U.S. patent application number 15/911595 was filed with the patent office on 2018-07-26 for transducer devices and methods for hearing.
The applicant listed for this patent is Earlens Corporation. Invention is credited to Jonathan Fay, Sunil Puria, Micha Rosen, Paul Rucker.
Application Number | 20180213331 15/911595 |
Document ID | / |
Family ID | 42039909 |
Filed Date | 2018-07-26 |
United States Patent
Application |
20180213331 |
Kind Code |
A1 |
Rucker; Paul ; et
al. |
July 26, 2018 |
TRANSDUCER DEVICES AND METHODS FOR HEARING
Abstract
A device to transmit an audio signal to a user may comprise a
mass, a piezoelectric transducer, and a support to support the mass
and the piezoelectric transducer with the eardrum. The
piezoelectric transducer can be configured to drive the support and
the eardrum with a first force and the mass with a second force
opposite the first force. The device may comprise circuitry
configured to receive wireless power and wireless transmission of
an audio signal, and the circuitry can be supported with the
eardrum to drive the transducer in response to the audio signal,
such that vibration between the circuitry and the transducer can be
decreased. The transducer can be positioned away from the umbo of
the ear to drive the eardrum, for example on the lateral process of
the malleus.
Inventors: |
Rucker; Paul; (San
Francisco, CA) ; Puria; Sunil; (Boston, MA) ;
Fay; Jonathan; (Dexter, MI) ; Rosen; Micha;
(Tzur Hadassah, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Earlens Corporation |
Menlo Park |
CA |
US |
|
|
Family ID: |
42039909 |
Appl. No.: |
15/911595 |
Filed: |
March 5, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15042595 |
Feb 12, 2016 |
9949035 |
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15911595 |
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13069282 |
Mar 22, 2011 |
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15042595 |
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PCT/US2009/057716 |
Sep 21, 2009 |
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13069282 |
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61217801 |
Jun 3, 2009 |
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61139526 |
Dec 19, 2008 |
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61109785 |
Oct 30, 2008 |
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61099087 |
Sep 22, 2008 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04R 25/02 20130101;
H04R 25/652 20130101; H04R 17/00 20130101; H04R 2225/025 20130101;
H04R 2460/09 20130101; H04R 11/02 20130101; H04R 25/606 20130101;
H04R 25/65 20130101; H04R 23/008 20130101; H04R 25/554 20130101;
H04R 2460/13 20130101 |
International
Class: |
H04R 11/02 20060101
H04R011/02; H04R 25/00 20060101 H04R025/00; H04R 23/00 20060101
H04R023/00; H04R 25/02 20060101 H04R025/02; H04R 17/00 20060101
H04R017/00 |
Claims
1.-65. (canceled)
66. A method of transmitting an audio signal to a user, the user
having an ear comprising an eardrum, the method comprising:
supporting a mass and a piezoelectric transducer with a support on
the eardrum of the user; driving the support and the eardrum with a
first force and the mass with a second force, the second force
opposite the first force.
67. The method of claim 66 wherein the ear comprises a mechanical
impedance and wherein the mass, the piezoelectric transducer and
the support comprise a combined mechanical impedance and wherein
the combined mechanical impedance matches the mechanical impedance
of the eardrum for at least one audible frequency within a range
from about 1 kHz to about 6 KHz.
68. A method of transmitting an audio signal to a user, the user
having an ear comprising an eardrum, the method comprising:
supporting circuitry and a transducer coupled to the circuitry with
the eardrum; and transmitting the audio signal with a wireless
signal to the circuitry to drive the transducer in response to the
audio signal.
69. A method of transmitting an audio signal to a user, the user
having an ear comprising an eardrum having a mechanical impedance,
the method comprising: supporting a transducer and a support
coupled to the eardrum with the eardrum, wherein a combined mass of
the support and the transducer supported thereon matches the
mechanical impedance of the eardrum for at least one audible
frequency between about 0.8 kHz and about 10 kHz.
70. A method of transmitting an audio signal to a user, the user
having an ear comprising an eardrum and a malleus connected to the
ear drum at an umbo, the method comprising: supporting a transducer
with a support positioned on the eardrum; vibrating the support and
the eardrum with the transducer positioned away from the umbo.
71. The method of claim 70 wherein a first movement of the
transducer is decreased relative to a second movement of the umbo
when the eardrum is vibrated and wherein the second movement of the
umbo is amplified relative to the first movement of the
transducer.
72. A method of transmitting an audio signal to a user, the user
having an ear comprising an eardrum and a malleus connected to the
eardrum at an umbo, the method comprising: supporting a first
transducer and a second transducer with a support positioned on the
eardrum; and driving the first transducer and the second transducer
in response to the audio signal to the twist the malleus such that
the malleus rotates about an elongate longitudinal axis of the
malleus.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of
PCT/US2009/057716 (Attorney Docket No. 026166-002010PC), filed Sep.
22, 2009, which claims priority to U.S. Patent Application Nos.;
61/139,526 filed Dec. 19, 2008 (Attorney Docket No.
026166-002300US, entitled "Balanced Armature Devices and Methods
for Hearing"; 61/217,801 filed on Jun. 3, 2009 (Attorney Docket No.
026166-002310US); 61/099,087 filed Sep. 22, 2008 (Attorney Docket
No. 026166-002000US), entitled "Transducer Devices and Methods for
Hearing"; and 61/109,785 filed Oct. 30, 2008 (Attorney Docket No.
026166-002010US), entitled "Transducer Devices and Methods for
Hearing"; the full disclosures of which are incorporated herein by
reference.
STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED
RESEARCH AND DEVELOPMENT
[0002] This invention was supported by grants from the National
Institutes of Health (Grant No. R.44DC008499-02A1). The Government
may have certain rights in this invention.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0003] The present invention is related to hearing systems, devices
and methods. Although specific reference is made to hearing aid
systems, embodiments of the present invention can be used in many
applications in which a signal is used to stimulate the ear.
[0004] People like to hear. Hearing allows people to listen to and
understand others. Natural hearing can include spatial cues that
allow a user to hear a speaker, even when background noise is
present.
[0005] Hearing devices can be used with communication systems to
help the hearing impaired. Hearing impaired subjects need hearing
aids to verbally communicate with those around them. Open canal
hearing aids have proven to be successful in the marketplace
because of increased comfort and an improved cosmetic appearance.
Another reason why open canal hearing aides can be popular is
reduced occlusion of the ear canal. Occlusion can result in an
unnatural, tunnel-like hearing effect which can be caused by large
hearing aids which block the ear canal. In at least some instances,
occlusion be noticed by the user when he or she speaks and the
occlusion results in an unnatural sound during speech. However, a
problem that may occur with open canal hearing aids is feedback.
The feedback may result from placement of the microphone in too
close proximity with the speaker or the amplified sound being too
great. Thus, feedback can limit the degree of sound amplification
that a hearing aid can provide. Although feedback can be decreased
by placing the microphone outside the ear canal, this placement can
result in the device providing an unnatural sound that is devoice
of the spatial location information cues present with natural
hearing.
[0006] In some instances, feedback may be decreased by using
non-acoustic means of stimulating the natural hearing transduction
pathway, for example stimulating the tympanic membrane, bones of
the ossicular chain and/or the cochlea. An output transducer may he
placed on the eardrum, the ossicles in the middle ear, or the
cochlea to stimulate the hearing pathway. Such an output transducer
may be electro magnetically based. For example, the transducer may
comprise a magnet and coil placed on the ossicles to stimulate the
hearing pathway. Surgery is often needed to place a hearing device
on the ossicles or cochlea, and such surgery can be somewhat
invasive in at least some instances. At least some of the known
methods of placing an electromagnetic transducer on the eardrum may
result in occlusion in some instances.
[0007] One promising approach has been to place a magnet on the
eardrum and drive the magnet with a coil positioned away from the
eardrum. The magnets can be electromagnetically driven with a coil
to cause motion in the hearing transduction pathway thereby causing
neural impulses leading to the sensation of hearing. A permanent
magnet may be coupled to the ear drum through the use of a fluid
and surface tension, for example as described in U.S. Pat. Nos.
5,259,032 and 6,084,975.
[0008] However, there is still room for improvement. For example,
with a magnet positioned on the eardrum and coil positioned away
from the magnet, the strength of the magnetic field generated to
drive the magnet may decrease rapidly with the distance from the
driver coil to the permanent magnet. Because of this rapid decrease
in strength over distance, efficiency of the energy to drive the
magnet may be less than ideal. Also, placement of the driver coil
near the magnet may cause discomfort for the user in some
instances. There can also be a need to align the driver coil with
the permanent magnet that may, in some instances, cause the
performance to be less than ideal.
[0009] For the above reasons, it would be desirable to provide
hearing systems which at least decrease, or even avoid, at least
some of the above mentioned limitations of the current hearing
devices. For example, there is a need to provide a comfortable
hearing device which provides hearing with natural qualities, for
example with spatial information cues, and which allow the user to
hear with less occlusion, distortion and feedback than current
devices.
2. Description of the Background Art.
[0010] Patents and publications that may be relevant to the present
application include: U.S. Pat. Nos. 3,585,416; 3,764,748;
3,882,285; 5,142,186; 5,554,096; 5,624,376; 5,795,287; 5,800,336;
5,825,122; 5,857,958; 5,859,916; 5,888,187; 5,897,486; 5,913,815;
5,949,895; 6,005,955; 6,068,590; 6,093,144; 6,139,488; 6,174,278;
6,190,305; 6,208,445; 6,217,508; 6,222,302; 6,241,767; 6,422,991;
6,475,134; 6,519,376; 6,620,110; 6,626,822; 6,676,592; 6,728,024;
6,735,318; 6,900,926; 6,920,340; 7,072,475; 7,095,981; 7,239,069;
7,289,639; D512,979; 2002/0086715; 2003/0142841; 2004/0234092;
2005/0020873; 2006/0107744; 2006/0233398; 2006/075175;
2007/0083078; 2007/0191673; 2008/0021518; 2008/0107292; commonly
owned U.S. Pat. No. 5,259,032 (Attorney Docket No.
026166-000500US); U.S. Pat. No. 5,276,910 (Attorney Docket No.
026166-000600US); U.S. Pat. No. 5,425,104 (Attorney Docket No.
026166-000700US); U.S. Pat. No. 5,804,109 (Attorney Docket No.
026166-000200US); U.S. Pat. No. 6,084,975 (Attorney Docket No.
