U.S. patent number 3,764,748 [Application Number 05/254,930] was granted by the patent office on 1973-10-09 for implanted hearing aids.
Invention is credited to Jack P. Branch, Noel O. Durham.
United States Patent |
3,764,748 |
Branch , et al. |
October 9, 1973 |
IMPLANTED HEARING AIDS
Abstract
Several hearing aid configurations for implantation within the
middle ear cavity are disclosed. Each hearing aid is minute in size
and is joined in operative relationship interiorly of the ear drum
to the ossicle bone chain situated within the middle ear cavity.
Each hearing aid is characterized by: (1) picking up or "reading"
auditory signals off the ear drum, (2) subsequently amplifying
and/or transmitting such signals directly to appropriate sound
receiving mechanisms, natural or solid-state or both, located on
the oval window, the round window, or the promontory leading into
the inner ear, and (3) relying upon the automatic gain control
(AGC) function performed by the tensors and flexors of the ossicle
bone chain to prevent loud sounds from damaging the ear drum.
Inventors: |
Branch; Jack P. (Memphis,
TN), Durham; Noel O. (Charlotte, NC) |
Family
ID: |
22966150 |
Appl.
No.: |
05/254,930 |
Filed: |
May 19, 1972 |
Current U.S.
Class: |
607/57; 381/190;
600/25 |
Current CPC
Class: |
H04R
25/606 (20130101); A61F 2002/183 (20130101); H04R
2225/31 (20130101) |
Current International
Class: |
H04R
25/00 (20060101); H04r 025/00 () |
Field of
Search: |
;179/17R,17E ;128/1R
;3/1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Blakeslee; Ralph D.
Claims
We claim:
1. An implantable, sound powered hearing aid comprising:
a. transducer means positioned interiorly of the ear drum in
proximity to the oval window within the middle ear cavity,
b. said transducer means being pressure sensitive so as to generate
a variable voltage output in response to the application of
pressure thereto,
c. stylus means secured to either the hammer, anvil or stirrup of
the ossicle bone chain located in the middle ear cavity in
operative relationship to said pressure sensitive transducer
means,
d. said stylus means being pressed against said transducer means by
the ossicle bone chain with a variable force when sound strikes the
ear drum to thereby produce a variable voltage, and
e. conducting means to lead said variable voltage to the area of
the oval window to electrically stimulate same.
2. The hearing aid as defined in claim 1 further including a
piezoelectric crystal positioned in the area of the oval window,
said conducting means impressing said variable voltage upon said
crystal to cause same to vibrate and thus stimulate the auditory
nerve.
3. The hearing aid as defined in claim 1 further including a diode
positioned in the area of the oval window, said conducting means
leading said variable voltage to said diode which rectifies same
into pulsating D.C. voltage and thus stimulates the auditory
nerve.
4. The hearing aid as defined in claim 2 further including an
amplifying circuit connected between said pressure sensitive
transducer means and said piezoelectric crystal, said amplifying
circuit amplifying the variable voltage produced by said transducer
means before said voltage is impressed upon said crystal.
5. The hearing aid as defined in claim 2 further including an
auxiliary power supply, connected to said piezoelectric crystal, to
impress its voltage thereupon.
6. The hearing aid as defined in claim 5 further including a tuning
circuit connected between said pressure sensitive transducer means
and said piezoelectric crystal and in operative relationship to
said power supply, said tuning circuit adjusting the frequency at
which said crystal will vibrate.
7. The hearing aid as defined in claim 5 further including
recharging means for said auxiliary power supply, said recharging
means comprising a button under the skin of the wearer of the
hearing aid, a stylus secured to said button, and a pressure
sensitive transducer means situated in operative relationship to
said transducer means, said transducer means connected to said
auxiliary power supply to supply a variable voltage thereto, said
button being manually depressed to press the stylus against the
transducer means whenever said auxiliary power supply requires
recharging.
8. The hearing aid as defined in claim 2 wherein said stylus means
comprises a piezoelectric bar with a pin extending outwardly
therefrom.
9. The hearing aid as defined in claim 8 wherein said piezoelectric
bar produces a variable voltage as said bar is stressed when sound
striking the ear drum is transmitted through the ossicle bone
chain, and circuit means for amplifying the variable voltage before
applying same to the oval window area.
10. The hearing aid as defined in claim 1 wherein the transducer
means are held in a rectangular package, said package being
positioned in the opening of the stapes of said ossicle bone chain
with one corner of the package bearing against the footplate of the
stapes.
11. The hearing aid as defined in claim 1 further including a
resilient fluid filled sack interposed between the ossicle bone
chain and the area of the oval window and a piezoelectric crystal
disposed thereupon, said conducting means impressing said variable
voltage produced by said pressure sensitive device upon said
crystal which vibrates atop the sack and transmits said vibrations
therethrough to the area of the oval window.
12. The hearing aid as defined in claim 11 further including a
collar situated atop said transducer means, said collar engaging
the free end of the anvil of the ossicle bone chain.
13. The hearing aid as defined in claim 1 wherein said transducer
means and said stylus means are slipped between the joint formed by
the anvil and stirrup of the ossicle bone chain.
14. An implanted hearing aid comprising:
a. a transmitting unit encased in a housing and positioned within
the ear canal, said transmitting unit including:
1. a miniature microphone for producing a variable voltage
proportional to the sound striking same,
2. a power source for energizing said microphone,
3. an amplifying circuit for increasing the voltage produced by
said microphone,
4. a transmitting coil operatively connected to said microphone,
said power source, and said amplifying circuit for radiating an
electromagnetic field of variable intensity, and
b. a receiving unit including:
1. a receiving coil implanted in the mastoid bone in proximity to
said transmitting coil, said coils being inductively coupled
together, and
2. conducting means implanted in the mastoid bone to lead the
variable voltage received by said coil to the area of the oval
window to electrically stimulate same.
15. The hearing aid as defined in claim 14 further including a
piezoelectric crystal positioned in the area of the oval window,
said conducting means impressing said variable voltage upon said
crystal to cause same to vibrate and thus stimulate the auditory
nerve.
16. The hearing aid as defined in claim 14 further including a
diode positioned in the area of the oval window, said conducting
means leading said variable voltage to said diode which rectifies
same into pulsating D.C. voltage and thus stimulates the auditory
nerve.
17. An improved hearing aid comprising:
a. transmitting means secured to the inner surface of the eardrum
in the area of the junction defined by the hammer and the ear drum,
said transmitting means radiating magnetic waves into the middle
ear cavity,
b. receiving means situated within the middle ear cavity on the
promontory in the area of the oval window, said receiving means
including:
1. magnetically responsive means retained upon a flexible
diaphragm,
2. a stylus connected to said diaphragm,
3. a pressure sensitive transducer for producing a variable voltage
in response to the application of pressure thereto, said stylus
being positioned in operative relationship to said transducer,
4. said stylus being pressed against said transducer when the
transmitting moves relative to the receiving means as sound energy
strikes the ear drum to thereby produce a variable voltage, and
c. conducting means to lead said variable voltage to the area of
the oval window to electrically stimulate same.
18. The hearing aid of claim 17 wherein the transmitting means is a
permanent magnet.
19. The hearing aid of claim 17 wherein the transmitting means is a
fragment of phosphor.
