I. General
Assistive listening devices (ALD's) are auxiliary hearing devices
used for specific purposes to assist hearing impaired individuals. Examples
of these include amplified telephone receivers, amplified telephone ringers,
multi-sensory signaling devices, infrared television listeners, personal
FM systems and others. These devices come in a variety of styles to match
an individual's specific auditory needs.
II. Personal
FM Systems
Personal FM Systems (PFM's) are designed to provide hearing impaired
listeners the best possible signal-to-noise ratio in difficult listening
environments, such as classrooms, churches and theaters. These systems utilize
a frequency band specific to its transmitter and receiver combination to
provide clear, undistorted signals with minimal interference. These systems
come in a wide variety of styles and sizes to match virtually every situation
imaginable. The range of the transmitter is limited to a few hundred feet,
although that usually covers most listening situations. The signal can transmit
around corners and through walls, therefore care must be used when transmitting,
especially in the school environment. The system can be used with headphones,
earphones, or can be adapted into certain types of hearing aids, either
direct wired or wireless.
Fitting PFM's requires ascertation of a person's unique hearing
needs and desires. Cost of PFM's can range from a few hundred dollars to
several thousand, depending on the situation. The vast array of products
and components are endless, therefore consultation with your audiologist
is highly recommended.
III. Amplified
Telephones and Ringers
Amplified telephones are designed to improve a person's ability
to hear an incoming caller with decreased effort. This is accomplished in
a variety of ways. The easiest way to do this is to amplify all sounds,
i.e., a simple volume control. Another method amplifies all sounds, but
emphasizes more in the higher frequencies (pitch) which ultimately improves
speech understanding for many hearing impaired people with high frequency
hearing loss.
There are a number of different commercially available amplified
telephones. Most people can usually find something that satisfies his/her
needs. Although, if you cannot find a satisfactory fit, or wish to try a
more sophisticated frequency matched variety, you will want to consult with
your audiologist.
Amplified ringers may or may not be incorporated in the amplified
telephone, therefore auxiliary units are available. Auxiliary ringers help
to increase the volume of the audible ring, and/or change the frequency
(pitch) of the ring, thus making it more easily heard.
IV. Infrared Systems
Infrared assistive listening devices are designed to provide an
improved signal to noise ratio in difficult listening environments such
as theaters and or at home watching television.
These infrared systems utilize an infrared light transmitter and
headphone receiver to provide the clearest reproduction of sound in a wireless
system. They are very easy to install and use. The only limitations are
that the system is line of sight only, i.e., they do not transmit around
corners or through walls. They also have much less range than a typical
FM wireless system, and are not usually used in combination with hearing
aids. They are, however, simple to operate, universally fit and relatively
inexpensive when compared to FM systems.
Most private practice audiologists carry or can order these systems
V. Multi-sensory
Signaling Systems
Multi-sensory signaling systems are yet another category of Assistive
Listening Devices (ALD's). Once a person's hearing loss becomes severe enough
to not give them adequate benefit from increased amplification, then alternative
methods of signaling must be explored. Multi-sensory signaling systems allow
the severely hearing impaired to be aware of the telephone ringing, doorbells,
fire alarms and even babies crying in the nursery.
The application of wired and wireless technology with visual signaling
devices give a variety of alternatives for most every situation. Flashing
lamps, strobe lights, vibrating beds and pillows alert the severely hearing
impaired individual to a variety of different situations.
Multi-sensory systems are custom designed for each individual
and are usually available in audiology clinics. Some systems are relatively
easy to install while others require a handyman or electrician to wire it
into your existing home wiring. Most systems are easy to use with a little
counseling.
The types, styles and cost of the systems vary widely depending
on your specific situation. You may want to consult with your audiologist
to see which system is best for you.
VI. Classroom
Systems
Classroom ALD's can either be personal FM systems, or general room amplification
systems. Personal FM systems were discussed previously in Section II. Modified
or hybrid systems utilize the FM transmitter and a stand-alone speaker/receiver
combination, which can be situated near the hearing impaired child. This hybrid
system has been used to improve the signal (teacher's voice) to noise (background
classroom noise) ratio, without bringing attention to the child in need of
hearing assistance. In this way, the child is not singled out as the "deaf
kid". In fact, we have used this system in classrooms to help children
with central auditory processing disorders.
General amplification systems may be one of the most under-rated
methods to improve hearing and learning in the classroom setting. Many children
with fluctuating hearing losses go undetected and suffer from learning difficulties
due to poor classroom acoustics. This can be reduced by incorporating general
amplification systems, as well as consulting an architectural/acoustical
engineer to make physical changes to the room to improve classroom acoustics.
This type of modification is usually costly in existing classrooms, but
should not be overlooked in new construction. Audiologists are not usually
trained in this field of expertise, but should be able to put you in contact
with the right professional who can help.