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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 RESEARCH REPORT 175 2017 Research sponsored by the Federal Aviation Administration Subscriber Categories Aviation â¢ Passenger Transportation â¢ Terminals and Facilities Improving Intelligibility of Airport Terminal Public Address Systems Wilson Ihrig Emeryville, 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 nationâs 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 100â Century of Aviation Reauthorization Act. The primary participants in the ACRP are (1) an independent governing board, the ACRP Oversight Committee (AOC), appointed by the Secretary of the U.S. Department of Transportation with representation from airport operating agencies, other stakeholders, and relevant industry organizations such as the Airports Council International-North America (ACI-NA), the American Associa- tion of Airport Executives (AAAE), the National Association of State Aviation Officials (NASAO), Airlines for America (A4A), and the Airport Consultants Council (ACC) as vital links to the airport community; (2) TRB as program manager and secretariat for the governing board; and (3) the FAA as program sponsor. In October 2005, the FAA executed a contract with the National Academy of Sciences formally initiating the program. ACRP benefits from the cooperation and participation of airport professionals, air carriers, shippers, state and local government officials, equipment and service suppliers, other airport users, and research organi- zations. Each of these participants has different interests and responsibili- ties, and each is an integral part of this cooperative research effort. Research problem statements for ACRP are solicited periodically but may be submitted to TRB by anyone at any time. It is the responsibility of the AOC to formulate the research program by identifying the highest priority projects and defining funding levels and expected products. Once selected, each ACRP project is assigned to an expert panel appointed by TRB. Panels include experienced practitioners and research specialists; heavy emphasis is placed on including airport professionals, the intended users of the research products. The panels prepare project statements (requests for proposals), select contractors, and provide technical guidance and counsel throughout the life of the project. The process for developing research problem statements and selecting research agencies has been used by TRB in managing coop- erative research programs since 1962. As in other TRB activities, ACRP project panels serve voluntarily without compensation. Primary emphasis is placed on disseminating ACRP results to the intended users of the research: airport operating agencies, service pro- viders, and academic institutions. ACRP produces a series of research reports for use by airport operators, local agencies, the FAA, and other interested parties; industry associations may arrange for workshops, training aids, field visits, webinars, and other activities to ensure that results are implemented by airport industry practitioners. ACRP RESEARCH REPORT 175 Project 07-14 ISSN 2572-3731 (Print) ISSN 2572-374X (Online) ISBN 978-0-309-44643-3 Library of Congress Control Number 2017942593 Â© 2017 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 research 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. Trade or manufacturersâ names appear herein solely because they are considered essential to the object of the report. Published research reports of the AIRPORT COOPERATIVE RESEARCH PROGRAM are available from Transportation Research Board Business Office 500 Fifth Street, NW Washington, DC 20001 and can be ordered through the Internet by going to http://www.national-academies.org and then searching for TRB Printed in the United States of America
The National Academy of Sciences was established in 1863 by an Act of Congress, signed by President Lincoln, as a private, non- governmental institution to advise the nation on issues related to science and technology. Members are elected by their peers for outstanding contributions to research. Dr. Marcia McNutt is president. The National Academy of Engineering was established in 1964 under the charter of the National Academy of Sciences to bring the practices of engineering to advising the nation. Members are elected by their peers for extraordinary contributions to engineering. Dr. C. D. Mote, Jr., is president. The National Academy of Medicine (formerly the Institute of Medicine) was established in 1970 under the charter of the National Academy of Sciences to advise the nation on medical and health issues. Members are elected by their peers for distinguished contributions to medicine and health. Dr. Victor J. Dzau is president. The three Academies work together as the National Academies of Sciences, Engineering, and Medicine to provide independent, objective analysis and advice to the nation and conduct other activities to solve complex problems and inform public policy decisions. The National Academies also encourage education and research, recognize outstanding contributions to knowledge, and increase public understanding in matters of science, engineering, and medicine. Learn more about the National Academies of Sciences, Engineering, and Medicine at www.national-academies.org. The Transportation Research Board is one of seven major programs of the National Academies of Sciences, Engineering, and Medicine. The mission of the Transportation Research Board is to increase the benefits that transportation contributes to society by providing leadership in transportation innovation and progress through research and information exchange, conducted within a setting that is objective, interdisciplinary, and multimodal. The Boardâs varied committees, task forces, and panels annually engage about 7,000 engineers, scientists, and other transportation researchers and practitioners from the public and private sectors and academia, all of whom contribute their expertise in the public interest. The program is supported by state transportation departments, federal agencies including the component administrations of the U.S. Department of Transportation, and other organizations and individuals interested in the development of transportation. Learn more about the Transportation Research Board at www.TRB.org.