026166-000300US); U.S. Pat. No. 6,554,761 (Attorney Docket No.
026166-001700US); U.S. Pat. No. 6,629,922 (Attorney Docket No.
026166-001600US); U.S. Publication Nos. 2006/0023908 (Attorney
Docket No. 026166-000100US); 2006/0189841 (Attorney Docket No.
026166-000820US); 2006/0251278 (Attorney Docket No.
026166-000900US); and 2007/0100197 (Attorney Docket No.
026166-001100US). Non-U.S. patents and publications that may be
relevant include EP1845919 PCT Publication Nos. WO 03/063542; WO
2006/075175; U.S. Publication Nos. Journal publications that may be
relevant include: Ayatollahi et al., "Design and Modeling of 114
Micromachines Condenser MEMS Loudspeaker using Permanent Magnet
Neodymium-Iron-Boron (Nd--Fe--B)", ISCE, Kuala Lampur, 2006; Birch
et al, "Microengineered Systems for the Hearing Impaired", IEE,
London, 1996; Cheng et al., "A silicon microspeaker for hearing
instruments", J. Micromech. Microeng., 14(2004) 859-866; Yi et al.,
"Piezoelectric microspeaker with compressive nitride diaphragm",
IEEE, 2006, and Zhigang Wang et al., "Preliminary Assessment of
Remote Photoelectric Excitation of an Actuator for a Hearing
Implant", IEEE Engineering in Medicine and Biology 27th Annual
Conference, Shanghai, China, Sep. 1-4, 2005. Other publications of
interest include: Gennum GA3280 Preliminary Data Sheet, "Voyager
TD.TM. Open Platform DSP System for Ultra Low Power Audio
Processing" and National Semiconductor LM4673 Data Sheet, "LM4673
Filterless, 2.65W, Mono, Class D audio Power Amplifier"; Puria, S.
et al., Middle ear morphometry from cadaveric temporal bone microCT
imaging, Invited Talk. MEMRO 2006, Zurich; Puria, S. et al, A gear
in the middle ear ARO 2007, Baltimore, Md.
BRIEF SUMMARY OF THE INVENTION
[0011] The present invention is related to hearing systems, devices
and methods. Although specific reference is made to hearing aid
systems, embodiments of the present invention can be used in many
applications in which a signal is used to stimulate the ear.
[0012] Embodiments of the present invention can provide improved
hearing which overcomes at least some of the aforementioned
limitations of current systems. In many embodiments, a device to
transmit an audio signal to a user may comprise a transducer
assembly comprising a mass, a piezoelectric transducer, and a
support to support the mass and the piezoelectric transducer with
the eardrum. The piezoelectric transducer can be configured to
drive the support and the eardrum with a first force and the mass
with a second force opposite the first force. This driving of the
ear drum and support with a force opposite the mass can result in
more direct driving of the eardrum, and can improve coupling of the
vibration of transducer to the eardrum. The transducer assembly
device may comprise circuitry configured to receive wireless power
and wireless transmission of an audio signal, and the circuitry can
be supported with the eardrum to drive the transducer in response
to the audio signal, such that vibration between the circuitry and
the transducer can be decreased. The wireless signal may comprise
an electromagnetic signal produced with a coil, or an
electromagnetic signal comprising light energy produce with a light
source. In at least some embodiments, at least one of the
transducer or the mass can be positioned on the support away from
the umbo of the ear when the support is coupled to the eardrum to
drive the eardrum, so as to decrease motion of the transducer and
decrease user perceived occlusion, for example when the user
speaks. This positioning of the transducer and/or the mass away
from the umbo, for example on the short process of the malleus, may
allow a transducer with a greater mass to be used and may even
amplify the motion of the transducer with the malleus. In at least
some embodiments, the transducer may comprise a plurality of
transducers to drive the malleus with both a hinging rotational
motion and a twisting motion, which can result in more natural
motion of the malleus and can improve transmission of the audio
signal to the user.
[0013] In a first aspect, embodiments of the present invention
provide a device to transmit an audio signal to a user. The user
has an ear comprising an ear drum. The device comprises a mass, a
piezoelectric transducer, and a support to support the mass and the
piezoelectric transducer with the eardrum. The piezoelectric
transducer is configured to drive the support and the eardrum with
a first force and the mass with a second force opposite the first
force.
[0014] In many embodiments, the piezoelectric transducer is
disposed between the mass and the support.
[0015] In many embodiments, the device further comprises at least
one flexible structure disposed between the piezoelectric
transducer and the mass.
[0016] In many embodiments, the piezoelectric transducer is
magnetically coupled to the support.
[0017] In many embodiments, the piezoelectric transducer comprises
a first portion connected to the mass and a second portion
connected to the support to drive the mass opposite the
support.
[0018] In many embodiments, the support comprises a first side
shaped to conform with the eardrum. A protrusion can be disposed
opposite the first side and affixed to the piezoelectric
transducer.
[0019] In many embodiments, the device further comprises a fluid
disposed between the first side and the eardrum to couple the
support to the eardrum. The fluid may comprise a liquid composed of
at least one of an oil, a mineral oil, a silicone oil or a
hydrophobic liquid. In some embodiments, the support comprises a
second side disposed opposite the first side and the protrusion
extends from the second side to the piezoelectric transducer.
[0020] In many embodiments, the support comprises a first component
and a second component. The first component may comprise a flexible
material shaped to conform to the eardrum and flex with motion of
the eardrum. The second component may comprise a rigid material
extending from the transducer to the flexible material to transmit
the first force to the flexible material and the eardrum. In at
least some embodiments, the rigid material comprises at least one
of a metal, titanium, a stainless steel or a rigid plastic, and the
flexible material comprises at least one of a silicone, a flexible
plastic or a gel.
[0021] In many embodiments, the device further comprises a housing,
the housing rigidly affixed to the mass to move the housing and the
mass opposite the support. In some embodiments, the support
comprises a rigid material that extends through the housing to the
transducer to move the mass and the housing opposite the
support.
[0022] In many embodiments, the mass comprises circuitry coupled to
the transducer and supported with the support and the transducer.
The circuitry is configured to receive wireless power and wireless
transmission of the audio signal to drive the transducer in
response to the audio signal.
[0023] In many embodiments, the piezoelectric transducer comprises
at least one of a piezoelectric unimorph transducer, a
bimorph-bender piezoelectric transducer, a piezoelectric multimorph
transducer, a stacked piezoelectric transducer with a mechanical
multiplier or a ring piezoelectric transducer with a mechanical
multiplier.
[0024] In some embodiments, the piezoelectric transducer comprises
the bimorph-bender piezoelectric transducer and the mass comprises
a first mass and a second mass. The bimorph bender comprises a
cantilever extending from a first end supporting the first mass to
a second end supporting the second mass. The support is coupled to
the cantilever between the first end and the second end to drive
the ear drum with the first force and drive the first mass and the
second mass with the second force.
[0025] In some embodiments, the piezoelectric transducer comprises
the stacked piezoelectric transducer with the mechanical
multiplier. The mechanical multiplier comprises a first side
coupled to the support to drive the eardrum with the first force
and a second side coupled to the mass to drive the mass with the
second force.
[0026] In some embodiments, the piezoelectric transducer comprises
the ring piezoelectric transducer with the mechanical multiplier.
The mechanical multiplier comprises a first side and a second side.
The first side extends inwardly from the ring piezoelectric
transducer to the mass. The second side extends inwardly toward a
protrusion of the support. The mass moves away from the protrusion
of the support when the ring contracts and toward the protrusion of
the support when the ring expands. The ring piezoelectric
multiplier may define a center having central axis extending there
through. The central protrusion and the mass may be disposed along
the central axis.
[0027] In some embodiments, the piezoelectric transducer comprises
the bimorph bender. The mass comprises a ring having a central
aperture formed thereon. The bimorph bender extends across the ring
with a first end and a second end coupled to the ring. The support
extends through the aperture and connects to the piezoelectric
transducer between the first end and the second end to move the
support opposite the ring when the bimorph bender bends. The
bimorph bender can be connected to the ring with an adhesive on the
first end and the second end such that the first end and the second
end are configured to move relative to the ring with shear motion
when the bimorph bender bends to drive the support opposite the
ring.
[0028] In another aspect, embodiments of the present invention
provide a device to transmit an audio signal to a user. The user
has an ear comprising an eardrum. The device comprises a
transducer, circuitry coupled to the transducer, and a support
configured to couple to the eardrum and support the circuitry and
the transducer with the eardrum. The circuitry is configured to
receive at least one of wireless power or wireless transmission of
the audio signal to drive the transducer in response to the audio
signal.
[0029] In many embodiments, the transducer is configured to drive
the support and the eardrum with a first force and drive the
circuitry with a second force opposite the first force.
[0030] In many embodiments, the circuitry is rigidly attached to a
mass and coupled to the transducer to drive the circuitry and the
mass with the first force. In some embodiments, the circuitry is
rigidly attached to the mass and coupled to the transducer to drive
the circuitry and the mass with the second force.
[0031] In many embodiments, the circuitry is flexibly attached to a
mass and coupled to the transducer to drive the circuitry and the
mass with the first force. In some embodiments, the circuitry is
flexibly attached to the mass and coupled to the transducer to
drive the circuitry and the mass with the second force.
[0032] In many embodiments, the circuitry comprises at least one of
a photodetector or a coil supported with the support and coupled to
the transducer to drive the transducer with the at least one of the
wireless power or wireless transmission of the audio signal.
[0033] In many embodiments, the transducer comprises at least one
of a piezoelectric transducer, a magnetostrictive transducer, a
magnet or a coil.
[0034] In another aspect, embodiments of the invention provide a
device to transmit an audio signal to a user. The user has an ear
comprising an eardrum having a mechanical impedance. The device
comprises a transducer and a support to support the transducer with
the eardrum. A combined mass of the support and the transducer
supported thereon is configured to match the mechanical impedance
of the eardrum for at least one audible frequency between about 0.8
kHz and about 10 kHz.
[0035] In many embodiments, the combined mass comprises no more
than about 50 mg. In some embodiments, the combined mass is within
a range from about 10 mg to about 40 mg.
[0036] In many embodiments, the combined mass comprises at least
one of a mass from circuitry to drive the transducer, a mass from a
housing disposed over the transducer or a metallic mass coupled to
the transducer opposite the support. In some embodiments, the
transducer, the circuitry to drive the transducer, the housing
disposed over the transducer and the metallic mass are supported
with the eardrum when the support is coupled to the eardrum.
