Note: Descriptions are shown in the official language in which they were submitted.
CA 02479822 2004-09-14
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IMPROVED MICROPHONES FOR AN IMPLANTABLE HEARING AID
This is a division of Canadian Patent Application Serial
Number 2,256,389, filed May 23, 1997.
Technical Field
The present invention relates to fully implantable hearing
aid systems, and more particularly to an electret microphone
adapted for use in such fully implantable hearing aid systems,
and how such an electret microphone or other type of microphone
may be incorporated into the fully implantable hearing aid
system.
nacJcc~round Art
Patent Cooperation Treaty ("PCT") patent application no.
. PCT/US96/15087 filed September 19~, 1996, entitled "Tmplantable
Hearing Aid" ("the PCT Patent~Application") describes a fully
implantable hearing aid system'. which uses a very small
implantable microactuator. The 'PCT Patent Application also
discloses a ICynar~ microphone which may be physically separated
far enough from the implanted microactuator so that no feedback
occurs. The fully implantable hearing aid system disclosed in
the PCT Patent Application can operate for a period of five years
on a set of batteries, and produce sound levels of 110 dI3. The
fully implantable hearing aid system described in the PCT Patent
Applications is extremely compact, sturdy, rugged, and provides
significant progress towards addressing problems with presently
available hearing aids.
While the lCynar microphone disclosed in the PCT hatent
Application enables an operable fully implantable hearing aid
system, that system's performance 'may be improved through the use
of a more sensitive electret microphone. United States patents
nos.4,957,478 ("the '978 patent") and 5,015,224, a division of
the '4713 patent, disclose incorporating a conventional electret
' microphone into an outer ear~canal unit 3A of a parti~-llly
implantable hearing aid system. United States patent no.
' 35 5,40F3,53~1 entitled "hlectret Microphone Assembly, and t9ethod of
Manufacture" discloses an improved structure and method for
coupling a charge plate of the electret microphone u~ec1 in a
hearing aid to an input terminal of an impedance matching circuit.-.
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or internal amplifier. One difficulty with using an electret
microphone for a fully implantable hearing aid system not
addressed by the patents identified above is that the
microphone must be hermetically sealed to prevent electric de-
polarization while simultaneously permitting sound waves to
impinge upon the microphone.
Because the hearing aid system disclosed in the PCT Patent
Application is fully implanted, it is presently estimated that
after a five year interval of use the system's battery may
likely need replacement which necessarily involves surgery.
Another aspect of a fully implantable hearing aid system is
ensuring reliable electrical interconnection of the system's
microphone and microactuator to the system's signal-processing
amplifier throughout a five year interval prior to battery
replacement, and subsequently after the battery has been
replaced.
Disclosure of Invention
Briefly, the present invention includes, a sealed
microphone adapted for inclusion in an implantable hearing aid
system. The sealed implantable microphone provides an input
signal to an amplifier included in the implantable hearing aid
system. The microphone includes a diaphragm having a thin
central region surrounded by a thicker rim. An electret, which
is bonded to the diaphragm, contacts a roughened plate included
in the microphone. The rim of the diaphragm is bonded to a
surface of a housing to hermetically enclose the electret and
the plate, the plate being electrically insulated from the
housing. The microphone also includes an electrical connector
coupled both to the plate and through the housing to the
electret for providing the input signal to the amplifier of the
implantable hearing aid system.
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In another embodiment of the invention, there is provided
a sealed, implantable electronics module adapted for inclusion
in an implantable hearing aid system, the electronics module
comprising a microphone; an amplifier for receiving an input
signal from the microphone, and for providing an output signal
to a microactuator also included in the implantable hearing aid
system; an energy storage device for powering operation of the
implantable hearing aid system; a housing for receiving and
hermetically enclosing the microphone, the amplifier and the
energy storage device; and an electrical connector coupled to
the amplifier for providing the output signal to the
microactuator of the implantable hearing aid system.
