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ASSISTIVE LISTENING DEVICES
Ruth Warick, Catherine Clark, Jesse Dancer, Stephen Sinclair 1At one time technology was viewed as dehumanizing and threatening.
For me it was the opposite. Technology opened up brave new worlds.
Through hearing aids and sound amplification devices I was able to
be part of the mainstream of society (Warick, 1994).
INTRODUCTION
New technology. For most hard of hearing students, and for some who are deaf, hearing aids and related sound amplification devices are of great benefit in their communication and learning. We are all familiar with hearing aids. If we don't wear a hearing aid ourselves, almost certainly we know others who do.
Technology has more recently produced an additional array of electronic devices which benefit many hard of hearing students. This report will deal primarily with the relatively new and growing family of such devices called auditory assistive listening devices or ALDs, i.e., auditory amplification devices.
ALDs are used in face-to-face or telephone communication as a form of providing accessibility for people who are hard of hearing. Parenthetically, it should be added that while hard of hearing people (and of course those with whom they engage in communication), are the principal users of ALDs, they are sometimes used also by people considered to be deaf.
ALDs are used both with and without hearing aids and are most effective when the individual has developed speechreading, listening, and other techniques that help supplement verbal learning. Also, their effectiveness is greatly enhanced when persons with whom they are communicating understand how to communicate effectively with a person with a hearing loss. One such classroom example is for the instructor and peers not to speak with their backs to the hard of hearing listener. Another is for only one person to speak at a time. These and other strategies often improve communication for everyone in the classroom (See Appendix -" Communication tips for instructors").
But while recent and ongoing developments in ALDs, and their broader
applications, have reduced barriers to communication for many hard
of hearing persons, they cannot reproduce the normal listening environment
for the hard of hearing person. Nor can they provide access in the
same way that glasses do for persons with visual differences.
DISTINCTION BETWEEN HEARING AIDS AND ASSISTIVE LISTENING DEVICES
Hearing aids. Hearing aids, the predecessor to ALDs, have been in existence for over a hundred years in one form or another, and have become increasingly sophisticated over the years. Unlike ALDs, hearing aids amplify sound through a single unit leading into the ear. There are different types of hearing aids such as behind-the-ear aids, in-the-ear aids and body aids.
Basically, a hearing aid system consists of a tiny microphone that picks up sound waves from the air and converts them into electrical signals, an amplifier that increases the strength of the electrical signals, a battery that provides electrical energy to operate the hearing aid, and a tiny loudspeaker called a receiver that converts the amplified signals back into sound waves and directs them into the ear through a specially fitted mold.
Most behind-the-ear and body aids have a "t-switch" that controls a telecoil which in turn picks up electromagnetic signals from a telephone or another listening device. This is reconverted into sound, magnified, and sent to the listener through his/her earmold. This offers enhanced sound quality and avoids picking up extraneous sounds. One disadvantage is that, besides blocking out erroneous sounds, it also blocks out the wearer's own voice. This problem can be solved by using a combined microphone/telecoil mode. If the student uses two hearing aids, he/she may choose to wear one in the customary microphone mode and the other in the telecoil mode. Alternatively, the student may be using only one hearing aid.
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