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 CRP STAFF FOR ACRP RESEARCH REPORT 175 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs Michael R. Salamone, Manager, Airport Cooperative Research Program Theresia H. Schatz, Senior Program Officer Hana Vagnerova, Senior Program Assistant Eileen P. Delaney, Director of Publications Hilary Freer, Senior Editor ACRP PROJECT 07-14 PANEL Field of Design Timothy M. Mitchell, Boeing, Seattle, WA (Chair) Christopher Blasie, Rockwell Collins/ARINC Airports, Annapolis, MD Alan G. Hass, Landrum and Brown, Boston, MA Darryl K. McDonald, Austin Commercial, LP, Orlando, FL Heather McKee, Denver International Airport, Denver, CO Amiel Porta, San Diego County Regional Airport Authority, San Diego, CA Holly Cyrus, FAA Liaison AuTHOR ACkNOwLEdGMENTS The research on which this report is based was performed under ACRP Project 07-14 by Wilson, Ihrig & Associates, Inc. (Wilson Ihrig). Wilson Ihrig was supported by Chips Davis Designs (Chips Davis); Cross-Spectrum Acoustics, Inc. (CSA); CCD Design and Ergonomics (CCD); HKS Architects, Inc.; and Joel Lewitz, PE, FASA, FAES. Richard Carman, PhD, PE, was the principal investigator. The primary editor and author was Deborah Jue. Other authors of this report are Gary Glickman of Wilson Ihrig; Joel Lewitz; Chips Davis; Adam Parkes, David Watts, and Karen Jackson of CCD; and Lee Glenn and Rick Lee of HKS. CSA provided valuable assistance with the field measurements. Joel Lewitz and Chips Davis provided important practical insight and knowledge regarding the design, installation, and commissioning of public address (PA) systems. CCD developed and conducted the pilot passenger study and prepared the human factors chapter based on their experience and research. HKS brought the architectâs lens to help develop the practical design issues. We would also like to thank Silas Bensing of Wilson Ihrig for his detailed attention to the field data analyses and Herb Singleton of CSA for his insight during this project. Wilson Ihrig greatly appreciates the experience and professionalism that these authors and team members have brought to this research. In addition to the airports listed, the research team would like to thank members of the air terminal facilities community who really went out of their way to assist us with our research: Suzanne Boda, Henry Chan, Jim Chiu, Norman Clevenger, Joe Collins, Kyle Mobley, Harry Sigley, Todd VanGerpen, Tom Rafter, David Sylvia, and Anne Tyska. We also thank the following organizations which participated in the study: â¢ Anchorage International Airport â¢ Broward County Aviation Department â¢ Burlington International Airport â¢ City of Boise/Boise Airport â¢ City of Chicago/Department of Aviation â¢ City of Phoenix Aviation Department â¢ City of San Antonio/SAAS â¢ Corpus Christi International Airport â¢ Dallas/Fort Worth International Airport â¢ Denver International Airport â¢ Fairbanks International Airport â¢ Fort Wayne International Airport â¢ Los Angeles World Airports â¢ Maryland Aviation Administration â¢ Maryland Aviation Administration (BWI) â¢ McCarran International Airport â¢ Metropolitan Airports Commission â¢ Monterey Regional Airport â¢ Nantucket Memorial Airport â¢ Oakland International Airport â¢ Philadelphia International Airport â¢ Pittsburgh International Airport â¢ Portland International Airport â¢ Prince George Airport Authority â¢ Salt Lake City/Department of Airports â¢ San Diego County Regional Airport â¢ San Francisco International Airport â¢ Savannah Airport Commission â¢ Seattle-Tacoma International Airport â¢ Stockton Metropolitan Airport â¢ Wichita Airport Authority