[0037] In many embodiments, at least one audible frequency is
between about 1 kHz and about 6 KHz.
[0038] In many embodiments, the transducer and the mass are
positioned on the support to place at least one of the transducer
or the mass away from an umbo of the eardrum when the support is
placed on the eardrum. This positioning can decrease a mechanical
impedance of the support to sound transmitted with the eardrum When
the support is positioned on the eardrum.
[0039] In many embodiments, the piezoelectric transducer comprises
a stiffness. The stiffness of the piezoelectric transducer is
matched to the mechanical impedance of the eardrum for the at least
one audible frequency.
[0040] In many embodiments, the eardrum comprises an umbo and the
acoustic input impedance comprises an acoustic impedance of the
umbo. The stiffness of the piezoelectric transducer is matched to
the acoustic input impedance of the umbo.
[0041] In another aspect, embodiments of the present invention
provide a device to transmit an audio signal to a user. The user
has an ear comprising an eardrum and a malleus connected to the ear
drum at an umbo. The device comprises a transducer and a support to
support the transducer with the eardrum. The transducer is
configured to drive the eardrum. The transducer is positioned on
the support to extend away from the umbo when the support is placed
on the eardrum.
[0042] In many embodiments, a mass is positioned on the support for
placement away from the umbo when the support is placed against the
eardrum, and the transducer extends between the mass arid a
position on the support that corresponds to the umbo so as to
couple vibration of the transducer to the umbo. The mass can be
positioned on the support to align the mass with the malleus away
from the umbo when the support is placed against the eardrum.
[0043] In many embodiments, the transducer is positioned on the
support so as to decrease a first movement of the transducer
relative to a second movement of the umbo when the eardrum vibrates
and to amplify the second movement of the umbo relative to the
first movement of the transducer when the transducer vibrates. In
some embodiments, the first movement of the transducer is no more
than about 75% of the second movement of the umbo and the second
movement of the umbo is at least about 25% more than the first
movement of the transducer. The first movement of the transducer
may be no more than about 67% of the second movement of the umbo
and the second movement of the umbo may be at least about 50% more
than the first movement of the transducer.
[0044] In many embodiments, the device further comprises a mass,
and the transducer is disposed between the mass and the
support.
[0045] In many embodiments, the support is shaped to the eardrum of
the user to position the support on the eardrum in a predetermined
orientation. The transducer is positioned on the support to align
the transducer with a malleus of the user with the eardrum disposed
between the malleus and the support when the support is placed on
the eardrum. In some embodiments, the support comprises a shape
from a mold of the eardrum of the user.
[0046] In many embodiments, the transducer is positioned on the
support to place the transducer away from a tip of the malleus when
the support is placed on the eardrum.
[0047] In many embodiments, the transducer is positioned on the
support to place the transducer away from the tip when the support
is positioned on the eardrum. The malleus comprises a head and a
handle. The handle extends from the head to a tip near the umbo of
the eardrum.
[0048] In many embodiments, the transducer is positioned on the
support to align the transducer with the lateral process of the
malleus with the eardrum disposed between the lateral process and
the support when the support is placed on the eardrum. In some
embodiments, the support comprises a rigid material that extends
from the transducer toward the lateral process to move the lateral
process opposite the mass.
[0049] In many embodiments, the transducer comprises at least one
of a piezoelectric transducer, a magnetostrictive transducer, a
photostrictive transducer, a coil or a magnet.
[0050] In many embodiments, the transducer comprises the
piezoelectric transducer. The piezoelectric transducer may comprise
a cantilevered bimorph bender, which has a first end anchored to
the support and a second end attached to a mass to drive the mass
opposite the lateral process when the support is placed on the
eardrum.
[0051] In many embodiments, the device further comprises a mass
coupled to the transducer and circuitry coupled to the transducer
to drive the transducer. The mass and the circuitry is supported
with the eardrum when the support is placed on the ear. The
support, the transducer, the mass and the circuitry comprise a
combined mass of no more than about 60 mg, for example, a combined
mass of no more than about 40 mg or even a combined mass of no more
than 30 mg.
[0052] In another aspect, embodiments of the present invention
provide a device to transmit an audio signal to a user. The user
has an ear comprising an ear drum. The device comprises a first
transducer, a second transducer, and a support to support the first
transducer and the second transducer with the eardrum when the
support is placed against the eardrum. The first transducer is
positioned on the support to couple to a first side of the malleus.
The second transducer positioned on the support to couple to a
second side of the malleus.
[0053] In many embodiments, the first transducer is positioned on
the support to couple to the first side of the malleus and the
second transducer is positioned on the support to coupled to the
second side of the malleus which is opposite the first side of the
malleus.
[0054] In many embodiments, the support comprises a first
protrusion extending to the first transducer to couple the first
side of the malleus to the first transducer and a second protrusion
extending to the second transducer to couple the second side of the
malleus to the second transducer.
[0055] In many embodiments, the first transducer and second
transducer are positioned on the support and configured to twist
the malleus with a first rotation about a longitudinal axis of the
malleus when the first transducer and second transducer move in
opposite directions. The first transducer and second transducer can
be positioned on the support and configured to rotate the malleus
with a second hinged rotation when the first transducer and second
transducer move in similar directions.
[0056] In many embodiments, the device further comprises circuitry
coupled to the first transducer and the second transducer. The
circuitry is configured to generate a first signal to drive the
transducer and a second signal to drive the second transducer. In
some embodiments, the circuitry is configured to generate the first
signal at least partially out of phase with the second signal and
drive the malleus with a twisting motion. The circuitry can be
configured to drive the first transducer substantially in phase
with the second transducer at a first frequency below about 1 kHz,
and the circuitry can be configured to drive the first transducer
at least about ten degrees out of phase with the second transducer
at a second frequency above at least about 2 kHz.
[0057] In many embodiments, the first transducer comprises at least
one of a first piezoelectric transducer, a first coil and magnet
transducer, a first magnetostrictive transducer or a first
photostrictive transducer, and the second transducer comprises at
least one of a second piezoelectric transducer, a second coil and
magnet transducer, a second magnetostrictive transducer or a second
photostrictive transducer.
[0058] In another aspect, embodiments of the present invention
provide a method of transmitting an audio signal to a user. The
user has an ear comprising an eardrum. The method comprises
supporting a mass and a piezoelectric transducer with a support on
the eardrum of the user and driving the support and the eardrum
with a first force and the mass with a second force, the second
force opposite the first force.
[0059] In many embodiments, the ear comprises a mechanical
impedance. The mass, the piezoelectric transducer and the support
comprise a combined mechanical impedance. The combined mechanical
impedance matches the mechanical impedance of the eardrum for at
least one audible frequency within a range from about 1 kHz to
about 6 KHz.
[0060] In another aspect, embodiments of the present invention
provide a method of transmitting an audio signal to a user. The
user has an ear comprising an eardrum. The method comprises
supporting circuitry and a transducer coupled to the circuitry with
the eardrum and transmitting the audio signal with a wireless
signal to the circuitry to drive the transducer in response to the
audio signal.
[0061] In another aspect, embodiments of the present invention
provide a method of transmitting an audio signal to a user. The
user has an ear comprising an eardrum having a mechanical
impedance. The method comprises supporting a transducer and a
support coupled to the eardrum with the eardrum. A combined mass of
the support and the transducer supported thereon matches the
mechanical impedance of the eardrum for at least one audible
frequency between about 0.8 kHz and about 10 kHz.
[0062] In another aspect, embodiments of the present invention
provide a method of transmitting an audio signal to a user. The
user has an ear comprising an eardrum and a malleus connected to
the ear drum at an umbo. The method comprises supporting a
transducer with a support positioned on the eardrum and vibrating
the support and the eardrum with the transducer positioned away
from the umbo. In many embodiments, a first movement of the
transducer is decreased relative to a second movement of the umbo
when the eardrum is vibrated and the second movement of the umbo is
amplified relative to the first movement of the transducer.
[0063] In another aspect, embodiments of the present invention
provide a method of transmitting an audio signal to a user. The
user has an ear comprising an eardrum and a malleus connected to
the eardrum at an umbo. The method comprises supporting a first
transducer and a second transducer with a support positioned on the
eardrum. The first transducer and the second transducer are driven
in response to the audio signal to the twist the malleus such that
the malleus rotates about an elongate longitudinal axis of the
malleus.
BRIEF DESCRIPTION OF THE DRAWINGS
[0064] A hearing aid system using wireless signal transduction is
shown in FIG. 1, according to embodiments of the present
invention;
[0065] FIG. 1A shows the lateral side of the eardrum and FIG. 1B
shows the medial side of the eardrum, suitable for incorporation of
the hearing aid system of FIG. 1;
[0066] FIGS. 1C and 1D show the eardrum coupled to the ossicles
including the malleus, incus, and stapes, and locations of
attachment for the hearing aid system shown in FIG. 1;
[0067] FIG. 2 shows the sensitivity of silicon photovoltaics to
different wavelengths of light, suitable for incorporation with the
system of FIGS. 1A to 1D;
[0068] FIG. 3 shows the mechanical impedance of the eardrum in
relation to that of various masses, in accordance with the system
of FIGS. 1A to 2;
[0069] FIG. 4 shows a simply supported bimorph bender, in
accordance with the systems of FIGS. 1A to 3;
[0070] FIG. 5A shows a cantilevered bimorph bender, in accordance
with the system of FIGS. 1A to 3;
[0071] FIG. 5B shows cantilevered bimorph bender which includes a
first mass and a second mass, in accordance with the system of
FIGS. 1A to 3;
[0072] FIG. 6 shows a stacked piezo with mechanical multiplier, in
accordance with the system of FIGS. 1A to 3;
[0073] FIG. 7 shows a narrow ring piezo with a mechanical
multiplier, in accordance with the system of FIGS. 1A to 3;
[0074] FIG. 8 shows a ring mass with bimorph piezo, in accordance
with the system of FIGS. 1A to 3;
[0075] FIGS. 8A and 8B show a cross-sectional view and a top view,
respectively, of a ring mass with bimorph piezo, in accordance with
the system of FIGS. 1A to 3;
[0076] FIGS. 8B1 and 8B2 shows a perspective view of ring mass with
a bimorph piezo with flexible structures to couple the bimorph
piezo to the ring mass, in accordance with the system of FIGS. 1A
to 3;
[0077] FIGS. 8C and 8D show a cross-sectional view and a top view,
respectively, of a ring mass with dual bimorph piezo, in accordance
with the systems of FIGS. 1A to 3;
[0078] FIG. 8E shows a plot of phase difference versus frequency
for the first and second transducers of the dual bimorph piezo of
FIGS. 8C and 8D;
[0079] FIG. 9 shows a simply supported bimorph bender with a
housing, in accordance with the systems of FIGS. 1A to 4;
[0080] FIG. 9A shows an optically powered output transducer, in
accordance with the systems of FIGS. 1A to 3;
[0081] FIG. 9B shows a magnetically powered output transducer, in
accordance with the systems of FIGS. 1A to 3;
[0082] FIG. 10 shows a cantilevered bimorph bender placed on the
eardrum away from the umbo and on the lateral process, in
accordance with the systems of FIGS. 1A to 3;
[0083] FIG. 10A shows an output transducer assembly comprising a
cantilevered bimorph bender placed on the ear drum with a mass on
the lateral process away from the umbo and an elongate member
comprising a cantilever extending from the mass toward the Limbo so
as to couple to the eardrum at the umbo, in accordance with the
systems of FIGS. 1A to 3;
[0084] FIG. 10B shows the cantilevered bimorph bender of FIG. 10A
from another view;
[0085] FIG. 11 shows a side view of a transducer comprising two
cantilevered bimorph benders placed on different locations on the
eardrum, in accordance with the systems of FIGS. 1A to 3;
[0086] FIG. 11A shows two cantilevered bimorph benders placed on
the ear drum over the umbo and the lateral process, in accordance
with the systems of FIGS. 1A to 3;
[0087] FIG. 12 shows an exemplary graph of simulation results for
an output transducers in accordance with the systems of FIGS. 1A to
3;
[0088] FIG. 13A shows a stacked piezo and FIG. 13B shows a plot of
displacement per voltage for the stacked piezo of FIG. 13A;
[0089] FIG. 14A shows a series bimorph and FIG. 14B shows a plot of
displacement per voltage for the series bimorph of FIG. 14A;
[0090] FIG. 15A shows a single crystal bimorph cantilever and FIG.