20. The hearing aid as defined in claim 17 wherein the transmitting
means is a radioactive isotope.
21. The hearing aid as defined in claim 17 wherein the magnetically
responsive means is a field-effect transistor gate.
22. The hearing aid as defined in claim 17 wherein the magnetically
responsive means is a Hall-effect element.
23. The hearing aid as defined in claim 17 further including a
piezoelectric crystal positioned in the area of the oval window,
said conducting means impressing said variable voltage upon said
crystal to cause same to vibrate and thus stimulate the auditory
nerve.
24. The hearing aid as defined in claim 17 further including a
diode positioned in the area of the oval window, said conducting
means leading said variable voltage to said diode which rectifies
same into pulsating D.C. voltage and thus stimulates the auditory
nerve.
25. An implanted hearing aid comprising:
a. a transmitting unit encased in a housing and positioned within
the ear canal, said transmitting unit including:
1. a miniature microphone for producing a variable voltage
proportional to the sound striking same,
2. a power source for energizing said microphone,
3. an amplifying circuit for increasing the voltage produced by
said microphone,
4. a light emitting device connected to said microphone, said power
source, and said amplifying circuit for projecting a light beam of
variable intensity,
b. a receiving unit including:
1. a light responsive sensor implanted on the promontory in the
area of the oval window, said light emitting device and said light
responsive device being in substantial alignment with one another
and on opposite sides of the opaque ear drum,
2. said sensor producing a variable voltage proportional to the
intensity of the light beam falling thereupon,
3. amplifying means for increasing the voltage produced by said
light responsive sensor, and
4. conducting means to lead the variable voltage produced by said
sensor and said amplifying means to the area of the oval window to
electrically stimulate same.
26. An implanted hearing aid for the treatment of tinnitus
comprising:
a. a transmitting unit encased in a housing and positioned within
the ear canal, said transmitting unit including:
1. a miniature microphone for producing a variable voltage
proportional to the sound striking same,
2. a power source for energizing said microphone,
3. an amplifying circuit for increasing the voltage produced by
said microphone,
4. a transmitting coil operatively connected to said microphone,
said power source, and said amplifying circuit for radiating an
electromagnetic field of variable intensity,
b. a receiving unit implanted in the mastoid bone surrounding the
ear canal including:
1. a second miniature microphone responsive to the electromagnetic
field radiated by the transmitting for producing a variable
voltage,
2. a power source for energizing the second microphone, and a
3. crystalline device that vibrates in response to the voltage
applied thereto by the second microphone, the vibrations being
conducted through the mastoid bone to the inner ear to stimulate
the auditory nerve.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The instant invention relates to surgically implantable hearing
aids for stimulating the auditory system of the human body.
2. Description of the Prior Art
In recent years the medical arts have been, to a large extent,
directed to surgical means for the correction of human bodily
defects, i.e., those defects which occur in the human body due to
injury, congenital malfunction, or the like. Thus, for example,
there have been disclosed in the medical arts a variety of elements
capable of implantation within the human body. These elements in
many instances comprise transplanted human organs. In many other
instances, they comprise artificial members or prosthetic devices,
such as, artificial hearts, heart valves, artificial kidneys,
artificial limbs, and the like.
The population of the United States, as of the date of this
invention, is approximately 210,000,000 people. Of such number,
approximately 15 percent over 30,000,000 persons, have some form of
inability to adequately perceive auditory information by means of
their auditory sensory powers.
These forms of inability may be classified as follows: first, a
conductive loss; secondly, a nerve loss; thirdly, a mixed type loss
including body nerve and conductive losses; and fourthly, a
psychogenic loss.
A conductive loss usually is attributable to excessive calcium or
cartilaginous deposits on the joints on the ossicle bone chain of
the middle ear. These deposits restrain movement of the conductive
bone chain, and in most instances, also restrict movement of the
ovular window leading to the inner ear. Other conductive losses may
be caused by damage to the ear drum or tympanum through subjection
to concussion, extreme atmospheric pressure, or the like.
Additionally, the ossicle bone chain may be eroded by chronic
infection, congenital conditions, or the like.
Nerve loss is the most common type of hearing inability. Such loss
may be attributable to deterioration of the auditory nerves through
heredity, disease, noise damage or the like.
The third type of hearing inability, designated above as mixed
nerve-conductive loss, includes those instances in which an
individual has present in his auditory system a combination of the
losses described above.
Referring again to condition one, the conductive loss, there are
cases wherein the ear drum is eroded, ruptured, or otherwise
impaired, and/or the bone movement is restricted through hardening
and malfunction. Thus, in effect, the auditory signals received are
reduced in intensity due to this loss of transmission
effectiveness. Therefore, the necessary threshold level of
desirable signals which must be transmitted to the brain by means
of the auditory nerves is not achieved. Consequently, the signals
perceived by the brain are inadequate to allow the brain to
translate such signals into intelligible information.
Referring again to condition two, the nerve loss, it should be
understood that such nerve damage may occur when fibers of the
auditory nerves are damaged through disease or hereditary
congenital defects. The cochlea within the inner ear functions as a
receiving mechanism similar to piano keyboard. When the cochlea or
any other portion of the auditory nervous system is damaged, only a
portion of the auditory energy which is received thereby is
transmitted to the brain. These losses occur particularly in the
upper end of the range of audible sounds, because of subjection to
industrial noises, jet noises, explosions, atrophy age or the
like.
Certain infectious conditions, such as scarlet fever, measles,
sinusitis, or the like, are also known as common causes of the
three above noted types of auditory losses.
A fourth type of loss, generally designated as psychogenic, usually
occurs when there is a loss in energy transmission due to a mental
blockage.
While the present invention is primarily directed to the correction
of the first three hearing loss conditions described above, it will
be understood that there may be instances in which the fourth
condition may be corrected or alleviated by the insettion or
implantation of the present devices.
Each of the above described conditions may be caused by congenital
defects occurring within the human body, these defects usually
being apparent within two and one-half decades from the birth of
the individual, and at that time, generally perceivable by skilled
examination.
The prior art has disclosed various means for aiding in the
correction of the above-identified and described auditory defects.
These corrective devices have fallen into three basic categories.
First, those devices which mechanically direct to the human ear, by
means of filtration or the like, that portion of received auditory
oscillations which contain intelligible information. Secondly,
those devices which convey to the inner ear, via insertion within
the outer ear and ear canal or via bone transmission, electrical
and/or mechanical amplification of received auditory signals.
Thirdly, corrective or prosthetic devices which are intended to be
substituted for various elements of the human auditory system.
Broadly speaking, the implanted transducer of the instant invention
is a hybrid of the second and third categories of corrective
devices.
The ear trumpet is deemed to be representative of the first
category of corrective devices, for the trumpet merely funnels the
sound received in the outer ear down the ear canal toward the ear
drum without mechanically or electrically amplifying such auditory
energy.
The majority of the hearing aids or corrective devices utilized
today fall within the second category, for such hearing aids rely
upon a sound amplifier-transmitter unit carried upon the person,
with a wire connecting the transmitter to a receiver unit which is
stuck into the outer ear and extends inwardly into the ear canal.