ACRP Research Report 175: Improving Intelligibility of Airport Terminal Public Address Sys- tems provides design guidelines to improve public address speech intelligibility for passenger- processing interfaces for all types and sizes of airport terminal environments. These guidelines are intended to be used by airport operators and design consultants. The guidelines include (1) a summary of data on public address systems, terminal finishes (e.g., walls, floors and ceilings) and background noise levels in a variety of airport terminals, (2) identification of acoustical shortcomings and the results of impacts on existing public address systems; and options for enhancing intelligibility in existing airport terminals as well as ensuring intelligibility in new terminal designs. Audible announcements in airport terminals are often hard to understand. Given that the airport terminal environment is dynamic, the speech intelligibility of public address systems can decline and people can find it hard to understand announcements due to background noise and/or poor system design. Understanding announcements is even harder for (1) hearing-impaired travelers, (2) people for whom English is not their native language, and (3) distracted travelers. Poor intelligibility in public address systems degrades the efficacy of fire alarm notifications and other public service and emergency announcements that are critical in airport terminals. The report reflects empirical research on existing acoustical conditions in airport terminals and demonstrates how terminal architecture and the design of public address systems within terminals affect intelligibility of announcements. Under ACRP Project 07-14, research was conducted by a team of specialists led by Wilson Ihrig. The design guidelines were developed through field measurements at airports as well as an online questionnaire to collect information from the airport industry (airlines, airports, and consultants) to review how the industry understands factors related to speech intelligibility. A passenger survey was also developed to gain insight on ways airports can conduct their own research on human factors specific to their airports. F O R E W O R D By Theresia H. Schatz Staff Officer Transportation Research Board
1 Summary 2 Chapter 1 Introduction 2 1.1 Background 3 1.2 Current Need for Guidelines 3 1.3 Previous Studies 4 1.3.1 Acoustics and Speech Intelligibility 4 1.3.2 The Human Factor 4 1.4 Organization of Guidelines 5 1.5 How To Use These Guidelines 7 Chapter 2 Industry and Passenger Perspectives 7 2.1 Introduction 7 2.2 Overall Industry Perspectives 10 2.3 Airports and Airport-Based Staff 10 2.3.1 Summary 10 2.3.2 Detailed Results 15 2.4 Airlines 15 2.5 Consultants 15 2.6 Passengers 16 2.7 Conclusions 18 Chapter 3 Speech Intelligibility 18 3.1 Introduction 18 3.2 Background 19 3.3 Qualitative Measures of Intelligibility 20 3.4 Signal-to-Noise Ratio 21 3.5 Quantitative Measures of Intelligibility 21 3.5.1 Speech Transmission Index 21 3.5.2 Speech Transmission Index for PA Systems 23 3.6 Code Requirements 23 3.7 Other Considerations 23 3.7.1 Non-native Language Listeners 24 3.7.2 Hearing Impairment, Age-Related Hearing Loss, and ADA Considerations 25 3.8 Effect of Ambient Noise on STI 26 3.9 Guidance Targets 26 3.9.1 Design 27 3.9.2 Performance and Commissioning C O N T E N T S
28 Chapter 4 Physical Factors Affecting PA Intelligibility 28 4.1 General Acoustical Principles 28 4.2 Spatial ConsiderationsâVolume and Shape 30 4.3 Reverberation 34 4.3.1 Acoustical Finishes 35 4.3.2 Passengers 35 4.4 Sound Reflections and Strong Echoes 36 4.5 Ambient and Background Noise 36 4.5.1 Steady Noises 36 4.5.2 Transient Noises 36 4.5.3 Ambient Noise Measurements (Interior Sources) 37 4.5.4 Ambient Noise Measurements (Exterior Sources) 38 4.6 PA System Design 38 4.7 Announcement Quality 39 4.8 Guidance Targets 40 Chapter 5 Human Factors Affecting PA System Intelligibility 40 5.1 Introduction 40 5.2 Psychology of PA Announcement Intelligibility: Attention and Perception 41 5.2.1 Passenger Attention/Distraction 42 5.2.2 Barriers to Attention and Perception 44 5.3 Message Content of Announcements 44 5.3.1 Relevance 45 5.3.2 Repetition 45 5.3.3 Message Content: Types of Speech 46 5.3.4 Message Content: Non-native Language Listeners 46 5.4 Message Delivery: Gender 48 5.5 Message Cuing 49 5.6 Passenger Journey Maps and Passenger Information Needs 49 5.7 The Experience of Passengers with Impairments in Hearing and Sight 49 5.7.1 Passengers Who Have Hearing Impairments and/or Are Older 53 5.7.2 Passengers with Visual Impairments 53 5.8 Interplay between Flight Information Displays and PA Announcements 54 5.9 Guidance 54 5.9.1 Attention and Perception and Message Content 54 5.9.2 Message Cuing 55 Chapter 6 Architectural Design 55 6.1 Key Concepts and Design Principles 56 6.1.1 Design Phases 57 6.1.2 Summary of Architectural and Mechanical Factors 58 6.2 Room Volume and Shape 59 6.3 Acoustical Finishes 60 6.3.1 Ceilings 61 6.3.2 Walls 61 6.3.3 Floors 61 6.4 Acoustical Considerations by Terminal Functional Area 61 6.5 Concept of Acoustically Distinguishable Space (ADS) 63 6.6 Ambient and Background Noise Considerations for Interior Spaces 64 6.6.1 Mechanical Equipment 64 6.6.2 Airport Passengers 65 6.6.3 Airport TV Monitors
