired simultaneous measurements were made at the Barrier and No Barrier sites at each location under the same traffic and meteorological conditions, following the Phase 1 protocol as outlined in the Amplified Work Plan (AWP). Approximately four hours of data collection took place at each site. Instrumentation included the following: • Three sound level analyzers at each of the Barrier and No Barrier sites with digital audio recorders. o One analyzer between the barrier and the roadway for reference and as a primary indicator of reflected noise—named BarRef01 and NoBarRef02 at I-75 and I-70; however, no BarRef01 microphone was placed atop the I-270 barrier because the barrier was at the edge of the shoulder and there were concerns that reflections off vehicles’ bodies would bias the results. o One analyzer opposite the barrier at a lower height or closer distance—named BarCom03 and NoBarCom05. o One analyzer opposite the barrier at a higher height or farther distance—named BarCom04 and NoBarCom06. • A precision meteorological station. • A video camera and laser speed gun to capture traffic volumes and speeds. The general configuration of microphones is shown in Figure 1. Specifically, the community microphone positions were as follows: • I-75: two heights at two different distances from the center of the near travel lane. • I-70: two heights at the same distance from the center of the near travel lane. • I-270: two heights at different distances from the center of the near travel lane. The sound level analyzers logged sound levels once per second, including unweighted one-third octave band spectra and overall unweighted and A-weighted levels. Meteorological data were wind speed and direction at 15 ft. above ground and temperature at 5 ft. and 15 ft. above ground, logged once per second.

B-5 Figure 1. General microphone placement and naming convention diagram. Table 1 summarizes the characteristics of the three locations.

Table 1. Studied Phase 2 locations. Location Roadway City, State Road Class Lanes Pavement Type Geometry Relative to Adjacent Land Uses AADT (vpd) and Year Percent Trucks Barrier Location Barrier Material Barrier Height at Study Site OH-1 I-75 Troy, Ohio Freeway 6 Portland cement concrete (PCC) At-Grade 63,273 (2015) 21% ROW Concrete with rubber tire chip sound- absorbing face 16-18 ft. OH-2 I-70 South Vienna, Ohio Freeway 6 Asphalt (DGAC) Slight cut 45,923 (2015) 30% ROW Concrete with rubber tire chip sound- absorbing face 18-20 ft. OH-3 I-270 Grove City, Ohio Freeway 6 Portland cement concrete (PCC) At-Grade 63,768 (2015) 29% (during sampling from midnight to 4 a.m.) EOP Concrete / wood fiber aggregate sound- absorbing face 14-16 ft.

B-7 C H A P T E R B - 3 Results – I-75, Troy, Ohio (Location OH-1) As shown in Figure 2, the I-75 location in Troy, Ohio, is a six-lane freeway. The barrier is approximately 3,370 ft. long, 15 ft. high, and offset 50 ft. from the edge of the nearest travel lane. The barrier is a precast concrete post-and-panel design, with a proprietary rubber tire chip sound-absorbing face on the highway side. Sound absorption test results for this barrier were not available. However, results for a panel from the same company with the same Noise Reduction Coefficient (NRC) show the sound absorption coefficients in Table 2. Table 2. Sound absorption coefficients and NRC for a barrier similar to the I-75 barrier. Octave Band Center Frequency (Hz) Sound Absorption Coefficient 125 0.09 250 0.25 500 1.25 1,000 0.74 2,000 1.03 4,000 1.07 NRC 0.80

B-8 Figure 2. I-75 No Barrier view (top left), Barrier view (top right), Roadway close-up (bottom left), and Barrier (highway side) close-up (bottom right). (Source: research team.) Figure 3 shows a site map of the measurement positions for the Barrier microphones (with yellow icons), No Barrier microphones (green icons), Speed and Traffic site, and the meteorological station. Table 3 gives each microphone’s position, distance to the edge of nearest travel lane, and height above roadway grade. Figure 4 shows pictures of each microphone at its measurement position.

B-9 Figure 3. I-75 microphone positions. (Aerial Photo Source: Google Earth.) Table 3. Microphone positions at I-75 location. Microphone Name Side of Road Distance from Edge of Nearest Travel Lane (ft.) Height Above Roadway Plane (ft.) BarRef01 NB 25 10 (12 ft. above ground, near midpoint of barrier) NoBarRef02 NB 25 10 (11.5 ft. above ground) BarCom03 SB 50 10 (9 ft. above ground) BarCom04 SB 100 20 (19 ft. above ground) NoBarCom05 SB 50 10 (10 ft. above ground) NoBarCom06 SB 100 20 (19 ft. above ground)

B-10 Figure 4. I-75 BarRef01 (top left), NoBarRef02 (top right), BarCom03 (middle left), BarCom04 and meteorological station (middle right), NoBarCom05 (bottom left), and NoBarCom06 (bottom right). (Source: research team.)

B-11 Figure 5 shows cross-sections at the Barrier and No Barrier sites. The cross-section at the No Barrier site is virtually identical to the Barrier site: the ground elevation is 0.5 ft. lower at BarRef01 compared to NoBarRef02 and 1 ft. higher at BarCom03 compared to NoBarCom05. A concrete median barrier is present at both the Barrier and No Barrier sites. The Com microphones were set at 10 ft. and 20 ft. above the roadway elevation to minimize the shielding of the direct noise coming from tires on vehicles traveling on the northbound side of I-75. Figure 5. Cross-sections at the I-75 Barrier (top) site and No Barrier (bottom) sites. Measurements were conducted on Tuesday, November 15, 2016, from approximately 17:00 to 21:00. The field crew observed no insect or other natural sounds audible at night—only highway noise—and no significant differences were noted between the highway noise at BarCom04 and NoBarCom06. There was steady traffic for the first hour and a half. Traffic eased after approximately 18:40. Heavy truck volume percentage remained high throughout the measurement. Even when there was no traffic immediately in front of the microphone, the background level of the sound environment was still set by distant traffic noise. No other contributors to the background level were audible. Measured Broadband Levels and Level Differences for I-75 The running Leq (5 min.) for each site are presented in the following figures to give an overall picture of the measured levels, both in terms of unweighted sound pressure levels and A-weighted sound levels: BarRef01 and NoBarRef02—Figure 6 (unweighted) and Figure 7 (A-weighted); then Figure 8 shows the differences in the unweighted and A-weighted levels for this mic pair.

B-12 BarCom03 and NoBarCom05—Figure 9 (unweighted) and Figure 10 (A-weighted); then Figure 11 shows the differences in the unweighted and A-weighted levels for this mic pair. BarCom04 and NoBarCom06—Figure 12 (unweighted) and Figure 13 (A-weighted); then Figure 14 shows the differences in the unweighted and A-weighted levels for this mic pair. The following observations are prior to any attempt to group data into equivalent periods. For virtually all the running 5-minute Leq periods, the unweighted BarRef01 levels are higher than the unweighted NoBarRef02 levels by a range of 0.4 dB to 2.6 dB, averaging approximately 1.4 dB higher; the A-weighted levels are higher by a range of 0.2 dB to 1.8 dB, averaging approximately 1.4 dB higher. The BarRef01 microphone was located halfway between the barrier and I-75. These results suggest noise is being reflected off the barrier. At BarCom03, the unweighted levels range from 0.9 dB lower than at NoBarCom05 to 1.5 dB higher, averaging approximately 0.3 dB higher. The A-weighted levels at BarCom03 range from 0.9 dB lower than at NoBarCom05 to 1.4 dB higher, averaging approximately 0.5 dB higher. At the more distant BarCom04 position, the unweighted levels range from 0.5 dB lower than at NoBarCom06 to 1.9 dB higher, averaging approximately 0.6 dB higher. The A-weighted levels at BarCom04 range mostly from 0.8 dB lower to 1.4 dB higher than at NoBarCom06, averaging approximately 0.5 dB higher. Figure 6. Running Leq (5 min.), I-75, unweighted sound pressure level, dBZ, BarRef01 and NoBarRef02. 83 84 85 86 87 88 89 17 :1 2 17 :2 2 17 :3 2 17 :4 2 17 :5 2 18 :0 2 18 :1 2 18 :2 2 18 :3 2 18 :4 2 18 :5 2 19 :0 2 19 :1 2 19 :2 2 19 :3 2 19 :4 2 19 :5 2 20 :0 2 20 :1 2 20 :2 2 20 :3 2 20 :4 2 20 :5 2 21 :0 2 So un d Pr es su re L ev el , d BZ Time BarRef01 NoBarRef02

B-13 Figure 7. Running Leq (5 min.), I-75, A-weighted sound level, dBA, BarRef01 and NoBarRef02. Figure 8. Differences in running Leq (5 min.), I-75, BarRef01 minus NoBarRef02. 80 81 82 83 84 85 86 17 :1 2 17 :2 2 17 :3 2 17 :4 2 17 :5 2 18 :0 2 18 :1 2 18 :2 2 18 :3 2 18 :4 2 18 :5 2 19 :0 2 19 :1 2 19 :2 2 19 :3 2 19 :4 2 19 :5 2 20 :0 2 20 :1 2 20 :2 2 20 :3 2 20 :4 2 20 :5 2 21 :0 2 So un d Le ve l, dB A Time BarRef01 NoBarRef02 -3 -2 -1 0 1 2 3 17 :1 2 17 :2 2 17 :3 2 17 :4 2 17 :5 2 18 :0 2 18 :1 2 18 :2 2 18 :3 2 18 :4 2 18 :5 2 19 :0 2 19 :1 2 19 :2 2 19 :3 2 19 :4 2 19 :5 2 20 :0 2 20 :1 2 20 :2 2 20 :3 2 20 :4 2 20 :5 2 21 :0 2 D iff er en ce in le ve l, dB Time dBA dBZ

B-14 Figure 9. Running Leq (5 min.), I-75, unweighted sound pressure level, dBZ, BarCom03 and NoBarCom05. Figure 10. Running Leq (5 min.), I-75, A-weighted sound level, dBA, BarCom03 and NoBarCom05. 80 81 82 83 84 85 86 17 :1 2 17 :2 2 17 :3 2 17 :4 2 17 :5 2 18 :0 2 18 :1 2 18 :2 2 18 :3 2 18 :4 2 18 :5 2 19 :0 2 19 :1 2 19 :2 2 19 :3 2 19 :4 2 19 :5 2 20 :0 2 20 :1 2 20 :2 2 20 :3 2 20 :4 2 20 :5 2 21 :0 2 So un d Pr es su re L ev el , d BZ Time BarCom03 NoBarCom05 77 78 79 80 81 82 83 17 :1 2 17 :2 2 17 :3 2 17 :4 2 17 :5 2 18 :0 2 18 :1 2 18 :2 2 18 :3 2 18 :4 2 18 :5 2 19 :0 2 19 :1 2 19 :2 2 19 :3 2 19 :4 2 19 :5 2 20 :0 2 20 :1 2 20 :2 2 20 :3 2 20 :4 2 20 :5 2 21 :0 2 So un d Le ve l, dB A Time BarCom03 NoBarCom05

B-15 Figure 11. Differences in running Leq (5 min.), I-75, BarCom03 minus NoBarCom05. Figure 12. Running Leq (5 min.), I-75, unweighted sound pressure level, dBZ, BarCom04 and NoBarCom06. -3 -2 -1 0 1 2 3 17 :1 2 17 :2 2 17 :3 2 17 :4 2 17 :5 2 18 :0 2 18 :1 2 18 :2 2 18 :3 2 18 :4 2 18 :5 2 19 :0 2 19 :1 2 19 :2 2 19 :3 2 19 :4 2 19 :5 2 20 :0 2 20 :1 2 20 :2 2 20 :3 2 20 :4 2 20 :5 2 21 :0 2 D iff er en ce in le ve l, dB Time dBA dBZ 77 78 79 80 81 82 83 17 :1 2 17 :2 2 17 :3 2 17 :4 2 17 :5 2 18 :0 2 18 :1 2 18 :2 2 18 :3 2 18 :4 2 18 :5 2 19 :0 2 19 :1 2 19 :2 2 19 :3 2 19 :4 2 19 :5 2 20 :0 2 20 :1 2 20 :2 2 20 :3 2 20 :4 2 20 :5 2 21 :0 2 So un d Pr es su re L ev el , d BZ Time BarCom04 NoBarCom06

B-16 Figure 13. Running Leq (5 min.), I-75, A-weighted sound level, dBA, BarCom04 and NoBarCom06. Figure 14. Differences in running Leq (5 min.), I-75, BarCom04 minus NoBarCom06. Data Analysis for I-75 - FHWA Method Equivalent Groups All but one of the groupings of 5-minute periods that were judged equivalent for traffic parameters at the I-75 location fell into a single meteorological class: Calm Inversion. There were 15 groupings in this class, each with three to four 5-minute equivalent periods. A small amount of data was collected in the Upwind Inversion class, enough for a single grouping of three nonoverlapping equivalent 5-minute periods. As 74 75 76 77 78 79 80 17 :1 2 17 :2 2 17 :3 2 17 :4 2 17 :5 2 18 :0 2 18 :1 2 18 :2 2 18 :3 2 18 :4 2 18 :5 2 19 :0 2 19 :1 2 19 :2 2 19 :3 2 19 :4 2 19 :5 2 20 :0 2 20 :1 2 20 :2 2 20 :3 2 20 :4 2 20 :5 2 21 :0 2 So un d Le ve l, dB A Time BarCom04 NoBarCom06 -3 -2 -1 0 1 2 3 17 :1 2 17 :2 2 17 :3 2 17 :4 2 17 :5 2 18 :0 2 18 :1 2 18 :2 2 18 :3 2 18 :4 2 18 :5 2 19 :0 2 19 :1 2 19 :2 2 19 :3 2 19 :4 2 19 :5 2 20 :0 2 20 :1 2 20 :2 2 20 :3 2 20 :4 2 20 :5 2 21 :0 2 D iff er en ce in le ve l, dB Time dBA dBZ

B-17 described in the AWP, source equivalence was determined by the NoBarRef02 A-weighted Leq (5 min.) in each period and averages of speeds in each period (for the second lane from the outside for each direction, for the overall speed by direction, and for the overall combined speed for both directions). For I-75, the allowable variation in the NoBarRef02 Leq (5 min.) was 0.1 dB in most cases, 0 dB in a few cases, and 0.2 dB for the Upwind Inversion grouping; for all groups, the allowable speed range was 5 mph. Figure 16 shows these groupings graphically for the Calm Inversion class. The times along the top represent the starting minute of each 5-minute period. Each group has a unique name, starting with “CIG.” Note that all the 5-minute periods in a group are nonoverlapping in time, and the same 5-minute periods do not appear in more than one equivalent group. Not shown in a figure, the three equivalent 5-minute periods for the Upwind Inversion grouping were: 18:06, 18:32, and 18:38. Figure 15 shows the 15-minute counts for autos, heavy trucks, and total traffic by direction over the 4-hour period. While heavy truck counts were relatively constant over that time, auto counts—and thus the total counts—decreased steadily as the evening proceeded from rush hour. The periods for the selected groupings had greatly varying traffic volumes, as show in Table 4, which ranks the Calm Inversion groups by total two-way volume averaged across the periods in that group (i.e., Factored Hourly Volume, vph), and includes the one Upwind Inversion group. The total two-way volume of the highest Calm Inversion group was roughly 2.7 times greater than that for the lowest group. In terms of equivalent hourly volumes, the overall two-way range for these periods was from 1,984 vph to 5,328 vph. The two-way factored hourly volume for the Upwind Inversion group was 3,340 vph. Speeds across the groups were consistent, ranging from averages of 66 mph to 75 mph for the Calm Inversion groups, and 69 mph to 70 mph for the Upwind Inversion group. Figure 15. 15-minute traffic counts by direction for autos, heavy trucks, and total flow, I-75. 0 100 200 300 400 500 600 700 800 17 :1 2 17 :2 7 17 :4 2 17 :5 7 18 :1 2 18 :2 7 18 :4 2 18 :5 7 19 :1 2 19 :2 7 19 :4 2 19 :5 7 20 :1 2 20 :2 7 20 :4 2 20 :5 7 V eh ic le C ou nt Time NB Total SB Total NB Auto SB Auto NB HT SB HT

