Assistive Listening Devices and Systems: Amplification Technology for Consumers with Hearing Loss.
Amplification in the form of hearing aids is the primary rehabilitative tool the audiologist has to offer an individual with a hearing loss. Although the benefits of hearing aids in the population with hearing loss are well documented (Harless & McConnell, 1982; Kricos, Lesner, Sandridge & Yanke, 1987; Malinoff & Weinstein, 1989; Mulrow, et al., 1990), factors such as the presence of background noise and distance from the speaker or sound source can reduce the amount of benefit received from traditional heating aids.
Assitive listening devices (ALDs) have been developed to help individuals in communication and environmental setting when hearing aids are insufficient. The purpose of the article is to present the advantages and disadvantages of ALDs, audiologist assessment and rehabilitation counseling considerations, and a discussion of types of assistive listening devices.
In 1990, the Americans with Disabilities Act (ADA) provided the legislative foundation to vastly expand legal rights of individuals who have disabling conditions (Public Law 101-336). The ADA is composed of five titles covering the areas of employment, public services, and programs and communication. Private employers, state and local governments, and public accommodation establishments are covered under Titles I, II, and III (Strauss, 1994). Of paramount importance are the phrases 'qualified individual with a disability, who with or without reasonable accommodation, can perform the essential functions of the employment position.' Reasonable accommodation are considered those that do not place an 'undue hardship' on the business.
The Department of Justice in its regulations concerning Title II, provides a list of aids and services for individuals with hearing impairments:
'[q]ualified interpreters, notetakers, transcription services, written materials, telephone handset amplifiers, assistive listening devices, assistive listening systems, telephones compatible with hearing aids, closed caption decoders, open and closed captioning, telecommunications devices for deaf persons (TDD's) [and] video text displays....' [28 C.F.R. [sections] 36.303(b) (1)]
Holt and Seeger (1995) studied 390 individuals who were admitted to a rehabilitation unit of a hospital. The subjects were divided into six age groupings: less than 40 age group (n=11), 40-49 age groups (n=31), 50-59 age group (n=35), 60-69 age group (n=107), 70-79 age group (n=134), and over 80 age group (n=72). They found that hearing loss was related to the age group with poorer hearing in the older groups. The most common hearing impairment across age groups was in the mild to moderate range. They state, 'this type of hearing loss is very difficult to identify without formal audiological evaluation.' (p. 59) An individual with mild to moderate hearing loss may not have difficulty communicating in a quiet environment, but have significant difficulty communicating in a noisy environment. This could account for the fact that twenty-two percent of the subjects in this study who had a significant hearing impairment denied any hearing difficulty. Smith and Kampfe (1997) point out that hearing loss not only caused pronounced modifications in relationships and interpersonal functioning, but also causes fatigue, isolation, reduction in recreational activities, anxiety, fear and distrust.
Assistive listening devices (ALDs) are various types of amplification equipment designed to improve the communication of persons with hearing loss in instances where traditional hearing aids are not sufficient. These assistive devices can facilitate listening in noisy environments and group conversations. They also can improve distance listening and help in alerting to and identifying important warning signals both on and off the job.
Types of Assistive Devices
ALDs can be used as large area systems such as those used in churches and theaters or as personal communication aids for individual use on the telephone, small group activity, or television/radio involvement. ALDs can also serve as simple alerting devices informing the individual with a hearing loss of a knock at the door or the cry of a baby. Assistive devices also vary in their internal electronic components ranging from simple hardwire microphone-amplifier units to more sophisticated infrared or FM systems.
Hardwire devices require wires to connect the microphone, amplifier, and receiver/speaker in the stethoscope earphone or ear-mold. For personal systems, the amplifier is small and can be held in the hand or placed in a pocket. The listener can be 'self-wired' with all parts of the system on their person, or the listener can give the microphone to the talkers. This latter form of wearing the device enhances communication by decreasing the distance from the speaker's mouth to the microphone hence improving the signal to background noise ratio.
These personal systems are intended for personal user applications (i.e., listening while in the car, at restaurants, etc.) and for use by professionals providing services to hard of hearing individuals (i.e., physician consultations). Hardwire devices can also be designed for specific purposes, such as an amplified stethoscope for the use by a healthcare worker with hearing loss. Personal assistive listening devices vary greatly in sound quality as well as price (Dempsey, 1994).