In a further embodiment of the present invention, there
is provided a hearing aid system that is adapted for
implantation into a subject whose body has a head that includes
a bony otic capsule which encloses a fluid-filled inner ear;
the hearing aid system including a microactuator adapted for
implantation in the subject in a location from which a
transducer included in the microactuator may mechanically
generate vibrations in the fluid within the inner ear of the
subject, the microactuator receiving an electrical driving
signal and producing vibrations in the fluid within the inner
ear responsive to the received electrical driving signal; and
a sealed, implantable electronics module including a
microphone; an amplifier for receiving an input signal from the
microphone, and for providing the electrical driving signal to
the microactuator; an energy storage device for powering
operation of the hearing aid system, and a housing for
receiving and hermetically enclosing the microphone, the
amplifier and the energy storage device.
In yet another embodiment of the invention there is
provided a hearing aid system that is adapted for implantation
into a subject, the hearing aid system including a
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microactuator adapted for implantation in the subject in a
location from which a transducer included in the microactuator
may mechanically generate vibrations in the fluid within the
inner ear of the subject, the microactuator receiving an
electrical driving signal and producing vibrations in the fluid
within the inner ear responsive to the received electrical
driving signal; and a sealed, implantable electronics module
including a microphone; an amplifier for receiving an input
signal from the microphone, and for providing the electrical
driving signal to the microactuator; an energy storage device
for powering operation of the hearing aid system; and a disk-
shaped housing for receiving and hermetically enclosing the
microphone, the amplifier and the energy storage device, the
disk-shaped housing being adapted for implantation into a
depression surgically sculpted into a mastoid cortical bone
behind an external ear of a subject, disposed in this location
the microphone is adapted to press against skin overlying the
mastoid cortical bone.
In another embodiment of the invention, there is provided
a sealed, implantable electronics module adapted for inclusion
in an implantable hearing aid system, the electronics module
comprising a microphone; an amplifier for receiving an input
signal from the microphone, and for providing an output signal
to a microactuator also included in the implantable hearing aid
system; an energy storage device for powering operation of the
implantable hearing aid system; a housing for receiving and
hermetically enclosing the microphone, the amplifier and the
energy storage device; and a sleeve adapted a) for receiving
the housing; b) for coupling the output signal between the
amplifier and the microactuator; and c) for permanent
implantation into a subject to thereby facilitate replacement
of the electronics module.
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In another embodiment of the invention, there is provided
a hearing aid system that is adapted for implantation into a
subject, the hearing aid system including a microactuator
adapted for implantation in the subject in a location from
which a transducer included in the microactuator may
mechanically generate vibrations in the fluid within the inner
ear of the subject, the microactuator receiving an electrical
driving signal and producing vibrations in the fluid within the
inner ear responsive to the received electrical driving signal;
and a sealed, implantable electronics module including a
microphone; an amplifier for receiving an input signal from the
microphone, and for providing the electrical driving signal to
the microactuator; an energy storage device for powering
operation of the hearing aid system; and a housing for
receiving and hermetically enclosing the microphone, the
amplifier and the energy storage device; and a sleeve adapted:
a) for mechanically receiving the housing; b) for coupling the
output signal between the amplifier and the microactuator; and
c) for permanent implantation into a subject to thereby
facilitate replacement of the electronics module.
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This implantable microphone can preferably be incorporated
into a hermetically sealed electronics module. In addition to
the microphone, the electronics module includes an amplifier
that receives the input signal from the microphone's plate and
the electret, and provides an output signal to a microactuator
also included in the implantable hearing aid system. The
electronics module also includes a battery for energizing
operation of the implantable hearing aid system. A housing for
the electronics module receives the battery, the amplifier, the
plate, and the electret. The microphone's diaphragm forms a
surface of the housing with the rim of the diaphragm being
bonded to the housing thereby hermetically sealing the
electronics module. An electrical connector coupled to the
amplifier provides the output signal to the microactuator of
the implantable hearing aid system.
These and other features and advantages will be understood
or apparent to those of ordinary skill in the art from the
following detailed description of the preferred embodiment as
illustrated in the various drawing figures.