Figure 16. Equivalent 5-minute periods for Calm Inversion groups at I-75. 17 :1 2 17 :1 4 17 :2 0 17 :2 1 17 :2 6 17 :2 9 17 :3 7 17 :3 8 17 :4 0 17 :5 6 18 :1 2 18 :1 3 18 :1 9 18 :2 3 18 :2 4 18 :4 1 18 :5 2 18 :5 4 18 :5 6 18 :5 7 19 :0 1 19 :1 5 19 :1 7 19 :2 1 19 :2 2 19 :2 7 19 :4 1 19 :4 3 19 :4 4 19 :4 7 19 :4 8 19 :4 9 19 :5 4 20 :0 0 20 :0 1 20 :0 2 20 :0 3 20 :1 1 20 :1 3 20 :1 4 20 :1 5 20 :1 6 20 :2 5 20 :2 6 20 :2 7 20 :2 8 20 :4 4 20 :5 3 21 :0 4 21 :0 5 21 :0 6 CIG-1-1: 20:03, 20:14, 21:06 1 1 1 CIG-3-1: 20:16, 20:28, 21:04 1 1 1 CIG-4-1: 20:02, 20:15, 21:05 1 1 1 CIG-6-1: 20:13, 20:27, 20:44 1 1 1 CIG-7-1: 19:48, 20:11, 20:26 1 1 1 CIG-9-1: 19:47, 20:01, 20:25, 20:53 1 1 1 1 CIG-11-1: 18:19, 19:01, 19:49 1 1 1 CIG-13-1: 18:57, 19:15, 19:41, 20:00 1 1 1 1 CIG-15-1: 18:13, 18:52, 19:43 1 1 1 CIG-17-1: 18:12, 18:23, 19:27, 19:44 1 1 1 1 CIG-19-1: 18:41, 18:56, 19:17, 19:54 1 1 1 1 CIG-21-1: 17:26, 17:37, 17:56, 19:21 1 1 1 1 CIG-23-1: 17:38, 18:54, 19:22 1 1 1 CIG-25-1: 17:12, 17:21, 18:24 1 1 1 CIG-27-1: 17:14, 17:20, 17:29, 17:40 1 1 1 1 Starting Time of 5-minute Periods Group ID

B-19 Table 4. Two-way traffic volumes in 5-minute periods, by equivalent group for Calm Inversion and Upwind Inversion conditions, sorted by factored hourly volume, I-75. Two-Way Traffic Volumes (5 minutes) Group Period 1 Period 2 Period 3 Period 4 Factored Hourly Volume, vph Calm Inversion CIG-27-1 469 476 437 394 5,328 CIG-25-1 457 457 305 n/a 4,876 CIG-21-1 390 416 356 227 4,167 CIG-23-1 398 251 241 n/a 3,560 CIG-17-1 315 295 212 235 3,171 CIG-15-1 301 237 218 n/a 3,024 CIG-19-1 263 229 247 189 2,784 CIG-11-1 277 205 178 n/a 2,640 CIG-13-1 231 222 202 179 2,502 CIG-7-1 187 183 157 n/a 2,108 CIG-4-1 175 190 158 n/a 2,092 CIG-9-1 203 171 163 141 2,034 CIG-6-1 191 161 155 n/a 2,028 CIG-3-1 189 160 150 n/a 1,996 CIG-1-1 169 181 146 n/a 1,984 Upwind Inversion UIG-1-1 311 254 270 n/a 3,340 Sound Pressure Level Spectra Before discussing the differences in levels between the Barrier and No Barrier sites, typical sound pressure level spectra are shown to give some perspective on the data upon which the differences are based. One of the 5-minute periods in the one of the Calm Inversion groups was chosen as typical. Figure 17, Figure 18, and Figure 19 present the overall A-weighted sound levels and unweighted sound pressure levels and the unweighted pressure level spectra for, respectively: BarRef01/NoBarRef02. BarCom03/NoBarCom05. BarCom04/NoBarCom06.

B-20 Figure 17. Sample sound pressure level spectra for BarRef01 and NoBarRef02, I-75, Calm Inversion group CIG-1-1, 20:03-20:08 (Leq (5 min.), dBZ). 35 40 45 50 55 60 65 70 75 80 85 90 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k So un d Pr es su re L ev el , d BZ 1/3 Octave Band Frequency, Hz BarRef01 NoBarRef02

B-21 Figure 18. Sample sound pressure level spectra for BarCom03 and NoBarCom05, I-75, Calm Inversion group CIG-1-1, 20:03-20:08 (Leq (5 min.), dBZ). 35 40 45 50 55 60 65 70 75 80 85 90 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k So un d Pr es su re L ev el , d BZ 1/3 Octave Band Frequency, Hz BarCom03 NoBarCom05

B-22 Figure 19. Sample sound pressure level spectra for BarCom04 and NoBarCom06, I-75, Calm Inversion CIG-1-1, 20:03-20:08 (Leq (5 min.), dBZ). Calm Inversion Class Figure 20 shows three graphs of the differences in level between comparable microphones for an average of all the Calm Inversion groups with their error bars. The error bars are +/- one standard deviation for each average value. This figure compares the following: • BarRef01 and NoBarRef02 in the upper graph. • BarCom03 and NoBarCom05 in the middle graph. • BarCom04 and NoBarCom06 in the lower graph. Each graph shows the averages of the average level differences for the A-weighted sound level, the unweighted sound pressure level, and the one-third octave band sound pressure levels from 20 Hz to 10 kHz. Graphs for all the individual Calm Inversion groups are in spreadsheet files in the project record. 35 40 45 50 55 60 65 70 75 80 85 90 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k So un d Pr es su re L ev el , d BZ 1/3 Octave Band Frequency, Hz BarCom04 NoBarCom06

B-23 The trends across the one-third octave band frequencies, described below, are generally similar in these individual groups of equivalent periods, with some differences likely related to background noise and the uniqueness of vehicle noise sources in each period. Figure 20 shows in the upper graph that the BarRef01 levels are roughly 0.6 dB to 2.7 dB higher than the NoBarRef02 levels across the entire spectrum, except at 20 Hz, where the difference is only 0.2 dB. From 80 Hz to 400 Hz, the difference is 2 dB or more; from 500 Hz to 1,600 Hz, the difference is 1 dB or less. These bands are the ones at which the sound-absorbing material would be expected to be most effective. Above 2 kHz, the difference is over 1.5 dB. The middle graph shows the differences in levels between BarCom03 and NoBarCom05, both of which were 10 ft. above the roadway elevation. Through 1.25 kHz, the BarCom03 levels are within +/- 1 dB of the NoBarCom05 levels (being slightly lower than NoBarCom05 at 125 Hz and 160 Hz). At 1.6 kHz and 2 kHz, the BarCom03 levels are 1.3 dB and 1 dB higher than at NoBarCom05, while the NoBarCom05 levels are slightly higher than BarCom03 above 3.15 kHz. In any case, the levels in these higher frequencies are much lower than in the middle frequencies. The lower graph compares the levels at BarCom04 and NoBarCom06, both of which were 20 ft. above the roadway surface and farther away than BarCom03 and NoBarCom05. Through 2 kHz, the BarCom04 levels are from 0 dB to 1.1 dB higher than at NoBarCom06. From 2.5 kHz to 5 kHz, the NoBarCom06 levels are 0.5 to 1.1 dB higher than those at BarCom04, while above 6.3 kHz, they are 0.8 dB to 1 dB lower. The reason for NoBarCom06 being higher in some of the higher frequencies is not clear since no insect noises were present.

B-24 Figure 20. Averages of the differences in Leq (5 min.) +/- one standard deviation (dB), all microphones, for all Calm Inversion groups, I-75. -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarRef01 - NoBarRef02 All CIG Groups -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom03 - NoBarCom05 All CIG Groups -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom04 - NoBarCom06 All CIG Groups

B-25 Effects of Traffic Volume and Speed While all the 5-minute periods in all the groups were not equivalent in traffic volume across all the groups, the average differences in the paired microphone levels are consistent with the results in the individual groups. As evidence of that consistency, Figure 21 and Figure 22 show the level difference graphs for, respectively, a group of higher-volume periods (CIG-27-1) and then a group of lower-volume periods (CIG-1-1). Across the spectrum for each microphone pair, the level differences are within 0.5 dB of each other and of the average differences shown in Figure 20 for virtually all the one-third octave bands. Regarding speed, there was only a 4.8-mph spread in the average two-way speed over all lanes across all the Calm Inversion groups. While not shown here, the average differences for each group were, for the most part, relatively consistent with each other and with the averages for all the groups shown above in Figure 20.

B-26 Figure 21. Differences in Leq (5 min.) +/- one standard deviation (dB), all microphones, for CIG-27-1 (higher traffic volume), I-75. -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarRef01 - NoBarRef02 CIG-27-1: 17:14, 17:20, 17:29, 17:40 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom03 - NoBarCom05 CIG-27-1: 17:14, 17:20, 17:29, 17:40 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom04 - NoBarCom06 CIG-27-1: 17:14, 17:20, 17:29, 17:40

B-27 Figure 22. Differences in Leq (5 min.) +/- one standard deviation (dB), all microphones, for CIG-1-1 (lower traffic volume), I-75. -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarRef01 - NoBarRef02 CIG-1-1: 20:03, 20:14, 21:06 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom03 - NoBarCom05 CIG-1-1: 20:03, 20:14, 21:06 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom04 - NoBarCom06 CIG-1-1: 20:03, 20:14, 21:06

B-28 Upwind Inversion Class Figure 23 shows three graphs of the differences in level between comparable microphones for the single Upwind Inversion groups with their error bars. This figure compares the following: BarRef01 and NoBarRef02 in the upper graph. BarCom03 and NoBarCom05 in the middle graph. BarCom04 and NoBarCom06 in the lower graph. In the upper graph, the BarRef01 levels are higher than the NoBarRef02 levels across the entire spectrum. At 25 Hz and from 100 Hz to 400 Hz, the differences range from 2 dB to 2.8 dB (at 160 Hz). From 500 Hz to 1.6 kHz, the difference is 1 dB or less. Above 2 kHz, the difference is over 1.5 dB. These results are like those for the Calm Inversion class. The middle graph shows the differences in levels between BarCom03 and NoBarCom05. Through 1 kHz, the BarCom03 levels are within +/- 1 dB of the NoBarCom05 levels, being lower than NoBarCom05 at 80 Hz through 250 Hz, by a range of 0.1 dB (at 100 Hz) to 1.1 dB (at 160 Hz). In contrast, for the Calm Inversion class, the NoBarCom05 levels were higher in only the 125 Hz and 160 Hz bands. At 1.6 kHz and 2 kHz, the BarCom03 levels are 1.6 and 1.4 dB higher than at NoBarCom05, which is slightly more than for the Calm Inversion class. Above 3.15 kHz, the NoBarCom05 levels are slightly higher than those at BarCom03, like the results for the Calm Inversion class. The lower graph compares the level differences at BarCom04 and NoBarCom06. Through 1.6 kHz, the BarCom04 levels are from 0.4 dB lower to 0.8 dB higher than at NoBarCom06, except at 100 Hz where the BarCom04 level is 2.2 dB higher than NoBarCom06. Between 2.5 kHz and 6.3 kHz, the NoBarCom06 levels are slightly higher than BarCom04 levels.

B-29 Figure 23. Averages of the differences in L eq (5 min.) +/- one standard deviation (dB), all microphones, for the single Upwind Inversion group, I-75. -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarRef01 - NoBarRef02 Single UIG Group -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom03 - NoBarCom05 Single UIG Group -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom04 - NoBarCom06 Single UIG Group

B-30 Comparison of Upwind Inversion and Calm Inversion Results Figure 24 compares the differences in one-third octave band levels for the single group in the Upwind Inversion class and the averages for all the Calm Inversion groups. The data values are the Upwind Inversion differences minus the average Calm Inversion differences for each frequency band. The data show that the Upwind Inversion differences tend to be within the following: +/-0.5 dB of the Calm Inversion differences for the reference microphones over the entire spectrum. +/-0.5 dB of the Calm Inversion differences between BarCom03 and NoBarCom05, except for 200 Hz and 250 Hz, where the Upwind Inversion differences are approximately 0.7 dB and 0.9 dB less than those that for the Calm Inversion class. 0.5 dB of the Calm Inversion differences between BarCom04 and NoBarCom06 over the entire spectrum, with the exceptions of 100 Hz, where the Upwind Inversion difference is 1 dB greater than that for the Calm Inversion class and 160 Hz to 250 Hz, where the Upwind Inversion differences are 0.7 dB to 1.4 dB less than those for the Calm Inversion class.

B-31 Figure 24. Differences in the Upwind Inversion average differences and the Calm Inversion average differences (Leq (5 min.) +/- one standard deviation, dB), all microphones, I-75. -3 -2 -1 0 1 2 3 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarRef01 - NoBarRef02 UIG-CIG -3 -2 -1 0 1 2 3 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom03 - NoBarCom05 UIG-CIG -3 -2 -1 0 1 2 3 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom04 - NoBarCom06 UIG-CIG

B-32 Additional Sound Level Analysis for I-75 – Ln Descriptors In addition to the examination of the differences in levels for the equivalent pairs of running 5-minute Leq data, the differences in the Ln descriptors for the overall data without segregation into equivalent periods were investigated. The focus was on the possible change in the background level in the presence of the noise barrier. Figure 25 presents the L90 (5 min.) and L99 (5 min.) for BarRef01 and NoBarRef02, in terms of overall A-weighted sound level and unweighted sound pressure level. The upper graphs are L90 (A-weighted on the left and unweighted on the right). The lower graphs are L99 (A-weighted on the left and unweighted on the right). Then, Figure 26 presents the differences in L90 (5 min.) and L99 (5 min.) along with Leq (5 min.), computed as BarRef01 minus NoBarRef02 for the A-weighted sound levels. The results show that while the Leq (5 min.) are from 0.1 dB to 1.7 dB higher at BarRef01 than at NoBarRef02, almost all the L90 at BarRef01 are higher than at NoBarRef02, with a range from -0.5 dB to 3.1 dB, except for some large differences of 3 dB to 5.5 dB in the period from approximately 20:20 to 20:48. A review of the field notes offered no explanation. The L99 differences are more variable: less than a quarter of the L99 are lower at BarRef01 than at NoBarRef02; the rest are higher than at NoBarRef02, with unexplained large differences of 6 dB to 7.5 dB from around 20:20 to 20:48, as also seen in the L90 data. The generally higher L90 at BarRef01 than at NoBarRef02 suggests an increase in the background level in front of the barrier that could be attributed to the presence of reflected sound rays reaching the microphone in addition to the direct rays from the passing vehicles. However, those times when the L99 is lower at BarRef01 than at NoBarRef02 do not support this theory. Figure 25. L90 (5 min.) and L99 (5 min.), I-75, BarRef01 and NoBarRef02 – broadband A-weighted sound level and sound pressure level.

