Assistive Listening Systems for People with Hearing Impairments

What is an Assistive Listening System?

    Assistive Listening Systems (ALS) and/or Assistive Listening Devices (ALD) are any technology developed to enhance the abilities of a person who has a hearing impairment. These systems can be used with a television set, in small gatherings, in class or meeting rooms, and in venues like auditoriums and theatres.

What does it do?

    ALS's and ALD's amplify sound. Because these systems and devices frequently tap directly into the source of the sound by using a microphone clipped to the speaker or suspended above a stage they also appear to clarify sound by cutting down or eliminating ambient noise. But, primarily the job of the ALS or ALD is to make the sound louder and give volume control to the individual.

Who uses Assistive Listening Systems?

    America has an estimated 21 million people with hearing impairments. Of these, 19 million have some residual hearing that enables them to benefit from the use of assistive listening systems. 15 million people who can benefit from the use of an ALS do not use hearing aids and 4 million use hearing aids. *Source: The United States Architectural & Transportation Barriers Compliance Board, Data on Disability, National Health Interview Survey for 1983-1985.

Four Basic Systems:

Types of Headsets:

Types of Receivers:

How do Assistive Listening Systems Work?

    There are two primary modes of transmitting sound: via radio waves and via infrared waves. There are basically four types of systems which all include a microphone, a transmitter, receiver and headset. The mixer/amplifier and transmitter are frequently one unit.

    The hardwire system is a closed system, meaning the sound is never broadcast outside of the cables. This is the type of system used in airplanes where the headset is plugged directly into the jack at your seat. The induction loop system broadcasts via radio waves within an area encompassed by a big directional antenna which means to get amplification the individual must be seated within the area the antenna circles. The FM system operates just like a small radio station with pre-set frequencies, which the FCC has determined and restricted for use by assistive listening systems only. The infrared system is known as a "line of sight" system since the receiver must be in line of sight of the emitter since infrared waves will not go through a solid object.

Suppliers and Manufacturers:

    The following is a list of manufactures and/or suppliers who carry assistive listening systems that are used in facilities and venues like classrooms or theatres. This is not a comprehensive list nor does inclusion on this list imply any kind of an endorsement of the product.

    The best thing to do is call the manufacture or supplier and find a vendor in your area who can sell, install and help you maintain your equipment. Some manufactures will sell directly to the public and some will not.         (M=Manufacture, S=Supplier)

All Systems:

Am. Loop Systems Belmont, MA 627-267-0859 (S)
Audio Enhancement Riverton, UT 801-254-9263 (S)
Cardinal Sound Silver Spring, MD 301-589-3700 (S)
HARC Mercantile, Ltd. Kalamazoo, MI 800-445-9968 (S)
Hear You Are, Inc. Stanhope, NJ 201-347-7662 (S)
Phonic Ear, Inc. Petaluma, CA 415-383-4000 (M)
Potomac Technology Rockville, MD 800-433-2838 (S)

FM and Infrared Systems Only:

Sennheiser Electronic Corp. Old Lyme, CT 860-434-9190 (M)
Williams Sound Eden Prairie, MN 800-328-6190 (M)

Infrared Systems Only:

Audex Longview, TX 800-237-0716 (M)
Siemens Hearing Instruments Piscataway, NJ 908-321-4500 (M)

                                                
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