Brief Description of Drawings
FIG. 1 is a schematic coronal, partial sectional view
through a human temporal bone illustrating the external, middle
and inner ears, and showing the relative positions of the
components of a fully implantable hearing aid system disclosed
in the PCT Patent Application;
FIG. 2a is an exploded, cross-sectional elevational view
illustrating an electret microphone in accordance with the
present invention including a diaphragm, an electret, a plate
CA 02479822 2004-09-14
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that contacts a surface of the electret, and a hermetically
sealed housing that encloses the electret and plate;
FIG. 2b is an enlarged cross-sectional elevational view
taken along the line 2b-2b of FIG. 2a illustrating contact '
between the electret and the plate;
FIG. 2c is a plan view taken along the line 2c-2c of FIG. '
2a illustrating the diaphragm and reinforcing ribs that subdivide
a thinned central region of the diaphragm;
FIG. 3a is a plan view of an alternative embodiment
structure for the plate depicted in the cross-sectional view of
FIG. 2a;
FIG. 3b is a cross-sectional view, similar to the view of
FIG. 2b, of the alternative embodiment structure for the plate
depicted in the plan view of FIG. 3a;
FIG. 4 is a cross-sectional elevational view illustrating
implantation into a cavity sculpted into a mastoid bone located
behind the ear of an electronics module that includes an electret
microphone, an amplifier and battery for energizing operation of
the fully implantable hearing aid system;
FIG. 5 is an elevational view of a disk-shaped implantable
electronics module taken along a line ~-4 in FIG 3 that illus-
trates a preferred arrangement for the electronics module, and
indicates a preferred vertical location for its implantation on
the mastoid bone;
FIG. 6 is an elevational view of an alternative embodiment
of an oval-shaped implantable electronics module, similar to the
disk-shaped electronics module depicted in FIG. 5, that includes
a plurality of microphones;
FIG. 7 is a partial cross-sectional view depicting a perma
nently implanted sleeve adapted to receive and facilitate
replacement of the electronics module such as those depicted in
FIGS. 4, 5 and 6;
FIG. 8 is a schematic coronal, partial sectional view
through a human temporal bone, similar to the partial sectional
view of FIG. 1, illustrating implantation into a cavity sculpted
there of an electronics module that includes an amplifier, a
battery, and a microphone which presses against the skin of the
extern«1 auditory canal; and
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FIG. 9 is an enlarged cross-sectional view of a sleeve
preferably used for supporting the electronics module when
implanted as depicted in FIG. 8.
Best Mode for CarrvincLOut the InventioQ
I The Overall System
FIG. 1 illustrates relative locations of components of a
fully implantable hearing aid 10 after implantation in a temporal
bone 11 of a human subject 12. FIG. 1 also depicts an external
ear 13 located at one end of an external auditory canal 14,
commonly identified as the ear canal. An opposite end of the
external auditory canal 14 terminates at an ear drum 15. The ear
drum 15 mechanically vibrates in response to sound waves that
travel through the external auditory canal 14. The ear drum 15
serves as an anatomic barrier between the external auditory canal
14 and a middle ear cavity 16. The ear drum 15 amplifies sound
waves by collecting them in a relatively large area and transmit-
ting them to a much smaller area of an oval-shaped window 19.
An inner ear 17 is located in the medial aspects of the temporal
bone 11. The inner ear 17 is comprised of otic capsule bone
containing the semi-circular canals for balance and a cochlea 20
for hearing. A relatively Large bone, referred to as the
promontory 18, projects from the otic capsule bone inferior to
the oval window 19 which overlies a basal coil of the cochlea 20.
A round window 29 is located on the opposite side of the
promontory 18 from the oval window 19, and overlies a basal end
of the scala tympani.
Three mobile bones (malleus, incus and stapes), referred to
as an ossicular chain 21, span the middle ear cavity 16 to
connect the ear drum 15 with the inner ear 17 at the oval window
19. The ossicular chain 21 conveys mechanical vibrations of the
ear drum 15 to the inner ear 17, mechanically de-amplifying the
motion by a factor of 2.2 at 1000 Hz. Vibrations of a stapes
footplate 27 in the oval window 19 cause vibrations in perilymph
fluid 20A contained in scala vestibuli of the cochlea 20. These
pressure wave 'vibrations" travel through the perilymph fluid 20A
and endolymph fluid of the cochlea 20 to produce a traveling wave
of the basilar membrane. Displacement of the basilar membrane
CA 02479822 2004-09-14
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bends "cilia" of the receptor cells 20B. The shearing effect of
the cilia on the receptor.cells 208 causes depolarization of the
receptor cells 208. Depolarization of the receptor cells 2oB
causes auditory signals to travel in a highly organized manner '
along auditory nerve fibers .20C, through the brainstem to
eventually signal a temporal lobe of a brain of the subject 12 '
to perceive the vibrations as "sound."
