Assistive Technology

Assistive Listening Devices

Thomas J. Brown
Whitfield County Schools, Georgia

Humans rely on five senses to provide them with input about their environment. Through the senses we learn and experience new things, and the more information we receive through our senses the greater our learning and understanding. Our sense of hearing is important to learning and is a crucial element in the development of speech and language development as well as social skills and academic achievement. Through the use of assistive listening devices those with hearing impairments are better able to communicate and enjoy an improved ease of hearing. Assistive listening devices help students to maximize their learning capabilities.

Many hearing impaired persons use hearing aids effectively in most situations, but hearing aids may be inadequate in classrooms, meetings, theatres, places of worship, or any other places where a large number of people gather. Hearing aids magnify all sounds; the voice of the speaker, teacher, or performer must compete with all the background noises, echo, and, distance factor. Assistive listening devices provide hard of hearing individuals with clear sound over long distances, or amidst distracting background noise, echoes, and poor acoustics.

Assistive listening systems transmit sound as directly as possible to the listener utilizing several different technologies. There are differences among specific assistive listening devices (ALDs), some listening devices are hardwired, such as a headphone set wired directly to a microphone and amplifier, while others utilize wireless radio transmitters or infrared waves and a small receiver unit. Though various types of ALDs may vary with the technologies used, they share some common features. ALDs can: "(a) amplify sound over considerable distance, (b) provide clear sound over distances by eliminating echoes and reducing surrounding noise, (c) overcome poor sound quality when a microphone/public address system is use, (d) amplify sound from several vantage points" (Warick, Clark, Dancer, and Sinclair, 1997). Examples of various types of ALDs include hardwire systems, FM systems, infrared systems, induction loop systems, one-to-one communicators, and others such as telephone amplifying devices.

Hardwire systems have served education since the 1930's. Consisting of a microphone connected to an amplifier, hardwire systems can provide amplified sound to one or more headphones. There are variations in design that may range from a small microphone attached by a wire to a Walkman style headset, to those, which resemble foreign language sound labs. Hardwire systems are easy to operate, inexpensive, durable, and produce high quality acoustics with little distortion.

Frequency modulated or FM systems include personal systems and systems which may be built in to a sound system, for example at a theatre or house of worship. Personal FM systems typically consist of a battery powered wireless transmitter and lapel microphone, which transmit the speaker's voice directly to a receiver worn by a hearing impaired person. From the receiver, sound is transmitted to the hearing aid via an induction neck-loop system or to direct audio input cables. Other types of personal systems include miniature receivers, which attach directly to the hearing aid called boot receivers.

ALDs are not limited to only individuals wearing hearing aids. Persons who may have only minor or moderate hearing loss can use headsets or earphones. There are also individuals who enjoy the benefits of improved concentration from the use of ALDs.

FM systems vary in transmission range, from thirty feet up to 1000 feet, depending on the transmitter power and antennae type. FM systems can transmit within buildings and are not affected by walls.

Another common assistive listening system is infrared. As with FM, infrared
systems utilize transmitters and receivers. Infrared systems as their name implies rely on the transmission of sound using infrared waves. Infrared light waves are a part of the light spectrum that is invisible to the eye, and are broadcast from an emitter unit. The same technology is used with television remote controls. The infrared signal is intercepted by a sensor located on the receiver unit and is converted into an electrical signal which is amplified and sent to the earpiece. Infrared systems vary in range from as little as twenty feet to 150 feet or more. A typical system costs about $1000.

Induction loop systems are typically utilized in large group areas. This type of
system requiring permanent installation consists of an induction wire that loops around the perimeter of a room or even perhaps an auditorium. The microphone converts the speakers voice into an electric current which creates an electromagnetic field in the loop circling the room. The listener picks up the signal through a telecoil in their hearing aid, which is converted into sound a transmitted into sound. Induction loop systems can be utilized by any one wearing a hearing aid, all that is required is changing a switch to the t mode. Loop systems compare favorably with FM and infrared with regard to cost, averaging about $1000.

It is no surprise that language development, speech development, social skills, and
academic achievement depend greatly upon a person's ability to hear. Using assistive listening devices can help the hearing impaired improve their ability to communicate and help to maximize their full learning potential.

Web addresses of companies providing amplification devices. (This is not by any means a complete comprehensive list, nor is it an endorsement):

Warick, R., Clark, C., Dancer, J., & Sinclair, S. (1997) Assistive Listening Devices: A report of the National Task Force in Quality of Services in the Post Secondary Education of Deaf and Hard of Hearing Students. Rochester, N.Y. Northeast Technical Assistance Center, Rochester Institute of Technology. [Online] Available: http://www.netac.rit.edu/publication/taskforce/device1.html

What are assistive listening devices or “ALDS”? American Speech, Language, and Hearing Association. Assistive Technology. [Online] Available: http://www.ashs.org/hearing/rehab/assist_tech.cfm