B-33 Figure 26. Differences in broadband A-weighted 5-minute L90, L99 and Leq, I-75, BarRef01 and NoBarRef02. Figure 27 presents the same data—L90 (5 min.) and L99 (5 min.)—for BarCom03 and NoBarCom05 (the closer microphones across from the barrier) for overall A-weighted sound levels and unweighted sound pressure levels. Figure 28 presents the differences in L90 (5 min.) and L99 (5 min.) along with Leq (5 min.) for the A-weighted sound levels, computed as BarCom03 minus NoBarCom05. While the Leq (5 min.) are generally slightly higher at BarCom03 than at NoBarCom05, the L90 and L99 differences are much more variable. The A-weighted L90 ranges from 2 dB lower to 2.5 dB higher at BarCom03 compared to NoBarCom05, while the A-weighted L99 fall in a +/-4 dB range from 0.5 dB to 1.5 dB higher at BarRef01 than at NoBarRef02 Then, Figure 29 presents the L90 (5 min.) and L99 (5 min.) for BarCom04 and NoBarCom06 (the more distant microphones across from the barrier) for overall A-weighted sound levels and unweighted sound pressure levels. Figure 30 presents the differences in L90 (5 min.) and L99 (5 min.) along with Leq (5 min.) for the A-weighted sound levels, computed as BarCom04 minus NoBarCom06. The results for this microphone pair are like those for BarCom03 and NoBarCom05, with little evidence of a consistent elevation of the background level at BarCom04 compared to NoBarCom06. -2 -1 0 1 2 3 4 5 6 7 8 17 :1 2 17 :2 1 17 :3 0 17 :3 9 17 :4 8 17 :5 7 18 :0 6 18 :1 5 18 :2 4 18 :3 3 18 :4 2 18 :5 1 19 :0 0 19 :0 9 19 :1 8 19 :2 7 19 :3 6 19 :4 5 19 :5 4 20 :0 3 20 :1 2 20 :2 1 20 :3 0 20 :3 9 20 :4 8 20 :5 7 21 :0 6 So un d Le ve l D iff er en ce , d B Time L90 L99 Leq

B-34 Figure 27. L90 (5 min.) and L99 (5 min.), I-75, BarCom03 and NoBarCom05 – broadband A-weighted sound level (left) and sound pressure level (right). Figure 28. Differences in broadband A-weighted 5-minute L90, L99 and Leq, I-75, BarCom03 and NoBarCom05. -5 -4 -3 -2 -1 0 1 2 3 4 5 17 :1 2 17 :2 2 17 :3 2 17 :4 2 17 :5 2 18 :0 2 18 :1 2 18 :2 2 18 :3 2 18 :4 2 18 :5 2 19 :0 2 19 :1 2 19 :2 2 19 :3 2 19 :4 2 19 :5 2 20 :0 2 20 :1 2 20 :2 2 20 :3 2 20 :4 2 20 :5 2 21 :0 2 So un d Le ve l D iff er en ce , d B Time L90 L99 Leq

B-35 Figure 29. L90 (5 min.) and L99 (5 min.), I-75, BarCom04 and NoBarCom06 – broadband A-weighted sound level (left) and sound pressure level (right). Figure 30. Differences in broadband A-weighted 5-minute L90, L99 and Leq, I-75, BarCom04 and NoBarCom06. Figure 31 expands the analysis broadband A-weighted sound levels and unweighted sound pressure levels to include the individual one-third octave bands using color shading. The brown color means that the -5 -4 -3 -2 -1 0 1 2 3 4 5 17 :1 2 17 :2 2 17 :3 2 17 :4 2 17 :5 2 18 :0 2 18 :1 2 18 :2 2 18 :3 2 18 :4 2 18 :5 2 19 :0 2 19 :1 2 19 :2 2 19 :3 2 19 :4 2 19 :5 2 20 :0 2 20 :1 2 20 :2 2 20 :3 2 20 :4 2 20 :5 2 21 :0 2 So un d Le ve l D iff er en ce , d B Time L90 L99 Leq

B-36 BarRef01 levels are higher than the NoBarRef02 levels and blue means that NoBarRef02 is higher. In the graph, time runs from top to bottom (increasing as one moves down each figure, with each row representing the starting minute of a running 5-minute period) and the total block representing approximately 4 hours. The one-third octave bands run from left to right, with the broadband A-weighted sound levels and unweighted sound pressure levels on the far left. Within each band’s column of data are the differences for seven Ln sound pressure level Ln values (L1, L5, L10, L33, L50, L90, and L99) and Leq in the order illustrated in Figure 32 for a single one-third octave band. In general, the overall brownish tone to the figure indicates that the BarRef01 levels are slightly higher than the NoBarRef02 levels across most of the frequencies and all Ln descriptors. In several higher frequency bands, there are occasional blue blocks for the L99 (5 min.) data at 3.15 kHz and above. The coloring is more neutral in the 500 Hz to 2 kHz bands, indicating little difference in the levels across the Ln descriptors; if anything, the BarRef01 L99 (5 min.) are somewhat elevated for some of the periods, although this trend is not consistent over most of the periods. An elevated L99 (5 min.) (or L90 (5 min.)) would be an indication that the BarRef01 background levels are higher than the NoBarRef02 background levels, evidence of a sustaining of a vehicle’s pass-by noise due to the creation of an image source for each vehicle as the sound reflects off the barrier. The evidence of that possible effect is not strong. Figure 31. I-75 Differences in Ln (5 min.) by one-third octave frequency bands: BarRef01 and NoBarRef02. Figure 32. Order of statistical levels for a single one-third octave band. Figure 33 presents the Ln differences for BarCom03 and NoBarCom05. Again, brown means Barrier levels are higher, and blue means the No Barrier levels are higher. The lower frequencies (20 Hz through 63 Hz) and upper-middle frequencies (800 Hz through 2 kHz) are neutral to light brown, across most of the descriptors, suggesting no difference or slightly higher levels at BarCom03. The lower-middle lower frequencies (80 Hz through 315 Hz) and upper frequencies (2.5 kHz and above) are neutral to light blue across most of the descriptors, suggesting no difference or slightly higher levels at NoBarCom05. The exception is the L99 (5 min.) data at 4 kHz and above, which shows a stronger blue tone, meaning the background level at NoBarCom05 was consistently higher than at BarCom03. The results show no evidence of a sustaining of the sound due to reflected noise off the sound-absorbing barrier.

B-37 Figure 34 presents the Ln differences for BarCom04 and NoBarCom06. Below 2 kHz, there is not strong color indication of higher levels at BarCom04, perhaps except for the 63 Hz to 100 Hz range. In the 2.5 kHz to 5 kHz bands, there is an indication of slightly higher levels at NoBarCom06 than at BarCom04, across most of the Ln descriptors, with greater differences for the L99 descriptor. The field team did not notice any localized noise sources that might be a cause of the higher background levels at NoBarCom06, as evidenced by the higher L99 values. Figure 33. I-75 Differences in Ln (5 min.) by one-third octave frequency bands: BarCom03 and NoBarCom05. Figure 34. I-75 Differences in Ln (5 min.) by one-third octave frequency bands: BarCom04 and NoBarCom06. Data Analysis – Spectrograms for I-75 Spectrograms show the frequency content of sound as a function of time. This section presents results of the spectrogram analysis for the I-75 Ohio site. Data were examined in 5-minute blocks and for vehicle pass-by events. Presented here are two 5-minute time blocks and two vehicle pass-by events. Spectrograms for the two 5-minute data blocks are shown in Figure 35 through Figure 40. Figure 35 through Figure 37 show a 5-minute time block from 17:55 to 18:00 for the barrier side (reference) positions (Figure 35, Mics 1 and 2), the near-microphone community positions 50 ft. from the edge of the nearest travel lane (Figure 36, Mics 3 and 5), and the far-microphone community positions 100 ft. from the edge of the nearest travel lane (Figure 37, Mics 4 and 6). Figure 38 through Figure 40 show a 5-minute time block from 19:05 to 19:10 for the barrier side (reference) positions (Figure 38, Mics 1 and 2), the near- microphone community positions 50 ft. from the edge of the nearest travel lane (Figure 39, Mics 3 and 5), and the far-microphone community positions 100 ft. from the edge of the nearest travel lane (Figure 40, Mics 4 and 6).

B-38 The 5-minute data block spectrograms indicate the following trends: 1. For the barrier side of the highway reference positions, where the microphone is placed between the road and barrier at the Barrier site and at the same position for the No Barrier site, the hottest spots (dark red) in the spectrograms appear to be broader in frequency (from 500 Hz to 2000 Hz) and time and darker for the microphone adjacent to the Barrier compared to No Barrier. The broadening also applies to the other lighter red parts of the spectrogram. 2. For the community side near positions, where the microphones are placed on the opposite side of the road from the barrier at the Barrier site and the same positions for the No Barrier site, it is difficult to see any differences in the shapes or intensity of the hottest spots (dark red) in the spectrograms for the near positions. One observation is that the light blue appears to expand to lower frequencies for the site with No Barrier. 3. For the community side far positions, the dark red hotspots, from 500 Hz to 1,600 Hz, appear to be more filled in (a distinct shape) with the barrier present. Spectrograms for two pass-by events are shown in Figure 41 through Figure 44. Figure 41 and Figure 42 show a heavy truck pass-by event at approximately 18:18 for the near-microphone community positions 50 ft. from the edge of the nearest travel lane (Figure 41, Mics 3 and 5) and the far-microphone community positions 100 ft. from the edge of the nearest travel lane (Figure 42, Mics 4 and 6). Figure 43 and Figure 44 show a heavy truck pass-by event at approximately 18:33 for the near-microphone community positions 50 ft. from the edge of the nearest travel lane (Figure 43, Mics 3 and 5) and the far- microphone community positions 100 ft. from the edge of the nearest travel lane (Figure 44, Mics 4 and 6). It was difficult to extract the events for Mics 1 and 2 because events were not distinguishable, so these are not shown. For all pass-by plots, the vehicle is traveling northbound (barrier side of road), arriving first at the No Barrier site and second at the Barrier site about 20 seconds later. The vehicle pass-by event spectrograms indicate the following trends: 1. For the community side near positions, where the microphones are placed on the opposite side of the road from the barrier at the Barrier site and the same positions for the No Barrier site, it is difficult to see any differences. One noted observation is that the light blue appears to expand to lower frequencies for the site with No Barrier. 2. For the community side far positions, it is difficult to see any differences. For one of the events, it appears the darkest red is a more distinguishable shape for the Barrier site. In general, for the I-75 location, sound levels opposite the absorptive noise barrier in some cases appear to be slightly higher than those with No Barrier at key frequencies, ones that contribute most to the overall noise level. When comparing trends for absorptive noise barriers to trends for reflective noise barriers, a more objective examination of the data was applied. Spectrogram difference plots allow for a more objective comparison of vehicle pass-by events. These difference plots were generated for both absorptive and reflective spectrogram results to determine trends due to the presence of each type of barrier. A more detailed description of spectrogram difference plots and the results for reflective and absorptive barriers are covered in Appendix C.

B-39 Figure 35. I-75 5-minute spectrograms; top: BarRef01, bottom: NoBarRef02, start time 17:55.

B-40 Figure 36. I-75 5-minute spectrograms; top: BarCom03, bottom: NoBarCom05, start time 17:55.

B-41 Figure 37. I-75 5-minute spectrograms; top: BarCom04, bottom: NoBarCom06, start time 17:55.

B-42 Figure 38. I-75 5-minute spectrograms; top: BarRef01, bottom: NoBarRef02, start time 19:05.

B-43 Figure 39. I-75 5-minute spectrograms; top: BarCom03, bottom: NoBarCom05, start time 19:05.

B-44 Figure 40. I-75 5-minute spectrograms; top: BarCom04, bottom: NoBarCom06, start time 19:05.

B-45 Figure 41. I-75 heavy truck pass-by event at ~18:18 spectrograms; top: BarCom03, bottom: NoBarCom05.

B-46 Figure 42. I-75 heavy truck pass-by event at ~18:18 spectrograms; top: BarCom04, bottom: NoBarCom06.

B-47 Figure 43. I-75 heavy truck pass-by event at ~18:33 spectrograms; top: BarCom03, bottom: NoBarCom05.

B-48 Figure 44. I-75 heavy truck pass-by event at ~18:33 spectrograms; top: BarCom04, bottom: NoBarCom06.

B-49 C H A P T E R B - 4 Results – I-70, South Vienna, Ohio (Location OH-2) As shown in Figure 45, the I-70 location in South Vienna, Ohio, is a six-lane freeway. The barrier is approximately 900 ft. long, 17 ft. high, and offset 80 ft. from the edge of the nearest travel lane. The barrier is a precast concrete post-and-panel design, with a proprietary rubber tire chip sound-absorbing face on the highway side. Sound absorption test results for this barrier were not available. However, results for a panel from the same company with the same NRC show the sound absorption coefficients in Table 5. Table 5. Sound absorption coefficients and NRC for a barrier similar to the I-70 barrier. OCTAVE BAND CENTER FREQUENCY (HZ) SOUND ABSORPTION COEFFICIENT 125 0.09 250 0.25 500 1.25 1,000 0.74 2,000 1.03 4,000 1.07 NRC 0.80

B-50 Figure 45. I-70 No Barrier view (top left), Barrier view (top right), Roadway close-up (bottom left), and Barrier (highway side) close-up (bottom right). (Source: research team.) Figure 46 shows a site map of the measurement positions. Table 6 gives each microphone’s position, distance to the edge of nearest travel lane, and height above roadway grade. Figure 47 shows pictures of each microphone at its measurement position. The tree and underbrush cover at this site restricted how far back the microphones could be placed. Instead of putting one set of microphones closer to the road, where the direct near-lane traffic noise would dominate, both sets of microphones were placed at the same distance from the road, but at different heights. BarCom03 was at a height of 5 ft. above ground and was approximately 11 ft. above road grade, being located on a hill approximately 6 ft. above the road elevation. BarCom04 was approximately 10 ft. above ground, on the same pole as BarCom03. NoBarCom05 was located at 5 ft. above ground level on a tripod that was at the top of a sloped area that was approximately 6 ft. above road grade. NoBarCom06 was approximately 10 ft. above ground on the top of a hill and close to NoBarCom05. The met station was located near NoBarRef02 with its sensors 5 ft. and 15 ft. above ground.

B-51 Figure 46. I-70 microphone positions. (Aerial Photo Source: Google Earth.) Table 6. Microphone positions at I-70 Location. MICROPHONE NAME SIDE OF ROAD DISTANCE FROM EDGE OF NEAREST TRAVEL LANE (ft.) HEIGHT ABOVE ROADWAY PLANE (ft.) BarRef01 WB 40 11 (11 ft. above ground, near midpoint of barrier) NoBarRef02 WB 40 11 (12 ft. above ground) BarCom03 EB 75 11 (5 ft. above ground) BarCom04 EB 75 16 (10 ft. above ground) NoBarCom05 EB 75 11 (5 ft. above ground) NoBarCom06 EB 75 16 (10 ft. above ground)

B-52 Figure 47. I-70 BarRef01 (top left), NoBarRef02 (top right), BarCom03 and BarCom04 (middle left), NoBarCom05 and NoBarCom06 (middle right), and the meteorological station with NoBarRef02 (bottom). (Source: research team.)

