Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs (2016)

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A I R P O R T C O O P E R A T I V E R E S E A R C H P R O G R A M ACRP REPORT 152 TRANSPORTAT ION RESEARCH BOARD WASHINGTON, D.C. 2016 www.TRB.org Research sponsored by the Federal Aviation Administration Subscriber Categories Aviation • Environment Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs Paul Schomer Schomer & ASSociAteS Champaign, IL Jack Freytag FreytAg & ASSociAteS San Rafael, CA Randy Waldeck cSDA DeSign group San Francisco, CA

AIRPORT COOPERATIVE RESEARCH PROGRAM Airports are vital national resources. They serve a key role in trans- portation of people and goods and in regional, national, and interna- tional commerce. They are where the nation’s aviation system connects with other modes of transportation and where federal responsibility for managing and regulating air traffic operations intersects with the role of state and local governments that own and operate most airports. Research is necessary to solve common operating problems, to adapt appropriate new technologies from other industries, and to introduce innovations into the airport industry. The Airport Cooperative Research Program (ACRP) serves as one of the principal means by which the airport industry can develop innovative near-term solutions to meet demands placed on it. The need for ACRP was identified in TRB Special Report 272: Airport Research Needs: Cooperative Solutions in 2003, based on a study spon- sored by the Federal Aviation Administration (FAA). ACRP carries out applied research on problems that are shared by airport operating agen- cies and not being adequately addressed by existing federal research programs. ACRP is modeled after the successful National Cooperative Highway Research Program (NCHRP) and Transit Cooperative Research Program (TCRP). ACRP undertakes research and other technical activi- ties in various airport subject areas, including design, construction, legal, maintenance, operations, safety, policy, planning, human resources, and administration. ACRP provides a forum where airport operators can cooperatively address common operational problems. ACRP was authorized in December 2003 as part of the Vision 100— Century of Aviation Reauthorization Act. 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ACRP REPORT 152 Project 02-51 ISSN 1935-9802 ISBN 978-0-309-37505-4 Library of Congress Control Number 2016933058 © 2016 National Academy of Sciences. All rights reserved. COPYRIGHT INFORMATION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply TRB, AASHTO, FAA, FHWA, FMCSA, FRA, FTA, Office of the Assistant Secretary for Research and Technology, PHMSA, or TDC endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP. NOTICE The report was reviewed by the technical panel and accepted for publication according to procedures established and overseen by the Transportation Research Board and approved by the National Academies of Sciences, Engineering, and Medicine. The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research and are not necessarily those of the Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; or the program sponsors. The Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; and the sponsors of the Airport Cooperative Research Program do not endorse products or manufacturers. 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C O O P E R A T I V E R E S E A R C H P R O G R A M S AUTHOR ACKNOWLEDGMENTS The research report herein was performed under ACRP Project 02-51 by Paul Schomer, Principal Investigator (Schomer & Associates); Jack Freytag, Lead Researcher (Freytag & Associates); and Randy Waldeck, Project Manager (CSDA Design Group). They were assisted by Herb Singleton at Cross- Spectrum Acoustics and Greg Baker at CSDA Design Group. The team would like to acknowledge San Diego International Airport and Boston Logan International Airport staff for their assistance in organizing the field measurements. CRP STAFF FOR ACRP REPORT 152 Christopher W. Jenks, Director, Cooperative Research Programs Michael R. Salamone, ACRP Manager Joseph D. Navarrete, Senior Program Officer Terri Baker, Senior Program Assistant Eileen P. Delaney, Director of Publications Scott E. Hitchcock, Editor ACRP PROJECT 02-51 PANEL Field of Environment Sjohnna Knack, San Diego County (CA) Regional Airport Authority, San Diego, CA (Chair) Traci Clark, Cleveland Hopkins International Airport, Cleveland, OH Viola Murphy, Cool Valley, MO Michael Payne, The Jones Payne Group, Inc., Boston, MA Eugene M. Reindel, Harris Miller Miller & Hanson, Inc., Sacramento, CA Robert H. Slattery, Jr., Louisville Regional Airport Authority, Louisville, KY James B. Byers, III, FAA Liaison Hua (Bill) He, FAA Liaison Katherine B. Preston, Airports Council International - North America Liaison Christine Gerencher, TRB Liaison