15B shows a plot o displacement per voltage for the single crystal
bimorph cantilever of FIG. 15A;
[0091] FIG. 16A shows a bimorph on a washer and FIG. 16B shows a
plot of displacement per voltage for the bimorph on a washer of
FIG. 16A;
[0092] FIG. 17A shows a stacked piezo pair, FIG. 17B shows a plot
of displacement per voltage for the stacked piezo pair of FIG. 17A,
and FIG. 17C shows a plot of lever ratio for the stacked piezo pair
of FIG. 17C;
[0093] FIG. 18A shows a plot of peak output for a bimorph piezo
placed on the Limbo, and FIG. 18B shows a plot of feedback for a
bimorph piezo placed on the umbo;
[0094] FIG. 19A shows a plot of peak output for a bimorph piezo
placed on the center of pressure on an eardrum, and FIG. 19B shows
a plot of feedback for a biomorph piezo placed on the center of
pressure on an eardrum; and
[0095] FIG. 20A shows a plot of peak output for a stacked piezo
placed on the center of pressure on an eardrum, and FIG. 20B shows
a plot of feedback for a stacked piezo placed on the center of
pressure on an eardrum.
DETAILED DESCRIPTION OF THE INVENTION
[0096] Embodiments of the present invention can provide optically
coupled hearing devices with improved audio signal transmission.
The systems, devices, and methods described herein may find
application for hearing devices, for example open ear canal hearing
aides. Although specific reference is made to hearing aid systems,
embodiments of the present invention can be used in any application
in which a signal is wirelessly received and converted into a
mechanical output.
[0097] As used herein, the umbo of the eardrum encompasses a
portion of the eardrum that extends most medially along the ear
canal, so as to include a tip, or vertex of the ear canal. As used
herein, a twisting motion and/or twisting encompass a rotation of
an elongate body about an elongate axis extending along the
elongate body, for example rotation of a rigid elongate bone about
an elongate axis of the bone. Twisting as used herein encompasses
rotation of the elongate body both with torsion of the elongate
body about the elongate axis and also without torsion of the
elongate body about the elongate axis. As used herein torsion
encompasses a strain, or deformation, that can occur with twisting,
such that one part of the elongate body twists, or rotates, more
than another part of the elongate body.
[0098] FIG. 1 shows a hearing aid system using wireless signal
transduction. The hearing system 10 includes an input transducer
assembly 20 and an output transducer assembly 30. Hearing system 10
may comprise a behind the ear unit BTE. Behind the ear unit BTE may
comprise many components of system 10 such as a speech processor,
battery, wireless transmission circuitry and input transducer
assembly 10. Behind the ear unit BTE may comprise many component as
described in U.S. Pat. Pub. Nos. 2007/0100197, entitled "Output
transducers for hearing systems"; and 2006/0251278, entitled
"Hearing system having improved high frequency response". The input
transducer assembly 20 is located at least partially behind the
pinna P, although an input transducer assembly may be located at
many sites such as in pinna P or entirely within ear canal EC. The
input transducer assembly 20 can receive a sound input, for example
an audio sound. With hearing aids for hearing impaired individuals,
the input can be ambient sound. The input transducer assembly
comprises an input transducer, for example a microphone 22.
Microphone 22 can be positioned in many locations such as behind
the ear, if appropriate. Microphone 22 is shown positioned within
ear canal near the opening to detect spatial localization cues from
the ambient sound. The input transducer assembly can include a
suitable amplifier or other electronic interface. In some
embodiments, the input may comprise an electronic sound signal from
a sound producing or receiving device, such as a telephone, a
cellular telephone, a Bluetooth connection, a radio, a digital
audio unit, and the like.
[0099] Input transducer assembly 20 includes a signal output source
12 which may comprise an electromagnetic source such as a light
source such as an LED or a laser diode, an electromagnet, an RF
source, or the like. Alternatively, an amplifier of the input
assembly may be coupled to the output transducer assembly with a
conductor such as a flexible wire, conductive trace on a flex
printed circuitry board, or the like. The signal output source can
produce an output signal based on the sound input. Output
transducer assembly 30 can receive the output source signal and can
produce mechanical vibrations in response. Output transducer
assembly 30 may comprise a transducer responsive to the
electromagnetic signal, for example at least one photodetector, a
coil responsive to the electromagnet, a magenetostrictve element, a
photostrictive element, a piezoelectric element, or the like. When
properly coupled to the subject's hearing transduction pathway, the
mechanical vibrations caused by output transducer assembly 30 can
induce neural impulses in the subject which can be interpreted by
the subject as the original sound input.
[0100] The output transducer assembly 30 can be configured to
couple to a point along the hearing transduction pathway of the
subject in order to induce neural impulses which can be interpreted
as sound by the subject. As shown in FIG. 1, the output transducer
assembly 30 may be coupled to the tympanic membrane or eardrum TM.
Output transducer assembly 30 may be supported on the eardrum TM by
a support, housing, mold, or the like shaped to conform with the
shape of the eardrum TM. A fluid may be disposed between the
eardrum TM and the output transducer assembly 30 such as an oil, a
mineral oil, a silicone oil, a hydrophobic liquid, or the like.
Output transducer assembly 30 can cause the eardrum TM to move in a
first direction 40 and in a second direction 45 opposite the first
direction 40, such that output transducer assembly 30 may cause the
eardrum TM to vibrate. Specific points of attachment are described
in prior U.S. Pat. Nos. 5,259,032; and 6,084,975, the full
disclosures of which are incorporated herein by reference and may
be suitable for combination with some embodiments of the present
invention,
[0101] FIG. 1A shows structures of the ear suitable for placement
of the output transducer assembly from the lateral side of the
eardrum TM, and FIG. 1B shows structures of the ear from the medial
side of the eardrum TM. The eardrum TM is connected to a malleus
ML. Malleus ML comprises a head H, a manubrium MA, a lateral
process LP, and a tip T. Manubrium MA is disposed between head H
and tip T and coupled to eardrum TM, such that the malleus ML
vibrates with vibration of eardrum TM.
[0102] FIG. 1C. shows output transducer assembly 30 coupled to the
eardrum TM on the umbo UM to transmit vibration so that the user
can perceive sound. Eardrum TM is coupled to the ossicles including
the malleus ML, incus IN, and stapes ST. The manubrium MA of the
malleus ML can be firmly attached to eardrum TM. The most depressed
or concaved point of the eardrum TM comprises the umbo UM. Malleus
ML comprises a first axis 110, a second axis 113 and a third axis
115. Incus IN comprises a first axis 120, a second axis 123 and a
third axis 125. Stapes ST comprises a first axis 130, a second axis
133 and a third axis 135.
[0103] The axes of the malleus ML, incus IN and stapes ST can be
defined based on moments of inertia. The first axis may comprise a
minimum moment of inertia for each bone. The second axis comprises
a maximum moment of inertia for each bone. The first axis can be
orthogonal to the second axis. The third axis extends between the
first and second axes, for example such that the first, second and
third axes comprise a right handed triple. For example first axis
110 of malleus ML may comprise the minimum moment of inertia of the
malleus. Second axis 113 of malleus ML may comprise the maximum
moment of inertia of malleus ML. Third axis 115 of malleus ML can
extend perpendicular to the first and second axis, for example as
the third component of a right handed triple defined by first axis
110 and second axis 113. Further first axis 120 of incus IN may
comprise the minimum moment of inertia of the incus. Second axis
123 of incus IN may comprise the maximum moment of inertia of incus
IN. Third axis 125 of incus IN can extend perpendicular to the
first and second axis, for example as the third component of a
right handed triple defined by first axis 120 and second axis 123.
First axis 130 of stapes ST may comprise the minimum moment of
inertia of the stapes. Second axis 133 of stapes ST may comprise
the maximum moment of inertia of stapes ST. Third axis 135 of
stapes ST can extend perpendicular to the first and second axis,
for example as the third component of a right handed triple defined
by first axis 130 and second axis 133.
[0104] Vibration of the output transducer system induces vibration
of eardrum TM and malleus ML that is transmitted to stapes ST via
Incus IN, such that the user perceives sound. Low frequency
vibration of eardrum TM at umbo UM can cause hinged rotational
movement 125A of malleus ML and incus IN about axis 125.
Translation at umbo UM and causes a hinged rotational movement 125B
of the tip T of malleus ML and hinged rotational movement 125A of
malleus ML and incus IN about axis 125, which causes the stapes to
translate along axis 135 and transmits vibration to the cochlea.