B-53 Figure 48 shows cross-sections at the I-70 Barrier and No Barrier sites. The cross-section at the No Barrier site is like the Barrier site, with the ground elevation being a foot lower at BarRef01 compared to NoBarRef02. No concrete median barrier is present at either site. The Com microphones were set at 11 ft. and 16 ft. above the roadway elevation to study potential effects of height above roadway on reflected noise. Figure 48. Cross-sections at the I-70 Barrier (top) and No Barrier (bottom) sites. Measurements were conducted on Wednesday, November 16, 2016, from approximately 14:30 to 18:30. There was almost no cloud cover and the temperature dropped swiftly as the sun went down during these measurements. Winds were calm after sunset, and since most of the leaves had fallen off trees in this tree/brush line, wind noise through the foliage was not audible. There was heavy and steady traffic flow for the first two hours of data collection. Traffic was noticeably reduced for the last 30 minutes of data collection. Few individual pass-by candidates were observed since gaps of 6 to 7 seconds between vehicles were rare. Vehicles were audible to the west for several seconds longer than to the east likely because of the hill to the east. Louder heavy trucks could be heard for 20 seconds to the west if no other loud vehicle was in front of the microphones. No other noise sources, like insects or birds, were audible at the microphones. At BarCom03 and BarCom04, there was no influence from local traffic on the overpass that was approximately 400 ft. away. Likewise, there was no sense of reverberant noise from I-70 traffic passing under the overpass. There were no discernible differences between the sound being heard at the community microphones at the Barrier and No Barrier sites.

B-54 Measured Broadband Levels and Level Differences for I-70 The running Leq (5 min.) for each site are presented in the following figures to give an overall picture of the measured levels, both in terms of unweighted sound pressure levels and A-weighted sound levels: • BarRef01 and NoBarRef02—Figure 49 (unweighted) and Figure 50 (A-weighted); then Figure 51 shows the differences in unweighted and A-weighted levels for this mic pair. • BarCom03 and NoBarCom05—Figure 52 (unweighted) and Figure 53 (A-weighted); then Figure 54 shows the differences in unweighted and A-weighted levels for this mic pair. • BarCom04 and NoBarCom06—Figure 55 (unweighted) and Figure 56 (A-weighted); then Figure 57 shows the differences in unweighted and A-weighted levels for this mic pair. The following observations are prior to any attempt to group data into equivalent periods. In general, both the unweighted sound pressure levels and A-weighted sound levels are slightly higher at the Barrier microphones than at the No Barrier microphones. Over all the running 5-minute Leq periods, the BarRef01 unweighted sound pressure levels range from 0.1 dB lower than those at NoBarRef02 to 1.5 dB higher, averaging approximately 0.7 dB higher. The BarRef01 A-weighted sound levels range from 0.2 dB lower than those at NoBarRef02 to 1 dB higher, being approximately 0.5 dB higher on average. Somewhat higher levels could be expected at BarRef01 because it was located halfway between the barrier and I-70 and the barrier was not totally sound-absorbing (i.e., while all the barrier panels were sound-absorbing, the NRC for each panel was less than 1.00). For nearly all the running 5-minute Leq periods, the BarCom03 unweighted sound pressure levels range from 0.3 dB to 1.7 dB higher than those at NoBarCom05, averaging approximately 0.7 dB higher. The BarCom03 A-weighted sound levels range from 0 dB to 1.2 dB higher than those at NoBarCom05 averaging approximately 0.7 dB higher. For nearly all the running 5-minute Leq periods, the BarCom04 unweighted sound pressure levels range from 0.5 dB to 2 dB higher than those at NoBarCom06 averaging approximately 1.1 dB higher. The A-weighted sound levels at BarCom04 range mostly from 0.5 dB to 1.5 dB higher than those at NoBarCom06 averaging approximately 1 dB higher. Figure 49. Running Leq (5 min.), I-70, unweighted sound pressure level, dBZ, BarRef01 and NoBarRef02. 82 83 84 85 86 87 14 :3 5 14 :4 5 14 :5 5 15 :0 5 15 :1 5 15 :2 5 15 :3 5 15 :4 5 15 :5 5 16 :0 5 16 :1 5 16 :2 5 16 :3 5 16 :4 5 16 :5 5 17 :0 5 17 :1 5 17 :2 5 17 :3 5 17 :4 5 17 :5 5 18 :0 5 18 :1 5 18 :2 5 So un d Pr es su re L ev el , d BZ Time BarRef01 NoBarRef02

B-55 Figure 50. Running Leq (5 min.), I-70, A-weighted sound level, dBA, BarRef01 and NoBarRef02. Figure 51. Differences in running Leq (5 min.), I-70, BarRef01 minus NoBarRef02. 79 80 81 82 83 84 14 :3 5 14 :4 5 14 :5 5 15 :0 5 15 :1 5 15 :2 5 15 :3 5 15 :4 5 15 :5 5 16 :0 5 16 :1 5 16 :2 5 16 :3 5 16 :4 5 16 :5 5 17 :0 5 17 :1 5 17 :2 5 17 :3 5 17 :4 5 17 :5 5 18 :0 5 18 :1 5 18 :2 5 So un d Le ve l, dB A Time BarRef01 NoBarRef02 -3 -2 -1 0 1 2 3 14 :3 5 14 :4 5 14 :5 5 15 :0 5 15 :1 5 15 :2 5 15 :3 5 15 :4 5 15 :5 5 16 :0 5 16 :1 5 16 :2 5 16 :3 5 16 :4 5 16 :5 5 17 :0 5 17 :1 5 17 :2 5 17 :3 5 17 :4 5 17 :5 5 18 :0 5 18 :1 5 18 :2 5 D iff er en ce in le ve l, dB Time dBA dBZ

B-56 Figure 52. Running Leq (5 min.), I-70, unweighted sound pressure level, dBZ, BarCom03 and NoBarCom05. Figure 53. Running Leq (5 min.), I-70, A-weighted sound level, dBA, BarCom03 and NoBarCom05. 82 83 84 85 86 87 14 :3 5 14 :4 5 14 :5 5 15 :0 5 15 :1 5 15 :2 5 15 :3 5 15 :4 5 15 :5 5 16 :0 5 16 :1 5 16 :2 5 16 :3 5 16 :4 5 16 :5 5 17 :0 5 17 :1 5 17 :2 5 17 :3 5 17 :4 5 17 :5 5 18 :0 5 18 :1 5 18 :2 5 So un d Pr es su re L ev el , d BZ Time BarCom03 NoBarCom05 78 79 80 81 82 83 14 :3 5 14 :4 5 14 :5 5 15 :0 5 15 :1 5 15 :2 5 15 :3 5 15 :4 5 15 :5 5 16 :0 5 16 :1 5 16 :2 5 16 :3 5 16 :4 5 16 :5 5 17 :0 5 17 :1 5 17 :2 5 17 :3 5 17 :4 5 17 :5 5 18 :0 5 18 :1 5 18 :2 5 So un d Le ve l, dB A Time BarCom03 NoBarCom05

B-57 Figure 54. Differences in running Leq (5 min.), I-70, BarCom03 minus NoBarCom05. Figure 55. Running Leq (5 min.), I-70, unweighted sound pressure level, dBZ, BarCom04 and NoBarCom06. -3 -2 -1 0 1 2 3 14 :3 5 14 :4 5 14 :5 5 15 :0 5 15 :1 5 15 :2 5 15 :3 5 15 :4 5 15 :5 5 16 :0 5 16 :1 5 16 :2 5 16 :3 5 16 :4 5 16 :5 5 17 :0 5 17 :1 5 17 :2 5 17 :3 5 17 :4 5 17 :5 5 18 :0 5 18 :1 5 18 :2 5 D iff er en ce in le ve l, dB Time dBA dBZ 81 82 83 84 85 86 87 14 :3 5 14 :4 5 14 :5 5 15 :0 5 15 :1 5 15 :2 5 15 :3 5 15 :4 5 15 :5 5 16 :0 5 16 :1 5 16 :2 5 16 :3 5 16 :4 5 16 :5 5 17 :0 5 17 :1 5 17 :2 5 17 :3 5 17 :4 5 17 :5 5 18 :0 5 18 :1 5 18 :2 5 So un d Pr es su re L ev el , d BZ Time BarCom04 NoBarCom06

B-58 Figure 56. Running Leq (5 min.), I-70, A-weighted sound level, dBA, BarCom04 and NoBarCom06. Figure 57. Differences in running Leq (5 min.), I-70, BarCom04 minus NoBarCom06. Data Analysis for I-70 - FHWA Method Equivalent Groups All the groupings of three or more 5-minute periods that were judged equivalent for traffic parameters at the I-70 location fell into three meteorological classes: Calm Lapse, Calm Neutral, and Calm Inversion. There were some data in the Downwind Lapse class, but only enough to provide two nonoverlapping 5-minute time periods (starting at 14:36 and 14:42). Nonetheless, this Downwind Lapse data is included. For 78 79 80 81 82 14 :3 5 14 :4 5 14 :5 5 15 :0 5 15 :1 5 15 :2 5 15 :3 5 15 :4 5 15 :5 5 16 :0 5 16 :1 5 16 :2 5 16 :3 5 16 :4 5 16 :5 5 17 :0 5 17 :1 5 17 :2 5 17 :3 5 17 :4 5 17 :5 5 18 :0 5 18 :1 5 18 :2 5 So un d Le ve l, dB A Time BarCom04 NoBarCom06 -3 -2 -1 0 1 2 3 14 :3 5 14 :4 5 14 :5 5 15 :0 5 15 :1 5 15 :2 5 15 :3 5 15 :4 5 15 :5 5 16 :0 5 16 :1 5 16 :2 5 16 :3 5 16 :4 5 16 :5 5 17 :0 5 17 :1 5 17 :2 5 17 :3 5 17 :4 5 17 :5 5 18 :0 5 18 :1 5 18 :2 5 D iff er en ce in le ve l, dB Time dBA dBZ

B-59 source equivalence for I-70, the allowable variation in the NoBarRef02 Leq (5 min.) between the periods in a group was 0 dB in most cases and 0.1 dB in a few cases, and the allowable average speed differences between periods was 5 mph. There were seven groupings in the Calm Lapse class, each with three to five 5-minute equivalent periods; two groupings in the Calm Neutral class, each with three 5-minute equivalent periods; and 11 groupings in the Calm Inversion class, each with three to five 5-minute equivalent periods. Figure 59 shows these groupings graphically for the Calm Lapse class. The times along the top represent the starting minute of each 5-minute period. Figure 60 and Figure 61 show the same for the Calm Neutral and Calm Inversion groups, respectively. Each group has a unique name, starting with “CLG-,” “CNG-,” or “CIG-.” Note that all the 5-minute periods in a group are nonoverlapping in time and the same 5-minute period does not appear in more than one equivalent grouping. Figure 58 shows the 15-minute counts for autos, heavy trucks and total traffic by direction over the 4-hour period. While heavy truck counts were relatively constant over that time, auto (and thus total) counts increased somewhat through approximately 16:30 period and then decreased slightly into the early evening. This location is not near an urban center, meaning there was less of a spike in rush hour traffic. The periods for the selected groupings had varying traffic volumes, as shown in Table 7. For the Calm Lapse group, the range in the total two-way factored hourly volume was from 3,432 vph to 3,918 vph, a 14% increase. For the two Calm Neutral groups, the total volumes were with 2% of each other at around 3,900 vph. For the Calm Inversion groups, there was a 35% difference in the two-way volumes, from 2,900 vph up to 3,904 vph. Speeds were more consistent, ranging from averages of 68 mph to 75 mph for the Calm Lapse groups, 70 mph to 74 mph for the Calm Neutral groups, and 69 mph to 75 mph for the Calm Inversion groups. Figure 58. 15-minute traffic counts by direction for autos, heavy trucks and total, I-70. 0 100 200 300 400 500 600 14 :3 5 14 :5 0 15 :0 5 15 :2 0 15 :3 5 15 :5 0 16 :0 5 16 :2 0 16 :3 5 16 :5 0 17 :0 5 17 :2 0 17 :3 5 17 :5 0 18 :0 5 18 :2 0 V eh ic le C ou nt Title EB Total WB Total EB Auto WB Auto EB HT WB HT

B-60 Figure 59. Equivalent 5-minute periods for Calm Lapse groups at I-70. 14 :4 4 14 :4 8 14 :5 0 14 :5 2 14 :5 3 15 :1 5 15 :2 2 15 :2 9 15 :4 0 15 :4 3 15 :4 7 15 :4 8 15 :4 9 15 :5 0 15 :5 2 15 :5 8 15 :5 9 16 :0 0 16 :1 0 16 :1 1 16 :1 9 16 :2 0 16 :2 7 CLG-1-1: 15:43, 15:48, 16:19 1 1 1 CLG-2-1: 14:53, 15:47, 16:20 1 1 1 CLG-3-1: 14:52, 15:40, 15:58 1 1 1 CLG-4-1: 15:22, 15:49, 16:10 1 1 1 CLG-5-1: 14:50, 16:00, 16:11, 16:27 1 1 1 1 CLG-6-1: 14:48, 15:50, 15:59 1 1 1 CLG-8-1: 14:44, 15:15, 15:29, 15:52 1 1 1 1 Group ID Starting Time of 5-minute Periods

Figure 60. Equivalent 5-minute periods for Calm Neutral groups at I-70. Figure 61. Equivalent 5-minute periods for Calm Inversion groups at I-70. 16 :2 8 16 :3 0 16 :3 5 16 :4 6 16 :4 9 16 :5 2 CNG-1-1: 16:28, 16:52, 16:46 1 1 1 CNG-2-1: 16:30, 16:35, 16:49 1 1 1 Group ID Starting Time of 5-minute Periods 16 :5 6 17 :0 0 17 :0 1 17 :0 2 17 :0 3 17 :0 4 17 :0 8 17 :1 1 17 :1 7 17 :1 8 17 :1 9 17 :2 3 17 :2 6 17 :3 5 17 :3 7 17 :3 9 17 :4 0 17 :4 2 17 :4 7 17 :4 9 17 :5 0 17 :5 7 17 :5 9 18 :0 5 18 :1 1 18 :1 2 18 :1 4 18 :1 5 18 :1 6 18 :1 7 18 :1 9 18 :2 0 18 :2 1 18 :2 3 18 :2 4 18 :2 8 18 :3 0 CIG-1-1: 16:56, 17:40, 18:20 1 1 1 CIG-2-1: 17:17, 17:42, 18:21 1 1 1 CIG-3-1: 17:00, 17:39, 18:11 1 1 1 CIG-5-1: 17:01, 17:37, 18:19 1 1 1 CIG-7-1: 17:02, 18:12, 18:17 1 1 1 CIG-8-1: 17:08, 17:23, 18:14 1 1 1 CIG-9-1: 17:04, 17:11, 17:18, 18:23, 18:30 1 1 1 1 1 CIG-10-1: 17:19, 17:59, 18:05, 18:24 1 1 1 1 CIG-11-1: 17:03, 17:47, 17:57, 18:15 1 1 1 1 CIG-13-1: 17:26, 17:49, 18:16 1 1 1 CIG-15-1: 17:35, 17:50, 18:28 1 1 1 Group ID Starting Time of 5-minute Periods

B-62 Table 7. Two-way traffic volumes in 5-minute periods, by equivalent group for Calm Inversion, Calm Lapse, Calm Neutral, and Downwind Lapse conditions, sorted by factored hourly volume, I-70. Two-Way Traffic Volumes (5 minutes) Group Period 1 Period 2 Period 3 Period 4 Period 5 Factored Hourly Volume, vph Calm Inversion CIG-8-1 299 310 259 n/a n/a 3,472 CIG-13-1 319 255 272 n/a n/a 3,384 CIG-11-1 297 285 264 268 n/a 3,342 CIG-5-1 293 292 236 n/a n/a 3,284 CIG-7-1 299 249 272 n/a n/a 3,280 CIG-15-1 315 260 239 n/a n/a 3,256 CIG-10-1 304 267 270 234 n/a 3,225 CIG-3-1 276 273 252 n/a n/a 3,204 CIG-9-1 298 302 290 233 211 3,202 CIG-2-1 278 243 209 n/a n/a 2,920 CIG-1-1 264 248 213 n/a n/a 2,900 Calm Lapse CLG-5-1 300 357 306 343 n/a 3,918 CLG-6-1 280 329 354 n/a n/a 3,852 CLG-8-1 298 300 319 341 n/a 3,774 CLG-3-1 284 312 340 n/a n/a 3,744 CLG-4-1 273 300 307 n/a n/a 3,520 CLG-2-1 279 289 300 n/a n/a 3,472 CLG-1-1 294 278 286 n/a n/a 3,432 Calm Neutral CNG-2-1 332 338 306 n/a n/a 3,904 CNG-1-1 357 290 306 n/a n/a 3,812 Downwind Lapse DLG-1-1 285 263 n/a n/a n/a 3,288 Sound Pressure Level Spectra Before discussing the differences in levels between the Barrier and No Barrier sites, typical sound pressure level spectra are shown to give some perspective on the data upon which the differences are based. One of the 5-minute periods in one of the Calm Inversion groups was chosen as typical.

