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Pages 95-138

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From page 95...
... 97 Comparison Finding 2: Differences in Broadband Levels Opposite the Barrier at Different Microphone Heights Broadband levels averaged slightly higher opposite the I-70 sound-absorbing barrier compared to the No-Barrier site for both microphone heights, similar to the sound-reflecting barriers. For the sound-absorbing barrier at I-70, the community microphones showed slightly higher levels opposite the Barrier compared to the No-Barrier site.
From page 96...
... -3 -2 -1 0 1 2 3 13 :1 3 13 :2 2 13 :3 1 13 :4 0 13 :4 9 13 :5 8 14 :0 7 14 :1 6 14 :2 5 14 :3 4 14 :4 3 14 :5 2 15 :0 1 15 :1 0 15 :1 9 15 :2 8 15 :3 7 15 :4 6 15 :5 5 16 :0 4 16 :1 3 16 :2 2 16 :3 1 16 :4 0 16 :4 9 16 :5 8 17 :0 7 D iff er en ce in L ev el , d B Time dBA dBZ Figure 96. I-24 -- differences in A-weighted and unweighted levels (dB)
From page 97...
... 99 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 A-weighted sound levels at BarCom03 range from 0 dB to 1.2 dB higher than those at NoBarCom05, averaging approximately 0.7 dB higher.
From page 98...
... 100 levels at BarCom04 range mostly from 0 dB to 4 dB higher and the A-weighted levels at BarCom04 ranged from 1 dB to nearly 4 dB higher. For both unweighted and A-weighted cases, the average difference is 2.1 dB higher at BarCom04 than at NoBarCom06.
From page 99...
... 101 Figure 102 shows the differences for the more distant BarCom04 and NoBarCom06 microphone positions at I-75. At BarCom04, the unweighted levels range from 0.5 dB lower to 1.9 dB higher than the levels at NoBarCom06, averaging approximately 0.6 dB higher.
From page 101...
... 103 The lower graph of Figure 103 compares the levels at upper microphones BarCom04 and NoBarCom06, both of which were positioned 15 ft. above the roadway surface.
From page 104...
... 106 Comparison Finding 5: One-Third Octave Band Differences at Different Microphone Distances One-third octave band levels are slightly higher opposite the I-75 sound-absorbing barrier compared to the No-Barrier site for the microphones at different distances from I-75. The differences at the larger distance were less than the differences at the sound-reflecting barriers.
From page 108...
... 110 NoBarCom05 at 125 Hz and 160 Hz)
From page 109...
... 111 -4 -3 -2 -1 0 1 2 3 4 5 13 :1 3 13 :2 2 13 :3 1 13 :4 0 13 :4 9 13 :5 8 14 :0 7 14 :1 6 14 :2 5 14 :3 4 14 :4 3 14 :5 2 15 :0 1 15 :1 0 15 :1 9 15 :2 8 15 :3 7 15 :4 6 15 :5 5 16 :0 4 16 :1 3 16 :2 2 16 :3 1 16 :4 0 16 :4 9 16 :5 8 17 :0 7 So un d Le ve l D iff er en ce , d B Time L90 L99 Leq Figure 110. I-24 -- differences in A-weighted levels (dB)
From page 110...
... 112 of the elevated background level at BarCom04 compared to NoBarCom06. For the first part of the afternoon measurements, the NoBarCom06 background level appears to be a bit higher than the level at BarCom04.
From page 111...
... 113 -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 Figure 114. I-70 -- differences in A-weighted levels (dB)
From page 112...
... 114 pairings: slightly higher Leq (5 min.) ; slightly higher L90 during the first half of data collection (but not higher than the Leq)
From page 113...
... 115 -4 -3 -2 -1 0 1 2 3 4 5 6 13 :0 0 13 :0 9 13 :1 8 13 :2 7 13 :3 6 13 :4 5 13 :5 4 14 :0 3 14 :1 2 14 :2 1 14 :3 0 14 :3 9 14 :4 8 14 :5 7 15 :0 6 15 :1 5 15 :2 4 15 :3 3 15 :4 2 15 :5 1 16 :0 0 16 :0 9 16 :1 8 16 :2 7 16 :3 6 16 :4 5 16 :5 4 So un d Le ve l D iff er en ce , d B Time L90 L99 Leq Figure 117. I-90 -- differences in A-weighted levels (dB)
From page 114...