Vibration of eardrum TM, for example at higher frequencies, may
also cause malleus ML to twist about elongate first malleus axis
110 in a twisting movement 110A. Such twisting may comprise
twisting movement 110B on the tip T of the malleus ML. The twisting
of malleus ML about first malleus axis 110 may cause the incus IN
to twist about first incus axis 120. Such rotation of the incus can
cause the stapes to transmit the vibration to the cochlea where the
vibration is perceived as sound by the user.
[0105] With the output transducer assembly positioned over the
eardrum TM on the umbo UM, the combined mass of the output
transducer assembly can be from about 10 to about 60 mg, for
example from about 10 to about 40 mg. In some embodiments, the
combined mass comprises no more than about 50 mg. The combined mass
may comprise the mass of the support, the transducer, a mass
opposite the support and/or the circuitry to receive a wireless
signal and drive the transducer. The support can be configured to
support the transducer, a mass opposite the support and/or the
circuitry to receive a wireless signal and drive the transducer
with the eardrum when the support is placed against the
eardrum.
[0106] FIG. 1D shows output transducer assembly 30 coupled on the
TM away from umbo UM, for example over the lateral process LP of
the malleus ML. Output transducer assembly 30 may be placed on
other parts of the eardrum as well. Depending on the placement of
output transducer assembly 30 on the eardrum TM, the mechanical
impedance of the output transducer assembly 30 and the eardrum TM
may vary. Placement of output transducer assembly 30 away from the
umbo UM allows for increased mass of the lateral process while
minimizing occlusion. For example, with placement over the lateral
process, the mass of the output transducer assembly may comprise
approximately twice the mass as when placed over the umbo without
causing occlusion. For example, an output transducer assembly
comprising a mass of 60 mg positioned over the lateral process will
provide a mechanical impedance and occlusion similar to a 30 mg
mass positioned over the umbo. Further the vibration of the
transducer at the lateral process is amplified from the lateral
process to the umbo, for example by a factor of two due to leverage
of the malleus with hinged rotation from the head of the malleus to
the tip near the umbo.
[0107] The mass of transducer assembly 30 for placement away from
the umbo can be similar to ranges described above for the
configuration placed over the umbo, and may be scaled accordingly.
For example, with the output transducer assembly positioned over
the eardrum TM away from the umbo UM, for example over the lateral
process, the combined mass of the output transducer assembly can be
from about 20 to about 120 mg, for example from about 40 to about
80 mg. In many embodiments, the combined mass of output transducer
assembly 30 over the lateral process can be from about 20 mg to
about 60 mg to provide occlusion and transmission losses similar to
a mass of about 10 mg to about 30 mg over the umbo.
[0108] Output transducer assembly 30 may have a number of exemplary
specifications for maximum output. Output transducer assembly 30
may produce a sound pressure level of up to 106 dB. For example, a
sound pressure level of up to at least about 90 dB can be
sufficient to provide quality hearing for many hearing impaired
users. The "center" of the eardrum, or the umbo, may move at 0.1
um/Pa at 1 kHz and 0.01 um/Pa at 10 kHz. The velocity can be 630
um/s/Pa from about 1 kHz and 10 kHz. The area of the eardrum may be
about 100 mm.sup.2. The ear drum may have an impedance of about 0.2
Ns/m for frequencies greater than 1 kHz, which may be damping in
nature, and an impedance of about 1000 N/m for frequencies less
than 1 kHz in nature, which may be stiffening in nature. Thus, the
power input into the ear at up to 106 dB SPL may be up to about 1
uW.
[0109] Output transducer assembly 30 may comprise a number of
exemplary specifications for frequency response. Output transducer
assembly 30 can have a frequency response of 100 Hz to 10 kHz. For
an open canal system, it may be acceptable if low frequency
response rolls off below 1 kHz since most hearing impaired subjects
have relatively good low frequency hearing and the natural sound
pathway can provide this portion of the sound spectrum. A
relatively flat response may be good and it may be ideal if a
resonance is generated at 2-3 kHz without affecting response at
other frequencies. Variability between subjects may be +/-3 dB.
This includes variability due to variable insertions and movement
of the transducer with jaw movements. Variability across subjects
may be +/-6 dB. Even in low responding subjects may need to have
adequate output above their thresholds at all frequencies. Subject
based calibrations may likely be problematic for clinicians and
best avoided if possible.
[0110] Output transducer assembly 30 may further comprise a number
of other exemplary specifications. For example, output transducer
assembly 30 may have less than 1 percent harmonic distortion of up
to 100 db SPL and less than 10 percent distortion of up to 106 db
SPL. Output transducer may have less than 30 dB SPL noise
equivalent pressure at the input. Output transducer may provide 15
dB of gain up to 1 kHz and 30 dB of gain above 1 kHz.
[0111] I. Power Sources:
[0112] Both power and signal may be transmitted to the output
transducer assembly 30. 1 uW of power into the ear may need to be
generated to meet maximum output specifications. Methods of
transmitting power may include light (photovoltaic), ultrasound,
radio frequency, magnetic resonant circuits.
[0113] In exemplary embodiments, a piezoelectric transducer driven
by a photovoltaic (PV) cell or a number of photovoltaic (PV) in
placed in series. The maximum voltage and current provided by the
cells can be limited by the area and the amount of incident light
upon them, 70 mW may be a good upper limit for the amount of
electrical power available for the output transducer at its maximum
output. This power can be limited by the amount of heat that can be
dissipated as well as battery life considerations.
[0114] LEDs may be about 5% efficient in their conversion of
electrical power into light power. The maximum light power coming
out of the LEDs may be near 3.5 mW. The light coming out of the LED
can cover a broader area than the area of the photovoltaic cell.
The broader area may be set based on the movement of the ear canal
and the ability to point the light directly at the photovoltaic
cells. For example, a spot with a diameter that is twice a wide as
a square 3.16 mm.times.3.16 mm photocell may be used. This spot
size would have an area of 31.4 mm.sup.2 (leading to an optical
efficiency of 32%). The photodetector area may comprise two
parts--one part to move the transducer in a first direction and
another part to move the transducer in a second direction, for
example as described in U.S. Pat. App. No. 61/073,271, filed on
Jun. 17, 2008, entitled "OPTICAL ELECTRO-MECHANICAL HEARING DEVICES
WITH COMBINED POWER AND SIGNAL ARCHITECTURES", (attorney docket no.
026166-001800US), the full disclosure of which is incorporated
herein by reference. This two part photodetector area may further
reduce the efficiency by a factor of two to 16%. This efficiency
may be improved depending on the result of studies showing how much
the motion of the ear canal moves the light as well as the ability
to initially point the light down the ear canal. With a 16%
efficiency, 560 uW of light power impinges on the surface of each
of the two photovoltaics. The device may comprise at least one
photo detector, for example as described in U.S. Pat. App. No.
61/071281, filed Jun. 17, 2008, entitled "OPTICAL
ELECTRO-MECHANICAL HEARING DEVICES WITH SEPARATE POWER AND SIGNAL
COMPONENTS", (attorney docket no. 026166-001900US), the full
disclosure of which is incorporated by reference.
[0115] FIG. 2 shows the sensitivity of silicon photovoltaics to
different wavelengths of light. The sensitivity of a photodetector
is how much current is produced per unit power of incident light
(A/W). In FIG. 2, maximum light intensity of 560 uW may be 336 uA
at infrared wavelengths (S=0.6 A/W @ 900-1000 nm) or 224 uA in the
"red" range (S=0.4 A/W @ 650 nm). Red LEDs may be more efficient
than infrared LEDs, so the increased efficiency of the LEDs may
overcome the decreased sensitivity of the photodetector at those
wavelengths. The maximum available currents may be in the 220-340
uA range. The voltage characteristic of the photodetector is set by
the "diode" action of the junction. Starting a 0.3 V, an
increasingly non-linear voltage response may be encountered. Hence
the maximum effective voltage of the photodetector for our
application may be 0.4V. Multiplying this 0.4V by the 224 uA one
obtains 90 uW. Taking this 90 uW and dividing by the 560 uW of
light power in gives an efficiency of 16%. One may also use the
photocells in series to increase the amount of voltage available.
However, the area of each photocell may need to be reduced to keep
the total area the same. This may have the effect that voltage may
be traded for current and vice versa, however the total amount of
power remains fixed.
[0116] The LED/photovoltaic system may supply approximately 224 uA
of current and 0.4V. Voltage can be increased by putting cells in
series but the voltage increase may be at the proportional cost of
current. 90 uW of power may be available to the transducer for
producing motion of the eardrum. However, the amount of power
utilized can depend on the load characteristics. The optimal load
may be a 1800 ohm resistor (0.4V/224 uA). In either the
piezoelectric case (capacitive load) or the voice coil case
(inductive load), the load impedance may change as a function of
frequency. A frequency at which this optimal impedance is matched
may be chosen. For the capacitive load case, the system may be
current limited above this frequency and voltage limited below this
frequency. For the inductive load case, the situation may reverse.
In the current limited cases, one may not be able to reach the
desired maximum output levels. In the voltage limited regions,
driving the system too hard may highly distort the output. If 2 kHz
is chosen as the optimal frequency, this impedance may correspond
to a capacitance of 44 nF or an inductance of 143 mH. Even with an
optimal load attached, the overall efficiency of the optical power
transfer is 0.04%. Yet even with this efficiency, the amount of
power produced by the PV is 90.times. greater than what we expect
to need to input into the ear.
[0117] Table 1 below summarizes the above-mentioned exemplary power
specifications.
TABLE-US-00001 TABLE 1 EXEMPLARY POWER SPECIFICATIONS FOR OUTPUT
TRANSDUCER Parameter Formula Value Comment Input Power Maximum 70
mW May be chosen based on magnetic system experience with head and
battery life. LED efficiency 5% May be based on literature and
experimental data Area of illumination pR.sup.2 R = 3.16 mm May be
a reasonable guess based A = 31.4 mm.sup.2 on what will be required
for robust illumination of photodetectors Area of photodetectors b
2 2 ##EQU00001## B = 3.16 mm A = 5 mm.sup.2 May be based on what
area of the eardrum is easily viewable from a mid ear canal
location. Remember that only half of the area is available for each
photodetectors (hence the divide by 2). Optical efficiency A illum
A pv .times. 100 % ##EQU00002## 16% Maximum optical power
E.sub.opticalE.sub.LEDP.sub.max 560 mW incident on photodetectors
Sensitivity of PV @ IR 0.6 A/W (~950 nm) Sensitivity of PV @ Red
0.4 A/W (~650 nm) Maximum PV current @ S.sub.PVP.sub..lamda.PV 336
mA IR Maximum PV current S.sub.PVP.sub..lamda.PV 224 mA @ Red
Maximum PV voltage 0.4 V Maximum voltage for ~10% distortion. (0.3
V for ~1%) Maximum PV power @ V.sub.PVmaxI.sub.PVmax 90 mW Red
Optimal Load for PV V PVmax I PVmax ##EQU00003## 1800 ohms Overall
efficiency P PV P max .cndot. .times. 100 % ##EQU00004## 0.13%
[0118] Other power transmission potions may include ultrasonic
power transmission, magnetic resonant circuits, and radiofrequency
power transmission. For magnetic resonant circuits, the basic
concept is to produce two circuits that resonant with each other.