B-63 Figure 62, Figure 63, and Figure 64 present the sound pressure level spectra for, respectively: î BarRef01/NoBarRef02. î BarCom03/NoBarCom05. î BarCom04/NoBarCom06. Figure 62. Sample sound pressure level spectra for BarRef01 and NoBarRef02, I-70, Calm Inversion group CIG-1-1, 16:56-17:01 (Leq (5 min.), dBZ). 35 40 45 50 55 60 65 70 75 80 85 90 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k So un d Pr es su re L ev el , d BZ 1/3 Octave Band Frequency, Hz BarRef01 NoBarRef02

B-64 Figure 63. Sample sound pressure level spectra for BarCom03 and NoBarCom05, I-70, Calm Inversion group CIG-1-1, 16:56-17:01 (Leq (5 min.), dBZ). 35 40 45 50 55 60 65 70 75 80 85 90 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k So un d Pr es su re L ev el , d BZ 1/3 Octave Band Frequency, Hz BarCom03 NoBarCom05

B-65 Figure 64. Sample sound pressure level spectra for BarCom04 and NoBarCom06, I-70, Calm Inversion group CIG-1-1, 16:56-17:01 (Leq (5 min.), dBZ). Calm Lapse Class Figure 65 shows three graphs of the differences in level between comparable microphones for an average of all the Calm Lapse groups with their error bars. The error bars are +/- one standard deviation for each average value. This figure compares the following: î BarRef01 and NoBarRef02 in the upper graph. î BarCom03 and NoBarCom05 in the middle graph. î BarCom04 and NoBarCom06 in the lower graph. Each graph shows the averages of the average level differences for the A-weighted sound level, the unweighted sound pressure level and the one-third octave band sound pressure levels from 20 Hz to 35 40 45 50 55 60 65 70 75 80 85 90 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k So un d Pr es su re L ev el , d BZ 1/3 Octave Band Frequency, Hz BarCom04 NoBarCom06

B-66 10 kHz. Graphs for all the individual Calm Lapse groups are in spreadsheet files in the project record. The trends across the one-third octave band frequencies, described below, are generally similar in these individual groups of equivalent periods, with some differences likely related to background noise and the uniqueness of vehicle noise sources in each period. Figure 65 shows in the upper graph that, in general, the BarRef01 levels are less than 1 dB higher than the NoBarRef02 levels across most of the spectrum, from 80 Hz through 3.15 kHz. Below 63 Hz, the BarRef01 levels are from 1 dB to 3 dB higher, and above 3.15 kHz, these levels are 1.2 dB to 2 dB higher. The field notes offer no explanation for these larger differences in these low- and high-frequency bands. The middle graph shows the differences in levels between BarCom03 and NoBarCom05, both of which were 5 ft. above the ground and 11 ft. above the roadway elevation. Over most of the spectrum between 80 Hz and 5 kHz, the BarCom03 levels are 0 dB to 1 dB higher than the NoBarCom05 levels. The exceptions are: at 315 Hz and 400 Hz, where the BarCom03 levels are approximately 3 dB higher than at NoBarCom05; and at 200 Hz and 250 Hz, where the BarCom03 levels are lower than the NoBarCom05 levels by 0.5 dB to 1 dB. Also, the BarCom03 levels are approximately 1.2 dB to 2.8 dB higher than NoBarCom05 below 80 Hz and 1.4 dB to 3 dB higher above 5 kHz. The site conditions were similar at the BarCom03 and NoBarCom05 sites, providing no ready explanation for the effects in the 200 Hz to 400 Hz bands, nor at the low and high ends of the spectrum. The lower graph compares the levels at BarCom04 and NoBarCom06, which were 10 ft. above the ground and 16 ft. above the roadway elevation. Over most of the spectrum between 50 Hz and 4 kHz, the BarCom04 levels are 0 dB to 1.1 dB higher than the NoBarCom06 levels. The exceptions are from 160 Hz to 315 Hz, where the BarCom04 levels range from 1.5 dB to 2.4 dB higher. Also, from 3.15 Hz to 6.3 kHz, the BarCom04 levels are lower than the NoBarCom06 levels by approximately 0.7 dB. Below 50 Hz, the BarCom04 levels are 1.4 to 3 dB higher than at NoBarCom06. Above 4 kHz, the BarCom04 levels are 1.5 dB to 5 dB higher than at NoBarCom06. No apparent reason exists for the large differences at the highest frequencies. During the data analysis phase, the BarCom04 microphone was tested and found to have poor high-frequency response. It was sent out for laboratory calibration and an adjustment factor was then applied to the data based on the calibration results. However, the differences in these high frequencies compared to NoBarCom06 are much larger than before the adjustments. The same microphone was used at the BarCom04 site for the I-75 location, but the level differences were within a decibel at the highest frequencies (see the lower graph in Figure 20). While all the 5-minute periods in all the groups were not equivalent in traffic volume and speed across all the groups, these average differences are representative of the results for the individual groups, especially in the frequencies from 200 Hz to 8 kHz. There was a bit more variability below 200 Hz and at 8 kHz and 10 kHz, as indicated by the size of the error bars in the graphs in Figure 65, but the trends were similar.

B-67 Figure 65. Averages of the differences in Leq (5 min.) +/- one standard deviation (dB), all microphones, for all Calm Lapse groups, I-70. -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarRef01 - NoBarRef02 All CLG Groups -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom03 - NoBarCom05 All CLG Groups -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom04 - NoBarCom06 All CLG Groups

B-68 Calm Neutral Class Figure 66 shows the averages of the average level differences between the Barrier and No Barrier microphones’ levels for all the Calm Neutral groups. Like the Calm Lapse groups, the BarRef01 levels (upper graph) are less than a decibel above the NoBarRef02 levels across most of the spectrum, in this case from 125 Hz through 3.15 kHz. At and below 100 Hz, the BarRef01 levels are from 1.1 dB to 3 dB higher, and above 3.15 kHz, 1.5 dB to 2 dB higher. In the middle graph, the BarCom03 levels are less than or equal to 1 dB higher than the NoBarCom05 levels from 100 Hz through 5 kHz, except for larger differences of 4 dB, 2.5 dB and 1.3 dB at 315 Hz, 400 Hz and 500 Hz, respectively. These results are similar to the Calm Lapse group results. Likewise, the BarCom03 levels are slightly lower than the NoBarCom05 levels at 200 Hz, as like the Calm Lapse data. The differences above a decibel at frequencies below 100 Hz and above 5 kHz are unexplained. The BarCom04/NoBarCom06 differences (lower graph) are also like those for the Calm Lapse data. Over most of the spectrum from 100 Hz to 4 kHz, the differences are between 0.5 dB and 1 dB, except for a bump in the 160 Hz to 315 Hz range, where the BarCom04 levels are approximately 2 dB to 2.6 dB higher, and at 630 Hz, where the difference is 1.5 dB. Also, as with the Calm Lapse data, the BarCom04 levels are much higher than the NoBarCom06 levels in the highest frequency bands by as much as 4.9 dB. There is no apparent explanation other than an adjustment was made to the BarCom04 data after laboratory calibration of that microphone, which made the comparison to NoBarCom06 worse. The results are similar to those for the Calm Lapse data. Although all the 5-minute periods in all the groups were not equivalent in traffic volume and speed, these average differences are representative of the results for the individual groups, especially in the frequencies from 200 Hz to 8 kHz. More variability exists below 200 Hz, as indicated by the size of the error bars in the graphs in Figure 66, but the trends are similar.

B-69 Figure 66. Averages of the differences in Leq (5 min.) +/- one standard deviation (dB), all microphones, for all Calm Neutral groups, I-70. -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarRef01 - NoBarRef02 All CNG Groups -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom03 - NoBarCom05 All CNG Groups -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom04 - NoBarCom06 All CNG Groups

B-70 Calm Inversion Class Figure 67 shows the averages of the average level differences between the Barrier and No Barrier microphones’ levels for all the Calm Inversion groups with their error bars. The results at the three microphone pairs are like those for the Calm Lapse and Calm Neutral groups. Only small differences exist over most of the spectrum for the reference microphones, except below 63 Hz. Small differences exist between BarCom03 and NoBarCom05, except at the following: 315 Hz and 400 Hz, where the differences are larger. 200 Hz to 250 Hz and 2.5 kHz to 3.15 kHz, where the NoBarCom05 levels are slightly higher. At BarCom04, most differences are 0 dB to 1 dB, except for differences of 1.5 dB to 2.5 dB from 160 Hz to 315 Hz, and the previously noted large differences at the lowest and highest frequencies. As with the Calm Lapse and Calm Neutral data, these average differences are representative of the results for the individual groups despite differences in traffic volume and speed across the groups, especially in frequencies from 200 Hz to 8 kHz. More variability exists below 200 Hz, but the trends are similar.

B-71 Figure 67. Averages of the differences in Leq (5 min.) +/- one standard deviation (dB), all microphones, for all Calm Inversion groups, I-70. -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarRef01 - NoBarRef02 All CIG Groups -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom03 - NoBarCom05 All CIG Groups -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom04 - NoBarCom06 All CIG Groups

B-72 Downwind Lapse Class Figure 68 shows the averages of the average level differences between the Barrier and No Barrier microphones. There were only two nonoverlapping 5-minute periods of Downwind Lapse data. The results are like those for the Calm Lapse, Calm Neutral, and Calm Inversion data groupings at BarCom03/NoBarCom05 and BarCom04/NoBarCom06. Again, the large differences are present at the highest frequencies for BarCom04 compared to NoBarCom06. The results are slightly different at the reference microphones: at 160 Hz, the BarRef01 level is about 0.5 dB lower than at NoBarRef02, whereas for the other meteorological groups, the level at BarRef01 was 0 dB to 0.8 dB higher than at NoBarRef02.

B-73 Figure 68. Averages of the differences in Leq (5 min.) +/- one standard deviation (dB), all microphones, for all Downwind Lapse groups, I-70. -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarRef01 - NoBarRef02 All DLG Groups -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom03 - NoBarCom05 All DLG Groups -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom04 - NoBarCom06 All DLG Groups

B-74 Comparison of Downwind Lapse and Calm Neutral Results Figure 69 compares the differences in one-third octave band levels for the Calm Neutral class and for the limited data in the Downwind Lapse class. As noted, there were only two nonoverlapping 5-minute periods of Downwind Lapse data, so any conclusions should be viewed with caution. The data values are the average Downwind Lapse differences minus the average Calm Neutral differences for each frequency band. The data show that the Downwind Lapse average differences tend to be within the following: 0.5 dB of the Calm Neutral differences for the reference microphones over most of the spectrum from 200 Hz to 10 kHz, with some greater differences below 200 Hz, where the Calm Neutral differences between BarRef01 and NoBarRef02 are greater than the Downwind Lapse differences. 1 dB of the Calm Neutral differences between BarCom03 and NoBarCom05 over almost the entire spectrum, except for 315 Hz, where the Calm Neutral average difference between BarCom03 and NoBarCom05 is approximately 1.6 dB greater than that for the Downwind Lapse group. 0.5 dB of the Calm Neutral differences between BarCom04 and NoBarCom06 from 31.5 Hz through 10 kHz, except for differences ranging from 1.2 dB to 2.4 dB at 20 Hz, 80 Hz, and 160 Hz, where the Calm Neutral differences are greater than the Downwind Lapse differences.

B-75 Figure 69. Differences in the Downwind Lapse average differences and the Calm Neutral average differences (Leq (5 min.) +/- one standard deviation, dB), all microphones, I-70. -3 -2 -1 0 1 2 3 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarRef01 - NoBarRef02 DLG - CNG -3 -2 -1 0 1 2 3 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom03 - NoBarCom05 DLG - CNG -3 -2 -1 0 1 2 3 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom04 - NoBarCom06 DLG - CNG

B-76 Additional Sound Level Analysis for I-70 – Ln Descriptors In addition to the examination of the differences in levels for the equivalent pairs of running 5-minute Leq data, the differences in the Ln descriptors for the overall data without segregation into equivalent periods were investigated. The focus was on the possible change in the background level in the presence of the noise barrier. Figure 70 presents the L90 (5 min.) and L99 (5 min.) for BarRef01 and NoBarRef02, in terms of overall A-weighted sound levels and unweighted sound pressure level. The upper graphs are L90 (A-weighted on the left and unweighted on the right). The lower graphs are L99 (A-weighted on the left and unweighted on the right). Then, Figure 71 presents the differences in L90 (5 min.) and L99 (5 min.) along with Leq (5 min.), computed as BarRef01 minus NoBarRef02 for the A-weighted sound levels. The results show that while the A-weighted Leq (5 min.) data average about 0.5 dB higher at BarRef01 than at NoBarRef02, the L90 at BarRef01 range from 0 dB to 2 dB higher than at NoBarRef02 up until around 17:00. After that, the L90 at BarRef01 fluctuates from a decibel lower to 2 dB higher than at NoBarRef02 through the end of data collection around 18:30. A smaller trend exists for the L99, with the BarRef01 value ranging above and below that for NoBarRef02 over the entire period. Thus, the first two hours of the L90 data suggest an increase in the background level in front of the barrier that could be attributed to the presence of reflected sound rays reaching the microphone in addition to the direct rays from the passing vehicles. However, the later L90 data and the L99 data does not support that conclusion. Figure 70. L90 (5 min.) and L99 (5 min.), I-70, BarRef01 and NoBarRef02 – broadband A-weighted sound level and sound pressure level.

