The
human ear does not just make sounds louder but it also processes the sound
information before transmitting it to the brain. Some hearing
losses only involve the loudness of sound. These are called a
"Conductive Loss". A hearing aid will be expected to
greatly benefit these patients. However, many of the conductive
losses can also be treated with medications or surgery.
As
we grow older, "nerve" or
inner ear
hearing losses become more
common and often involve the processing of sound. Hearing aids
will help these losses but rarely restores the hearing to a normal
condition.
Luckily, hearing aids have come a long way
in the last decade. Improved filters and circuits have resulted in
greater benefit to patients and improved patient usage. The new
digital hearing aids closely match the patient's hearing loss and
provides even greater help in the understanding of sounds.
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The cost of a hearing aid may
easily be over $1000. This does not include batteries to operate the
aid. The smaller the aid the higher the cost and also the higher the
battery cost. In general, small aids take smaller batteries which may
have a shorter life and cost about the same as the batteries for the
larger hearing aids. A cheaper alternative which may work for some
patients is a RadioShack Amplified Stereo Listener. These units cost
between $30 to $40 (price check June 2008) not including headphones. The
$40 unit has a three band equalizer. -- See Product.
All hearing aids, including digital hearing aids, are made up of a
microphone, a receiver, and an amplifier. The arrangement of these
components and type of components determine how you hear with a hearing aid.
The least complex amplifier is a fixed analog signal processor. The
sound is taken in through the microphone and amplified by the signal
processor. The signal processor determines how much the sound is
amplified, the slope the sounds are amplified, and the overall output of the
hearing aid. The amplified signal is converted to sound. The
amplified sound can be modified and noise eliminated using low cut and high cut-off
filters. This is
possible with fixed analog filters and amplifiers to help better shape the sound to better
fit your hearing loss. However, these are difficult to add to the small
completely-in-the-canal analogue hearing aids and the shaping of the sound will not
completely match the pattern of the hearing loss.
The next technological step is a programmable analog signal processor.
This amplifier works in much the same way as the fixed amplifier. However it can be
shaped and tuned via a computer connection which makes it possible to adjust
even the smallest of hearing aids. Typically there are controls to adjust
high cut, low cut, gain, output, and compression. These are
far superior hearing aids to the hearing aids of 10 years ago.
The newest technological advancement in hearing aids is programmable digital
signal processors. These digital hearing aids, features patented
algorithms based on new, advanced understanding of human hearing that delivers a
more natural, lifelike listening and communication experience. Unlike the
programmable analog signal processor, the programmable digital signal processor
is a tiny microprocessor (computer) that receives the sound from the microphone
and shapes it with a computer, then delivers the sound from the receiver into the
ear. The sound is much more natural in quality. These hearing aids
can be made in any style and without a
doubt the most adjustable on the market today.
There are different levels of digital hearing aids available with the most
advanced offering features such as feedback management, multi-channel expansion,
adaptive noise management and wide dynamic range compression.
Hearing aids come in many different styles and models. The four
physical style of hearing aids are BTE (behind-the-ear), ITE (in-the-ear), ITC
(in-the-canal), and CIC (completely-in-the-canal). Generally speaking, the
smaller the hearing aid the more expensive it will be. The BTE and ITE are
usually the least expensive with the ITC and CIC hearing aids more expensive.
The smaller the hearing aid the more
difficult it is to change the battery and adjust settings. For
example there is not manual volume control on Completely-In-The-Ear
hearing aids. In addition, the smaller the aid the further it
fits into the ear and the more susceptible it is to damage from ear wax and
ear drainage.
All types are available in analog, programmable and digital
models. It is very hard to tell which one will best suit the
patient. The following antidote is a true story which illustrates
the variety of patient preferences.
A prominent businessman in my town
brought his elderly mother to see me. The different types of
hearing aids were explained to them and he summed up the
presentation with stating: "The smaller CIC hearing aids seem to
work about the same but cost more." He then stated:
"We will get the behind-the-ear aid. This makes the most
sense." His mother even with her reduced hearing heard
his comments. She immediately interrupted. "Oh no, I
want the small one. I do not want anyone to see that I am
wearing a hearing aid." The businessman sensed his
mother's desire not to be seen wearing a hearing aid and
begrudgingly purchased
the most expensive hearing aid - a completely-in-the-canal model.
On the follow-up visit to see how
his mother was doing with the hearing aid, he was asked how his
mother liked the almost invisible hearing aid. He replied, fit
to be tied: "She loves it. The first thing she did was wear it
to church, then take it out of her ear and show everyone how small
her hearing aid was."
The BTE hearing aids are pre-made, not
custom made, this is one reason for the lower cost. They are used
by children and persons with severe to profound hearing losses.
They connect to an ear mold which fits in the ear. Because of the
rate a child's ears grow they are more economical than custom shelled
hearing aids because only the ear mold needs to be replaced
Key Benefits
Most powerful of the
hearing aid styles for severe to
profound losses
Good for children because
ear molds can be changed more
economically than the hearing aid shells
Can more easily be used
with auditory trainer or loop
system
Although the hearing aid
mold can become plugged with ear wax and drainage, the
hearing aid is away from the ear canal and is protected.
The ITE hearing aids are the largest of the custom made hearing
aids. They can be fit in a wide range of patients, from mild to
severe hearing losses. Because of the size they are much easier
to build than the smaller custom hearing aids.
Key Benefits
Inexpensive
Microphone closer to ear level than BTE
Can fit a wide range of patients
Key Disadvantages
Is susceptible to damage by ear wax
and ear drainage.
The ITC hearing aids are the next smallest custom made hearing
aids. They are visible, however smaller than the ITE hearing
aids. They are more difficult to build because they are smaller
and the placement of the electronics takes more time.
Key Benefits
Microphone is even closer to ear level than BTE and ITE
More cosmetically appealing
Fits hearing losses in the mild to moderate range
Key Disadvantages
Tend to be expensive
Changing the battery can be
difficult since battery and battery compartment is small
Is susceptible to damage by ear wax
and ear drainage.
CIC hearing aids have many benefits besides being discrete.
They are the smallest of the custom made hearing aids. The
electronics in the CIC hearing aids are miniaturized to the smallest
possible size and carefully placed by hand in the tiny shell.
They are much more difficult to make than the other custom made
hearing aids.
These hearing aids are best
for adult patients with a large ear canal and mild to moderate
hearing loss.
Completely-in-the-canal hearing aids have a number of potential
benefits that are unique to them (Mueller and Ebinger, Seminars in Hearing
17:1, Feb 1996).
Key Benefits
Increased Gain
Increased Output
Reduced Distortion
Reduction of the Occlusion Effect
Reduction of Acoustic Feedback
Ease of Removal
Comfort
Security of Fit
Telephone Use
Listening with Headsets
No VC Wheel
Improved Localization
Reduced Wind Noise
Cosmetic Appeal
Key Disadvantages
Tend to be the most expensive
Changing the battery can be
difficult since battery and battery compartment is small
Usually, does not have a manual
volume control, often this is a small screw which requires a small
screwdriver to adjust.
Of all the hearing aid types, is
most susceptible to damage by ear wax and ear drainage.