With the advent of solid-state electronics, the sound
amplifier-transmitter unit has been mounted in eyeglass frames,
earrings, necklaces or the like, with a wire connection between the
eyeglass frames, earrings, necklace, etc., and the receiver unit
inserted within the ear usually through the use of an earmold.
Many persons, however, despite their need for a corrective device
to overcome their hearing loss, refuse to wear a hearing aid for
esthetic or cosmetic reasons. Other persons cannot tolerate the
distortions in tone caused by the transmission between the
amplifier-transmitter unit and the receiver unit, in addition to
the distracting buzzing sound of the device itself. Furthermore,
conventional hearing aids may not provide effective relief for
certain persons since their hearing loss may be attributable to
auditory problems in the mddle ear and/or inner ear.
Consequently, an alternative type of corrective device of the
second category has been evolved. This corrective device relies
upon a surgically planted receiver that conducts auditory energy
through the bones of the ossicular chain or the bones of the skull
to the inner ear. The speech amplifier-transmitter, which supplies
the power to the receiver via remote transmission without
interconnecting wires, can be encased in a fountain pen shape,
cigarette pack shape, standard hearing aid shape or similar object.
Although the bone-conductive type of corrective device does
overcome the widespread esthetic or cosmetic objection to the more
conventional hearing aid, is has not met with complete accpetance
for numerous reasons. United States Pat. Nos. 2,402,392 3,209,081
and 3,346,704, granted to Goldschmidt, Ducote et al., and Mahoney,
respectively, disclose illustrative ear implants that rely upon
bone conduction to achieve improved hearing.
As previously noted, there has been constantly increasing attention
focused upon the utilization of artificial body members or
prosthetic devices. Hence, prosthetic stapes of stainless steel,
polyethylene, Teflon, platinum or other inert materials that are
autoclavable, have been fabricated; for example, see U.S. Pat. Nos.
3,191,188 and 3,196,462, granted to Mercandino et al., and
Robinson, respectively.
Such prosthetic devices, which fall within the third category of
corrective devices as outlined above, enable the recipient of such
implant to hear in the same fashion as a person with normal hearing
ability. Thus, the recipient can distinguish sounds clearly over a
wider range of frequencies and with greater fidelity than can be
obtained by a hearing aid of the second category for the prosthetic
device is operatively associated with the oval window leading into
the inner ear.
One of the major drawbacks of such prosthetic stapes, however, is
that the hearing loss may be attributable to defects in the
malleus, the incus, or the stapes or the oval window area, or any
combination of these elements. Accordingly, the implantation of the
stapes may have limited success in alleviating hearing losses
attributable to diseases of the middle ear. Furthermore, prior
prosthetic stapes are merely substitutive in nature and cannot
amplify the sound energy received at the inner ear.
More recently, attempts have been made to surgically implant a
hearing aid within the body of the person suffering from a hearing
loss. For example, U.S. Pat. No. 3,557,775 granted to Mahoney,
discloses the implantation of a microphone tube, amplifier unit and
a speaker tube in the antrum cell of the mastoid adjacent to the
auricular appendage of the external ear. The unit is powered by a
rechargeable battery, and the sound picked up by the microphone is
fed into the speaker tube and thence to a point closely adjacent to
the round window leading into the inner ear. The wave motion casued
in the inner ear is transmitted to the cochlea, which initiates the
electrical impulses to the brain which are translated into
intelligible sound.
U.S. Pat. No. 3,594,514, granted to Wingrove, also discloses an
implantable hearing aid including a piezoelectric ceramic element.
One end of the element is implanted in an area of the body that can
provide a stable platform, such as the mastoid bone. The opposite
end of the element is then placed adjacent one of the ossicle bones
in the middle ear or the oval window leading into the inner ear.
The piezoelectric crystal bends or vibrates in response to a
varying voltage signal delivered thereto over a receiving coil and
a related to circuit responsive to varying sound waves. A
microphone preferably located externally to the body. picks up
sound waves and changes such waves into modulated RF signals
through appropriate circuitry. The modulated RF signals are
transmitted by a transmitting coil to the above noted receiving
coil, and thence to the piezoelectric crystal.
Whereas Mahoney and Wingrove may suggest ways to resolve some of
the problems previously encountered in designing hearing aids, both
patents pick up sound at a point exterior of the middle ear cavity.
Additionally, both patents attempt to substitute electronic
components for the sound receiving function normally performed with
great accuracy by the ear drum and for the sound transmitting
function performed by the ossicle bone chain. Accordingly, whatever
sound receiving and transmitting capability still resides in one's
auditory system may work at cross-purposes to the electronic
implant suggested by Mahoney and Wingrove. The naturally received
sound energy may clash with the electronically received and
transmitted sound energy to produce distortion, and the automatic
gain control provided by the tensors and flexors of the ossicle
bone chain is totally overlooked.
SUMMARY
In light of the magnitude of the problem of hearing losses and in
view of the limited success of prior devices in correcting this
problem, the instant invention contemplates numerous configurations
of implanted transducers that combine the most desirable features
of the seond and third category of corrective devices. More
particlarly, the instant invention contemplates a transducer
implanted within the middle ear cavity so that it can pick up the
sound energy striking the ear drum and can amplify such energy
without distortion by causing the ossicle bone chain to
mechanically vibrate and transmit such energy to the oval window,
round window or promontory leading to the inner ear. Alternatively,
in those instances where the ossicle bone chain is damaged, the
instant invention contemplates numerous simple methods for reading
the vibrations of the ear drum and translating such vibrations into
electrical signals for application to the oval window, round window
or promontory leading to the inner ear. Furthermore, the instant
invention relies upon the natural automatic gain control of the
tensors and flexors of the ossicle bone chain to prevent loud
sounds from injuring the wearer to the implant, and also utilizes
the natural distortion-free transmission of sound through the
ossicle bone chain whenever possible.
Furthermore, the instant invention contemplates surgically drilling
through the mastoid bone to position the transducer in operative
relationship to the bones of the ossicle chain and/or the oval
window, round window or promontory leading into the inner ear while
minimizing the irritation to the ear drum.
Additionally, the implanted transducer constitutes an
"all-in-the-ear" device and does not require an external, visible
interconnection between the amplifier-transmitter and receiver
units, thus overcoming the current widespread objection to existing
unsightly corrective devices because of cosmetic or esthetic
reasons. Furthermore, the implanted hearing aids minimize, if not
eliminate, the distortion and buzzing and may be used to treat
other diseases of the ear, such as tinnitus.
Also the transducer can be fabricated in sundry shapes and from
diverse materials that are pre-selected in accordance with the
dimension of the bones within the inner ear of the recipient. Ear
molds with appropriate tuning and recharging circuits can be
utilized to periodically externally re-tune the implanted hearing
aid without resorting to a second operation or surgical procedure.