B-77 Figure 71. Differences in broadband A-weighted 5-minute L90, L99 and Leq, I-70, BarRef01 and NoBarRef02. Figure 72 presents the same data—L90 (5 min.) and L99 (5 min.)—for BarCom03 and NoBarCom05 (the lower microphones across from the barrier) for overall A-weighted sound levels and unweighted sound pressure level. Figure 73 presents the differences in L90 (5 min.) and L99 (5 min.) along with Leq (5 min.) for the A-weighted sound levels, computed as BarCom03 minus NoBarCom05. As with the reference microphones, on average, the Leq (5 min.) is on the order of 0 dB to 1 dB higher at the barrier site. Likewise, during the first two hours of data collection the L90 are slightly higher at BarCom03 compared to NoBarCom05, but the differences fluctuate positively and negatively during the last two hours. Also, no trend exists in the L99 data, with a range in differences from -5 dB to nearly +6 dB. Next, Figure 74 presents the L90 (5 min.) and L99 (5 min.) for BarCom04 and NoBarCom06 (the upper microphones across from the barrier) for overall A-weighted sound levels and unweighted sound pressure level. Figure 75 presents the differences in L90 (5 min.) and L99 (5 min.) along with Leq (5 min.) for the A-weighted sound levels, computed as BarCom04 minus NoBarCom06. The results are generally like the other microphone pairings: slightly higher Leq (5 min.); slightly higher L90 during the first half of data collection; and no trend in the L99 data. -6 -4 -2 0 2 4 6 8 14 :3 5 14 :4 4 14 :5 3 15 :0 2 15 :1 1 15 :2 0 15 :2 9 15 :3 8 15 :4 7 15 :5 6 16 :0 5 16 :1 4 16 :2 3 16 :3 2 16 :4 1 16 :5 0 16 :5 9 17 :0 8 17 :1 7 17 :2 6 17 :3 5 17 :4 4 17 :5 3 18 :0 2 18 :1 1 18 :2 0 18 :2 9 So un d Le ve l D iff er en ce , d B Time L90 L99 Leq

B-78 Figure 72. L90 (5 min.) and L99 (5 min.), I-70, BarCom03 and NoBarCom05 – broadband A-weighted sound level (left) and sound pressure level (right). Figure 73. Differences in broadband A-weighted 5-minute L90, L99 and Leq, I-70, BarCom03 and NoBarCom05. -6 -4 -2 0 2 4 6 8 14 :3 5 14 :4 5 14 :5 5 15 :0 5 15 :1 5 15 :2 5 15 :3 5 15 :4 5 15 :5 5 16 :0 5 16 :1 5 16 :2 5 16 :3 5 16 :4 5 16 :5 5 17 :0 5 17 :1 5 17 :2 5 17 :3 5 17 :4 5 17 :5 5 18 :0 5 18 :1 5 18 :2 5 So un d Le ve l D iff er en ce , d B Time L90 L99 Leq

B-79 Figure 74. L90 (5 min.) and L99 (5 min.), I-70, BarCom04 and NoBarCom06 – broadband A-weighted sound level (left) and sound pressure level (right). Figure 75. Differences in broadband A-weighted 5-minute L90, L99 and Leq, I-70, BarCom04 and NoBarCom06. Figure 76 expands the analysis broadband A-weighted sound levels and unweighted sound pressure levels to include the individual one-third octave bands using color shading. The brown color means that the -6 -4 -2 0 2 4 6 8 15 :2 0 15 :3 0 15 :4 0 15 :5 0 16 :0 0 16 :1 0 16 :2 0 16 :3 0 16 :4 0 16 :5 0 17 :0 0 17 :1 0 17 :2 0 17 :3 0 17 :4 0 17 :5 0 18 :0 0 18 :1 0 18 :2 0 18 :3 0 So un d Le ve l D iff er en ce , d B Time L90 L99 Leq

B-80 BarRef01 levels are higher than the NoBarRef02 levels and blue means that NoBarRef02 is higher. In the graph, time runs from top to bottom (increasing as one moves down each figure, with each row representing the starting minute of a running 5-minute period) and the total block representing approximately 4 hours. The one-third octave bands run across from left to right, with the broadband A-weighted sound levels and unweighted sound pressure levels on the far left. Within each band’s column of data are the differences for seven Ln sound pressure level Ln values (L1, L5, L10, L33, L50, L90, and L99) and Leq. In general, the overall brownish tone for the frequency bands of 20 Hz to 50 Hz and from 4 kHz to 10 kHz indicates that the BarRef01 levels are slightly higher than the NoBarRef02 levels across all Ln descriptors in those bands. In the upper-frequency bands, the L99 (5 min.) columns show some periods of higher background levels at one microphone position and some higher periods at the other microphone— no clear trend. Across the rest of the spectrum from 80 Hz through 3.15 kHz, only minor differences exist in levels at the two microphone positions, with some indication of higher L99 (5 min.) at NoBarRef02 at 160 Hz, 200 Hz, and 3.15 kHz, and some indication of higher L99 (5 min.) at BarRef01 from 250 Hz through 630 Hz. Figure 76. I-70 Differences in Ln (5 min.) by one-third octave frequency bands: BarRef01 and NoBarRef02. Figure 77 presents the Ln differences for BarCom03 and NoBarCom05. Again, brown means Barrier levels are higher, and blue means the No Barrier levels are higher. All the Ln descriptors at BarCom03 are clearly higher than at NoBarCom05 in the 315 Hz and 400 Hz bands. The L90 (5 min.) and L99 (5 min.) levels at NoBarCom05 are generally higher that at BarCom03 in the 160 Hz and 200 Hz bands, and at 250 Hz for the first half of the sample period. In many of the bands at and above 630 Hz, the L99 (5 min.) are higher at NoBarCom05. For the highest frequency bands, the L1 (5 min.) and L5 (5 min.) descriptors are higher for the BarCom03 position. Figure 78 presents the Ln differences for BarCom04 and NoBarCom06. In the 200 Hz and 250 Hz bands, the BarCom04 levels are higher than those at NoBarCom06 for most of the descriptors. From 315 Hz through 2.5 kHz, the Ln descriptors are quite close to each other, with BarCom04 being slightly higher than NoBarCom06. At 8 kHz and 10 kHz, the levels for all the descriptors are substantially higher at BarCom04 than at NoBarCom06.

B-81 Figure 77. I-70 Differences in Ln (5 min.) by one-third octave frequency bands: BarCom03 and NoBarCom05. Figure 78. I-70 Differences in Ln (5 min.) by one-third octave frequency bands: BarCom04 and NoBarCom06. Data Analysis – Spectrograms for I-70 Spectrograms show the frequency content of sound as a function of time. This section presents results of the spectrogram analysis for the I-70 Ohio site. Data were examined in 5-minute blocks and for vehicle pass-by events. Presented here are two 5-minute time blocks and two vehicle pass-by events. Spectrograms for the two 5-minute data blocks are shown in Figure 79 through Figure 84. Figure 79 through Figure 81 show a 5-minute time block from 15:30 to 15:35 for the barrier side (reference) positions (Figure 79, Mics 1 and 2), the low-microphone community positions 75 ft. from the edge of the nearest travel lane (Figure 79, Mics 3 and 5), and the high-microphone community positions 75 ft. from the edge of the nearest travel lane (Figure 80, Mics 4 and 6). Figure 82 through Figure 84 show a 5-minute time block from 17:20 to 17:25 for the barrier side (reference) positions (Figure 82, Mics 1 and 2), the low- microphone community positions 75 ft. from the edge of the nearest travel lane (Figure 83, Mics 3 and 5), and the high-microphone community positions 75 ft. from the edge of the nearest travel lane (Figure 84, Mics 4 and 6). The 5-minute data block spectrograms indicate the following trends: 1. For the barrier side of the highway reference positions, where the microphone is placed between the roadway and barrier at the Barrier site and at the same position for the No Barrier site, it is difficult to see any differences in the shapes and shades of the hottest spots (dark red) in the spectrograms for both the low and high microphones.

B-82 2. For the community side positions, where the microphones are placed on the opposite side of the roadway from the barrier at the Barrier site and the same positions for the No Barrier site, it is difficult to see any differences in the shapes and shades of the hottest spots (dark red) in the spectrograms for both the low and high microphones. However, the hottest spots in the frequency range of about 500 Hz to 2,000 Hz may be a darker red color and wider for the microphones opposite the Barrier site compared to those opposite the No Barrier site, as can be seen in Figure 84. Spectrograms for two pass-by events are shown in Figure 85 through Figure 88. Figure 85 and Figure 86 show a heavy truck pass-by event at approximately 17:45 for the low-microphone community positions 75 ft. from the edge of the nearest travel lane (Figure 85, Mics 3 and 5) and the high-microphone community positions 75 ft. from the edge of the nearest travel lane (Figure 86, Mics 4 and 6). Figure 87 and Figure 88 show two heavy truck pass-by events at approximately 17:50 for the low-microphone community positions 75 ft. from the edge of the nearest travel lane (Figure 87, Mics 3 and 5) and the high-microphone community positions 75 ft. from the edge of the nearest travel lane (Figure 88, Mics 4 and 6). It was difficult to extract the events for Mics 1 and 2 because events were not distinguishable, so these are not shown. For all pass- by plots, the vehicle is traveling eastbound (opposite side of roadway from the barrier), arriving first at the No Barrier site and second at the Barrier site about 32 seconds later. The vehicle pass-by event spectrograms indicate the following trends: 1. For the community side positions, both low and high positions show that the hot spots are broader in frequency and possibly in time (seen for some of the microphone comparisons) with the barrier present. In addition, the hottest spots in some cases appear to be a darker red color for the microphones opposite the Barrier compared to those opposite No Barrier, again from about 500 Hz to 2,000 Hz. In general, for the I-70 location, sound levels opposite the absorptive noise Barrier appear to be slightly higher than those with No Barrier at key frequencies, ones that contribute most to the overall noise level. When comparing trends for absorptive noise barriers to trends for reflective noise barriers, a more objective examination of the data was applied. Spectrogram difference plots allow for a more objective comparison of vehicle pass-by events. These difference plots were generated for both absorptive and reflective spectrogram results to determine trends due to the presence of each type of barrier. A more detailed description of spectrogram difference plots and results for reflective and absorptive barriers are covered in Appendix C.

B-83 Figure 79. I-70 5-minute spectrograms; top: BarRef01, bottom: NoBarRef02, start time 15:30.

B-84 Figure 80. I-70 5-minute spectrograms; top: BarCom03, bottom: NoBarCom05, start time 15:30.

B-85 Figure 81. I-70 5-minute spectrograms; top: BarCom04, bottom: NoBarCom06, start time 15:30.

B-86 Figure 82. I-70 5-minute spectrograms; top: BarRef01, bottom: NoBarRef02, start time 17:20.

B-87 Figure 83. I-70 5-minute spectrograms; top: BarCom03, bottom: NoBarCom05, start time 17:20.

B-88 Figure 84. I-70 5-minute spectrograms; top: BarCom04, bottom: NoBarCom06, start time 17:20.

B-89 Figure 85. I-70 heavy truck pass-by event at ~17:45 spectrograms; top: BarCom03, bottom: NoBarCom05.

B-90 Figure 86. I-70 heavy truck pass-by event at ~17:45 spectrograms; top: BarCom04, bottom: NoBarCom06.

B-91 Figure 87. I-70 two heavy truck pass-by events at ~17:50 spectrograms; top: BarCom03, bottom: NoBarCom05.

B-92 Figure 88. I-70 two heavy truck pass-by events at ~17:50 spectrograms; top: BarCom04, bottom: NoBarCom06.

B-93 C H A P T E R B - 5 Results – I-270, Grove City, Ohio (Location OH-3) As shown in Figure 89, the I-270 location in Grove City, Ohio, is a six-lane freeway. The barrier is approximately 2,000 ft. long, 10 ft. high, and offset 12-18 ft. from the edge of the nearest travel lane. The barrier is a precast concrete post-and-panel design, with a proprietary porous, free-draining concrete composed of a specially processed wood fiber aggregate blended with a Portland cement binder on the highway side. Exact sound absorption test results for this barrier were not available. However, results for a similar panel from the same company show the sound absorption coefficients in Table 8. Table 8. Sound absorption coefficients and NRC for a barrier similar to the I-270 barrier. OCTAVE BAND CENTER FREQUENCY (HZ) SOUND ABSORPTION COEFFICIENT 125 0.30 250 0.50 500 1.09 1,000 0.84 2,000 0.90 4,000 0.88 NRC 0.85

B-94 Figure 89. I-270 No Barrier view (top left), Barrier view (top right), Roadway close-up (bottom left), and Barrier (highway side) close-up (bottom right). (Source: research team.) Figure 90 shows a site map of the measurement positions. There was no BarRef01 microphone due to the barrier’s location at the edge of pavement. Table 9 gives each microphone’s position, distance to the edge of nearest travel lane, and height above roadway grade. No microphone was placed at BarRef01 because the barrier was right on the edge of the shoulder and there were concerns of reflected noise off the truck bodies biasing that data, making meaningful comparisons to the NoBarRef02 data difficult. Figure 91 shows pictures of each microphone at its measurement position.

B-95 Figure 90. I-270 microphone positions. (Aerial Photo Source: Google Earth.) Table 9. Microphone positions at I-270 Location. MICROPHONE NAME SIDE OF ROAD DISTANCE FROM EDGE OF NEAREST TRAVEL LANE (ft.) HEIGHT ABOVE ROADWAY PLANE (ft.) BarRef01 n/a n/a n/a NoBarRef02 WB 30 5 (5.5 ft. above ground) BarCom03 EB 30 5 (7 ft. above ground) BarCom04 EB 110 15 (19 ft. above ground) NoBarCom05 EB 30 5 (7 ft. above ground) NoBarCom06 EB 110 15 (9 ft. above ground)

B-96 Figure 91. I-270 NoBarRef02 (top), BarCom03 (middle left), BarCom04 and meteorological station (middle right), NoBarCom05 (bottom left), and NoBarCom06 (bottom right). (Source: research team.)

B-97 Figure 92 shows cross-sections at the Barrier and No Barrier sites. The cross-sections are similar at the BarCom03 and NoBarCom05 locations adjacent to I-270, but they are different moving back to the BarCom04 and NoBarCom06 positions farther from I-270. Higher microphone elevations were chosen to minimize possible ground effects differences between the two sites at these more distant positions. At BarCom04, the microphone was 19 ft. above the ground and 15 ft. above the road, while at NoBarCom06, the microphone was 9 ft. above the ground, while also being 15 ft. above the road. The median was grassy at both sites, with no concrete median barrier. NoBarCom06 is also at the end of a row of one-story houses parallel to I-270 and approximately 40 ft. behind the microphone. As will be described in this section of the report, the data suggests that reflected noise off the houses in this row is raising the NoBarCom06 levels, although no note of reflected noise was made during the field review as part of the location selection process or during the measurements. Figure 92. Cross-sections at the I-270 Barrier (top) site and No Barrier (bottom) sites. Measurements were conducted on Friday, November 18, 2016, from approximately 00:00 (midnight) to 04:00. A goal of the late-night measurements was to obtain data on individual vehicle pass-bys in addition to the 5-minute averages. Results on individual pass-bys are in the section on spectrograms. Truck traffic seemed to dominate the road late at night. There appeared to be a surge in traffic just after 02:00 and then traffic remained steady after 03:30, yielding few or no potential pass-bys during those periods. As observed from the BarCom04 position during the data collection, traffic volumes were relatively low with several candidate single vehicle pass-bys in any 30-minute measurement period. Heavy trucks were typically audible for 10 to 15 seconds to the east if other vehicles were not nearby. At BarCom04, the sound of the heavy trucks (and sometimes the autos) passed through the tree line along the

B-98 property line boundary to the east. No differences could be discerned in the characteristics of the noise at the NoBarCom06 position compared to the BarCom04 position. Winds were calm throughout the data collection. Skies were clear and temperatures were in the low to mid 40° F range. No insect or wind-in-trees sounds were audible during the measurement period. Measured Broadband Levels and Level Differences for I-270 The running Leq (5 min.) for each site are presented in the following figures to give an overall picture of the measured levels, both in terms of unweighted sound pressure levels and A-weighted sound levels: î NoBarRef02 - Figure 93 (unweighted) and Figure 94 (A-weighted). î BarCom03 and NoBarCom05 - Figure 95 (unweighted) and Figure 96 (A-weighted); then Figure 97 shows the differences in unweighted and A-weighted levels for this mic pair. î BarCom04 and NoBarCom06 - Figure 98 (unweighted) and Figure 99 (A-weighted); then Figure 100 shows the differences in unweighted and A-weighted levels for this mic pair. The following observations are prior to any attempt to group data into equivalent periods. The running 5-minute Leq data at NoBarRef02 show a fairly high variation in level from one period to the next, indicative of the relatively low traffic volumes from midnight to 04:00. For most of the periods, both the unweighted and A-weighted 5-minute Leq are lower at BarCom03 than at NoBarCom05, by ranges of approximately 0 dB to 1.5 dB and 0 dB to 1 dB, respectively. For some of the periods, the BarCom03 5-minute Leq are higher than the NoBarCom05 values by up to approximately a decibel. For nearly all the periods, the BarCom04 5-minute Leq are lower than those at NoBarCom06, by a range of approximately 0 dB to 3 dB for both the unweighted sound pressure levels and A-weighted sound levels. Interestingly, the A-weighted differences look more pronounced in the first 15 minutes of sampling, ranging from -1.8 dB to -3.2 dB. One possible reason for the higher levels at NoBarCom06 is that traffic noise may be reflecting off the single-family homes behind the NoBarCom06 microphone and increasing the level. Simplified image source modeling with the FHWA Traffic Noise Model (TNM) 2.5 showed a 0.8 dB increase in the A-weighted sound level at NoBarCom06 due to reflections the building. However, it seems unlikely that reflections could cause the higher levels measured at NoBarCom05 compared to BarCom03. This is because the latter two microphones are close to I-270 traffic and NoBarCom05 is much farther from the houses than NoBarCom06. The terrain between the houses and NoBarCom05 might also provide some shielding of any reflected noise. The simplified TNM modeling showed no increase in the NoBarCom05 level due to building reflections.

