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21.1 Background Air travel is a common experience for millions of people around the world. When navigating an airport, each traveler brings his or her own prior experience and expectations to the journey. These experiences reflect a broad spectrumâfrom the first-time flyer to the million-mile, busi- ness traveler. On arrival at the airport, an airline passenger normally follows a basic routine of checking in, passing through security, and finding the boarding gate. This routine may include eating and shopping. At the other end of the flight, those with checked luggage must find their baggage carousel and wait for baggage to arrive. Travelersâ experiences at airports can be pleasant or not, depending on many factors, including obtaining flight, gate, and boarding information, which may be fluid. A passengerâs journey from curbside to boarding is often assisted by announcements from the airportâs PA system. Although only a few announcements are relevant to any one passenger at a time, it is these announce- ment that matter most to those for whom they are intended and can have consequences if such announcements are not heard and understood. Whether an announcement is understood depends on human factors as well as physical factors and sometimes how they interact. Ways of communicating information to air travelers have improved with the use of electronic screens presenting relevant travel information. These screens are known as flight information display systems (FIDS) and wayfinding signs. Smartphone applications have become another way to convey information to travelers. However, audible communication through the PA sys- tem is still the primary means of conveying information, and, for travelers with hearing impair- ments and travelers whose first language is not English, the need for high speech intelligibility is particularly acute. Public service announcements made during an emergency are extremely important. In the event of a fire or a security threat, airport passengers must be made aware of and understand safety and/or evacuation instructions. Clarity of announcements can make a difference in whether or not a traveler hears and under- stands flight and gate information that is important to them or is irrelevant and can thus be ignored. Broadcasting a message does not guarantee it has been understood. A necessary condi- tion for understanding a message is that it be intelligible, which, in this context, means it was audible and sufficiently clear to be comprehensible. As travelers can attest, not all PA announce- ments are intelligible. These guidelines, which are intended for use by airport managers and technical staff, present (1) information on speech intelligibility, (2) guidance to use during the design process in order to improve the likelihood of intelligibility, and (3) guidance on operation policies to improve intelligibility (a) through training programs for those airport and airline employees who rou- tinely make public announcements via the PA system and (b) for using recorded messages that are clear and intelligible. C h a p t e r 1 Introduction
Introduction 3 1.2 Current Need for Guidelines Air travelers experience various airport environmentsâfrom large atriums to smaller gate hold areasâoften with significantly different levels of passenger activity in each. The wide array of sizes and shapes of terminal areas and range of background noise present challenges for air- port designers when it comes to ensuring announcements will be intelligible. Being aware of design challenges and how to approach and solve them can help increase the chances of success. A clear understanding of what physical factors affect intelligibility is essential to designing better airport terminals and the PA systems that serve them. It has been said that acoustics is the forgotten dimension in architectural design. The technology necessary to design and construct a terminal space in which the acoustics and amplified sound system achieve the appropriate goal is readily available, but not always incorporated. Even with the best design, inadequate implementation can affect the outcome and should be given careful consideration from conceptual design through final commissioning, lest the best of designs be compromised. Intelligibility is also affected by human factors related to passengersâ attention and expectations, thus adding another layer of complexity. The research included a literature review, an industry survey of airports and airlines, and extensive acoustical measurements in numerous terminal spaces at airports both large and small. To obtain passengersâ perspectives on intelligibility, a small pilot study of airport terminal public address systems was conducted at one airport. The primary goal of the research was to develop a basis for a comprehensive and practical set of guidelines for use in (1) designing new airport terminals and in renovating existing terminals and (2) guiding airport management. An online search of relevant literature and an industry survey concluded that no compre- hensive set of intelligibility guidelines for airport PA systems exists. A small percentage of the surveyed airports do apply limited, acoustical criteria when designing or renovating facilities. Guidelines are needed that present the concepts of good design and their implementation in a manner that can be understood by technical professionals and by airport decisionmakers and within the airline industry in general. The guidelines herein are intended to address these needs. 1.3 Previous Studies The research included a review of domestic and international literature on intelligibility stud- ies in airports related to the quantitative and human factor aspects of the subject. This review was accomplished through online search engines using appropriate search terms to focus on relevant studies. The literature review sought to identify existing resources that would be useful for evaluating the factors (physical and human) that affect PA system announcement intelligibil- ity in airports. The review produced few documents on the topic specifically relating to airports. A similar result was encountered in searching for literature on human factors. However, studies for other public transportation facilities (for example, transit) offer some guidance on PA system announcement intelligibility relevant to airports. Although rail transit and railway stations are dissimilar to airports, they share similar acousti- cal challenges. These similarities make general lessons learned in the design of new rail stations and the renovation of existing stations applicable to airports. Given that the investigation into the existing research on airport acoustics produced little information, the acoustical design les- sons learned from transit stations are helpful to consider. Architectural design in rail stations often includes spacious, reverberant spaces such as can be found in older railway stations (for example, New Yorkâs Pennsylvania Station and Grand Central Terminal and Washington, D.C.âs Union Station). Recently these stations have undergone renovation, which has included efforts to improve the intelligibility of the PA system and controlling reverberation in large arrivals halls with high ceilings so as to overcome some of the existing challenges.