ACRP Report 152: Evaluating Methods for Determining Interior Noise Levels Used in Airport Sound Insulation Programs provides guidance for selecting and implementing methods for measuring noise level reduction in dwellings associated with airport noise insulation programs. The research results will be of particular interest to airport industry practitioners who may be implementing such a program or who are responsible for con- ducting the measurement tests. Airports often undertake noise insulation programs to reduce impacts on homes within existing or forecast noise contours. Various methods for measuring noise level reduction are used to ensure that acoustical treatments meet the FAA’s noise reduction requirements. Yet the measurement of noise level reduction within a home is a complex process. Measurement results are affected by many factors, including instrument error, location of the sound source and microphone, ambient noise, and meteorological conditions. The issuance of FAA’s Pro- gram Guidance Letter 12-09, Eligibility and Justification Requirements for Noise Insulation Projects, resulted in the need to re-examine the methods used to determine whether existing interior noise levels are greater or less than 45 dB, the level required to qualify for federal funding for these projects. Although the criteria for the design of dwelling modifications are fairly well defined, there is limited measurement guidance for confirming a dwelling’s eligibility, which can result in inconsistencies when implementing airport sound insulation programs. Research was needed to gain a better understanding of the factors that lead to differences among measurement methods and to understand and minimize inaccuracies in estimating interior noise levels. The research, led by CSDA Design Group, complements the results of ACRP Report 89: Guidelines for Airport Sound Insulation Programs and was undertaken to assess the accu- racy and validity of various noise level reduction measurement procedures currently used in airport noise insulation programs. Acoustical field measurements were made at 10 homes near San Diego International Airport and nine homes near Boston Logan International Airport. Seven measurement methods were tested: • Outdoor ground-level artificial sound source (loudspeaker); • Outdoor elevated artificial source (loudspeaker); • Indoor artificial sound source (loudspeaker); • Aircraft flyover: fixed microphone; • Aircraft flyover: moving microphone; • Architectural survey and noise reduction calculations; and • Acoustic intensity measurements, exterior loudspeaker and interior intensity. F O R E W O R D By Joseph D. Navarrete Staff Officer Transportation Research Board

The report includes a summary of sound insulation theory and the science behind noise level reduction, and an overview of FAA-sponsored noise insulation programs. The report also provides guidance, including a decision matrix, for selecting an appropriate acoustical testing method. Lastly, the report provides suggested practices for each measurement technique, based on the results of the research.

1 Chapter 1 Overview 1 1.1 Purpose of Report 2 1.2 Summary of Findings 7 1.3 Acoustical Testing Matrix 7 1.4 Acoustical Testing Decision Matrix 10 1.5 Measurement Uncertainty – Present and Future 11 1.6 Acoustical Testing Best Practices 15 Chapter 2 Project Background and Study Scope 15 2.1 Sound Insulation History 18 Chapter 3 Research Approach 18 3.1 Objectives and Tasks 21 3.2 NLR Science 26 3.3 Basics of FAA-Sponsored Sound Insulation 31 3.4 Acoustical Testing 33 3.5 Overview of Tested Homes 41 Chapter 4 Findings and Applications 41 4.1 Aircraft Flyovers 54 4.2 Ground-Level Exterior Loudspeaker 59 4.3 Elevated Exterior Loudspeaker 67 4.4 Interior Loudspeaker 70 4.5 Architectural Survey and NLR Computation 76 4.6 Air Infiltration and Noise Reduction 80 4.7 Sound Intensity 104 4.8 Comparison of Results Across All Methods 107 4.9 Comparison of Measurement Results from Loudspeaker and Flyover Testing 110 4.10 Suggested Research 113 Bibliography 115 Definitions A-1 Appendix A Sound Intensity Measured Frequency Spectra B-1 Appendix B Sound Intensity: Vector Output Compared to Screen Output C-1 Appendix C Research Review D-1 Appendix D Computation of Uncertainty C O N T E N T S Note: Photographs, figures, and tables in this report may have been converted from color to grayscale for printing. The electronic version of the report (posted on the web at www.trb.org) retains the color versions.