The critical variable is whether you experience difficulty hearing or are
having increased stress and strain in your daily function. Amplification may
simply relieve the strain of hearing, as opposed to making sounds louder or even
improving your understanding of speech. However, this alone can be a very
significant benefit. You must ask yourself whether you find you are becoming
stressed or fatigued after a day of straining to listen. Ask yourself whether
the ability to hear, but not understand, is adequate for your needs. Unselfishly
examine whether you are becoming a burden to your family and friends, even if
you do not personally recognize difficulty hearing. Remember that wearing a
hearing aid is not necessarily a mark of infirmary, rather it is a mark of
courtesy to others. Thus, sometimes it is advisable to arrange to try hearing
aids within your own unique environments to determine whether the benefit
warrants the expense.

There are four main reasons why binaural (two eared) listening is superior to
monaural (one eared) listening. They are:

1. 
   

   Better Hearing in Noise: An individual's hearing in noise can be improved
   if the signal reaching each ear arrives at a slightly different moment in
   time. This is technically referred to as phase. When the brain receives
   slightly different, yet still audible signals at the two ears, it has the
   ability to cross-correlate and process the primary signal (usually speech)
   better than if the signal is received monaurally.

   
   
2. 
   

   Improved Signal versus Noise Level from Optimizing Position: Sound loses
   intensity (loudness) when it travels across the head. This occurs mostly for
   the high frequencies which are the most important for understanding of
   consonants, such as /s/, /t/, /f/, and /sh/. If you have a hearing aid on
   only one ear, say the left one; and the person you wish to hear is speaking
   to you from the right side, the consonants may be decreased by nearly 20
   decibels by the time it gets to your aided ear. Unfortunately, noise in the
   room may occur from any or all directions, so while the noise level is not
   decreased, the speech level is. Wearing two hearing aids ensures that the
   speech sounds will not be diminished any more than necessary because of your
   position in the room.

   
   
3. 
   

   Improved Localization Ability: We determine where a sound is coming from
   on the basis of 1) the relative time in which the sound arrives at each ear,
   2) the relative difference in loudness at the two ears, and 3) the relative
   difference in the pitch of the sound at the two ears. When there is a large
   difference in hearing between two ears (as might occur when a person with
   similar hearing in both ears only wears one hearing aid) the brain cannot
   make use of these subtle relative differences and their ability to locate
   sounds may suffer.

   
   
4. 
   

   Possible Deterioration of the Unaided Ear: We hear in our brain, not in
   our ears. The ultimate goal of hearing aids is not just to send sound into
   the ear. It is also essential to retrain the central auditory system in the
   brain. While it is uncertain whether hearing sensitivity (ability to hear
   soft sounds) will decrease if your ear is not stimulated adequately,
   research now suggests that there can be changes in the way in which your
   brain processes sound when it is "starved." Thus, providing
   stimulation may be important in preserving your auditory potential.

   
   

Some hearing aid users report that they feel as if they are in a barrel or
experiencing an echo when talking. This is called "the occlusion
effect." Normally, when your ear is unblocked and you are speaking, you
hear yourself both through the air traveling through your ear canal, (air
conduction) and through vibrations that you create in your skull and ear canal
(bone conduction). When your ear is occluded or blocked, however, air conduction
transmission is reduced and bone conduction perception enhanced. Try this
experiment. Hum aloud and then alternately plug and unplug one ear while
humming. Notice how the sound changes pitch and loudness in your plugged ear?
This happens because the vibrations are blocked from their usual escape route.
Most new users adapt to this effect and it isn't a problem. However for some,
the following steps might help:

1. 
   

   keeping the ear as open as possible.

   
   
2. 
   

   reducing the amount of gain (amplified volume) in the low frequencies.

   
   
3. 
   

   using an earmold that fits very deeply into the ear canal so that it
   contacts with the bony rather than the soft cartilaginous portion (to reduce
   vibration).

   
   

There are two types of acoustic feedback: that produced internally from the
hearing aid - indicating a device in need of repair; and the more common
external feedback produced by a leakage of amplified sound out of the ear canal
and back into the microphone of the hearing aid. Feedback that occurs when the
hearing aid is being inserted or removed or when your hand is cupped near the
device is common, and does not necessarily signal the need for action. If
however, you experience feedback when you speak, chew, yawn or change position,
you need to consult your audiologist. Feedback is more likely to occur in
smaller hearing devices because the microphone is closer to the area at which
the sound comes out into the ear. So, a behind-the-ear style may be less likely
to produce feedback than in in-the-canal style device. Usually, external
feedback can be corrected by:

1. 
   

   properly reinserting the hearing aid or earmold

   
   
2. 
   

   remaking the earmold (or in-the-ear shell)

   
   
3. 
   

   plugging, or reducing the diameter of any vents (holes)

   
   
4. 
   

   reducing the amount of high frequency gain, (typically an unacceptable
   trade-off because of the resultant loss of high frequency hearing)

   
   
5. 
   

   altering the sound by means of filters in the hearing aids or changes in
   the way the devices are programmed

   
   
6. 
   

   adding a "canal lock" (a piece of plastic) to better hold canal
   hearing aids in place so they don't work their way out of the ear canal as
   you chew

   
   

Recently some manufacturers have introduced digital feedback reduction. With
this technology, feedback is sensed by the hearing aid and canceled by means of
a new signal generated by the hearing aid itself.