Hearing aids utilizing means for converting audio impulses into
light are also envisioned. Yet, additional significant advantages
of the implanted transducer, and the surgical techniques employed
therewith, will become apparent in light of the following
description of the invention when construed in conjunction with the
accompanying sheets of drawings.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of the basic human auditory
system;
FIG. 1A is a front elevational view of the osseous labyrinth of the
human auditory system;
FIG. 1B is a horizontal cross-sectional view of a fragment of the
labyrinth, such view being taken along line 1B--1B in FIG. 1A in
the direction indicated;
FIG. 2 shows a preferred embodiment of the hearing aid implanted in
operative relationship to the ossicle bone chain within the middle
ear cavity, such hearing aid being sound powered and constructed in
accordance with the principles of the instant invention;
FIG. 3 shows, on an enlarged scale, details of the hearing aid of
FIG. 2;
FIGS. 4, 5, 6, 7 and 8 show five alternative embodiments of the
sound powered hearing aid;
FIG. 9 shows a hearing aid comprising a transmitting unit and a
receiving unit for delivering an electrical stimulus to the inner
ear to assist the natural hearing function;
FIG. 10 shows, in schematic fashion, the remotely situated control
circuitry utilized in conjunction with the various embodiments of
the hearing aid;
FIG. 11 shows a firt embodiment of the hearing aid utilizing
sensing means positioned within the middle ear to read or pick-up
the vibrations of the ear drum when sound strikes such member;
FIG. 12 shows a second embodiment of a hearing aid utilizing
magnetically responsive means to read the vibrations of the ear
drum;
FIG. 12a is a detaled view of that portion of the embodiment of
FIG. 12 that is located within the viewing circle;
FIGS. 13-15 diagrammatically show three alternative sensing
circuits that are responsive to the variations in magnetic field
transmitted by a magnet affixed to the ear drum in the manner shows
in FIG. 12;
FIG. 16 shows a first, or preferred, embodiment, of a hearing aid
utilizing light emitting means; and
FIG. 17 shows, in schematic fashion, the control circuitry for the
hearing aid of FIG. 16;
FIG. 18 shows an insertable hearing aid unit that may be used to
treat tinnitus; and
FIG. 19 shows an ear mold for tuning the controls circuits of FIG.
10.
DESCRIPTION OF THE INVENTION
Referring now in detail to the drawings in which similar reference
numerals refer to similar parts, FIG. 1 depicts the basic structure
of the human auditory system, such system being indicated generally
by reference numeral 10. It is understood that the following
description includes only those basic components of the human
auditory system which are essential to hearing. For further
reference to the exact details of the human auditory system,
reference may be made to any standard text, such as "The Physics of
the Ear" by T.S. Littler, published in 1965 by Pergamon Press,
Ltd., of London, England; see particularly pages 1-14.
The human auditory system comprises the outer ear, indicated
generally by reference numeral 10, and including an auricle 11, an
auditory canal 15 extending inwardly toward an ear drum or tympanum
16; a middle ear 12 including therein a malleus 17, an incus 18,
and a stapes 19 and an inner ear 13. The bones of the middle ear
collectively comprise the energy transmitting bone chain or ossicle
chain 20. These bones are sometimes, respectively, referred to as
the hammer 17, the anvil 18, and the stirrup 19. The stirrup is
connected to, in vibratory relation, the ovular window or fenestra
30 of a fluid filled sac 40, known as the labyrinth. The ovular
window 30, which is a membrane, separates the middle ear 12 from
the inner ear 13.
Referring particularly to 1A, it will be appreciated that ovular
window 30 forms the entry to the inner ear 11, which is enclosed
within the labyrinth. The labyrinth 40 consists of two parts, the
membranous labyrinth and the osseous labyrinth. The membranous
labyrinth is a system of interconnected canals and pouches within
the osseous labyrinth, or protective casing. Consequently, FIG. 1A
depicts the configuration of the osseous labyrinth, whereas FIG. 1B
illustrates a portion of the membranous labyrinth. The space
between the membranous labyrinth and the osseous labyrinth is
filled with a water-like fluid known as perilymph. The membranous
labyrinth contains another fluid known as endolymph.
Furthermore, as indicated by the appropriate reference numerals in
FIG. 1A, the osseous labyrinth is divided into three parts; the
vestibule 35, the cochlea 43, and the semi-circular canals 45.
There are three semi-circular canals disposed at right angles to
another and filled with fluid. These canals regulate the
individual's sense of balance and are not directly involved in the
hearing process.
The vestibule 35 is the central part of the osseous labyrinth and
the cochlea 43 is that porton of the labyrinth concerned
specifically with hearing. The cochlea 43 is snail-shaped and lies
horizontally in front of the vestibule 35. Such spacial
relationships can be best understood by realizing that FIG. 1A is a
front elevational view of the osseous labyrinth taken on a plane
substantially parallel to the plane of ear drum 16 in FIG. 1.
As shown by the cut-away section of the cochlea illustrated in FIG.
1B, the membranous cochlea is divided throughout the greater
portion of its spiral length into two passages by the basilar
membrane 44. The upper passage of the membranous cochlea terminates
at ovular window 30 while the lower passage terminates at round
window 42, which is a membrane similar to ovular window 30. The
windows are separated from each other by promontory 41. The basilar
member 44 has a large number of specialized hair cells 44A disposed
thereon; these cells collectively form the organ of Corti. These
hair cells respond to the sound waves passing through the fluid in
the cochlea and transmit such sound waves by way of acoustic nerves
46 to the brain.
The outer ear or auricle 11 serves as a horn for directing sound
vibrations into the auditory canal 15, thus impessing these sound
vibrations on the tympanum or ear drum 16. This member converts
such vibrations to mechanically transmittable energy via the
ossicle bone chain 20 thereby transmitting through the midle ear
cavity impulses capable of subsequent translation by the brain. As
previously noted, that portion of the human auditory apparatus
positioned anteriorly, i.e., towards the source of external
auditory energy from the tympanum 16, is generally designated as
the outer ear 11. The middle ear 12 is operatively connected to the
outer ear 11 through the auditory canal 15 and the tympanum 16. The
tympanum serves as the dividing line between the outer ear 11 and
the middle ear 12.
As explained above, the middle ear 12 incluces a cavity which
contains therein the above described ossicle bone chain 20. The
bone chain forms a linkage for transmitting sound vibrations from
the tympanum 16 to cause mechanical movement for pulsating or
vibrating the ovular window 30. The stapes is hinged at its upper
end at 19a so that the foot plate is pivoted or rocked aganst
window 30. In turn, window 30 pulses the fluids in the inner ear 13
to stimulate the organ of Corti and transmit impulses to the brain
via acoustic nerves 46.
Thus, the hearing process can be characterized as a chain reaction
involving the following four steps. First, sound vibrations are
caught by the external ear 11 and passed through auditory canal 15
to the tympanum or ear drum 16. Second, the vibrations of tympanum
16 are conducted by ossicle bone chain 20 to ovular window 30.
Third, movement of window 30 disturbs the perilymph between the
membranous labyrinth and the osseous labyrinth, which in turn,
disturbs the endolymph within the membranous labyrinth. Lastly, the
organ of Corti translates these liquid vibrations into electrical
impulses that are transmitted by acoustic nerves 46 to the
brain.
Referring now to FIGS. 2-8, it will be appreciated that the instant
invention comprises diverse transducers adapted to be implanted or
inserted within the human auditory system in operative relationship
to the middle ear structure. Obviously, the present invention is
intended to be so implanted by simple surgical procedures.
Keeping in mind the above description of the basic components of
the human auditory system, as shown in FIGS. 1, 1A and 1B,
reference is now made to the geometrical configurations, materials
and metods for surgical implantation of the transducers constructed
in accordance with the instant invention.