B-99 Figure 93. Running Leq (5 min.), I-270, unweighted sound pressure level, dBZ, NoBarRef02. Figure 94. Running Leq (5 min.), I-270, A-weighted sound level, dBA, NoBarRef02. 74 75 76 77 78 79 80 81 82 83 84 0: 00 0: 10 0: 20 0: 30 0: 40 0: 50 1: 00 1: 10 1: 20 1: 30 1: 40 1: 50 2: 00 2: 10 2: 20 2: 30 2: 40 2: 50 3: 00 3: 10 3: 20 3: 30 3: 40 3: 50 So un d Pr es su re L ev el , d BZ Time NoBarRef02 70 71 72 73 74 75 76 77 78 79 80 0: 00 0: 10 0: 20 0: 30 0: 40 0: 50 1: 00 1: 10 1: 20 1: 30 1: 40 1: 50 2: 00 2: 10 2: 20 2: 30 2: 40 2: 50 3: 00 3: 10 3: 20 3: 30 3: 40 3: 50 So un d Le ve l, dB A Time NoBarRef02

B-100 Figure 95. Running Leq (5 min.), I-270, unweighted sound pressure level, dBZ, BarCom03 and NoBarCom05. Figure 96. Running Leq (5 min.), I-270, A-weighted sound level, dBA, BarCom03 and NoBarCom05. 75 76 77 78 79 80 81 82 83 0: 00 0: 10 0: 20 0: 30 0: 40 0: 50 1: 00 1: 10 1: 20 1: 30 1: 40 1: 50 2: 00 2: 10 2: 20 2: 30 2: 40 2: 50 3: 00 3: 10 3: 20 3: 30 3: 40 3: 50 So un d Pr es su re L ev el , d BZ Time BarCom03 NoBarCom05 72 73 74 75 76 77 78 79 80 0: 00 0: 10 0: 20 0: 30 0: 40 0: 50 1: 00 1: 10 1: 20 1: 30 1: 40 1: 50 2: 00 2: 10 2: 20 2: 30 2: 40 2: 50 3: 00 3: 10 3: 20 3: 30 3: 40 3: 50 So un d Le ve l, dB A Time BarCom03 NoBarCom05

B-101 Figure 97. Differences in running Leq (5 min.), I-270, BarCom03 minus NoBarCom05. Figure 98. Running Leq (5 min.), I-270, unweighted sound pressure level, dBZ, BarCom04 and NoBarCom06. -4 -3 -2 -1 0 1 2 3 4 0: 00 0: 10 0: 20 0: 30 0: 40 0: 50 1: 00 1: 10 1: 20 1: 30 1: 40 1: 50 2: 00 2: 10 2: 20 2: 30 2: 40 2: 50 3: 00 3: 10 3: 20 3: 30 3: 40 3: 50 D iff er en ce in le ve l, dB Time dBA dBZ 70 71 72 73 74 75 76 77 78 0: 00 0: 10 0: 20 0: 30 0: 40 0: 50 1: 00 1: 10 1: 20 1: 30 1: 40 1: 50 2: 00 2: 10 2: 20 2: 30 2: 40 2: 50 3: 00 3: 10 3: 20 3: 30 3: 40 3: 50 So un d Pr es su re L ev el , d BZ Time Running Leq(5min), I-270, Unweighted Sound Pressure Level, dBZ BarCom04 NoBarCom06

B-102 Figure 99. Running Leq (5 min.), I-270, A-weighted sound level, dBA, BarCom04 and NoBarCom06. Figure 100. Differences in running Leq (5 min.), I-270, BarCom04 minus NoBarCom06. Data Analysis for I-270 - FHWA Method Equivalent Groups All the groupings of 5-minute periods that were judged equivalent for traffic parameters at the I-270 location fell into the single meteorological class of Calm Inversion. There were 15 groupings in the Calm Inversion class, each with three to seven 5-minute equivalent periods. For source equivalence for I-270, the 66 67 68 69 70 71 72 73 74 0: 00 0: 10 0: 20 0: 30 0: 40 0: 50 1: 00 1: 10 1: 20 1: 30 1: 40 1: 50 2: 00 2: 10 2: 20 2: 30 2: 40 2: 50 3: 00 3: 10 3: 20 3: 30 3: 40 3: 50 So un d Le ve l, dB A Time BarCom04 NoBarCom06 -4 -3 -2 -1 0 1 2 3 4 0: 00 0: 10 0: 20 0: 30 0: 40 0: 50 1: 00 1: 10 1: 20 1: 30 1: 40 1: 50 2: 00 2: 10 2: 20 2: 30 2: 40 2: 50 3: 00 3: 10 3: 20 3: 30 3: 40 3: 50 D iff er en ce in le ve l, dB Time dBA dBZ

B-103 allowable variation in the NoBarRef02 Leq (5 min.) between the periods in a group was 0 dB in most cases and 0.1 dB in one case, and the allowable average speed differences between periods was 5 mph. Figure 102 shows these groupings graphically for the Calm Inversion class. The times along the top represent the starting minute of each 5-minute period. Each group has a unique name, starting with “CIG.” Note that all the 5-minute periods in a group are nonoverlapping in time and none appear in more than one equivalent group. Figure 101 shows the 15-minute counts for autos, heavy trucks, and total traffic by direction over the 4-hour period. The total traffic volumes were low and were generally highest nearing the beginning and end of the sampling and lowest toward the middle. Heavy truck counts showed a similar variation. Table 10 ranks the selected Calm Inversion groups by total two-way volume averaged across the periods in that group (i.e., Factored Hourly Volume, vph). The volumes of the highest group were roughly 60% greater than the volumes of the lowest group. In terms of equivalent hourly volumes, the overall range for these periods was from 532 vph to 828 vph. Within the 4-hour period, heavy trucks were approximately 29% of the total volume. Speeds were more consistent, ranging from averages of 63 mph to 71 mph. Figure 101. 15-minute traffic counts by direction for autos, heavy trucks and total, I-270. 0 20 40 60 80 100 120 140 0: 00 0: 15 0: 30 0: 45 1: 00 1: 15 1: 30 1: 45 2: 00 2: 15 2: 30 2: 45 3: 00 3: 15 3: 30 3: 45 V eh ic le C ou nt Time EB Total WB Total EB Auto WB Auto EB HT WB HT

Figure 102. Equivalent 5-minute periods for Calm Inversion groups at I-270. 0: 36 0: 43 0: 44 0: 45 0: 52 0: 54 0: 56 0: 57 0: 58 1: 03 1: 05 1: 06 1: 10 1: 11 1: 15 1: 18 1: 19 1: 20 1: 22 1: 24 1: 25 1: 26 1: 37 1: 41 1: 42 1: 44 1: 51 1: 52 1: 53 1: 54 1: 57 2: 13 2: 14 2: 15 2: 16 2: 20 2: 21 2: 22 2: 23 2: 27 2: 28 2: 47 2: 49 2: 53 2: 55 2: 56 3: 26 3: 29 3: 30 3: 32 3: 33 3: 35 3: 36 3: 44 3: 45 3: 49 3: 50 3: 51 3: 52 CIG-7-1: 00:54, 01:06, 01:51 1 1 1 CIG-8-1: 01:44, 01:57, 02:49, 03:52 1 1 1 1 CIG-15-1: 01:37, 01:42, 02:56 1 1 1 CIG-16-1: 00:52, 02:22, 02:53 1 1 1 CIG-17-1: 01:10, 01:19, 03:32 1 1 1 CIG-19-1: 01:41, 01:54, 02:55 1 1 1 CIG-21-1: 01:05, 01:52, 02:21, 03:51 1 1 1 1 CIG-22-1: 00:43, 00:57, 02:21 1 1 1 CIG-23-1: 00:56, 01:25, 01:53, 02:13, 02:23, 03:33, 03:50 1 1 1 1 1 1 1 CIG-24-1: 01:03, 01:11, 01:20, 02:15, 03:29 1 1 1 1 1 CIG-26-1: 00:58, 01:18, 02:47, 03:30, 03:36 1 1 1 1 1 CIG-27-1: 00:36, 00:45, 01:26, 02:14, 02:20, 02:28 1 1 1 1 1 1 CIG-28-1: 00:44, 02:27, 03:44 1 1 1 CIG-29-1: 01:15, 01:22, 02:16, 03:26, 03:49 1 1 1 1 1 CIG-31-1: 01:24, 03:35, 03:45 1 1 1 Group ID Starting Time of 5-minute Periods

B-105 Table 10. Two-way traffic volumes in 5-minute periods, by equivalent group Calm Inversion conditions, sorted by factored hourly volume, I-270. Two-Way Traffic Volumes (5 minutes) Group Period 1 Period 2 Period 3 Period 4 Period 5 Period 6 Period 7 Factored Hourly Volume, vph Calm Inversion CIG-31-1 63 67 77 n/a n/a n/a n/a 828 CIG-22-1 64 72 66 n/a n/a n/a n/a 808 CIG-29-1 67 54 73 56 78 n/a n/a 787 CIG-27-1 64 60 55 70 65 62 n/a 752 CIG-28-1 61 52 75 n/a n/a n/a n/a 752 CIG-23-1 66 55 44 71 65 60 72 742 CIG-26-1 73 54 65 47 67 n/a n/a 734 CIG-24-1 55 67 48 70 47 n/a n/a 689 CIG-21-1 47 44 66 68 n/a n/a n/a 675 CIG-17-1 59 50 51 n/a n/a n/a n/a 640 CIG-8-1 50 48 57 57 n/a n/a n/a 636 CIG-16-1 51 65 43 n/a n/a n/a n/a 636 CIG-15-1 55 48 47 n/a n/a n/a n/a 600 CIG-19-1 49 39 49 n/a n/a n/a n/a 548 CIG-7-1 52 44 37 n/a n/a n/a n/a 532 Sound Pressure Level Spectra Before discussing the differences in levels between the Barrier and No Barrier sites, typical sound pressure level spectra are shown to give some perspective on the data upon which the differences are based. One of the 5-minute periods in one of the Calm Inversion groups was chosen as typical. Figure 103, Figure 104, and Figure 105 present the sound pressure level spectra for, respectively: NoBarRef02. BarCom03/NoBarCom05. BarCom04/NoBarCom06.

B-106 Figure 103. Sample sound pressure level spectra for NoBarRef02, I-270, Calm Inversion group CIG- 24-1 02:15-02:20 (Leq (5 min.), dBZ). 30 35 40 45 50 55 60 65 70 75 80 85 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k So un d Pr es su re L ev el , d BZ 1/3 Octave Band Frequency, Hz NoBarRef02

B-107 Figure 104. Sample sound pressure level spectra for BarCom03 and NoBarCom05, I-270, Calm Inversion group CIG-24-1 02:15-02:20 (Leq (5 min.), dBZ). 30 35 40 45 50 55 60 65 70 75 80 85 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k So un d Pr es su re L ev el , d BZ 1/3 Octave Band Frequency, Hz BarCom03 NoBarCom05

B-108 Figure 105. Sample sound pressure level spectra for BarCom04 and NoBarCom06, I-270, Calm Inversion group CIG-24-1 02:15-02:20 (Leq (5 min.), dBZ). Calm Inversion Class Figure 106 shows two graphs (no data were collected at BarRef01) of the differences in level between comparable microphones for an average of all the Calm Inversion groups with their error bars. The error bars are +/- one standard deviation for each average value. This figure compares the following: BarCom03 and NoBarCom05 in the upper graph. BarCom04 and NoBarCom06 in the lower graph. Each graph shows the averages of the average level differences for the A-weighted sound level, the unweighted sound pressure level and the one-third octave band sound pressure levels from 20 Hz to 10 kHz. Graphs for all the individual Calm Inversion groups are in spreadsheet files in the project record. The trends across the one-third octave band frequencies, described below, are generally similar in these 20 25 30 35 40 45 50 55 60 65 70 75 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k So un d Pr es su re L ev el , d BZ 1/3 Octave Band Frequency, Hz BarCom04 NoBarCom06

B-109 individual groups of equivalent periods, with some differences likely related to background noise and the uniqueness of vehicle noise sources in each period. Figure 106 shows in the upper graph the differences in levels between BarCom03 and NoBarCom05, both of which were close to the road and 5 ft. above the roadway elevation. The BarCom03 levels are lower than or equal to the NoBarCom05 levels over the entire frequency range, except for a slightly higher level at 2 kHz. The difference is a decibel or less from 80 Hz through 2.5 kHz, except at 315 Hz and 400 Hz where the difference is approximately 1.5 dB (BarCom03 being lower). The overall unweighted sound pressure level (labeled dBZ on the graph) is 0.6 dB higher at NoBarCom05 and the overall A-weighted sound level (labeled dBA on the graph) is 0.4 dB higher. The reason for NoBarCom05 being higher is not apparent at this point in the analysis, as NoBarCom05 is not close to the houses that were behind the more distant NoBarCom06. The lower graph compares the levels at BarCom04 and NoBarCom06, both of which were 15 ft. above the roadway surface. The BarCom04 levels are lower than the NoBarCom06 levels from 20 Hz to 100 Hz by a range of 0 dB to 3.5 dB and are also lower from 500 Hz to 5 kHz by a range of 0.2 dB to 2.3 dB. However, from 125 Hz to 400 Hz, the BarCom04 levels are higher than those at NoBarCom06 by 0.5 dB at 125 Hz and 400 Hz to approximately 3 dB from 160 Hz to 315 Hz. Above 5 kHz, the BarCo m04 levels are higher than the NoBarCom06 levels. The overall unweighted sound pressure level is 1.5 dB higher at NoBarCom06 and the overall A-weighted sound level is 1.6 dB higher. The higher levels at NoBarCom06 in the lower and certain higher frequency bands could be attributable to possible reflection of noise off the houses; the lower levels in the middle frequencies at NoBarCom06 compared to BarCom04 might be attributable to ground effects, despite the elevated position of the microphone.

