TCRP Report 12
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39 CHAPTER 8 ASSISTIVE LISTENING SYSTEMS, CUE SIGNS, ELECTRONIC VISUAL INFORMATION DISPLAYS, AND AUDIBLE SIGNS INTRODUCTION type of microphone and its placement at the sound source is crucial for the ALS to be effective. A variety of listening Travelers using large, multimodal transit systems often attachments (inductive telecoil couplers called neckloops, find them complicated and forbiddingly complex. For and the typical earbud or headphone type accessories) permit individuals with visual or hearing impairments, transit users of telecoil-equipped hearing aids to join others in systems that may be legally accessible from the ADA understanding more with the use of ALS. perspective often can be too complicated for these individuals to confidently and safely ride. In recent years, the FM Systems—Sound, via a microphone or public address transit industry, in partnership with the disability community, system, is fed into an FM transmitter. It sends sound to has begun to adopt technologies that provide increased small, individual FM receivers. Hearing-aid users with confidence, safety, and ease of use by individuals with hearing aids that are equipped with telecoils set the aid on the disabilities. The following discussion of assistive listening "T" setting and use a neckloop listening attachment; systems (ALS), dialog systems, cue signs, electronic visual earphones are used by everyone else. The FM systems information displays, and audible signs describes produce an excellent sound quality. The systems are not technologies that have great promise in increasing ridership subject to electrical interference and are highly portable, among the hearing and visually impaired. simple, and inexpensive to install. Maintenance and The technologies described in this chapter are evolving operating costs are low because the systems are highly rapidly. During the course of the development of these reliable. guidelines, the Federal Transit Administration (FTA), The major disadvantages of an FM system are its initial Transportation Research Board (TRB), U.S. Architectural equipments costs, which are greater than those for the AM and Transportation Barriers Compliance Board, and system or the audio loop system, and restricted access Transport Canada's Transportation Development Centre were (service is limited to the number of receivers). FM systems conducting numerous research projects to better define transmit through walls so adjacent facilities should be effective signage using these technologies. Research was equipped with other frequencies to avoid interference. also being conducted by numerous disability organizations to Induction Loops—A loop of wire circling the room (or better develop and define technological aids that would part of the room) near a ceiling or floor, receives input from provide greater access for individuals with disabilities. a PA or microphone through an amplifier and transmits the Because these technologies are evolving so rapidly, it is sound by creating a magnetic field with the loop. This field important for graphics designers to stay abreast of them in can be picked up by listeners with hearing aids on the "T" order to ensure that the techniques and materials selected are setting or with telecoil-equipped receivers and an earpiece. current and represent the best solutions for their riders. The receiver is equipped with an amplifier so that the sound Contacts with one or more of the organizations mentioned level can be controlled by the user. above can provide up-to-date guidance on the state of the art No special receivers are needed by people whose hearing for the signing technologies that follow. Further, local and aids are equipped with telecoils. Prepackaged systems can be national disability organizations are excellent resources and easily installed in small- and medium-sized spaces and are are eager to provide information and technical assistance in inexpensive. The disadvantages of this device are that users the use of current technology to increase access for their a) must be within the loop to receive information and b) must constituents. have telecoil-equipped hearing-aids or must be provided with loop receivers. Sound quality is often uneven throughout the ASSISTIVE LISTENING SYSTEMS looped area and fluorescent lighting can interfere with transmission. The electromagnetic field signal can "spill There are several types of ALS that signage designers may over" into adjacent areas. Temporary or portable loops are consider in providing information to individuals with hearing available but cannot be moved without difficulty. Systems impairments. These systems accept input from existing for large areas are complex to install and a high-powered public address systems, thereby reducing cost. However, the amplifier is required. 40 Infrared—Infrared systems use invisible light beams in CUE SIGNS FOR VISUALLY IMPAIRED the infrared range of the spectrum that carry information TRAVELERS from a transmitter connected to a PA system or microphone to a special portable receiver worn by the listener and Cue signs are raised letter and Braille directional signs that fitted with neckloops, earbuds or headphones to meet are placed at logical decision points along major trip the user's needs. For persons with mild to moderate losses segments in a transit facility. The signs provide users who of hearing, the sound quality is good. The system is easy are visually impaired directions from one cue sign to the next to operate and is not subject to electrical interference. It until they reach their final destination. Cue signs have not is contained within the walls of the area and it's the been used in a facility, but limited testing indicates that cue only system appropriate for confidential transmission. signs do provide assistance to patrons who have visual However, infrared light is present in sunlight, incandescent impairments. light and fluorescent light, so a large amount of light Each cue sign should be located at a landmark, a in the room may produce interference. Receivers must processing point, or at a point where the person must change be within the line of sight of the transmitter. direction. All direction changes are right angles (90 deg). AM Systems—AM systems are similar to FM systems in Cue sign messages are very brief and use a very limited that receivers, which may be AM radios, pick up the signal vocabulary so that the same words are used over and over broadcasted from an AM radio transmitter coupled to again. The repetition enables those who do not read raised a microphone or PA system. The technology is both letters or Braille well to adapt and become proficient in their simple and inexpensive. Patrons can use their own use within a short time. personal AM radio and attachments and fine-tune Cue signs within a facility should are always be the same to the broadcast. Unfortunately, AM systems have size. The recommended size is 8 in. × 8 in. (203 mm × 203 relatively poor sound quality, and they do not perform mm) with rounded corners. They should be mounted at well in buildings with substantial amounts of structural the same height above the floor (recommended 48 in. steel. [1,219 mm] from the floor to the horizontal centerline of the sign). They can be mounted on a wall or on a post. Mounting angles can vary from flat on a wall (perpendicular to the floor) to flat on the top of a pedestal DIALOG SYSTEMS post (parallel to the floor). The raised letters and Braille can be read more easily if the sign is mounted at a 45-deg angle Though in its embryonic stages, true dialog systems are from the floor on the top of a pedestal post or on a wall under development, which provide wayfinding information bracket. via a telephone handset. The user may interact with the The raised letters on the cue sign should be both tactile and system using a home telephone, a cellular telephone, or visual, permitting those who have limited vision to see and through a microphone-speaker device in an information feel the text, which increases reading speeds. The signs kiosk. The system is speaker independent and works through should be placed adjacent to and out of the way of the continuous speech recognition software. Thus, the system is normal patron flows so that the users do not have to stand in able to learn and recognize continuous speech of any speaker the flow of traffic as they read the sign. asking questions. The technology was developed in 1994 and Cue signs should be consistently placed to the right of the successfully demonstrated in a transit study by the flow of traffic. This standard placement helps users find the Massachusetts Bay Transportation Authority and the sign because they know in advance that signs will always be National Eye Institute. to the right and out of the flow of traffic. Consistent The system contains two major components of a fully placement of cue signs is critical for success. General rules specified spoken language system: a discourse system and for placement should be developed and coordinated with a dialog system. The discourse system remembers elements local disability organizations. Suggested general guidelines such as the origin and destination for a trip segment for placement are as follows: until they are redefined by a user during a dialog with the system. The dialog system makes use of aspects of Station Entrance—Within 10 ft and to the right of the the discourse where appropriate (for example, to interpret main entrance escalators, entrance stairways, or entrance incompletely specified follow-up questions presented by gates. the user). Level Changes—Within 10 ft and to the right at the top of The system also has the capability of taking charge of a the escalators or stairs, and within 10 ft and to the right at the dialog and asking questions where it is deemed necessary. bottom of the escalators or stairs.