The "far" coil should only draw enough power from the magnetic
fields to perform its task. Power transfer may be in the 30-40%
efficient range.
[0119] II. Output Transducer Specifications
[0120] In exemplary embodiments, an output transducer may comprise
two major characteristics; the physics used to generate motion and
the type of reference method used. The choices for the physics used
to generate motion can include electromagnetic (voice coils,
speakers, and the like), piezoelectric, electrostatic,
pryomechanical, photostrictive, magnetostrictive, and the like.
Regardless of what physics are used to generate motion, the energy
of the motion can be turned into useful motion of the eardrum. In
order to produce motion, forces or moments that act against the
impedance of the eardrum may be generated. To generate forces or
moments, the reaction force or moment is resisted. To resist such
forces or movements, a fixed anchor point may be introduced, a
floating inertia may be used, for example, utilizing translational
and rotational inertia, or deforming an object so that the
boundaries produce a net force that moves the object, i.e., using a
deformation transducer.
[0121] FIG. 3 is a graph showing the mechanical impedance of the
eardrum in relation to that of various masses of 100 mg, 50 mg, 20
mg, and 10 mg. The impedance of the eardrum matches the masses of
100 mg, 50 mg, 20 mg, and 10 mg at frequencies of about 450 Hz, 700
Hz, 1.5 kHz, 3 kHz, respectively. The impedance of the mass can be
dependent on the location of the eardrum. By placing the mass away
from the umbo, the impedance can be decreased, for example halved,
when the mass is positioned on the short or lateral process of the
malleus, for example. For example, a mass of 40 mg can have an
impedance at 1.5 kHz that is similar to a 20 mg mass so as to match
the impedance of the eardrum TM.
[0122] Exemplary physical specifications may be placed on the
transducer based on the size of the ear canal, the ability of an
output transducer to remain in position and the perception of
occlusion resulting from having a mass present on the eardrum.
Table 2 below show these specifications.
TABLE-US-00002 TABLE 2 EXEMPLARY PHYSICAL SPECIFICATIONS FOR OUTPUT
TRANSDUCER Parameter Value Comment Maximum dimension <5 mm If
the dimension gets larger, then in plane with manipulating the
transducer into annular place may become difficult ligament of TM
for physicians and may not fit down some ear canals. Maximum
dimension <2 mm If the dimension gets larger, then perpendicular
to the anterior wall that "hangs" over TM the TM may begin to get
in the way. Maximum mass 60 mg A mass of 46 mg may result in
significant "occlusion". Other embodiments may be able to hold more
weight. There may be evidence that at even this weight gravity may
shift the position of the transducer depending on the orientation
of the head and the support to TM coupling.
[0123] Output transducer assembly 30 may use a piezoelectric
element to generate motion. Material properties of exemplary
piezoelectric elements are shown in the table 3 below.
TABLE-US-00003 TABLE 3 MATERIAL PROPERTIES OF EXEMPLARY
PIEZOELECTRIC ELEMENTS TRS APC APC APC APC single single disk
bender Tapecast stacked STEMinc crystal crystal Material APC 855
APC 850 APC PST 7 .times. 7 .times. .2 TRS APC 150 SMQA PMN-PT
PMN-PT Density 7600 7700 8000 7900 7900 8200 (kg/m3) Curie 200 360
155 250 166 Temperature k33 0.76 0.72 0.91 0.92 d31 276 175 290 140
1000 930 (.times.10-12 m/V) d33 600 400 640 310 1900 2000
(.times.10-12 m/V) E33 (N/m2) 5.10E+10 5.40E+10 5.56E+10 7.30E+30
1.16E+10 relative 3400 1900 5400 1400 7700 4600 dielectric constant
(Er33) E11 (N/m2) 5.90E+10 6.30E+10 8.40E+10 2.48E+10 kp 0.68 0.63
0.58 0.92 kt 0.45 0.55 0.6 k31 0.4 0.36 0.34 0.51 0.72
[0124] III. Exemplary Output Transducers
[0125] Output transducer assembly 30 may comprise a piezoelectric
based output transducer, for example, a transducer comprising a
piezoelectric unimorph, piezoelectric bimorph, or a piezoelectric
multimorph. Exemplary output transducers may comprise a simply
supported bimorph bender 400 as shown in FIG. 4, a cantilevered
bimorph bender 500 as shown in FIG. 5, a stacked piezo with
mechanical multiplier 600 as shown in FIG. 6, a disk or narrow ring
piezo with a mechanical multiplier 700 as shown in FIG. 7 or a ring
mass with bimorph piezoelectric transducer 800 as shown in FIG.
8,
[0126] FIG. 4 shows a simply supported bimorph bender 400 suitable
for incorporation with transducer assembly 30 as described above.
Simply supported bimorph bender 400 comprises a first mass 410a, a
second mass 410b, a bimorph piezoelectric cantilever 420, and a
support 430. Cantilever 420 extends from a first end supporting
first mass 410a to a second end supporting second mass 410b.
Cantilever 420 is coupled with the support 430 comprising a
protrusion 430p extending from the support to the transducer to
couple the support to the transducer between the first and second
ends. Support 430 may be configured to support the first and second
masses 410a, 410b and the bimorph cantilever 420 on the eardrum TM.
For example, support 430 may comprise a mold shaped to conform with
the eardrum TM, for example support 430 can be shaped with known
molding techniques. The portion 430a of support 430 which is in
contact with the fluid that couples to the eardrum TM can be
flexible, for example, by comprising a flexible material such as
silicone, flexible plastic, a gel, or the like. Other portions of
support 430, for example protrusion 430P may be rigid, for example,
by comprising a metal, titanium, a rigid plastic, or the like.
Simply supported bimorph bender 400 may comprise circuitry which
receives an external, wireless signal and causes cantilever 420 to
change shape. Cantilever 420 may push against masses 410a, 410b
causing a force on the masses 410a, 4101) in a direction 445 and
also cause a force on support 430 in a direction 440 opposite
direction 445. The force on support 430 drives the eardrum TM to
produce sensations of sound.
[0127] FIG. 5A shows a cantilevered bimorph bender 500 suitable for
incorporation with transducer assembly 30 as described above.
Cantilevered bimorph bender 500 includes a mass 510, a bimorph
cantilever 520 extending from mass 510, and a support 530 coupled
with cantilever 520. Support 530 may be configured to support mass
510 and bimorph cantilever 520 on the eardrum TM, which may not be
drawn to scale in FIG. 5A. For example, support 530 may comprise a
mold shaped to conform with the eardrum TM. Cantilever 520 is
coupled with the support 530 comprising a protrusion 530p extending
from the support to the transducer. The portion 530a of support 530
which is in contact with the eardrum TM can be flexible, for
example, by comprising a flexible material such as silicone,
flexible plastic, a gel, or the like. Other portions of support 530
may be rigid, for example, by comprising a metal, titanium, a rigid
plastic, or the like. Cantilevered bimorph bender 500 may comprise
circuitry configured to receive an external, wireless signal and
cause cantilever 520 to bend and thus push against mass 510. The
pushing action causes a force in a direction 545 on the mass 510
and also a force on the support 530 in a direction 540 opposite the
direction 545. The force on the support 530 drives the eardrum TM
to produce sensations of sound.
[0128] Cantilevered bimorph bender 500 includes mass 510 and
cantilever 520. Some embodiments may include more than one mass,
cantilever, and/or support.
[0129] FIG. 5B shows cantilevered bimorph bender 550 suitable for
incorporation with transducer assembly 30 as described above.
Bimorph bender 550 includes a first mass 560a and a second mass
560b. A first cantilevered bimorph 570a is coupled to first mass
560a. A second cantilevered bimorph 570b is coupled to second mass
560E). A support 580 is coupled to the first cantilevered bimorph
570a and second cantilevered bimorphs 570b. First cantilevered
bimorph 570a is coupled with the support 580 comprising a
protrusion 580p. Second cantilevered bimorph 570b is coupled with
the support 580 comprising a protrusion 580pb. Support 580 may be
configured to support masses 560a, 560b and bimorph cantilevers
570a, 570b on the eardrum TM, which may not be drawn to scale on
FIG. 5B. For example, support 580 may comprise a mold shaped to
conform with the eardrum TM. The portion 580a of support 580 which
is in contact with the eardrum TM can be flexible, for example, by
comprising a flexible material such as silicone, flexible plastic,
a gel, or the like. Other portions of support 580 may be rigid, for
example, by comprising a metal, titanium, a rigid plastic, or the
like. Cantilevered bimorph bender 550 may comprise circuitry
configured to receive an external, wireless signal and cause
cantilevers 570a, 570b to bend and thus push against masses 560a,
560b, respectively. The pushing action causes force in a direction
595 on the masses 560a, 560b and also a force on the support 580 in
a direction 590 opposite the direction 595. The force on the
support 580 causes a translational movement which drives the
eardrum TM to produce sensations of sound Cantilevers 570a, 570b
may push masses 560a, 560b in tandem to cause support 540 to
translate and drive the eardrum TM. Cantilevers 570a, 570b may also
push masses 560a, 570b in different orders as to cause a rotational
or twisting movement of the support 580 and the eardrum TM.
