Welcome to General Technologies' Assistive Devices Customer Information
FM Devices or IR Systems, Which Is Clearer?
Every so often I hear someone praising the sound clarity of a wireless FM, or more
often, an Infrared (IR) device and recommending it to friends based upon whether
the one they like is FM or IR.
Let me set the record straight: Whether it's an IR device, or an FM device, the
method of transmission (IR, FM) has almost NOTHING to do with the clarity of the
sound you hear. So don't choose a device based on whether it's FM or IR. It's the
quality of the receiver that counts.
BTW, the same goes for an Audio Induction Loop system which allows you to pick up
the sound by simply switching on your T-switch. The "Receiver" in this case is the
T-coil in the hearing aid. If you have an inefficient T-coil, and/or poorly tuned
hearing aid, this system will have poor quality.
A while back I wrote an article about this and have reproduced it below:
IMPORTANT WORD ABOUT HEARING WITH WIRELESS SYSTEMS -- J.W. Marin
GET THIS: Transmitters (the device that has the microphone) have almost NOTHING
to do with how well you understand what you're listening to, so don't worry about
what transmitter comes with an ALD system. Transmitters have more to do with how
FAR you can listen and still pick up the signal. However, it's important to decrease
background noise -- increasing signal-to-noise ratio (SNR) -- by getting the transmitter
microphone near the source of sound, or plugging the transmitter directly into the
sound source (TV, VCR, public address system amplifier, your mother-in-law, etc.).
Quality and design, however, have almost EVERYTHING to do with how well you can
understand. Receivers are the devices with earphones or headphones that you listen
with. Hard-Of-Hearing (HOH) people need more SNR (signal-to-noise ratio --or--
speech-to-noise ratio) to be able to understand. This is primarily accomplished
in two important ways:· (1) By having a receiver that increases the higher frequencies
(signal) and (2) also inhibits the lower frequencies (noise). Thus this type of
receiver also increases the all-important SNR.
Why does this type of receiver increase your understanding? Ninety five percent
of HOH people have a high frequency loss. The high frequencies, which are the consonants
in speech, are also the low power elements of speech. Vowels are higher power, lower
frequency elements. So we tend to hear the vowels but miss the consonants. Let's
suppose that you write a word on the blackboard. Then erase the consonants, leaving
just the letters A, E, I, O, or U. What are your chances of understanding what is
written? Slim to none. This is why a receiver with excellent high frequency amplification
that can pick up the consonants is vital to understanding.
So, do all ALD (assistive listening device) receivers have a great high frequency
boost? Mostly NOT! Why? I don't know. I can only guess that most, if not all, design
engineers have normal hearing and must not realize the extent to which HOH people
need the high frequency boost -- as much as 15dB SNR (5.6 to 1) or more in noisy
situations. This means that the speech sound must be 5.6 times higher than the
background noise level. But, if a person with normal hearing listens to a receiver
with significant high frequency boost, it may sound tinny or scratchy to them. But
not to HOH people! Don't they test these out on HOH persons?
Here's A New IR System TV Watcher We Found With The Excellent High Frequency Response
We Have Been Discussing:
Of all the high-end devices we've tested, the best tone control/high frequency response
we found is in this 8008 system. Equal to or better than $$ Sennheiser or TV Ears
at 1/3 the price.
** Weighs Less Than 2 Oz. You will appreciate this if listening for over an hour)
** 12 Hours Listening On A Single Charge
** Comfortable In The Ear Design
** Automatic Volume Control Prevents Sudden Increases In Sound
** Many Other Technical Advantages Found In High-End Devices