The ossicular chain 21 is composed of a malleus 22, an incus
23, and a stapes 24. The stapes 24 is shaped like a "stirrup"
with arches 25 and 2G and a stapes footplate 27 which covers the
oval window 19. The mobile stapes 24 is supported in the oval
window 19 by an annular ligament which attaches the stapes
footplate 27 to the solid otic capsule margins of the oval window
19.
FIG. 1 also illustrates the three major components of the
hearing aid l0, a microphone 28, a signal-processing amplifier
30 which includes a battery not separately depicted in FIG. 1,
and microactuator 32. Miniature cables or flexible printed
circuits 33 and 34 respectively interconnect the
2o signal-processing amplifier 30 with the microactuator 32, and
with the microphone 28. The PCT Patent Application discloses
that. the microphone 28 consists of a very thin sheet of
biocompatible, and implantable polyvinylidenefluoride
("PVDF")that is identified commercially by a trademark KYNAR~.
The microphone 28 disclosed in the PCT Patent Application has an
area of approximately 0.5 to 2.~0 square centimeter ("cm?"). The
PCT Patent Application also discloses that the microphone 28 is
preferably to be implanted below the skin in the auricle, or
alternatively in the postauricular area of the external ear 13.
The signal-processing amplifier 30 is implanted subcutane-
ously behind the external ear 13 within a depression 38 surgical-
ly sculpted in a mastoid cortical bone 39 of the subject 12. The
signal-processing amplifier 30 receives a signal from the micro-
phone 28 via the miniature cable 33, amplifies and conditions
that signal, and then re-transmits the processed signal to the
microactuator 32 via the miniature cable 34 implanted below the
skin in the external auditory canal 14. The signal-processing
amplifier 30 processes the signal received from the microphone
CA 02479822 2004-09-14
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28 to optimally match characteristics of the processed signal to
the microactuator 32 to obtain the desired auditory response.
The signal-processing amplifier 30~may perform signal processing
' using either digital or analog signal processing, and may employ
both nonlinear and highly complex.'signal processing.
The microactuator 32 transduces the electrical signal
received from the signal-processing amplifier 30 into vibrations
that either directly or indirectly mechanically vibrate the
perilyfiph fluid 20A in the inner~ear 17. As described previous-
ly, vibrations in the pexilymph fluid 20A actuate the receptor
cells 20B to stimulate .the auditory nerve fibers 2oC which signal
the brain of the subject 12 to perceive the mechanical vibration
as sound.
FIG. 1 depicts the relative position of the microphone 28,
the signal-processing amplifier 30 and the microactuator 32 with
respect to the external ear 13. Even though the
signal-processing amplifier 30 is implanted subcutaneously, the
subject 12 may control the operation of the hearing aid l0 using
techniques analogous to those presently employed for controlling
the operation of miniaturized external hearing aids. Both the
microphone 28 and the microactuator 32 are so minuscule that
their implantation requires little or no destruction of the
tissue of the subject 12. Of equal importance, the microphone
28 and the signal-processing amplifier 30 do not interfere with
the normal conduction of sound through the ear, and thus will not
impair hearing when the hearing aid l0 is turned off or not
functioning.
The PCT Patent Application provides a more detailed descrip
tion of a signal-processing amplifier 30 and a microactuator 32
that are suitable for use in the present invention.
II Implantable Microphone
rIG. 2a depicts an exploded., cross-sectional, elevational
view of an implantable microphone 50 in accordance with the
present invention. The implantable microphone 50 includes a
diaphragm 52 preferably formed from a s:~eet of biocompatible
CA 02479822 2004-09-14
.' .
metallic material such as titanium that is one to two mils thick.