[0130] FIG. 6 shows a stacked piezo with mechanical multiplier 600
suitable for incorporation with transducer assembly 30 as described
above. The stacked piezo 600 comprises a plurality of piezoelectric
elements or a stacked piezoelectric array 610, mechanical
multiplier 620, a mass 630, and a support 640. The piezoelectric
array 610 may be held by mechanical multiplier 620. Mechanical
multiplier 620 is coupled to mass 630 on side 623 and support 640
on side 626. Mechanical multiplier 620 is coupled with the support
640 comprising a protrusion 640p extending from the support to the
transducer. Support 640 may be configured to support mechanical
multiplier 620 and the piezoelectric array 610 and the mass 630 on
the eardrum TM, which may not be drawn to scale in FIG. 6. For
example, support 640 may comprise a mold shaped to conform with the
eardrum TM. The portion 630a of support 630 which is in contact
with the eardrum TM can be flexible, for example, by comprising a
flexible material such as silicone, flexible plastic, a gel, or the
like. Other portions of support 640 may be rigid, for example, by
comprising a metal, titanium, a rigid plastic, or the like. Stacked
piezo 600 may comprise circuitry configured to receive an external,
wireless signal and cause the piezoelectric array 610 to expand or
contract along axis 650. Mechanical multiplier 620 uses leverage to
multiply this expansion and contraction and change its direction to
a direction along axis 655, thereby producing a force against mass
-630 and support 640. The force on support 640 drives the eardrum
TM to produce sensations of sound.
[0131] FIG. 7 shows a narrow ring piezo with a mechanical
multiplier 700 suitable for incorporation with transducer assembly
30 as described above. The narrow ring piezo 700 comprises a
piezoelectric ring 710, disc-shaped mechanical multiplier 720, a
mass 730, and a support 740. Mechanical multiplier 720 is coupled
to mass 730 and support 740. Mechanical multiplier 720 is coupled
with the support 740 comprising a protrusion 740p extending from
the support to the transducer. Support 740 may be configured to
support mechanical multiplier 720 and the piezoelectric ring 710
and the mass 730 on the eardrum TM. For example, support 740 may
comprise a mold shaped to conform with the eardrum TM. The portion
740a of support 740 which is in contact with the eardrum TM can be
flexible, for example, by comprising a flexible material such as
silicone, flexible plastic, a gel, or the like. Other portions of
support 740 may be rigid, for example protrusion 740P that extends
to the bimorph, by comprising a metal, titanium, a rigid plastic,
or the like. Mechanical multiplier 720 comprises a first side 723
and a second side 726, the first side 723 extends inwardly from
piezoelectric ring 710 to mass 730 and the second side 726 extends
inwardly from piezoelectric ring 710 to support 740. Narrow ring
piezo 700 may comprise circuitry configured to receive an external,
wireless signal and cause the piezoelectric ring 710 to expand or
contract along axis 750. Mechanical multiplier 720 uses leverage to
multiply this expansion and contraction and change its direction to
that along axis 755, producing a force against mass 730 and support
740. The force on support 740 drives the eardrum TM to produce
sensations of sound.
[0132] FIG. 8 shows a ring mass with bimorph piezoelectric
transducer 800 suitable for incorporation with transducer assembly
30 as described above. Piezoelectric transducer 800 comprises
contact elements contact elements 815 and 818 to connect a washer
ring 820 to a piezoelectric bimorph 810. Ring mass with bimorph
piezoelectric transducer 800 comprises a piezoelectric bimorph 810,
contact elements 815, 818, a washer ring 820 which can serve as a
mass and which defines an aperture 825, and a support 830 coupled
to the bimorph 810, the support 830 coupled with bimorph 810 and
passing through aperture 825 at least in part. Bimorph 810 may
comprise a single crystal bimorph. Support 830 may be configured to
support bimorph 810 on the eardrum TM. For example, support 830 may
comprise a mold shaped to conform with the eardrum TM. The portion
830a of support 830 which is in contact with the eardrum TM can be
flexible, for example, by comprising a flexible material such as
silicone, flexible plastic, a gel, or the like. Other portions of
support 830, for example protrusion 830p, may be rigid, for
example, by comprising a metal, titanium, a rigid plastic, or the
like. Bimorph 810 comprises a first end 813 and a second end 816.
First end 813 and second end 816 are respectively coupled to ring
820 through contact elements 815 and 818, for example, through the
use of an adhesive. Ring mass,with bimorph piezoelectric transducer
800 may be coupled to circuitry configured to receive an external,
wireless signal and cause bimorph 810 to flex in response. Flexion
of bimorph 810 produces a shearing force or shear motion of first
end 813 and second end 816 relative to washer ring 820 and produces
a translational force along axis 850 so as to drive support 830
against the eardrum TM, producing sensations of sound.
[0133] FIGS. 8A and 8B show a ring mass with bimorph piezoelectric
transducer 802 suitable for incorporation with transducer assembly
30 as described above. FIG. 8a shows a cross-sectional view of ring
mass with bimorph piezoelectric transducer 802. FIG. 8b shows a top
view of ring mass with bimorph piezoelectric transducer 802.
Bimorph 810 can be directly connected to washer ring 820 which can
serve as a mass. Bimorph 810 is coupled with a support 830
comprising a protrusion 830p extending from the support to the
transducer. Support 830 may be configured to support washer bimorph
810 and washer 820 on the eardrum TM. The portion of support 830
which is in contact with the eardrum TM can be flexible, for
example, by comprising a flexible material such as silicone,
flexible plastic, a gel, or the like. Other portions of support 830
may be rigid, for example, the portions may comprise a metal,
titanium, a rigid plastic, or the like. For example, support 830
may comprise a mold shaped to conform with the eardrum TM. Support
830 may be configured so that protrusion 830p is directly over the
umbo UM. Ring mass with bimorph piezoelectric transducer 802 may
comprise circuitry configured to receive an external, wireless
signal and cause bimorph 810 to bend or flex and thus push against
washer 820. The pushing action causes a force in a direction 852 on
washer 820 and also a force on the support 830 in a direction 853.
The force on the support 830 causes a translational movement of the
umbo UM which can rotate malleus ML to produce sensations of
sound.
[0134] FIGS. 8B1 and 8B2 show perspective views of mass, for
example a ring mass, with a piezoelectric transducer, for example a
bimorph piezoelectric transducer 803, in which the mass is coupled
to the piezoelectric transducer with a flexible intermediate
structure, for example intermediate element 815, suitable for
incorporation with transducer assembly 30 as described above. The
flexible intermediate structure can relax a boundary condition at
the edge of the piezoelectric transducer so as to improve
performance of the piezoelectric transducer coupled to the mass.
Although an elongate rod is shown, the flexible intermediate
structure may comprise many known flexible shapes such as coils,
spheres and leafs. Bimorph 810 is indirectly and flexibly connected
to washer ring 820. The ends of bimorph 810 can be directly
connected to intermediate elements 815. Intermediate elements 815
can in turn be directly connected to washer ring 820. Washer ring
820 can serve as a mass. The ends of bimorph 810 may be rigidly
attached to intermediate elements 815, for example, via an adhesive
or glue. Intermediate elements 815 may be rigidly attached to
intermediate elements 815, for example, via an adhesive or glue.
Intermediate elements 815 is flexible so as to provide a flexible
boundary condition or a flexible connection between bimorph 810 and
washer ring 820. For example, intermediate elements 815 may
comprise a rod made of a flexible material such as carbon fiber or
a similar composite material. Such a flexible material may be more
prone to twisting than bending. By providing such a flexible
boundary condition, the force outputted by transducer 803 can be
greater, for example, twice as great, as the force outputted if
bimorph 810 were instead directly and rigidly connected to washer
ring 820.
[0135] Bimorph 810 is coupled with a support 830. Support 830
comprises a protrusion 830P protruding from the bimorph 810 and a
support member 830E adapted to conform with the eardrum TM.
Protrusion 830P is coupled to support member 830E. For example,
protrusion 830P can comprise a first magnetic member 83IP and
support member 830E may comprise a complementary second magnetic
member 831E so that protrusion 830P and support member 830E are
magnetically coupled. Both first magnetic member 831 P and second
magnetic member 831E may comprise magnets. Alternatively, one of
first magnetic member 831P or second magnetic member 831E may
comprise a magnet while the other comprises a ferromagnetic
material. To position transducer 803 on the eardrum TM, support
member 830E may first be placed on the eardrum TM, followed by the
remainder of the transducer 803 as guided by first magnetic member
831 P and second magnetic member 831E.
[0136] The use of magnetism to guide the positioning of transducer
803 can reduce a hearing professional's reliance on vision to
position transducer 803 on the eardrum TM. 101381 Support member
830E may comprise a mold shaped to conform with the eardrum TM.
Support member 830E can comprise a flexible material such as
silicone, flexible plastic, a gel, or the like. The portion of
support member 830E in contact with protrusion 830P may be rigid,
for example, the portions may comprise a metal, titanium, a rigid
plastic, or the like. Support 830 may be configured so that
protrusion 830P is directly over the umbo UM. Transducer 803 may
also comprise circuitry 824. Circuitry 824 may be configured to
receive an signal, for example, an external, wireless signal.
Circuitry 824 can cause bimorph 810 to bend or flex and thus push
against washer 820. The pushing action causes a force in a
direction 852 on washer 820 and also a force on the support 830 in
a direction 853. The force on the support 830 causes a
translational movement of the umbo UM which can rotate malleus ML
to produce sensations of sound.
[0137] FIGS. 8C and 8D show embodiments that comprise more than one
bimorph, for example a ring mass dual bimorph piezoelectric
transducer 804, suitable for incorporation with transducer assembly
30 as described above. Transducer 804 may comprise a mass from
about 20 mg to about 60 mg, for example about 40 mg. Ring mass with
double bimorph piezoelectric transducer 804 comprises first
transducer, for example first bimorph 810a and second transducer,
for example second bimorph 810b. Malleus ML extends into the ear
canal, and first bimorph 810a and second bimorph 810b may extend
along a line substantially perpendicular to malleus ML, or first
bimorph 810a and second bimorph 810b may extend along a line
oblique to Malleus ML. Bimorph 810a and bimorph 810b are coupled to
a ring or washer 820 which comprises a mass. Bimorph 810a and
bimorph 810b are supported by support 830 comprising protrusions
830pa and 830pb, which are coupled to bimorph 810a and bimorph
810b, respectively. The portion of support 830 which is in contact
with the eardrum TM can be flexible, for example, by comprising a
flexible material such as silicone, flexible plastic, a gel, or the
like. Other portions of support 830 may be rigid, for example
comprising a metal, titanium, a rigid plastic, or the like. For
example, support 830 may comprise a mold shaped to conform with the
eardrum TM.