As explained above, the ear consists of an outer ear portion 10, a
middle ear portion 12, and an inner portion 13. Contained within
the middle ear portion 12, whose boundaries are roughly defined by
the tympanum 16 and the ovular window 30, there is the ossicle bone
chain consisting of the hammer 17, anvil 18, and stirrup 19. The
stirrup, in the normal human auditory system, is in operative
mechanical vibratory relationship to the ovular window 30. All of
these elements are contained within the middle ear cavity and
operate in the manner described above to coact with the other
above-described members of the human auditory system. Tensor
muscles 16b are disposed within the cavity to maintain the tympanum
16 properly tensioned, as shows in FIGS. 2, 4 and 5-8, and the
chorda tympanum 16a maintains the bone chain 20 in proper
orientation. Flexors 16c are also shown in FIGS. 2, 4 and 5-8; the
tensors and flexors work in concert with each other to prevent loud
noises from damaging the ear drum 16 and the other members of the
auditory system.
Referring now to FIGS. 2 and 3, a preferred embodiment of the
hearing aid is implanted in the middle ear cavity and is identified
generally by reference numeral 60. The stapes has been removed from
the ossicle bone chain, either through a simple surgical procedure
or through deterioration attributable to diseases of the auditory
system.
Hearing aid 60 includes a stylus 62 with an annular upper end 64
with a slot 66 passing therethrough; the slot enables stylus 62 to
be slipped onto, and retained in position upon, anvil 18 by
applying a crimping pressure to end 64. The point of the stylus
bears against the base of a pressure sensitive device 68. A
suitable pressure sensitive device is the Pitran piezojunction
transducer produced by Stow Laboratories, Inc. of Hudson,
Massachusetts; such transducer assumes the form of a planar NPN
transistor in which the emitter-base junction is responsive to the
application of a pressure or a point force to produce a linear,
amplified voltage. Numerous other pressure sensitive devices could
be utilized in place of the Pitran piezoelectric transducer; such
devices include piezoelectric crystals, diodes, strain gage
transducers or electrically conductive wires.
The variable voltage generated by the variable pressure upon device
68 is conducted by appropriate lead 70 to remotely situated tuning
circuit 72. Circuit 72, which is encased in a suitable housing, is
implanted in the mastoid bone near auricle or outer ear 11. A
representative circuit 72 may include a high gain FET circuit with
automatic gain control to provide external volume tuning for
implant 60. The variable amplified voltage signal is conducted over
lead 74 to one side of a pair of piezoelectric crystals retained
between the bottom face of pressure sensitive device 68 and oval
window 30. The crystals may be oriented either horizontally, as
shown in FIG. 3, or vertically, as shown in FIG. 4. The signals are
impressed upon the crystals, which may be benders, stretchers,
twisters, or combinations thereof, and the crystals vibrate against
or in proximity to the oval window 30 or cochlea 43.
Although the pressure of the stylus upon the pressure sensitive
device 68 may produce sufficient voltage to effectively vibrate the
crystals against oval window 30, an auxiliary power source may be
utilized to insure sufficient voltage for efficiently vibrating the
crystals for a prolonged period of time. The auxiliary power
source, which is designated by reference numeral 80, may assume the
form of a minute rechargable nickel-cadmium battery or other
suitable rechargable miniature power supply; power source 80 may
also be implanted in the mastoid bone at a location remote from the
middle ear cavitity. A charging circuit 82 is operatively
associated with power supply 80 and could be encased in the same
housing implanted in the mastoid bone. Power supply 80 and charging
circuit 82 are operatively associated with transducer 68 and
crystals 76, 78 by leads 84 and 86. The voltage from power supply
80 is impressed upon the crystals via lead 86, and tuning circuit
72 adjusts the frequency at which the crystals will deform or
vibrate.
FIG. 4 shows the first alternative embodiment of the instant
implanted, sound powered hearing aid. The term sound powered
indicates that the ear drum is intact and that the vibrations from
the sound striking same are transmitted mechanically through the
ossicle bone chain toward the inner ear. It will be noted that the
hearing aids shown in FIGS. 2, 4, 5, 6, 7 and 8 fall within the
broad category of sound powered devices.
In the embodiment of FIGS. 2 and 3 the piezoelectric crystals are
horizontally oriented whereas in the embodiment of FIG. 4,
identical crystals are vertically oriented in operative
relationship to oval window 30; the stapes or stirrup 19 has not
been removed from the ossicle bone chain, and no external control
circuits are utilized. The crystals are situated in operative
relationship to the footplate of stapes 19 and the vibrations of
the crystals assist the footplate in rocking the stapes about hinge
point 19. By virtue of leaving the ossicle bone chain intact, the
auditory energy striking the ear drum and passing through the bone
chain is distortion-free and hearing aid 88 need only supply
minimal assistance to the hearing process. Aid 88 is well suited
for overcoming mild hearing losses. Alternatively, the stapes 19
can be removed and the aid 88 placed in its place where conditions
permit; consequently, stapes 19 is shown in dotted outline in FIG.
4.
FIG. 5 shows a second alternative sound powered hearing aid 92 that
is located within the middle ear cavity in operative relationship
to the ossicle bone chain. As in the embodiment of FIGS. 2 and 3,
the stapes is removed from the ossicle bone chain, thus allowing
the end of incus 18 to be free hanging. Hearing aid 92 includes an
elongated piezoelectric crystal bar 94 that is clipped onto the
free end of incus 18 by means of crimpable rings 96, 98. A pin or
stylus 100 is secured to the lower end of bar 94 and extends
inwardly into contact with pressure sensitive device 102 situated
in proximity to a crystalline device 103 situated on promontory 41,
adjacent to, or near, oval window 30. Pressure sensitive device
102, which may be a Pitran piezoelectric transducer, a
piezoelectric crystal, a pressure sensitive diode, a strain gage
transducer or the like produces a voltage that stimulates the oval
window 30, and/or the cochlea 43, thus raising the threshold of
hearing. Crystalline device 103 may be a bucker, bender, or twister
crystal, or combinations thereof.
In addition to serving as a part of the mechanical linkage that
produces a significant mechanical advantage in transmitting forces
from ear drum 16 to oval window 30, the stresses placed upon
pressure sensitive device 102 produce a variable voltage which is
conducted by lead 101 to a remotely situated, high gain amplifying
circuit 104. The frequency of the voltage is adjusted to the
desired rate by circuit 104 and is then returned over lead 105 to
crystal 103 to cause same to vibrate or deform at the selected
frequency.
Although the pressure upon the pressure sensitive device 102 may
produce sufficient voltage to effectively vibrate crystal 103
against oval window 30, an auxiliary power supply 106 may be
connected over leads 107, 109 to opposite faces of crystal 103.
Furthermore, a charging circuit (not shown), similar to charging
circuit 82 of FIG. 3, could be implanted in the mastoid bone in
operative relationship to auxiliary power supply 106.
Since bar 94 is a piezoelectric crystal, a variable voltage is also
produced at opposite faces thereof when it is mechanically stressed
by the ossicle bone chain. Such voltage may be added to the voltage
produced by the pressure sensitive device 102 and the auxiliary
power supply 106, and the sum of the voltages may be applied to
crystal 103 for more efficient operation.