65 6.6.4 Competing PA Announcements 66 6.6.5 Background Music 66 6.6.6 Passenger Boarding Bridges 66 6.6.7 Electric Passenger Transport Carts 66 6.6.8 Interterminal Automated People Movers (APMs) 66 6.6.9 Aircraft Noise at the Terminal 67 6.6.10 Concession Areas 67 6.7 Ambient and Background Noise Considerations for Exterior Spaces 68 6.8 Airport Size Considerations 68 6.9 Sustainability Considerations 68 6.10 Computer Modeling Software for Acoustical Design 70 Chapter 7 Public Address System Design 70 7.1 Introduction 70 7.2 Terminology and Components 70 7.2.1 Terminology 71 7.2.2 Components 72 7.3 Microphones 73 7.3.1 Handheld Microphones 74 7.3.2 Other Paging Microphone Types 75 7.4 Headend Electronics 75 7.4.1 Digital Signal Processor 77 7.4.2 Ambient-Noise-Sensing System 77 7.5 Loudspeaker Type Selection 77 7.5.1 Cone Loudspeakers 78 7.5.2 Passive Column-Array Loudspeakers 79 7.5.3 Steerable Column-Array Loudspeakers 80 7.5.4 Horn Loudspeakers 81 7.5.5 Undesirable Loudspeaker Applications 81 7.6 Loudspeaker Layout 82 7.6.1 Loudspeaker Zones 82 7.6.2 Spatial Considerations 82 7.6.3 Audio Delay 82 7.6.4 Loudspeaker Grid: Distribution 83 7.6.5 Point Source Distribution 83 7.7 Loudspeaker Quality 84 7.8 Loudspeaker Terminal Location Considerations 85 7.9 System Interfaces 86 7.10 Computer Modeling for PA System Design 86 7.11 Considerations for Renovation Projects 87 7.12 Considerations for Combining Emergency and Non-Emergency Announcements 87 7.13 Sustainability and PA Systems 88 7.14 Induction Loops for Assisted Listening 89 Chapter 8 Construction Phase 89 8.1 Construction Review for Room Acoustics 89 8.2 PA System Bid Process 90 8.3 PA System Installation 90 8.3.1 Submittals 90 8.3.2 Shop Tests 90 8.3.3 Onsite Testing
91 8.4 Site Reviews and Inspections 91 8.4.1 Balancing the System 92 8.4.2 Setting PA Announcement Levels 92 8.4.3 Loudspeaker Zone Frequency Response Equalization 93 Chapter 9 Commissioning Public Address Systems 93 9.1 Introduction 94 9.2 Overview 94 9.3 Key Concepts 94 9.3.1 Verification 95 9.3.2 Optimization 95 9.4 Inspection and Testing 95 9.4.1 Balancing the System 95 9.4.2 Setting PA Announcement Levels 96 9.4.3 Loudspeaker Zone Equalization 96 9.4.4 Measuring and Reporting STI 98 9.4.5 Troubleshooting the Speech Intelligibility of the PA System Installation 99 9.4.6 Considerations for Combination Emergency and Non-Emergency Systems 99 9.5 Final Checkout and Verification 100 Chapter 10 Public Address System Announcements 100 10.1 Introduction 100 10.2 Announcement Content 100 10.2.1 Recording Quality 100 10.2.2 Announcement Information 101 10.3 Announcement Delivery and Live Announcements 101 10.4 Automated Announcements 101 10.5 Artificial Voice Systems 102 10.6 Message Cuing 103 Chapter 11 Operation and Maintenance of the PA System 103 11.1 Operation of the PA System 103 11.1.1 Employee Announcement Training 103 11.1.2 Use of Microphones 103 11.1.3 Voice Quality and Microphone Technique 104 11.1.4 Competing Announcements 104 11.1.5 Zoning Announcements 104 11.2 Maintenance of the PA System 105 Chapter 12 Decision Tools and Examples 105 12.1 Quick Reference for Guidance Tables and Charts 105 12.2 Examples from Field Measurements 125 Chapter 13 Future Research 126 References and Bibliography 128 Appendix A Annotated Bibliography 139 Appendix B Pilot Passenger Survey Questions and Results Summary
143 Appendix C Abbreviations, Acronyms, and Initialisms 145 Appendix D Glossary 148 Appendix E Examples of Acoustical Material Properties 149 Appendix F PA System Glossary 151 Appendix G Sample PA System Specification Relevant to Speech 155 Appendix H Sample Design Criteria Elements Relevant to Speech Intelligibility 157 Appendix I Summary of Field Measurement Results 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.