Assistive listening
devices (ALDs) are devices designed to enhance the ability
of hard of hearing people to hear speech or enjoy listening
to music. Some ALDs allow the hard of hearing individual to
increase the volume, thus allowing them to understand a quiet
speaker without straining to hear. ALDs are used in various
settings, including churches, theaters, classrooms, lecture
halls, meeting rooms, restaurants and in cars.
Assistive listening devices can bring clear sound directly
to a person’s ears by way of a headset, single or dual
ear-buds, neckloop, silhouette, DAI or a hearing aid equipped
with a telecoil switch. The use of ALDs reduces the degradation
and distortion of the desired sounds due to reverberation
or echo, background noise, poor room acoustics and other factors.
The importance of a clear signal pathway cannot be under-estimated
for hard of hearing individuals trying to comprehend information
or listen to music in a noisy environment. Examples of noise
sources are: background conversations, background noise from
a TV or radio, office equipment, heating, ventilation, air
conditioning, road traffic and many others. The four main
type of ALDs are: Acoustic, FM, Induction Loop and Infrared.
Acoustic ALDs pick up sound using a microphone and amplify
the sound to the ear. For example a hearing aid functions
by amplifying sounds it picks up and transmits the signal
to the ear. A Public Address system is another form where
various sized speakers are used to transmit the sound to the
audience. Depending on the sound system used, there may or
may not be distortion.
FM Systems
FM Systems involve the use of a single transmitter and one
or more receivers all of which must be tuned or switched to
the same FM channel. FMs operate by using dedicated FM radio
waves to transmit the signal using a microphone to the receiver.
The signal input can be either a microphone or audio feed.
The hard of hearing individual clips on a cigarette pack sized
receiver and selects the earpiece that best meets their needs.
Several microphone options are available to allow one speaker
or multiple speakers. Individual personal FM systems range
from $700 to $2000. They are commonly used in situations where
movement of the speaker is required, such meetings.
Induction Loops
Induction Loop ALDs use electromagnetic technology to transmit
a signal from the transmitter to the receiver. The magnetic
field is generated by looping a wire around a room attaching
it to an amplifier. This can be portable for transportation
from place to place or permanently installed depending on
use. The signal input can be either a microphone or an audio
feed. A user with a hearing aid equipped with a telecoil sits
within the loop and adjusts the setting on their hearing aid
to telecoil. They then begin to receive signals from the transmitter
and microphone. A user who does not wear hearing aids or does
not have a hearing aid equipped with a telecoil clips a cigarette
pack sized receiver at the waist and selects the earpiece
that best meets their needs. Multiple microphones can be added
to this system with some restrictions. Frequently used in
conference rooms, churches or classrooms.
Infrared Systems
Infrared ALDs use invisible infrared light to carry the sound
from the source to a receiver and are commonly used in courtrooms
or movie theatres because the signals stays contained within
the room. The signal input can be either a microphone or audio
feed. Infrareds use a single transmitter and one or more receivers
all of which must be on the same channel. In some cases, choices
of earpieces may be limited. An individual’s personal
infrared system may work in public places as long as the system
is on the same frequency. Individual units are inexpensive
and frequently used in the home to listen to the TV or stereo.
Corded ALDs
Corded ALDs are inexpensive systems that are ideal for one
on one communications with a doctor, bank teller, listening
to the TV or radio or when talking to family members. They
are not ideal for classrooms, churches, or large meetings,
but can still be used. Some systems may be coupled with a
telephone adapter for telephone amplification in or outside
of the home. Corded ALDs are usually purchased by those who
are considering amplification for the first time, as they
are very affordable. These devices can be used with a headset,
earbuds, neckloop or silhouette, depending on the individual’s
needs and preferences. Examples of Corded ALDs are PocketalkerPro,
SounDirector or the Sound Wizard. |