A diode could be utilized in lieu of the crystalline device
situated in proximity to oval window 30 in the hearing aid
embodiments of FIGS. 2-5. Such diode would receive the voltage
produced by pressure sensitive device 68 and rectify same into
pulsating D.C. voltage that could be applied directly to the oval
window, thus providing electrical stimulus to the auditory nerve.
Alternatively, the diode and the crystalline device could be
omitted, and the voltage from pressure sensitive device 68 could be
led over electrically conductive wires directly to the oval window
to shock same.
FIG. 6 shows a third alternative embodiment of the sound powered
hearing aid, such embodiment being indicated generally by reference
numeral 108. The ossicle bone chain is intact, and hearing aid 108
assumes the form of a pressure sensitive device of substantially
rectangular shape with a small stylus bearing thereagainst. One
corner of the pressure sensitive device is secured to the footplate
of stapes 19 to assist the stapes in rocking or pivoting against
window 30 about hinge 19c. The pressure transmitted through the
ossicle bone chain presses against the stylus of device 108 with
sufficient intensity to generate a voltage on leads 109 that
stimulate the area of oval window 30. If need be, additional
voltage may be supplied to pressure sensitive device 102 from a
remote power supply situated in the mastoid bone near auricle
11.
FIG. 7 shows a fourth alternative embodiment of the sound powered
hearing aid, such embodiment being indicated generally be reference
numeral 110. The stapes has been removed from the ossicle bone
chain, so that the inwardly extending, free end of anvil 18 can be
utilized to transmit vibrations from the ear drum to hearing aid
110. A collar 112 on hearing aid 110 is slipped over the free end
of anvil 18, so that the movement of the anvil causes movement of
stylus 114 situated on the underside of collar 112. The stylus
bears upon a pressure sensitive device 116, such as the Pitran
transducer described above, and produces a voltage proportional to
the force pressing thereagainst. The voltage is led over
appropriate leads 118 to a remotely situated tuning circuit 119
and/or an auxiliary power source 121. The voltage after appropriate
tuning and/or amplification, is returned via leads 120 to opposite
faces of a crystalline device 122, such as a piezoelectric crystal.
The crystal rests atop a fluid filled sack 124 that is secured to
oval window 30 by a layer 126 of plastic jelly-like foam known
commercially as Jel-Foam.
Consequently, sound striking the ear drum and passing through the
hammer to the free end of the anvil, produces a variable pressure
bearing against pressure sensitive device 116. Device 116, in turn,
generates a voltage proportional to the pressure applied thereto;
the voltage is led over leads 118 to the remote tuning and/or
amplification circuits 119 and 121, respectively, and then returned
over leads 120 for application to the opposite faces of crystal
122. The crystal, which may be a bender, twister, or bucker, or any
combination thereof, flexes and such movement is transmitted
through the fluid medium in sack 124 to oval window 30.
If desired, sack 124 may be designed as a truncated cone with the
broader surface providing increased support for crystalline device
122. The parallel, narrower surface would be affixed to oval window
30. The cone shape of the sack might well enhance the effectiveness
of the vibrations transmitted therethrough. Additionally, the
voltage produced by pressure sensitive device 116 may be amplified,
tuned, clipped, etc., by conventional circuits before being applied
to crystal 122.
FIG. 8 shows a fifth alternative embodiment of the sound powered
hearing aid, such embodiment being indicated generally by reference
numeral 125. Hearing aid 125 is similar to the hearing aid 110 of
FIG. 7 and includes a collar 126, a stylus 128, a pressure
responsive device 130, leads 132 and 134, control circuits 136 and
138, crystalline device 140, and a fluid filled sack 142 positioned
atop oval window 30. While hearing aid 110 in FIG. 7 requires the
removal of stapes 19, hearing aid 125 takes full advantage of the
ossicle bone chain and leaves same intact.
Pressure sensitive device 130, which is a minute element, is
slipped between anvil 18 and stirrup 19 at their juncture, and sack
142 is positioned between the footplate of stirrup 19 and oval
window 30. The movement of the inner end of anvil 18, in response
to sound striking the ear drum, thus presses stylus 128 against
pressure responsive device 128 to produce a variable voltage output
across leads 132, 134. The variable voltage is tuned by control
circuit 136, and the variable voltage is amplified by control
circuit 138. The voltage is then applied across the opposite faces
of crystalline device 140, and the resultant movement of device 140
is transmitted by sack 142 to oval window 30. The sack may be
adhered to the oval window by a suitable surgically acceptable
jelly, or the depth of the oval window with respect to promontory
41 may be such that the sack is retained in place, without
adhesive, by the surrounding walls of the promontory. The sack and
the pressure sensitive device are designated to take up any slack
in the ossicle bone chain, and thus maximize the effectiveness of
the sound conduction through the ossicle bone chain.
Variants of hearing aid 125 are equally feasible. For example, sack
142 may be omitted and crystalline device 140 may be positioned
against oval window 30. Alternatively, crystalline device 140 may
be implanted in the mastoid bone surrounding the middle ear cavity
and rely upon bone conduction techniques to send sound into the
inner ear. Additionally, the pressure sensitive device may be
slipped under the footplate of stapes 19 to take advantage of the
rocking motion of the stapes. As yet another variant, a first
pressure sensitive device may be slipped between teh anvil 18 and
the stirrup 19, and a second device may be slipped beneath the
footplate. In all instances, such hearing aids 125 are particularly
effective in overcoming hearing deficiencies attributable to
conductive losses.
Although the operation of hearing aids 60, 88, 92, 108, 110, and
125 has already been described in detail above, it is believed to
be expedient to briefly reiterate the salient features of such
hearing aids at this juncture. In all embodiments, sound passing
down ear canal 15 and striking ear drum 16, is, in normal sequence,
amplified twenty-two times by the fulcrum action of the ossicle
bone chain before reaching oval window 30. The stylus or the pin
function in the same capacity as the stapes without any reduction
in the mechanical amplification. Furthermore, the tensors and
flexors function as a natural automatic gain control circuit to
cushion the impact of loud sounds upon the auditory system.
Additionally, in all the above described sound-powered embodiments,
either the stapes 19 or the stylus that cooperates with the
pressure sensitive device, converts the movement of the ear drum
and the ossicle bones to movement of the pressure sensitive device
positioned over, or in operative relationship, to oval window 30.
The varied pressure of the sound striking the ear drum thus
produces a varied output voltage that may be fed directly to oval
window 30 for electrical stimulus, or may be amplified and then
impressed upon a crystalline device, such as a piezoelectric
crystal, adjacent to, or atop, the oval window. External tuning and
volume control circuits may also be utilized. In summary, the ear
drum and the ossicle bone chain replace the microphone in the
receiving unit of conventional hearing aids, for the sound from the
ear drum is mechanically amplified through the natural functions of
the ossicle bone chain; such variations in the bone chain are
pressed upon a pressure sensitive device to produce a
correspondingly varied electrical output that is sent to a high
gain amplifying circuit and then to a crystalline device
operatively associated with the oval window. Alternatively, the
high gain amplifying circuit may be omitted. The above described
hearing aids are considered to be sound powered devices, and will
probably correct one-half of the mild hearing losses.
