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FM Assistive
Listening Systems
What is FM?
FM stands for "frequency modulation" and is a common form of radio transmission.
FM is one of several wireless technologies that transmit sounds directly to a
hard of hearing person for optimal clarity and better understanding.
What's the benefit to you?
FM provides improved listening
clarity for people with hearing loss who experience difficulty and fatigue, when
trying to understand speech, because of distance, reverberation, and distracting background
noise.
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Reduced distracting background noise
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Reduced reverberation and sound distortion
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Reduced listening fatigue
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Improved voice clarity and understanding
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Improved hearing at a distance from the speaker
How
does FM technology reduce background noise and make listening easier?
The FM transmitter's
microphone picks up a speaker's words within inches of their mouth.
Consequently, the
sound that the listener hears (via their personal receiver) is in its optimal
state: free from attenuation (natural volume decay over distance), reverberation
and distortion, and (if unidirectional, noise canceling microphones are used)
background noise. The listener's headphones may also help to partially block
additional background noise surrounding the listener. If the hearing aid’s
“T” program (telecoil) is selected, to listen via an inductive device such as a
neck loop or inductive ear hooks (instead of headphones), then the hearing aid’s
external microphone is automatically disabled; eliminating annoying "feedback"
and greatly reducing distracting background noise.
These beneficial strategies provide the listener with a much clearer signal
from the sound source. This process is referred to as, improving the ‘speech
to noise ratio’ (SpNR) or 'signal to noise ratio' (SNR). Improving
the SpNR is the most beneficial strategy available for improving speech
comprehension for hard of hearing people.
Why use
a portable FM assistive listening system?
The greatest advantage of a portable FM assistive listening system is that it
is easy to set up and puts the user in complete control.
For instance, the COMTEK AT-216 FM Assistive Listening System comes in a very
practical carry case. The system is portable and completely self-contained. The owner of the
system has total control, and is not dependent on anyone
for maintenance or hygiene issues. The system is battery powered and can
be taken
anywhere. The user simply gives the wireless transmitter to any presenter,
teacher, work associate or friend who they wish to hear. The system is also
extremely versatile and can be used to listen to other sound sources such as TV
or audio from a facility's soundboard. You can even simultaneously monitor and
record presentations for later
review.
Having autonomy over a system that allows better hearing and
understanding, and being able to use it where and when you need it is extremely important to hard of
hearing individuals. Attempting to hear in many challenging sound environments,
without such technology, can lead to frustration, fatigue and withdrawal from
participation.
What are some advantages of
Large Area FM Assistive Listening Systems?
FM
is easy to set up and can be used in many environments.
From a business perspective, businesses can install Large Area FM
assistive listening systems very easily without disturbing
furnishings or the building structure. The most that might be required
would be the mounting of an external aerial but often the transmitter's
built-in aerial will provide sufficient range. FM systems provide
compliance with ADA accessibility requirements. If more than one systems
is needed in adjacent rooms, an additional system can be installed using a
separate FM frequency without interference.
From a user perspective, using wireless microphones that transmit
to a personal receiver is the most effective method for improving the
Speech to Noise Ratio for the hard of hearing listener and increasing
their ability to comprehend what is said.
FM Assistive Listening Systems use a dedicated frequency
range. The FCC, in the United States, has
assigned two separate FM frequency ranges for assistive listening systems.
This is important in order to minimize issues related to interference from
other radio users. The established 72-76 MHz range is somewhat prone to
intermittent interference from emergency vehicles etc. The newer 216-217
MHz range is assigned exclusively for low power assistive listening
systems and offers greater immunity from interference.
How do
FM Assistive Listening Systems work?
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Audio input from a microphone, TV, audio player or any electronic sound source
feeds into an FM transmitter.
The use of high quality, unidirectional, noise canceling microphones can
greatly improve the clarity of the sound source: microphone placement is also
important.
The transmitter may be permanently installed as in a church or theatre, or the
transmitter may be portable. Portable transmitters may be a hand held
microphone or a small body pack unit, worn on a belt clip, by a teacher
or presenter.
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The FM radio frequency signal is picked up by the user's FM receiver.
The FM receiver may be a small body pack unit worn on a belt-clip such as the
COMTEK PR-216, or it may even be a miniature component built-in to or attached
to a hearing aid. Each user requires a compatible FM receiver that is usually
maintained and supplied by the venue.
Do FM users still need T-Coil?
Yes and no - but probably yes...
Getting the received sound to your hearing aid isn't quite as simple as we might
hope. Those last few inches from a belt-clip worn receiver to your ear-level
hearing aid present several challenges.
