APPAREILS AUDITIFS EXTERNES

EXTERNAL HEARING AIDS

Abrégé anglais

The invention essentially consists of a new type of hearing aids in which all
components,
including the loudspeakers, will be located externally to the ears. This will
permit the use
of relatively large size components, which will ensure that sounds are
captured, amplified
and delivered to the hearing membranes with a sufficiently high level of
energy and
fidelity in the entire frequency spectrum of human speech. For instance, the
use of large
size loudspeakers is essential to the reproduction of sound particularly at
the lower
frequency range whose wavelength exceeds the physical size of the miniature
loudspeakers used in existing hearing aids that are either inserted inside or
located behind
the users' ears. The external hearing aids will also use existing
technologically advanced
microphone arrows that when combined with sophisticated electronic circuitry,
already
available in the market, will permit achieving good sound reception and
valuable noise
suppression.

Revendications

3. Claims
The embodiment of the invention in which an exclusive property and privilege
is claimed
is the design concept and the development of hearing enhancement devices whose
components will have the following properties:
(A) to permit the use of components of sufficiently large size, the loud
speakers will be
worn over the ears;
(B) to reproduce with accuracy and clarity the whole frequency spectrum of the
human
voice, the loud speakers will be similar to those used in telephone
communication
systems;
(C) to capture the sounds, arrays of directional microphones will be used
which will be
mounted inside appropriate housings to be worn either over the head (see
Figure 1) or
on the chest (see Figure 2);
(D) contained inside the microphones' housings will also be the electronic
circuitry for
amplifying the sound signal and filtering out the background noise;
(E) to overcome the specific hearing impairment of each user, the electronic
circuitry will
be customized;
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(F) to permit the user to more comfortably adapt the device to specific
circumstances,
manual adjustments of the intensity of the signals of the loudspeakers will be
provided;
(G) during the development, other microphones' configurations will be
experimented for
the purpose of optimizing the user's capability to capture sounds arriving
from any
direction;
(H) final development work will explore the possibilities of improving the
esthetic
aspects of its design for the purpose of enhancing users' acceptability.

Description

CA 02485475 2004-11-18
2. Specification
This invention is intended to overcome the major difficulties caused by the
miniature size
of the components that are currently used in hearing aids. The physical size
limitations of
the components used in current hearing aids impose a significant restriction
on the
fundamental requirement of capturing, amplifying and delivering to the
eardrums noise-
free sounds with sufficient energy, clarity and intelligibility.
Miniature size loudspeakers cannot reproduce, with sufficient fidelity and
energy, sound
waves particularly at the lower end of the frequency range of the human voice,
whose
wavelength exceeds their physical size. To compensate for the loss of the
lower
frequency sounds, these hearing devices tend to amplify excessively the higher
frequency
sounds, which does not enhance speech comprehension and it actually becomes a
significant source of irritation to the wearer. The use of currently available
telephone
type loudspeakers of relatively large size - that have been developed to
reproduce with
accuracy and clarity the whole frequency spectrum of the human voice - will
avoid this
type of sound distortion, as they better address the need of people with
hearing
difficulties.
Another limitation of some type of hearing aids is caused by the use of single
miniature
microphones, as they are ineffective in distinguishing the useful sounds and
filtering out
the noise distortion caused by the, at times, inevitable background noise,
reverberation
and feedback. Research work in the development of directional acoustic system
(References 1 to 4) has shown that arrays of directional microphones combined
with
signal processing electronics can overcome these problems by generating "an
amplified