B-110 Figure 106. Averages of the differences in Leq (5 min.) +/- one standard deviation (dB), all microphones, for all Calm Inversion groups, I-270. Additional Sound Level Analysis for I-270 – Ln Descriptors In addition to the examination of the differences in levels for the equivalent pairs of running 5-minute Leq data, the differences in the Ln descriptors for the overall data without segregation into equivalent periods were investigated. The focus was on the possible change in the background level in the presence of the noise barrier. Figure 107 presents the L90 (5 min.) and L99 (5 min.) for NoBarRef02, in terms of overall A-weighted sound levels and unweighted sound pressure level. The upper graphs are L90 (A-weighted on the left and unweighted on the right). The lower graphs are L99 (A-weighted on the left and unweighted on the right). Since no data were collected at BarRef01, no comparison is made to the data at NoBarRef02. Instead, the NoBarRef02 data show the variability in these background sound level descriptors, a likely result of the low traffic volumes in the middle of the night. -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom03 - NoBarCom05 All CIG Groups -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 dB A d BZ 2 0 2 5 3 1. 5 4 0 5 0 6 3 8 0 1 00 1 25 1 60 2 00 2 50 3 15 4 00 5 00 6 30 8 00 1 k 1. 25 k 1. 6k 2k 2. 5k 3. 15 k 4k 5k 6. 3k 8k 10 k D iff er en ce in L ev el , d B 1/3 Octave Band Frequency, Hz BarCom04 - NoBarCom06 All CIG Groups

B-111 Figure 107. L90 (5 min.) and L99 (5 min.), I-270, NoBarRef02 – broadband A-weighted sound level and sound pressure level. Figure 108 presents the same data—L90 (5 min.) and L99 (5 min.)—for BarCom03 and NoBarCom05 (the lower microphones across from the barrier), again for overall A-weighted sound levels and unweighted sound pressure level. Figure 109 presents the differences in L90 (5 min.) and L99 (5 min.) along with Leq (5 min.) for the A-weighted sound levels, computed as BarCom03 minus NoBarCom05. While the A-weighted Leq (5 min.) data at BarCom03 typically ranges between 0 dB to 1 dB lower than the same data at NoBarCom05, there is substantial variation in the L90 and L99 data, with many periods where the BarCom03 levels are higher than the NoBarCom05 values (e.g., largely from 00:50 to 01:40), and vice-versa (largely from 01:50 to 02:32). Two exceptions exist in the Leq (5 min.) data trend shown on the graphs that should be ignored: 1) from 00:22 to 00:27 when the BarCom03 Leq (5 min.) are 1.4 dB to 3 dB higher than NoBarCom05; and 2) 03:17 to 03:21 when the BarCom03 Leq (5 min.) are 3.6 dB to 4.3 dB higher than NoBarCom05. The first period was affected by loud exhaust noise on a truck that passed the Barrier and No Barrier sites in different minutes, affecting the running Leq (5 min.) values for several minutes. The second period was caused by fire trucks and their sirens passing the Barrier site and the No Barrier site and then returning and stopping at the No Barrier site. Next, Figure 110 presents the L90 (5 min.) and L99 (5 min.) for BarCom04 and NoBarCom06 for overall A-weighted sound levels and unweighted sound pressure level. Figure 111 presents the differences in L90 (5 min.) and L99 (5 min.) along with Leq (5 min.) for the A-weighted sound levels, computed as BarCom04 minus NoBarCom06. While the A-weighted Leq (5 min.) data at BarCom04 typically range between 1 dB to 2.5 dB lower than the same data at NoBarCom06, there is a great deal of variation in the L90 and L99 data, with many periods where the BarCom04 levels are higher than those at NoBarCom06, as is the case for BarCom03 and NoBarCom05. Similarly, the exceptions in the Leq (5 min.) data trends visible on the graphs from 00:22 to 00:27 and from 03:17 to 03:21 are due to unrepresentative events.

B-112 Figure 108. L90 (5 min.) and L99 (5 min.), I-270, BarCom03 and NoBarCom05 – broadband A-weighted sound level (left) and sound pressure level (right). Figure 109. Differences in broadband A-weighted 5-minute L90, L99 and Leq, I-270, BarCom03 and NoBarCom05. -8 -6 -4 -2 0 2 4 6 8 0: 00 0: 10 0: 20 0: 30 0: 40 0: 50 1: 00 1: 10 1: 20 1: 30 1: 40 1: 50 2: 00 2: 10 2: 20 2: 30 2: 40 2: 50 3: 00 3: 10 3: 20 3: 30 3: 40 3: 50 So un d Le ve l D iff er en ce , d B Time L90 L99 Leq

B-113 Figure 110. L90 (5 min.) and L99 (5 min.), I-270, BarCom04 and NoBarCom06 – broadband A-weighted sound level (left) and sound pressure level (right). Figure 111. Differences in broadband A-weighted 5-minute L90, L99 and Leq, I-270, BarCom04 and NoBarCom06. Figure 112 expands the analysis broadband A-weighted sound levels and unweighted sound pressure levels to include the individual one-third octave bands using color shading. The brown color means that the -8 -6 -4 -2 0 2 4 6 8 0: 00 0: 10 0: 20 0: 30 0: 40 0: 50 1: 00 1: 10 1: 20 1: 30 1: 40 1: 50 2: 00 2: 10 2: 20 2: 30 2: 40 2: 50 3: 00 3: 10 3: 20 3: 30 3: 40 3: 50 So un d Le ve l D iff er en ce , d B Time L90 L99 Leq

B-114 NoBarCom05. Figure 112. I-270 Differences in Ln (5 min.) by one-third octave frequency bands: BarCom03 and Figure 113. I-270 Differences in Ln (5 min.) by one-third octave frequency bands: BarCom04 and NoBarCom06. BarCom03 levels are higher than the NoBarCom05 levels and blue means that NoBarCom05 levels are higher. In the graph, time runs from top to bottom (increasing as one moves down each figure, with each row representing the starting minute of a running 5-minute period) and the total block representing approximately four hours. The one-third octave bands run across from left to right, with the broadband A-weighted sound levels and unweighted sound pressure levels on the far left. Within each band’s column of data are the differences for seven Ln sound pressure level Ln values (L1, L5, L10, L33, L50, L90, and L99) and Leq. The largely blue tone to the figure indicates that the levels at NoBarCom05 are higher than those at BarCom03 for most of the Ln descriptors for most of the one-third octave bands over much of the 4-hour sampling period. The L90 (5 min.) and L99 (5 min.) descriptors have noticeably higher levels at NoBarCom05 in the 50-100 Hz bands and the 2.5 kHz to 10 kHz bands. A stretch in the middle of the 4-hour sample exists when the L90 (5 min.) and L99 (5 min.) are also higher at NoBarCom05 in the 630 Hz to 2 kHz bands. Periods exist where the brown color indicates the BarCom03 L90 (5 min.) and L99 (5 min.) are higher at BarCom03, especially for the 160 Hz and 200 Hz bands. Also, there are time periods approximately one-third of the way into the sampling and near the end when L90 (5 min.) and L99 (5 min.) are higher at BarCom03 across most of the bands, which is likely due to localized unrepresentative events discussed previously. Figure 113 presents the Ln differences for BarCom04 and NoBarCom06. The data patterns are similar over most of the sample period. The NoBarCom06 levels are higher for all the Ln descriptors below 80 Hz and most of the Ln descriptors above 400 Hz. The BarCom04 levels are higher than NoBarCom06 from 125 Hz through 315 Hz for most of the descriptors. Evidence exists of the L90 (5 min.) and L99 (5 min.) being higher at BarCom04 for some periods in the 1.6 kHz through 4 kHz periods. However, above 4 kHz, the L90 (5 min.) and L99 (5 min.) are solidly higher at NoBarCom06 compared to BarCom04 while the lower-percentile Ln values at BarCom04 are higher than at NoBarCom06.

B-115 Data Analysis – Spectrograms for I-270 Spectrograms show the frequency content of sound as a function of time. This section presents results of the spectrogram analysis for the I-270 Ohio site. Data were examined in 5-minute blocks and for vehicle pass-by events. Presented here are two 5-minute time blocks and two vehicle pass-by events. Spectrograms for the two 5-minute data blocks are shown in Figure 114 through Figure 117. Figure 114 and Figure 115 show a 5-minute time block from 00:40 to 00:45 for the near-microphone community positions 30 ft. from the edge of the nearest travel lane (Figure 114, Mics 3 and 5) and the far-microphone community positions 110 ft. from the edge of the nearest travel lane (Figure 115, Mics 4 and 6). Figure 116 and Figure 117 show a 5-minute time block from 02:10 to 02:15 for the near-microphone community positions 30 ft. from the edge of the nearest travel lane (Figure 116, Mics 3 and 5) and the far-microphone community positions 110 ft. from the edge of the nearest travel lane (Figure 117, Mics 4 and 6). The 5-minute data block spectrograms indicate the following trends: 1. For the community side positions, where the microphones are placed on the opposite side of the road from the barrier at the Barrier site and the same positions for the No Barrier site, it is difficult to see any differences in the spectrograms for the near positions for the 00:40 time block. It does appear, however, that there is a little filling in of red/yellow/blue in between the peaks for the No Barrier site. For the 02:10 time block, the high and low frequency peaks appear to extend higher and lower for the No Barrier site. And as with the 00:40 time block, there appears to be a little filling in of red/yellow/blue in between the peaks for the No Barrier site. 2. For the community side far positions, the hot spots in the frequency range of about 500 Hz to 2,000 Hz are narrower both in frequency and time for the microphones opposite the Barrier site compared to those opposite the No Barrier site. In addition, as with the near position, there appears to be a little filling in of red/yellow/blue in between the peaks for the No Barrier site (more indication of events broadening in time). Spectrograms for two pass-by events are shown in Figure 118 through Figure 121. Figure 118 and Figure 119 show a heavy truck pass-by event at approximately 02:38 for the near-microphone community positions 30 ft. from the edge of the nearest travel lane (Figure 118, Mics 3 and 5) and the far-microphone community positions 110 ft. from the edge of the nearest travel lane (Figure 119, Mics 4 and 6). Figure 120 and Figure 121 show an automobile pass-by event at approximately 02:40 for the near-microphone community positions 30 ft. from the edge of the nearest travel lane (Figure 120, Mics 3 and 5), and the far- microphone community positions 110 ft. from the edge of the nearest travel lane (Figure 121, Mics 4 and 6). For all pass-by plots, the vehicle is traveling eastbound (opposite side of road from Barrier), arriving first at the Barrier site and second at the No Barrier site about 25 seconds later. The vehicle pass-by event spectrograms indicate the following trends: 1. For the community side positions, where the microphones are placed on the opposite side of the road from the barrier at the Barrier site and the same positions for the No Barrier site, each event is narrower/smaller for the microphones opposite the Barrier compared to the No Barrier site. This is clearly indicated over the entire frequency spectrum shown. 2. For the community side far positions, the shape of the red hot spot appears to be broader frequency (~500 Hz to 2,000 Hz) when the opposite Barrier is not present. Another observation is that the darkest red is darker for the No Barrier microphones.

B-116 In general, sound levels opposite the absorptive noise Barrier at the I-270 site are lower than those with No Barrier over a broad range of frequencies. The observed differences are subtle for the microphone positions close to the road and more apparent farther from the road. The general trend of the No Barrier site being louder is counter-intuitive and indicates that something at the No Barrier site was increasing the sound levels. Based on the proximity of the homes behind the far microphone, the increase in sound levels can be explained by highway noise reflecting off the homes and back toward the far and near receivers. The reflective effect due to the homes is more pronounced at the far microphone since it is closer to the homes and farther from the direct noise source. Based on the spectrogram findings, it is concluded that any effect due to the absorptive highway noise Barrier is not apparent when comparing to the No Barrier sound levels, since those have been amplified due to the community homes. Findings based on highway noise barrier reflections cannot be extracted from the I-270 data because events were not distinguishable. When comparing trends for absorptive noise barriers to trends for reflective noise barriers, a more objective examination of the data was applied. Spectrogram difference plots allow for a more objective comparison of vehicle pass-by events. These difference plots were generated for both absorptive and reflective spectrogram results to determine trends due to the presence of each type of barrier. A more detailed description of spectrogram difference plots and results for reflective and absorptive barriers are covered in Appendix C.

B-117 Figure 114. I-270 5-minute spectrograms; top: BarCom03, bottom: NoBarCom05, start time 00:40.

B-118 Figure 115. I-270 5-minute spectrograms; top: BarCom04, bottom: NoBarCom06, start time 00:40.

B-119 Figure 116. I-270 5-minute spectrograms; top: BarCom03, bottom: NoBarCom05, start time 02:10.

B-120 Figure 117. I-270 5-minute spectrograms; top: BarCom04, bottom: NoBarCom06, start time 02:10.

B-121 Figure 118. I-270 heavy truck pass-by event at ~02:38 spectrograms; top: BarCom03, bottom: NoBarCom05.

B-122 Figure 119. heavy truck pass-by event at ~02:38 spectrograms; top: BarCom04, bottom: NoBarCom06.

B-123 Figure 120. automobile pass-by event at ~02:40 spectrograms; top: BarCom03, bottom: NoBarCom05.

B-124 Figure 121. I-270 automobile pass-by event at ~02:40 spectrograms; top: BarCom04, bottom: NoBarCom06.

C-1 Comparison of Phase 1 and Phase 2 Results A P P E N D I X C William Bowlby BowlBy & AssociAtes, inc. Franklin, TN Judy Rochat ATS Consulting Pasadena, CA Ken Kaliski RSG White River Junction, VT

CONTENTS CHAPTER C-1 ..................................................................................................................................... C-3 Introduction to Appendix C ................................................................................................................................... C-3 CHAPTER C-2 ..................................................................................................................................... C-4 Study Locations ..................................................................................................................................................... C-4 CHAPTER C-3 ................................................................................................................................... C-12 Measured Broadband Level Differences at Reference Microphones Between the Road and the Barrier ......... C-12 CHAPTER C-4 ................................................................................................................................... C-16 Measured Broadband Level Differences at the Community Microphones Across the Road from the Barrier .. C-16 CHAPTER C-5 ................................................................................................................................... C-25 One-Third Octave Band Differences for Equivalent Leq (5 min.) Periods ............................................................ C-25 CHAPTER C-6 ................................................................................................................................... C-37 Broadband L90 and L99 Statistical Descriptors ..................................................................................................... C-37 CHAPTER C-7 ................................................................................................................................... C-49 Ln Descriptors for One-Third Octave Bands ........................................................................................................ C-49 CHAPTER C-8 ................................................................................................................................... C-60 Spectrograms ...................................................................................................................................................... C-60 CHAPTER C-9 ................................................................................................................................... C-82 Difference Spectrograms and Comb Filtering ..................................................................................................... C-82 REFERENCES .................................................................................................................................. C-109

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Field Evaluation of Reflected Noise from a Single Noise Barrier Get This Book
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TRB's National Cooperative Highway Research Program (NCHRP) Research Report 886: Field Evaluation of Reflected Noise from a Single Noise Barrier analyzes the characteristics of sound reflected from a noise barrier to the opposite side of a highway. State departments of transportation (DOTs) periodically receive complaints from residents about increases in traffic noise that residents believe are the result of noise reflected from a new noise barrier added across the roadway from them. Currently available analytical tools are limited in their ability to evaluate reflected noise and some of the subtle changes in the quality of sound that can occur when it is reflected. Therefore, it is a challenge for DOTs to determine conclusively if complaints about reflected noise are the result of actual or perceived changes in noise characteristics, and to identify locations where absorptive surface treatments could be beneficial.

The study compares reflected noise from sound-reflecting barriers and from barriers with a sound-absorptive surface. It examines both the levels and frequencies of reflected noise to better understand how reflected noise is experienced by communities.

The full report, which includes four detailed appendices, is 27 MB and may take time to download. It is accompanied by several appendices, a tool, and a guide:

A presentation file that summarizes the research also is available on the report project page.

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