A central region 54 of the diaphragm 52 is lithographically
etched to a thickness of approximately 5 to l2 microns. An
outside rim 56, that surrounds the central region 54, is left '
thicker for ease of attachment to a housing 58 also included in
the implantable microphone 50. The housing 58 is also preferably
fabricated from a biocompatible material such as titanium. A
sealing layer 62 may be applied to a surface of the diaphragm 52
nearest to the housing 58. The seating layer 62 preferably
l0 consists of a thin layer of sputtered chromium, a few hundred
angstroms thick, that is overcoated by a thicker layer of gold.
This sealing layer 62, that is one to several microns thick,
covers any potential cracks or pinholes in the thin central
region 54 of the diaphragm 52.
Etching of the diaphragm 52 may be patterned to produce a
grid of intersecting reinforcing ribs 64, depicted in FIG. 2c,
that protrude from a surface of the central region 54 furthest
from the housing 58. The reinforcing ribs 64 subdivide the
central region 54 into a plurality of separate membranes 66 that
are mechanically supported by the reinforcing ribs 64.
After fabricating the diaphragm 52 with its sealing layer
62, a sheet 72 of an electret material having a metalized
surface, such as a 0.5 mil thick Teflon film, is thermally bonded
to the sealing layer 62 with the metalized side of the sheet 72
contacting the diaphragm 52. A surface of the sheet 72 furthest
from the diaphragm 52 is then polarized by corona charging or
electron bombardment.
The assembly formed by the diaphragm 52 carrying the bonded
electret sheet 72 is then pressed against an electrically conduc
five plate 82 disposed within the housing 58. An electrically
insulating layer 84 is interposed between the plate 82 and the
housing 58. As depicted in FIG. 2b, the plate 82 either has a
naturally rough surface 86 that is juxtaposed with the electret
sheet 72, or the surface 86 may be formed with a knurled or other
controlled roughness. A contact 92 of an electrical connector
94 that pierces the housing 58 couples via the miniature cable
33 an input signal from the implantable microphone 50 to the
signal-processing amplifier 30 included in the hearing aid lo.
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The thickness of plate 82 and of the layer 84 are chosen so
the surface 86 of the plate 82 protrudes slightly above a rim 98
of the housing 58. The outside rim 56 of the diaphragm 52 is
welded to the rim 98 of the housing 58. Because the surface 86
of the plate 82 protrudes above the rim 98 of the housing 58,
welding the outside rim 56 to the rim 98 places the diaphragm 52
and the electret sheet 72 under'tension, and presses the sheet
72 into contact with the plate 82 at many points, as illustrated
in FIG. 2b. Acoustic waves impinging upon the central region 54
l0 deflect the electret sheet 72 to thereby generate charges on the
plate 82 that constitute an output signal from the implantable
microphone 50. The housing .58 forms one electrode of the
implantable microphone 50 while the contact 92 forms the other.
FIGs. 3a and 3b depict an alternative embodiment for the
plate 82. The embodiment of the plate 82 depicted in those FIGS.
includes an array of lithographically defined posts 99 which
establish a controlled roughness for the surface 8G of the plate
82 contacting the sheet 72. The posts 99, which are spaced 100
to 1000 microns apart, are formed by etching the surface 86 of
the plate 82 to a depth between a few and 100 microns.
The diameter of housing 58.may range from 5.0 mm to 25 mm,
but for acoustical reasons preferably does not exceed 10. o mm in
diameter. The hermetically sealed implantable microphone 50 may
be implanted subcutaneously, e.g, behind the external ear 13,
with the central region 54 of the diaphragm 52 in intimate
contact with skin 108 overlying the mastoid cortical bone 39 for
minimal attenuation of sound. The implantable microphone 50 is
rugged and can take direct blows.
