ASSISTIVE LISTENING DEVICES COMMONLY USED IN SCHOOLS
What are Assistive
Listening Devices (ALDs)?
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Transmit sound signals directly from a sound source to a
hearing impaired listener while bypassing most environmental
noises (Valente et al., 2000).
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Common components of all ALDs are a sound pick up (i.e. microphone),
a signal transfer method, and a receiver
(Valente et al. 2000).
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The signal pick-up is situated close to the sound source
(i.e. microphone placed on a teacher), while the receiver is worn by the
listener.
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Designed to be used in specific listening situations.
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ALDs differ in the signal transfer method.
FM Systems
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Frequency Modulating (FM) systems are wireless and transmit
the sound signal via FM waves in the air, similar to a radio.
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FM systems come in personal portable units for indoor and
outdoor use or as built-in units for educational/commercial use (i.e. classrooms)
(Valente, 2000).
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May be used with several students simultaneously (who need
different amounts of amplification) by utilizing several receivers.
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Personal systems may amplify up to 100 feet between the signal
and the receiver, and commercial systems amplify up to 1000 feet (Valente,2000).
Environmental Adaptations
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School bells and fire alarms are commonly adapted with flashing
lights to provide students a visual signal that alerts them when class
begins/ends or when evacuation is necessary.
Telephones have been adapted with the telecommunication devices
for the deaf (TDD), which is a keyboard with a small screen that holds
a phone receiver, and allows the hearing impaired individual to communicate
by typing and reading (Martin,1997).