... 116 respectively. These results suggest that the overall traffic noise levels are higher at the SR-71 Barrier site, not just the background levels.
From page 115...
... 117 differences occurring from around 20:20 to 20:48. The generally higher L90 at BarRef01 compared to NoBarRef02 suggest an increase in the background level in front of this soundabsorbing barrier.
From page 116...
... 118 Comparison Finding 8: One-Third Octave Band L90 and L99 Descriptors The one-third octave band L90 and L99 descriptors mostly support the conclusion that -- unlike at the sound-reflecting barriers -- the background noise is not elevated because of reflections opposite the sound-absorbing barriers. Comparison Finding 7 was based on analysis of the broadband A-weighted sound levels and unweighted sound pressure levels.
From page 117...
... 119 Ln differences for BarCom04 and NoBarCom06 at I-24. Some evidence exists of slightly higher Ln values at BarCom03 versus NoBarCom05 in the 315 Hz to 800 Hz bands and at BarCom04 versus NoBarCom06 over much of the lower frequency range.
From page 118...
... 120 These higher values are evidence of a sustaining of a vehicle's pass-by noise due to reflected sound, similar to the soundreflecting I-24 Barrier location. Figure 127 presents spectral Ln differences for BarCom03 and NoBarCom05 at SR-71.
From page 119...
... 121 Figure 128. MD-5 -- differences in Ln (5 min.)
From page 120...
... 122 Figure 129. MD-5 -- differences in Ln (5 min.)
From page 121...
... 123 Figure 131. I-75 -- differences in Ln (5 min.)
From page 122...
... 124 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.
From page 123...
... 125 -4 -3 -2 -1 0 1 2 3 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 Figure 136. I-270 -- differences in A-weighted and unweighted levels (dB)
From page 124...
... 126 and NoBarCom06. For most of the measurement 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.
From page 125...
... 127 The lower graph in Figure 138 compares the levels at BarCom04 and NoBarCom06, both of which were positioned 15 ft. above the roadway surface.
From page 126...
... 128 Figure 139. I-75 -- spectrograms at sound-absorbing barrier during heavy truck pass-by event at }18:33, BarCom04 (top)
From page 127...
... 129 Figure 140. I-70 -- spectrograms at sound-absorbing barrier during heavy truck pass-by event at }17:45, BarCom04 (top)
From page 128...
... 130 community positions (again labeled "Mic 4" and "Mic 6")
From page 129...
... 131 Figure 141. I-75 -- 5-minute spectrograms at sound-absorbing barrier, 17:55–18:00, BarCom04 (top)
From page 130...
... 132 Figure 142. I-70 -- 5-minute spectrograms at sound-absorbing barrier, 15:30–15:35, BarCom04 (top)
From page 131...
... 133 Figure 143. MD-5 -- spectrogram difference plot for sound-reflecting barrier pickup truck pass-by event at }20:09, BarCom04 and NoBarCom06.
From page 132...
... 134 Figure 144. MD-5 -- differences in levels (dB)
From page 133...
... 135 Figure 145. I-75 -- spectrogram difference plot for sound-absorbing barrier heavy vehicle (truck)
From page 134...
... 136 Figure 146. I-75 -- differences in levels (dB)
From page 135...
... 137 Site and Event Time Peak Difference Frequencies (Hz) Harmonic Relationships MD-5, 19:46 16, 20, 40, 80, 160, 400, 800, 1,600, 12,500 All except 16 are related to 20.
From page 136...
... 138 -2 -1 0 1 2 3 4 5 SR-71 (72 ft.)
From page 137...
... 139 Applications, Conclusions, Recommendations, and Suggested Research Applications Applications of the work follow, broken into sections focused on the FHWA Method of data analysis, the spectrograms, the psychoacoustics analysis, the layperson's guide, and the Barrier Reflections Screening Tool. FHWA Method The most immediate application of these results is the understanding by traffic noise analysts and abatement practitioners that traffic sound levels and sound characteristics for receptors across from a proposed single reflective noise barrier can change after the installation of the barrier.
From page 138...
... 140 Psychoacoustics Because the derived annoyance metrics were either uncorrelated with site location or were contra-indicative for continuous flow traffic, their direct use (as applied in this work) cannot be recommended for indicating increased annoyance due to single barriers in the presence of heavy traffic.

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