The implantable microphone 50 described above may be
combined with the signal-processing amplifier 30 to provide a
disk-shaped, integrated electronics module 100 for the hearing
aid l0, as illustrated in FIG. 4. Integrating both the
signal--processing amplifier 30 and the implantable Taicrophone 50
into the electronics module 100 as illustrated in FIG. 4 places
the implantable microphone 50 on a side of the electronics module
100. Disposed in this location, the housing 58 and diaphragm 52
of the implantable microphone 50 now form part of a wall 102 of
the electronics module 100, and the miniature cable 33 depicted
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- 10 -
in FTG. 1 passes directly between,the implantable microphone 50
and the signal-processing amplifier 30 internally within the
electronics module 100. The electronics module 100 essentially
eliminates the miniature cable .33 connecting the implantable '
microphone 50 to the signal-processing amplifier 30 together with
any possibility of its failure. '
For a hearing aid 10 having an integrated electronics module
100, as described in the PCT Patent Application the electronics
module 10o carrying both the signal-processing amplifier 30 and
the implantable microphone 50 may be implanted subcutaneously
behind the external ear 13 of the subject 12 within the depres-
sion 38 surgically sculpted in the mastoid cortical bone 39. The
depression 38, surgically sculpted to accept a biocompatible,
metallic sleeve 132 that receives the electronics module 100,
should not be more than 5 mm deep, and should be formed with
rounded corners to avoid concentrating stress at sharp corners
that would weaken the mastoid cortical bone 39. The sleeve 132
is permanently secured in the depression 38 to facilitate
removing and/or replacing the electronics module 100. Disposing
the electronics module 100 in this location leaves only the
miniature cable 34 that couples an output signal from the
signal-processing amplifier 30 to the microactuator 32.
The diaphragm 52 and the housing 58 of the implantable
microphone 50 as well as a disk-shaped housing 112 for the
electronics module 100 is typically made of biocompatible metals
such as titanium, titanium alloys or stainless steel. The disk-
shaped housing 112 may have a diameter of 1.0 to 3,0 cm, and a
height typically of 0.5 to 1.0 cm to accommodate the amplifier's
electronics and the battery. Even if the housing 112 for the
electronics module 100 were an elongated cylinder rather than
disk-shaped, a cylindrically-curved wall 102 can still incc.~po-
rate the implantable microphone 50. Under such circumstances,
the central region 54 of the diaphragm 52 has the same curvature
as that of the cylindrically-curved wall 102.
FIG. 5 is a plan view depicting another embodiment of the
electronics module 100 adapted for implantation as described
above in connection with FIG. 4: It appears that a preferred
location for implanting the electronics module 100 exist with the
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implantable microphone 50 located below a temporal line 122 on
the subject 12. This location provides for relatively thin
skin 108 over the implantable microphone 50 in the lower half
of the electronics module 100, and for thicker skin 108 over
the upper part of the electronics module 100. An on-off
pressure switch 124 may be located on the housing 112 of the
electronics module 100 above the temporal line 122 together
with a pressure volume-control 126. Disposed in this location,
the subject 12 may control operation of the hearing aid 10 by
pressing on the skin 108 overlying the on-off pressure switch
124 and the pressure volume-control 126.
FTG. 6 depicts an oval-shaped alternative embodiment of
the electronics module 100 depicted in FIG. 5. The embodiment
depicted in FIG. 6 includes an acoustic array 128 of individual
implantable microphones 50 arranged in a horizontal row across
the electronics module 100. As described in greater detail in
United States Patent No. 6,068,589, an appropriately adapted
signal-processing amplifier 30 sums independently generated
signals from the implantable microphones 50, applying
appropriate weighing factors to the signal from each
implantable microphone 50, to produce a desired characteristic
sensitivity pattern from the array 128. In this way the
hearing aid 10 can provide the subject 12 with directivity
which the subject 12 may use to enhance the sounds of interest
while concurrently reducing noise.
At 5000 Hz, the wavelength of sound in air is only 6.8 cm.
Providing a directional array that is one-half wavelength long
at 5000 Hz requires that the array 128 be only a few
centimeters long. Output signals from each of the implantable
microphones 50 of the array 128 are then coupled to the signal-
processing amplifier 30. The signal-processing amplifier 30
appropriately weighs the output signals from each of the
implantable micro-
CA 02479822 2004-09-14
- 12 -
phones 50 with a pre-established distribution to produce a
directional pattern for the sound perceived by the subject 12.