Approximately, 75 per cent of those persons suffering from hearing
losses fall within this extremely broad category.
In all of the embodiments of the instant hearing aid, the
crystalline devices, diodes and conductive wires (see FIG. 9) are
described and illustrated for the sake of clarity as if they were
in direct contact with oval window 30 or promontory area 41.
However, the actual implantation of the hearing aids has shown that
an alternative method of fixation is more desirable. Such method
relies upon a pliable substance, such as a Jel Foam, to be packed
about the innermost end of the device to be coupled to oval window
30. The pliable substance dissolves partially and leaves a
protective sac of minute dimension, the sac functioning in much the
same manner as a balloon loosely filled with water. This resilience
helps to adjust the linkage differential in the bone displacement
of the ossicle bone chain. The sac also reduces the danger of
rupturing the oval window, and does prevent electrical shock or
stimulus from passing therethrough to the oval window.
FIG. 9 shows a hearing aid that delivers an electrical stimulus to
oval window 30, such hearing aid comprising two units, a first, or
transmitting unit 144 and a second, or receiving, unit 146. Unit
144, which is encased within plastic housing 148 and has an
outwardly extending pull tab 150, is situated within ear canal 15.
Unit 144 includes a microphone 152, such as an electret microphone,
a battery 154 or other suitable power source; a volume control
circuit 156; and a transmitting coil 158. Transmitting coil 158 can
radiate RF energy or magnetic vibrations through the skin to
energize receiving unit 146.
Unit 146, which is implanted just beneath the skin in the mastoid
bone defining the ear canal, includes a receiving coil 160, a
conducting wire 162, and an electrically stimulated device 164
affixed to promontory 41 between the oval and round windows leading
into the inner ear. Device 164 may be a piezoelectric crystal, a
diode or may merely be a continuation of conducting wire 130. In
all instances, the electric stimulation cooperates with the natural
functioning of the ossicle bone chain to increase the hearing of
the wearer of this two unit hearing aid.
FIG. 10 shows a pressure sensitive device 166 and an actuating
button or diaphragm 168 positioned immediately adjacent thereto.
The button is implanted just under the skin behind auricle 11. The
pressure sensitive device may well be a Pitran transducer of the
type discussed above, so that manual pressure applied to button 168
will press the stylus 170 postioned therebelow against the
transducer and produce a variable voltage. Such voltage can be fed
into the implanted battery or power source 172 to recharge same,
whenever needed. A second button 174 and a second pressure
sensitive device 176 can produce a voltage to be fed to volume
control circuit 178; when such circuit is sensitive to voltage
levels. If circuit 178 is not so responsive, button 174 and second
pressure sensitive device 176 can be omitted without serious
impairment to the efficiency of the implanted hearing aid.
FIG. 11 shows a first, or preferred, embodiment of a hearing aid
that utilizes transmitting means secured to the inner side of ear
drum 16 to transmit signals through the air in the middle ear
cavity to sensing means disposed adjacent to the oval window 30,
promontory 41, or round window 42. Whereas the sound powered
embodiments of FIGS. 2-9 utilize mechanical transmission of sounds
through the ossicle bone chain, and the embodiment of FIG. 10
relies upon electrical stimulation, the embodiments of FIGS. 11-17
focus primarily upon transmission between the ear drum and
implanted sensing means and pay only incidental attention to the
sound mechanically transmitted through the ossicle bone chain.
The hearing aid of FIG. 11 is identified generally by reference
character 180 and includes a small transmitter 182 which assumes
the form of a charged piece of material on the inner side of ear
drum 16; the transmitter may be a magnet, a fragment of phosphor, a
radio active isotope or a charged particle. The receiving unit
includes either an electret microphone 184, a magnetic diode, or a
transistor gate that is sensitive to magnetic variations, and a
piezoelectric crystal 186 positioned in the area of promontory 41.
The electret microphone might be one-eighth inch in diameter, and
can be obtained from Bell Laboratories and numerous other
commercial sources; the magnetic diodes are also available from
similar sources. It will be noted that the ossicle bone chain can
be left intact while utilizing hearing aid 180.
The negatively or postively charged piece of material 182 serves to
vary the output of electret microphone 184. The electret in
microphone 184 has a static potential, and the plus or minus charge
held by piece 182 will repel, or attract, the electret at the same
rate that sound is striking drum 16. The minute voltage variations
produced by the electret are sent via appropriate leads (not shown)
to a remotely situated high gain amplifier circuit 188; after
suitable amplification, the voltage is returned over lead 190 and
is impressed upon crystal 186 situated adjacent to oval window 30
to cause same to vibrate. Additionally, hearing aid 180 may employ
a remotely located power source 192 with, or without, a remote
volume control circuit; the power source and the volume control are
implanted in the mastoid bone at locations removed from one
another. Both power source 192 and high gain amplifier circuit 188
(if such circuit employs a FET or other magnetic responsive device)
are recharged by magnetic induction in a manner that has already
been explained in connection with FIG. 10. A reed switch 194 is
inserted into the circuitry of FIG. 11 to cut off the power to
crystal 186 while the battery or power source 192 is being
recharged.
FIG. 12 shows an alternative form of hearing aid, designated
generally by reference numeral 196, that relies upon transmitting
means affixed to the inner side of the ear drum and sensing means
disposed adjacent to the oval window 30, promontory 41, or round
window. The distance between the transmitting means on the eardrum
and the sensing means on the promontory is approximately
one-quarter of an inch; obviously, effectively bridging such a
small distance without transmission loss or distortion is a
relatively simple task for existing solid-state devices.
Hearing aid 196 includes a first minute magnet 198 with a hook 200
that is slipped over the malleus or hammer 17 near its point of
contact with the inner face of ear drum 16. Hook 200 might also be
anchored in the vicinity of chorda typanum 16a; see FIG. 1.
Continuing interiorly through the middle ear cavity, hearing aid
196 further includes a second magnet 202 that is operatively
associated with a stylus 204 affixed to diaphragm 206. The stylus
is positioned in operative relationship to a pressure sensitive
device 208, such as a Pitran transducer, which produces a variable
voltage proportional to the pressure applied thereto by the stylus.
The voltage output from device 208 is led over leads 210 and 212 to
a remote tuning and amplifying circuit 212 and a remote charging
circuit 214, respectively. The output from control circuits 212 and
214 is applied to crystalline situated in the area of promontory
41, which device may be a piezoelectric crystal capable of bucking,
twisting or bending. Under certain circumstances control circuits
212 and 214 may be omitted. In either event, the motion of the
crystalline device is related directly to the sound striking ear
drum 16 and the ossicle bone chain is left intact, thus leaving the
natural automatic gain control (AGC) facility of the ossicle bone
chaim unimpaired.
FIG. 13 diagrammatically shows another sensing circuit that will
respond to the variations in the magnetic field transmitted thereto
by magnet 198. The circuit of FIG. 13 also includes the second
magnet 202 which is secured to the diaphragm 218 of an electret
microphone 220. The movement of magnet 198 as sound energy strikes
the ear drum causes magnet 202 to move in response to changes in
the magnetic field established therebetween. The movement of magnet
202 pumps electret microphone 220 and produces a variable voltage
output that is led, over appropriate leads, to remote tuning
circuit 222 and remote charging circuit 224. After the voltage has
been properly regulated, it is applied to crystalline device 226,
which vibrates in the area of promontory 41.