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The
most logical solution is to have the receiver be a component of your
hearing aid. Phonak has been a leader in FM receiver and hearing aid integration. Until
recently, hearing aid FM receivers had to be attached to a special boot/shoe on
the base of the BTE hearing aid. The boot/shoe provided an adapter or interface
to the direct audio input (DAI) terminals on the base of the BTE hearing aid.
Unfortunately, this configuration, of three components instead of one,
contributed to
fragility of connections and increased size of the BTE hearing aid. As hearing
aid components have become smaller, Phonak has been working to integrate the FM
receiver into the hearing aid and eliminate the need for a boot/shoe.
Practical issues associated with this solution, related to miniaturization
and integration, include: increased cost, increased power requirements, sound quality, FM frequency
selection etc. Although this technology is often used in specialized
environments, such as school classrooms for hearing impaired children, it has not
been a widely available or viable solution for the majority of hearing aid users.
Phonak BTE hearing aid FM receivers
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The
most obvious solution is to use headphones. However, headphones have
their own set of issues. Some hearing aid users may experience hearing aid
feedback when wearing headphones. In public facilities, there maybe concerns
related to hygiene issues of shared headphones and the replacement of headphone
cushions. Systems that use ear buds or stethoscope style headphones require the
removal of the user's custom programmed hearing aids; a solution which is both
counter productive and unacceptable. Also, believe it or not, hard of hearing people may be reluctant to
wear headphones that advertise their disability to all. How successful is a system that people feel uncomfortable about and
are reluctant to use?
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The
best solution might be to use direct audio input wires. Best, because
this offers a direct connection from the receiver to the hearing aid that is not
subject to electromagnetic interference or background noise. However, this would
involve using delicate connector wires and would only be helpful to a small percentage of BTE hearing aid users whose hearing
aids are fitted with DAI capability.
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And that brings us back to T-coil. If a neck loop or inductive ear
hooks are plugged into the FM receiver, the user can switch their hearing aid to
the "T" program, cut out background noise and listen to the audio transmission
without having to wear headphones or be annoyed by feedback.
Where
are FM Assistive Listening Systems used?
Anywhere!
Large public facilities like churches, concert halls and
meeting rooms are ideal places for Large Area Assistive Listening Systems.
Hard of hearing people can easily
take the portable AT-216 assistive listening system with them to
presentations, lectures, meetings and social gatherings. Because it is
completely battery powered, it can be used anywhere, indoors or outside.
Can non-Hearing Impaired people benefit from FM Assistive Listening Systems?
Yes, and they do! Think of tour guides, interactive exhibitions, factory tours,
language translation etc. All a non-hearing impaired person needs, is a receiver
and a set of headphones or ear buds. Non-hearing impaired users are often
impressed by how much easier it is to hear clearly in many sound environments
with a greatly improved speech to noise ratio. Non-hearing impaired users will share
the benefits of reduced background noise, reverberation, sound distortion
and listening fatigue plus improved clarity and ease of listening at a distance.
Are there
FM Assistive Listening Systems for personal use?
Yes,
personal assistive listening devices (ALDs),
utilizing FM technology, available from TecEar include:
The COMTEK AT-216 FM Assistive Listening System comes in a very
practical carry case. The system is completely self-contained. The owner of the
system has total control, and is not dependent on anyone
for maintenance or hygiene issues. The system is completely battery powered and can
be taken
anywhere. The user simply gives the wireless transmitter to any presenter,
teacher, work associate or friend who they wish to hear. The system is also
extremely versatile and can be used to listen to other sound sources such as TV
or audio from a facility's soundboard. You can even simultaneously monitor and
record presentations for later
review.
Having autonomy over a system that allows better hearing and
understanding, and being able to use it where and when you need it is extremely important to hard of
hearing individuals. Attempting to hear in many challenging sound environments,
without such technology, can lead to frustration, fatigue and withdrawal from
participation.
Are the two FCC FM frequency ranges 72-76 MHz and 216-217 MHz compatible?
The unfortunate answer is no.
Some FM assistive listening system manufacturers are slowly phasing out the
older 72-76 MHz range in favor of the newer 216-217MHz frequency range. The
newer 216-217 MHz dedicated frequency range should be less prone to interference
issues than the older range which is shared by other users such as emergency
vehicles.
However, many facilities still use the 72-76 MHz frequency range and
manufacturers supply equipment to support these installations.
Hearing aid manufacturers that integrate receivers into BTE hearing aids, such
as Phonak, utilize the newer 216-217 MHz frequency range. COMTEK's use of the
newer 216-217 MHz range offers full compatibility with hearing aid
manufacturers' FM receivers.
COMTEK Assistive
Listening Frequency Chart
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