Implanting the array 128 on the mastoid cortical bone 39 of the
subject 12 near the external ear 13 provides such a directional '
sound receiving pattern. By directing the maximum sensitivity
of the array 128 toward sounds, of interest, it is readily '
apparent that the subject 12 may use the radiation pattern to
advantage in improving reception of such sounds, and to reject
noise.
l0, With the configurations for the electronics module 100
depicted in FIGS. 4, 5 and 6, the electronics module 100 is
preferably received into the sleeve 132 that is permanently
implanted (e.g. tapped) into the mastoid cortical bone 39 of the
subject 12. An outer surface of the permanently implanted sleeve
132 may contain ridges 80-130 micron deep to encourage post-
implantation growth of bone to lock the housing 112. The perma-
nently implanted sleeve 132 includes a center post 134 that
provides a permanent connection for the miniature cable 34 from
the microactuator 32. The electronics module 100 is retained
within the sleeve 132 by a locking ring 136, and O-rings 138 seal
between the electronics module 100 and both the sleeve 132 and
the locking ring i36. The 0-rings 138 block entry of body fluids
into any gap 142 between the electronics module 100 and the
sleeve 132. Moreover, the gap 142 may be ffilled with an
electrically insulating, biocompatible gel material preferably
having a cohesive strength that exceeds the material's adhesive
strength with the outer surface.of the electronics module 100,
the sleeve 132 and the center post 134.
If the electronics module 100 is cylindrically-shaped rather
disk-shaped, then the implantable microphone 50 may be preferably
disposed at another location on the housing 112. For such a
configuration of the electronics module 100, as illustrated in
FIG. 8 the implantable microphone 50 is preferably located at one
end of the cylindrically shaped housing 112. Such a cylindrical
ly-shaped electronics module 100 is preferably implanted
subcutaneously with the implantable microphone 50 located
adjacent to the skin 108 of the external auditory canal 14 or
adjacent to the conchal cartilage in the posterior external
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- 13 -
auditory canal 14. Disposed in such a location, the implantable
microphone 50 presses downward against the skin 108 of the
external auditory canal 14 as illustrated in FIG. 8, or against
the conchal cartilage. The diaphragm 52 of the implantable
microphone 50 may be domed outward to improve contact with the
skin 108 or the conchal cartilage. Disposing the implantable
microphone 50 in contact with skin 108 or the conchal cartilage
of the external auditory canal 14 benefits from a substantial
enhancement of sound waves at the implantable microphone 50
provided by the external ear 13. The housing 112 is made long
enough so controls are available through the skin 108 at the end
of the housing 112 distal from the implantable microphone 50.
As illustrated in FIG. 9, a biocompatible, metallic support
sleeve 152 is preferably permanently anchored to the mastoid
cortical bone 39 to receive the cylindrically-shaped electronics
module 100, to facilitate its replacement, and to provide a fixed
attachment for the electronics module 100. The housing 112 of
the electronics module 100 is encircled by corrugated bellows 156
to accommodate anatomical differences by adjusting the length of
the electronics module 100, and to facilitate installing the
electronics module 100. Implanted in this way, the implantable
microphone 50 is protected from direct blows which permits using
types of microphones other than the electret implantable
microphone 50.
Industrial Applicability
Referring. back to FIG. 4, with the electronics module loo
implanted subcutaneously behind the external ear I3 of the
subject 12 the electronics module 100 may be adapted for non-
contact recharging of an energy storage device such as a battery,
or equivalently a super capacitor, which powers operation of the
hearing aid 10. Such non-contact recharging can be effected by,
disposing an induction coil 160 adjacent to the skin 108 covering
the electronics module 100 as indicated by an arrow 162 in FIG.
4.
Although the present invention has been described in terms
of the presently preferred embodiment, it is to be understood
that such disclosure is purely~illustrative and is not to be
CA 02479822 2004-09-14
l~
interpreted as limiting. Consequently, without departing from
the spirit and scope of the invention, various alterations,
modifications, and/or alternative applications of the invention
will, no doubt, be suggested to those skilled in the art after '
having read the preceding disclosure. Accordingly, it is intended
that the following claims be interpreted as encompassing all '
alterations, modifications, or alternative applications as fall
within the true spirit and scope of the invention.