Hardwire personal listening systems can also be used in meeting rooms, churches or theaters. Typically, the microphone from the standard amplifier for the facility is also wired to personal amplifiers in selected seats. The individual with heating loss would be required to sit in these seats wired with the equipment and use some type of receiver such as a headset or earphone.
FM SOUND SYSTEMS
Free-field wireless frequency modulated (FM) sound systems can improve listening in noisy environments or when distance from the speaker is a problem. These systems send the auditory message through frequency modulated radio waves from a wireless transmitter directly to a small receiver worn by the listener with hearing loss. The result is improved signal to noise ratio and improved distance listening. The wireless transmitters can send the signal from the speaker's microphone or from the output of most common sound systems, radio, televisions or stereos.
FM systems can work alone, in conjunction with the sound systems usually found in auditoriums and churches, or with portable PA systems used for meeting and lectures. Receivers can be coupled to hearing aids through currently available direct audio input adapters, or via teleloop or telecoil induction coupling. FM systems can now also be built into personal hearing aids or be attached to behind-the-ear hearing aids via a 'boot', a miniature adapter.
INFRA-RED SOUND SYSTEMS
An infra-red system transmits the sound to the audience via invisible infrared light waves. A transmitter uses light waves to send speech or music to individual wireless headset receivers. The receivers are lightweight and can be worn anywhere in the audience. The receiver can be hooked to headphones or can be used with any heating aid having a telephone switch. The systems are not subject to electromagnetic interference but are vulnerable to interference from natural light; therefore infrared systems cannot be used in direct bright sunlight.
There is considerable overlap in the possible uses of infra-red and FM systems. Infra-red advantages include the ability to contain the signal within a room, increased privacy of the signal information, the ability to have an unlimited number of receivers and excellent sound quality. The signal of a FM system cannot however be blocked by a physical obstruction, and FM units are more portable (Ross, 1994).
AUDIO LOOP SYSTEMS
An audio or induction loop system transmits sound via a loop of wire that surrounds the seating area. The electric current that flows through the loop creates an electromagnetic field that can be received and then amplified by a hearing aid equipped with a telecoil (T-Coil) or telephone switch (Lederman & Hendricks, 1995). Audio loop systems can be permanently installed in meeting rooms or theaters or portable loop systems can be setup as needed.
The major limiting factor of the audioloop system is the need for the person with the hearing loss to have a hearing aid with a functional T-coil or telephone switch and to know how to effectively use that option. The latter lack of knowledge is problematic as Centa (1992) noted many hearing aid users are not instructed in the proper use of their T-Coil switches. Both professional audiology training programs and new user hearing aid orientation classes need to emphasize the benefits of T-Coil use in hearing aid classes for both telephone listening and for use with assistive listening devices.
TELEPHONE LISTENING DEVICES
Telephone communication can pose a unique problem for individuals with heating loss in that they are required to rely totally on their damaged auditory system rather than being able to benefit from visual cues and speechreading. Several ALDs have been designed specifically for telephone communication. One of the most common and useful ALD is the telephone amplifier that allows the user to adjust the volume of the telephone receiver. These amplifiers can be built into the telephone or its handset or they can be 'in line' units connected between a standard telephone and the wall jack. Portable snap-on amplifiers that are battery operated and may be attached to any telephone are also available (Holmes, 1994).
For people with very limited or no usable hearing, Telecommunication Devices for the Deaf (TDD) or Teletypewriters (TTY) are available for people to type messages through the telephone lines. People at both ends must have a TDD, each person types a message on a teletype keyboard that is transmitted from a modem through the telephone line to the receiver's keyboard for printout on a screen.
Currently telecommunication relay systems are being developed and used which permit a TDD user to make calls to a standard telephone user and vice versa. In one system, the call is placed to a relay station where a relay operator transmits the message in the proper form. In another system, the TDD user talks to the standard telephone user who types his or her portion of the conversation using the touch tone keys of the telephone. This method requires the individual with hearing loss to be able to speak clearly enough to be understood (Castle, 1994).
Visual alerting devices hooked to lights and telephone finger amplifiers can be used to help a person know their telephone is ringing. Another simple ALD is the placement of remote fingers throughout the house thereby increasing the chance the person with hearing loss will hear the ringing telephone.