CA 02485475 2004-11-18
output sigiaal whicl2 emphasizes sounds of interest arriving in a direction
forward to the
user".
Microphone arrays are used in current hearing enhancement instruments. In some
of
them, the electrical output signals generated by microphone arrays are
directly connected
to their respective loudspeakers, and are mounted along with all other
components in
special housings that are generally worn behind the ears (Reference 3). In
others, the
microphone arrays are located inside a necklace type of housing to generate "a
time-
variable magnetic field that is representative of the received sound'. To
capture the
sound signal carried by this magnetic field, special hearing aids are used
that contain pick
up coils that are located along with the required electronics circuitry in
housings that are
generally worn behind the ears (Reference 1).
Modern hearing aids, regardless of the method adopted for utilizing microphone
arrays,
still use, however, miniature loudspeakers that are unable to deliver to the
eardrums the
captured speech with sufficient sound energy and fidelity.
As mentioned above, loudspeakers that are currently used in high quality
telephone
systems when mounted on a special over-the-ear headset would be able to
overcome the
limitations of those used in current hearing aids. The novelty of this
invention is to use
over-the-ear telephone type loudspeakers combined with technologically
advanced
microphone arrows along with sophisticated electronic circuitry.
Initially two sets of microphones will be used. Each set will include two
directional and
one omni-directional microphones, which will be located and positioned inside
an
external housing. The location of the two sets of microphones will ensure a
stereo
reception of the sound coming from the front of the wearer. The microphones'
housing
will also contain the electronic circuitry for amplifying, manually
controlling the intensity
of the sound signals and filtering out the background noise. The stereo
signals of the
amplifiers will be connected to the over-the-ear loudspeakers.
The microphones' housing can be worn either over the head (see Figure 1) or on
the chest
(see Figure 2). The over-the-head housing has the potential advantage of
adopting other
microphones' configurations. For instance, the use of two or more sets of
three
microphones properly arranged inside the housing may further enhance the
user's ,
capability to capture sounds arriving from any direction.
The use of this type of hearing instrument will overcome the difficulties of
the wearers to
hear and understand speech, and to appreciate music sounds in the following
ways:
(a) since the microphones will be strategically located to capture the sounds
from several
directions, the users will be more alert to the surrounding audio signals, and
the same
time any undesirable noise generated by the natural environment will be
filtered out;
(b) since the amplifiers and associated electronic circuitry will be mounted
inside the
microphone housing, each set can be made of sufficiently large size, and they
can be
customized to overcome the specific hearing impairment of the user;
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CA 02485475 2004-11-18
(c) the physical distance between the microphones and the loudspeakers will
permit high
level of signal amplification, and at the same time avoid any disturbing
feedback
ringing noise;
(d) the use of high quality telephone loudspeakers, each of which will be
connected to the
output of its own customized amplifier, will ensure stereophonic perception of
the
audio signal, so that each eardrum will receive its own signal with the
required level
of energy and clarity, as the intensity of each signal will be manually tuned
to suit
each specific circumstance;
(e) since no considerable electromagnetic energy of any health significance
will be
generated by this type of hearing instrument, there is no danger of exposing
the user's
head to the potential health risk that this type of energy may cause.
For all these advantages, it is recognized that - due to its visibility and
its impact on the
appearance of the wearer - this type of hearing aids may initially have a
relatively low
level of acceptability. The inventor, however, believes that the benefits that
people with
hearing impairments will derive from its use will overcome these appearance
concerns. It
is noted that the wearing of headsets for portable radios, telephones, or
music players has
become popular particularly among young people. Also, based on well-
established
individual civil rights the sight of people with physical disabilities is
considered
increasingly more acceptable in our modern society. Hence, although proper
appearance
is still a fundamental value a discrete hint to a personal disability is no
longer considered
cause of embarrassment to people, but rather an essential element of our
individuality.

CA 02485475 2004-11-18
4. Drawings
Figure 1 - Head-Mounted Hearing Aids
Figure 2 - Chest-Mounted Hearing Aids
5. References:
1. "A Microphone Array for Hearing Aids", by Bernard Widrow, Stanford
University,
U.S. Patent No. 5,793,857
2. Etymotic Research Directional Microphones, Patent No. 5,878,147
3. Siemens Directional Microphone Technology, TRIANO 3 and TRIANO SP Hearing
Instruments
4. Miles, R. N., Robert, R., and Hoy, R. R. [1995] "Mechanically coupled ears
for
directional hearing in the parasitoid fly Ormia ochracea." Journal of the
Acoustic
Society of America 98 (6) 3059-3070.

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