4 Improving Intelligibility of airport terminal public address Systems Another similarity between rail stations and airports is the large volume of passengers that pass through themâsuch volumes result in higher levels of background noise and create a need for durable and easily maintainable room surfaces (both floors and walls). With maintenance in mind, surfaces that are easiest to maintain are generally hard and smooth, which makes such sur- faces acoustically reflective and results in more reverberation. Similar to larger transit stations, airports have a wide variety of spaces with different sizes and shapes that must be accommodated and that serve different purposes. The public address system in transit stations, although used somewhat less than in airports, serves the same purpose to communicate schedule and departure information to passengers. 1.3.1 Acoustics and Speech Intelligibility The physical parameters that affect speech intelligibility include the speech intelligibility (SI) evaluation method, hearing acuity and perception issues, and architectural acoustic conditions (e.g., reverberation time, diffusion and obstructions, background noise, PA system design, and announcement quality). The literature review uncovered few documents on acoustics and speech intelligibility specifi- cally relating to airports. Five physical factors affect speech intelligibility: (1) room volume and shape, (2) reflection and echoes, (3) reverberation, (4) architectural design, and (5) PA system design and announcement quality. These factors are discussed in greater depth in Chapter 4. 1.3.2 The Human Factor Although the literature review found few documents on human factors concerning airports, the review did produce useful information about speech intelligibility relevant to human factors. Usually, the intelligibility of an announcement is considered in terms of such features as pitch, tone, and loudness. However, the human factor in the equation is often overlooked. Many factors can impede attention to hearing, understanding, and attending to a message. Some factors are influenced by context and location (such as the number and variety of competing auditory stimuli within a particular environment), but many factors may be seen as a result of the attention and perception of the individual person. Chapter 5 provides guidance on addressing these factors and discusses the following key topics: â¢ Attention and perception â¢ Message content â¢ Message cuing 1.4 Organization of Guidelines The guidelines present material to help nontechnical and the technical users understand the physical and human factors affecting intelligibility. Important concepts are illustrated and design details that can be applied are discussed. This information serves as a basis for appreciating the key points of a good design and the steps that can be followed to implement one. The guidelines are organized into chapters. Chapter 1 presents background. Survey find- ings on the industryâs perception of this issue are presented in Chapter 2. Chapter 3 discusses speech intelligibility, provides background and information on how it is measured, and lists rel- evant codes and standards. Chapter 4 presents material on concepts and physical factors affect- ing intelligibility, including acoustics, architectural design, and PA system design. Chapters 5 through 7 provide guidelines for good design and implementation. Chapter 5 addresses human factors and how humans respond to messages and auditory input in an airport environment
Introduction 5 and ways to improve messages and announcement practice. Chapter 6 presents information on architectural design and includes guidance on how to improve room acoustics and the ambient environment. Chapter 7 presents guidance on PA systems, including information on electron- ics and equipment, loudspeaker configuration (layout and proximity), loudspeaker quality, and appropriate types of loudspeakers for different circumstances (e.g., high ceilings and large atri- ums). Chapters 8 and 9 present information and guidelines on the PA system bid and installation process, and the commissioning of the PA system, respectively, followed by chapters on announce- ments (Chapter 10) and operations, maintenance, and training (Chapter 11). Chapter 12 includes decision tools and examples to follow. Chapter 13 suggests ideas for future research. Icons, as presented in Figure 1-1, are used throughout the report. 1.5 How To Use These Guidelines Figure 1-2 illustrates the basic relationships among topics discussed in this report. The material starts with an introduction and foundational information in Chapters 1 through 5. These chapters support the relevant guidance for design in Chapters 6 and 7, which are followed by guidance relevant to procuring and executing design (in Chapters 8 and 9) and operation (in Chapters 10 and 11). The guidelines have been structured with the expectation that most users will focus on Chap- ters 6 and 7, using Chapters 2 through 5 for background. Much of the discussion in Chapters 6 This information is of particular importance. This indicates information related to design. This indicates information related to implementation. Figure 1-1. Icons used. Figure 1-2. The relationships among various speech intelligibility topics.
6 Improving Intelligibility of airport terminal public address Systems and 7 is intended for standalone consumption, so there is some duplication, given that users may not have fully read and digested the background information. Chapters 8 through 11 are much shorter than Chapters 6 and 7, so they rely more on references to previous chapters. Supple- mentary material is presented in the appendices. The References section lists all references used throughout the document, including those used only in the appendices. Different users will review this material at different phases of the project. Table 1-1 outlines when key issues can be affected by design. The basic priorities for speech intelligibility of public address systems are as follows: â¢ Primary: â Control reverberation â PA system design appropriate to the architectural and acoustical environment â¢ Secondary: â Reduce ambient noise â Implement PA system optimization and commissioning â¢ Tertiary: Proper training and instruction for announcements and microphone technique Physical Factor Project Timing Primary Discipline Related Disciplines Room shape/volume Conceptual or schematic design Architect Owner, structural engineer Reflections/echoes Design development Architect Acoustical consultant Reverberation Design development Architect Architectural finishes consultant, acoustical consultant Ambient noise Design development and/or construction documents Architect Mechanical engineer, acoustical consultant PA system Design development and/or construction documents Audiovisual (A/V) designer Architect, acoustical consultant Commissioning Substantial completion A/V commissioning agent Airport operations staff Announcements Training and operations Airport operations staff A/V commissioning agent Table 1-1. Project timing chart for physical factors that affect PA system speech intelligibility.