Some of the characteristics of the sound produced by hearing aids can be
modified using computers or other devices. Hearing aids that have this
capability are called "digitally programmable."

They have several advantages over non-programmable instruments.

1. 
   

   Flexibility: changes in hearing can easily be accommodated, as can
   unusually shaped and fluctuating hearing losses.

   
   
2. 
   

   Multiple Programs: It is often useful to be able to change the hearing
   aid characteristics depending on the environment one encounters. With these
   hearing aids, you can change program with the touch of a button or a remote
   control.

   
   
3. 
   

   Advanced Compression Circuitry: Most hearing impaired people suffer from
   an abnormally rapid growth in loudness perception. This is why some hearing
   aid users complain that they can't hear soft sounds, but when sounds are
   made just a little louder, they are much too loud for comfort. Therefore,
   hearing aids are designed so that they will amplify soft sounds more than
   they will amplify loud sounds. This is called compression. Compression works
   almost like an invisible finger reaching up and changing the volume control
   so that soft sounds are made loud enough to hear and loud sounds are turned
   down so that they don't become uncomfortable.

   
   

Now that audiologists have a better understanding of the importance of
providing adequate gain without exceeding the physical saturation limit of the
aid and the individual's loudness discomfort level at each frequency, the
accurate measurement of these features have become an essential part of the
fitting process. As a result of these enhanced procedures, it has become
abundantly clear that significant differences exist not only among individuals
with nearly identical audiograms, but also among the loudness growth of specific
frequencies for a given individual. In other words, a patient can demonstrate
loudness tolerance problems for certain frequencies, but not for others.
Therefore, the electroacoustic characteristics programmed into the hearing aid
should differ for the various frequencies. Through the use of multiple
compression channels (some systems have two, some have three) a completely
unique set of signal processing instructions can be utilized. As such, a certain
acoustic environment can trigger a response which, for example, produces
additional high frequency boost while simultaneously reducing low frequency
gain.

In addition, hearing aids containing single channel compression unfairly
penalize certain sounds. For example, if a low frequency noise exceeds a certain
level, compression (a reduction in gain) will occur for ALL frequencies, not
just the offending ones. With multi-band compression, the reduction in gain is
limited to those frequencies containing the offending signal. This may be the
most important advantage of all.

Most of the time, listeners are facing the person they are speaking to.
Noise, however, is often located in front of, behind, and/or to the sides of the
listener. Some hearing aids now contain directional or multiple microphones
which "communicate" with each other in a manner such that sounds
originating from the front of the hearing aid receive maximum amplification and
sounds originating to the sides or behind the hearing aid receive considerably
less amplification. This effectively suppresses some of the annoying background
noise that creates so much difficulty for hearing impaired listeners. The
technology using these types of microphone arrangements is very promising. They
can be found in several different hearing aids but are generally limited to
behind-the-ear or full shell in-the-ear hearing aids due to size restrictions.

The future of hearing aid technology has arrived! Advancements in the ability
to manufacture hearing aids that process sound digitally offer the potential for
dramatic improvements over previously available instruments. Hearing aid
researchers have been investigating the use of true digital technology for over
a decade but were held back because the increased power consumption needed to
operate such instruments required the instruments to either be very large, or to
be connected to a separate power source worn on the body. As a compromise,
digitally programmable hearing aids were introduced on the market about six
years ago. These devices represented an improvement over previous technology in
that they were extremely flexible, could be fine-tuned, and had advanced
compression (loudness limiting) capabilities. They were still somewhat limited,
however, because even though they were programmed by a computer (the digital
portion) they still operated in an analog fashion. This meant that sound
entering the hearing aid microphone would be amplified and filtered by a variety
of electronic components. Because hearing is such a complex sense, the extent of
filtering and amplifying required to partially correct an impairment added to
the limitations of the hearing instrument by producing distortion and noise.