FIG. 14 diagrammatically shows another sensing circuit that will
respond to the variations in the magnetic field transmitted thereto
by magnet 198 affixed to the inner side of the ear drum. The second
or receiving magnet 202 utilized in the ambodiments of FIGS. 12 and
13 is replaced by a transistor gate 228 that is responsive to
changes in the intensity and polarity of magnetic fields; one
common type of gate 228 is a field-effect transistor (F.E.T.). The
small output voltage across gate 228 is suitable regulated by
control circuits 222, 224, before being applied to a crystalline
device 229 situated in the area of promontory 41.
FIG. 15 diagrammatically shows yet another sensing circuit that
will respond to the variations in the magnetic field transmitted
thereto by magnet 198 affixed to the inner side of the ear drum.
The second or receiving magnet 202 utilized in the embodiments of
FIGS. 12 and 13, or the transistor gate 228 of FIG. 14, is replaced
by a Hall-effect device 230 that is responsive to changes in the
intensity and polarity of magnetic fields. The small output voltage
across device 230 is suitably regulated by control circuits 222,
224 before being applied to a crystalline device 231 situated in
the area of promontory 41.
Numerous modifications can readily be effectuated in the hearing
aid depicted in FIGS. 12-15. For example, a small fragment of
phosphor or other radio-active isotope could be substituted for
magnet 198. Also, crystalline devices 216 and 226 (FIGS. 12 and 13,
respectively) could be eliminated, and the variable voltage
appearing across the receiving means could be utilized directly to
stimulate, or shock, the oval window, promontory, or round window.
Alternatively, the crystalline devices could be eliminated and a
diode substituted therefore; such diode would receive the voltage
produced by the sensing means and rectify same into pulsating D.C.
voltage that could be applied directly to oval window 30, thus
providing electrical stimulus to the auditory nerves of the inner
ear.
FIGS. 16-17 disclose a two unit hearing aid that employs an audio
responsive light emitting unit and light sensing means on opposite
sides of the ear drum that respond to sounds striking the ear drum.
The audio responsive unit is identified by reference numeral 230
and is encased in a plastic housing 232 that fits within ear canal
15; the housing has a pull tab 234 for removing the unit. Within
housing 232 is a miniature microphone 236, a long-lived rechargable
battery 238, an amplifier 240 and a circuit 242 for energizing
light source 244 that extends through the housing and emits a beam
of collimated light down the ear canal.
The light sensing means is disposed on the opposite side of ear
drum 16 in the area of promontory 41 and in substantial alignment
with light source 244. The light sensing means includes a light
responsive resistor 246 connected to an amplifier 248, the output
of such amplifier being fed to remote control circuits 250, 252 and
thence to crystalline device 254. A suitable resistor 246 would be
a cadmium sulphide cell or photocell or a selenium cell. The
vibration of device 254 in the area of promontory 41 augments the
sound energy mechanically transmitted from the ear drum through the
ossicle bone chain. If desired, crystalline device 254 could be
omitted and the output voltage from amplifier 248 could be
impressed directly upon the area of promontory 41 to electrically
stimulate the auditory nerves. Alternatively, crystalline device
254 could be omitted and the output voltage from amplifier 248
could be fed to a diode that would convert the voltage into a
pulsating D. C. stimulus.
The transmitting unit 230 converts the sound or audio energy
striking microphone 236 into light pulses emanating from light
source 244. Since ear drum 16 is opaque and the ear canal is dark,
the light pulses are easily detected by diode 246 and the circuitry
associated therewith for converting the light energy into
electrical energy.
FIG. 18 shows yet another embodiment of a hearing aid constructed
in accordance with the principles of the instant invention. This
embodiment also comprises two units, a first or transmitting unit
256, and a second , or receiving unit 258. Unit 256, which is
encased within plastic housing 260 and has an outwardly extending
pull tab 262, is situated within ear canal 15. Unit 256 includes a
microphone 264 for receiving auditory energy, a battery 266 or
other suitable power source, an amplifying circuit 268, and a
transmitting device 270, such as a coil. Unit 258 comprises a
receiver 272 operatively associated with a small, rechargeable
battery 274 and a crystalline device 276. The receiver, the battery
and the crystalline device are implanted within the mastoid bone a
short distance from ear canal 15. Unit 256 sends RF, magnetic or
elecrostatic signals to implanted receiving unit 258. Unit 258 then
converts the signal into vibratory movement of crystalline device
276; such movement is transmitted to the cochlea by bone conduction
through the mastoid bone.
The hearing aid embodiment of FIG. 18 is particularly well suited
to overcome tinnitus, a physical and/or mental disease associated
with the auditory system that produces a sensation of ringing,
whistling or buzzing in the ears of the person so afflicted. The
transmitting units can be removed from the ear canal and tuned so
as to transmit various sounds to the ear nerve, the characteristics
of the transmitted sound being selected so as to mask the
unpleasant sounds associated with tinnitus.
FIG. 19 illustrates an ear mold 278 that fits into auricle 11 and
extends into ear canal 15 towards ear drum 16. Ear mold 278, which
may be utilized in connection with the manually operable recharging
devices of FIG. 10 or in lieu thereof, is a custom-made, hollow
shell with a first charging coil 280 secured therein in a fixed
position consistent with the fixed position of implanted power
source 172 which has a receiving coil 173. Charging coil 280
radiates energy to coil 173 for implanted power source 172 to
thereby recharge same. A second charging coil 282 may be used to
adjust the implanted volume and/or frequency tuning circuit 178;
however, care must be exercised to position the coils as far apart
as space will permit, thus isolating the coils and circuits from
one another.
A charging magnet 284, or other polarizing device, is situated at
the innermost end of ear mold 278, which is reduced in diameter to
avoid discomfort to the person temporarily wearing same during the
fitting process. The charging magnet or polarizing device causes
variations in the polarity and intensity of the magnet or
radioactive fragment attached to the inner side of ear drum 16, as
shown in FIGS. 11-15. The charging coils 280 and 282 in ear mold
278 are powered over appropriate leads from a remote, adjustable
control device 284 that is simply plugged into a conventional wall
outlet.
At periodic intervals, the wearer of the hearing aid will visit a
clinic and have the ear mold inserted into his ear. Trained
personnel will then readjust the control circuits for the hearing
aid without resort to surgical procedures.
Many of the above described hearing aids can be implanted in the
first instance by the simple surgical procedure of cutting and
laying back the ear drum to expose the middle ear cavity. Other
hearing aids can be implanted by drilling through the mastoid bone
behind the ear toward the middle ear cavity; an accurately drilled
hole will be aligned with the area of the oval window 30,
promontory 41 and the round window so that the various sensing
devices can be positioned thereagainst. Drilling through the
mastoid leaves the ear drum intact and reduces the potential
side-effects of such initial surgical procedure.
Since sundry additional modifications may be made in the
configuration and materials of the instant implanted hearing aids,
it is to be understood that all matter herein set forth or shown in
the accompanying drawings is to be interpreted as illustrative in
nature and not in a limiting sense.
* * * * *