Alternative listening systems are also available for television. Amplifiers with earphones/headphones can plug directly into the TV. Wireless systems including FM systems, infrared listening systems and audio loop systems can all be used in conjunction with television listening. TV band radios are also an option as the person with a hearing loss can use an earphone with the radio at their comfortable volume while other viewers can adjust the television volume to their preferred listening level.
Another excellent option for television viewing is closed captioning. Using a television with either built-in or an external caption decoder, the viewer is able to see real time captions of the auditory portion of a program. The result is similar to viewing a dubbed movie. As of July 1, 1993 and in accordance with the Americans with Disabilities Act, all televisions 13 inches or larger that are manufactured or sold in the United States must have closed captioning capabilities (Public Law 101-336). Because most programming includes background music or noise the ability to read the spoken word greatly enhances understanding on this media. The use of closed captioning can benefit clients with hearing impairment when viewing programs or videos for on- the-job training.
Alerting devices have also been developed to aid in the detection of both convenience and safety/alarm equipment. Wake-up alarms using flashing lights or bed vibrators can be plugged into an alarm clock. Multipurpose light flashing or vibrating systems are available for doorbell, smoke alarm, baby cry, kitchen timers, or other signal needs.
In keeping with the current spirit of rehabilitative service provision, ALDs permit greater autonomy for the individual with hearing loss. Many of these systems have specific requirements for use such as the need for different channels for multiple FM users in a small area or the requirement of a darkened room for infrared use. ALD technology continues to progress. Advances in computer technology, miniaturization and human engineering continue to promise newer devices and improvements to current devices including better interfaces to personal hearing aids in the future.
Audiologists can assist in planning for ALD use. A complete audiologic evaluation should be completed before any ALD recommendations are made. By taking an extensive case history of where clients are having communication difficulties and problems heating important environmental and auditory warning cues, the audiologist can make recommendations for and dispense the appropriate ALD. Many audiologists have ALD demonstration units in their clinics to allow the clients to try various devices. Along with the rehabilitation counselor, the audiologist can train the individual on the care and use of the device. For example, if the client is a supervisor in noisy factory and is having difficulty hearing his/her employees in the field with hearing aids, an FM system may be appropriate for this individual. In another case a simple recommendation of an amplified telephone handset could assist a secretary in functioning on the job. The benefits to all these devices must be thoroughly discussed with the clients. At the same time the client must be willing to use the device even if it is visible to those around them. Counseling is of utmost importance.
Assistive listening devices have grown in popularity over the past decade. This popularity will probably continue to grow as America experiences the aging of the Baby Boom generation. Baby Boomers are more comfortable with technology than their parents and they are known to demand and expect the best in medical care (von Mering, 1995). The economic benefits to the hearing health professional serving this aging population is obvious, however more important is the professional satisfaction in providing optimal care. Assistive listening devices can make huge differences in alleviating the daily grind of a hard of hearing individual. ALDs make hearing easier and therefore improve life quality.
Rehabilitation Counselors as client advocates need to assure that their clients' other disabling conditions are not additionally exacerbated by a hearing impairment. During the initial interview, the vocational rehabilitation counselor should be alert to any signs that the individual has a hearing problem. Does the client ask that questions be repeated? Does the client seem to `miss' information when not looking at the counselor? Questions covering the client's work history should include noises in the work environment. Surely, these are minimum factors that all vocational rehabilitation counselors must be aware of when working with their clients. If the counselor's caseload has a high frequency of potentially hearing impaired clients, the vocational rehabilitation counselor should takes steps to involve an audiologist to be an active participant on the rehabilitation team. With this interaction, the vocational rehabilitation counselor and audiologist can become aware of the specific information each need so that the client can be most effectively served. Rehabilitation Counselors must be knowledgeable of the potential advantages of ALDs in relation to the various work environments, whereas, audiologists must acquaint themselves with specific factors related to needs in the work environment. With this type of team approach, clients who could benefit from ALD technology, in the work place, will not be `missed' during the vocational process.
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Holly S. Kaplan University of Georgia
Alice E. Holmes, Ph.D., Department of Communicative Disorders, Box 100174, University of Florida, Gainesville, FL 32610.
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|Author:||Kaplan, Holly S.|
|Publication:||The Journal of Rehabilitation|
|Date:||Jul 1, 2000|
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