Digitization means that incoming sounds are converted to numbers, which are
then analyzed and manipulated via a set of rules (algorithms) programmed into
the chip controlling the hearing aid. There are now nearly a dozen digital
hearing devices available. Some of these digital aids analyze incoming sound,
make a determination regarding speech versus noise content, then convert this
information to numbers. The resultant digitized numbers are then manipulated
according to algorithm instructions, reconverted to an analog form (sound waves)
and delivered to the ears without producing the types of distortion that were
often associated with analog technology hearing aids.

Among the most frequent complaints voiced by hearing aid users are that noise
is amplified too much and that certain sounds become too loud for the user to
bear. Some modern hearing aids contain sensors that allow the hearing aid to
detect sounds exceeding a certain loudness level, and then self-adjust to reduce
the amplification (gain) for those sounds. Unfortunately, because noise is
comprised of many of the same frequencies as speech, it is virtually impossible
to "shut out" noise without also adversely affecting the quality of
the speech signal. The good news is that audiologists have learned to utilize
modern technology to measure and control the maximum sound intensity reaching
your ear. If sounds (speech or noise) exceed either the saturation level
(maximum level the hearing aid can amplify without distortion) or your personal
loudness discomfort level, distortion or discomfort will be the result. Modern
hearing aids utilize technology that allows for adequate gain for soft sounds
while minimally (or not at all) amplifying loud input signals. Concerning
background noise, new techniques using multiple microphones within the same
hearing aid aids are improving the listener's ability to function in noisy
environments. With regard to clarity, even the most sophisticated hearing aids'
ability to clarify speech is limited by the degree of inner ear and/or central
auditory nervous system distortion.

Among the most frequent complaints voiced by hearing aid users are that noise
is amplified too much and that certain sounds become too loud for the user to
bear. Some modern hearing aids contain sensors that allow the hearing aid to
detect sounds exceeding a certain loudness level, and then self-adjust to reduce
the amplification (gain) for those sounds. Unfortunately, because noise is
comprised of many of the same frequencies as speech, it is virtually impossible
to "shut out" noise without also adversely affecting the quality of
the speech signal. The good news is that audiologists have learned to utilize
modern technology to measure and control the maximum sound intensity reaching
your ear. If sounds (speech or noise) exceed either the saturation level
(maximum level the hearing aid can amplify without distortion) or your personal
loudness discomfort level, distortion or discomfort will be the result. Modern
hearing aids utilize technology that allows for adequate gain for soft sounds
while minimally (or not at all) amplifying loud input signals. Concerning
background noise, new techniques using multiple microphones within the same
hearing aid aids are improving the listener's ability to function in noisy
environments. With regard to clarity, even the most sophisticated hearing aids'
ability to clarify speech is limited by the degree of inner ear and/or central
auditory nervous system distortion.

Generally speaking, hearing aids should last for at least five years. The
need for new hearing aids may occur if a patient's hearing status changes, but
with the availability of programmable and digital hearing aids, changes can be
made in the audiologist's office and should reduce the need to order new hearing
aids merely because of changes in hearing status.

One of the major goals of signal processing schemes is to enhance the signal
to noise ratio perceived by the listener. The use of aids with automatic low
frequency reduction represent an attempt at this goal. Unfortunately, despite
all the new technological advances, a basic problem remains for which wearable
amplification falls woefully short. That problem relates to the physical
distance between the microphone of the hearing aid and the source of the sound
desired to be heard. Intensity (loudness) decreases as physical distance
increases. Unfortunately most background noise surrounds the listener, so while
the intensity of the speech decreases with distance, the intensity of the noise
may not. This is one reason why hearing aids transmit sound so well if the
speaker talks directly into the microphone, but at longer, more realistic
distances reception diminishes. It would be ideal to have the sound produced at
the source transferred directly to the listener without losing any intensity. It
is usually impractical to ask the speaker to move closer to the listener's ear.
One way of achieving this effect is with direct audio input, in which the
speaker holds a microphone that is hard wired to the hearing aid itself near his
mouth. Many hearing aid wearers are reluctant to ask the speaker to do this. An
alternative approach is available through infrared transmission, FM
transmission, or inductance loop transmission. These systems are currently used
in many theaters, concert halls, houses of worship and households. One of the
best uses is for television listening. The portable transmitter (usually smaller
than most cable boxes) and microphone are located near the TV loudspeaker. The
sound picked up by the microphone is then transmitted in the same intensity to a
receiver worn by the listener. These devices can transmit with minimal
distortion over a considerable distance (up to 50 feet). ALDs are becoming
increasingly common in public places, due to the legislative enactment of the
Americans with Disabilities Act. Other non-wearable devices that assist the
hearing impaired listener include telephone amplifiers, vibrating alarm clocks,
TV closed caption decoders, inexpensive personal hand held or body borne
amplifiers, visual alarm systems, and TDDs (telephone devices for the deaf).