[0138] Ring mass with double bimorph piezoelectric transducer 804
may comprise circuitry configured to receive an external, wireless
signal and cause bimorph 810a and bimorph 810b to bend and/or flex
and thus push against washer 820. The wireless signal may comprise
a first signal configured to drive first bimorph 810a and a second
signal configured to drive second bimorph 810b. The pushing action
of the first transducer in response to the first signal causes a
first force in a first direction 852a on washer 820 and an opposite
force on the support 830 in an opposite direction 853a. The pushing
action of the second transducer in response to the second signal
causes a second force in a second direction 852b on washer 820 and
an opposite force on the support 830 in an opposite direction 853b.
The force on the support 830 in first direction 853a and second
direction 853b causes a translational movement which drives the
eardrum TM to produce sensations of sound.
[0139] The dual transducer 804 allows the malleus to be driven in
more than one dimension, for example with a first translational
motion to rotate the malleus with hinged motion about the head of
the malleus and second rotational motion to twist the malleus about
an elongate axis of the malleus extending from a head of the
malleus toward the umbo. When bimorphs 810a and 810b are flexed at
the same time and in the same
direction,'ring-mass-double-bimorph-piezoelectric-transducer 804
may work similar to same as
ring-mass-double-bimorph-piezoelectric-transducer 804. However,
flexion of bimorphs 810a and 810b at different times and/or in
different directions or phase may produce a rotational twisting
motion along the elongate axis of the malleus with support 830 and
thus induce rotation at the umbo of eardrum TM. For example, the
received external, wireless signal may cause only one of bimorph
810a and bimorph 810b to bend or flex. Alternatively or in
combination, the received external, wireless signal may cause
bimorph 810a to bend or flex more than bimorph 810b, or vice versa,
so as to cause a rotational twisting motion of the malleus to occur
along with the hinged rotation motion of the malleus to translate
the umbo of eardrum TM. Arrows 853TW show twisting motion of the
malleus at umbo UM with a first rotation of the malleus about an
elongate axis of the malleus. Arrows 853TR show translational
motion of the umbo UM with hinged rotation of the malleus
comprising pivoting of the malleus about the head of the malleus.
The first transducer and the second transducer can be driven with a
signal having a time delay, for example a phase delay of 90
degrees, such that translation movement and twisting of the malleus
and umbo occur. Thus, a first portion support 830 may translate in
a first direction 853 and a second portion of support 830 may
translate in a second direction 853b opposite first direction 853a
so as to rotate the malleus with twisting motion.
[0140] Thus, the first transducer and the second transducer
comprising bimorphs 810a and 810 can be driven so as to cause
translational movement and a rotational movement of eardrum TM.
Hinged rotational movement of the malleus to effect translational
movement of the umbo UM may be made at low frequencies less than
about 5 kHz, for example frequencies less than about 1 kHz.
Rotational twisting movement of the malleus may be made at
frequencies greater than about 2 kHz, for example high frequencies
greater than 5 kHz.
[0141] FIG. 8E shows a plot of phase difference versus frequency
for the first and second transducers of the dual bimorph piezo of
FIGS. 8C and 8D. This phase difference can result in increased
frequency gain at high frequencies above about 5 kHz, such that the
user can hear the high frequency sounds more clearly due to the
twisting of the malleus. At a first frequency below about 1 kHz,
for example 0.5 kHz, the phase difference between the first
transducer and the second transducer is substantially zero. At a
second frequency above from about 3 to 6 kHz, for example above
about 5 KHz, the phase difference between the first transducer and
the second transducer is at least about 10 degrees. For example, at
about 9 kHz, the phase difference between the first transducer and
the second transducer may comprise about 100 degrees. The phase
difference between the first transducer and the second transducer
can be provided in many ways, for example with the audio processor
as described above, configured to output a first channel to the
first transducer and a second channel to the second transducer. The
circuitry coupled to the first transducer and the second transducer
may be configured to provide the first signal phase shifted from
the second signal in response to the audio signal, for example with
circuitry comprising at least one of a capacitor, a resistor or an
inductor configured to provide a phase shift of the audio signal
such that the first signal is phase shifted from the second
signal.
[0142] FIG. 9 shows simply supported bimorph bender 400 housed in a
hermetically sealed housing 900 suitable for incorporation with
transducer assembly 30 as described above. Housing 900 may comprise
many known biocompatible materials. In many embodiments, an output
transducer may comprise a hermetically sealed housing. Housing 900
may be rigidly affixed to masses 410a and 410b with rigid
connections. First mass 410a is connecting to housing 900 with
rigid connections 900RA1 and 900RA2. Second mass 410b is connecting
to housing 900 with rigid connections 900RB1 and 900RB2. Housing
900 can provide additional mass for bimorph 420 to push against. A
rigid portion 430P of support 430 extends through housing 900 to
bimorph 420. Hermitically sealed housing 900 may be configured for
many of the above described transducers, for example piezoelectric
at least one of cantilevered bimorph bender 500, 550, stacked piezo
with mechanical multiplier 600, disk or narrow ring piezo with a
mechanical multiplier 700, or transducer 800.
[0143] FIG. 9A shows an output transducer 902 which receives power
through optical transmission suitable for incorporation with
transducer assembly 30 as described above. Output transducer 902
may comprise a piezoelectric transducer, a magnetostrictive
transducer, a photostrictive transducer, a coil and a magnet, or
the like. As shown in FIG. 9A, output transducer 902 comprises a
piezoelectric transducer 910 which is coupled to annular mass 920.
Piezoelectric transducer 910 and mass 920 are both supported by
support 930. Piezoelectric transducer 910 may comprise many of the
piezoelectric elements described above, for example at least one of
a bimorph, a cantilevered bimorph, a stacked piezo, or a disc or
ring piezo. Mass 920 may be similar to many of the masses as
previously discussed. Piezoelectric transducer 910 can be powered
by a photodetector 940 which receives light 945. Light 945 may
comprise a signal, for example, a signal representative of sound as
described above. Photodetector 940 can be coupled to circuitry
940c. Circuitry 940c can be supported with support 930, mass 920,
piezoelectric transducer 930 and support 930. Circuitry 940 can be
coupled to piezoelectric transducer 910 to convert light 945 into
an electrical signal which can cause piezoelectric transducer 910
to move and cause vibrations on eardrum TM which may lead to a
sensation of sound. A housing 903 extends around piezoelectric
transducer 910, circuitry 940c, mass 920 and photodetector 940 to
hermetically seal transducer 902.
[0144] FIG. 98 shows an output transducer 904 which receives power
through magnet and/or electric power transmission suitable for
incorporation with transducer assembly 30 as described above.
Output transducer 904 may comprise a piezoelectric transducer, a
magnetostrictive transducer, a photostrictive transducer, a coil
and a magnet, or the like. Output transducer 904 comprises a
piezoelectric transducer 910 coupled to a mass 920B. Piezoelectric
transducer 910 and mass 920B are both supported by support 930.
Piezoelectric transducer 910 may comprise many of the piezoelectric
elements described above, for example at least one of a bimorph, a
cantilevered bimorph, a stacked piezo, or a disc or ring piezo.
Mass 920B may be similar to many of the masses as previously
discussed. Piezoelectric transducer 910 can be powered by an
external coil 955 which produces a magnetic field 957 which causes
a magnetic field 952 and a voltage in coil 950. Coil 950 is coupled
to and powers piezoelectric transducer 910. Coil 950 can be
supported with mass 920B, transducer 910 and support 930. The
electromagnetic field 957 produced by external coil 955 may provide
a signal, for example, a signal representative of sound, to coil
950. Appropriate variations in magnetic field 957 and magnetic
filed 952 can cause piezoelectric transducer 910 to cause
vibrations on eardrum TM which may lead to a sensation of
sound.
[0145] Tables 4 and 5 below show characteristics of exemplary
piezoelectric output transducers as described above, including
simply supported bimorph bender 400, cantilevered bimorph bender
500, stacked piezo with mechanical multiplier 600, disk or narrow
ring piezo with a mechanical multiplier 700, and bimorph or wide
ring piezo 800,
TABLE-US-00004 TABLE 4 EXEMPLARY PARAMETERS OF PIEZOELECTRIC OUTPUT
TRANSDUCERS Variable Symbol Comments Displacement w Simply
Supported Bimorph - Mid span at point of Cantilever Bimorph - Free
end interest Stack - Free end Narrow Ring - Mid radius Wide Ring -
Outer radius Beam or stack L length Beam or stack b Stack is
assumed to have a square width Wide cross section ring outer radius
Wide ring a inner radius Thickness h Bimorph - 1/2 total thickness
Stack - single layer thickness Ring - total thickness Number of n
Bimorph - number of layers in 1/2 thickness layers Stack - total
number of layers Ring - total number of layers Piezoelectric
d.sub.11, d.sub.33 constant Elastic moduli E.sub.11, E.sub.33
Density .rho. Permittivity .di-elect cons..sub.o 8.854E-12 (F/m) of
free space Relative .di-elect cons..sub.33 permittivity Applied
.DELTA.V voltage Applied F Simply Supported Bimorph - Force (N) at
mid force span Cantilever Bimorph - Force (N) at free end Stack -
Force (N) at free end Narrow Ring - Ring load (N/m) at mid radius
Wide Ring - Ring load (N/m) at outer radius
TABLE-US-00005 TABLE 5 EXEMPLARY MECHANICAL FORMULAS FOR
PIEZOELECTRIC OUTPUT TRANSDUCERS Type Formulas Comments Simply
Supported Bimorph Bender 400 Displacement per Volt w .DELTA.V = 3
16 nd 31 ( L h ) 2 Capacitance C = 2 n 2 0 _ 32 b ( L h ) Stiffness
F w = 32 E 11 b ( h L ) 2 1 st Mechanical Resonance f 1 = ( .pi. )
2 2 .pi. E 11 h 2 3 .rho. L 4 ##EQU00005## Cantilevered Bimorph
Bender 500 Displacement per Volt w .DELTA.V = 3 4 nd 31 ( L h ) 2
Capacitance C = 2 n 2 0 _ 32 b ( L h ) Stiffness F w = 2 E 11 b ( h
L ) 2 1 st Mechanical Resonance f 1 = ( 1.875 ) 2 2 .pi. E 11 h 2 3
.rho. L 4 ##EQU00006## Stac (shown with displacement amplifier) 600
Displacement per Volt w .DELTA.V = nd 32 Stiffness F w = E 32 B 2 L
Capacitance C = n 0 _ 32 b 2 h 1 st Mechanical Resonance f 1 = 1 4
L E 32 .rho. ##EQU00007## The 1.sup.st mechanical resonance
equation may be the 1/4 wave "rod" resonance which can tend to be
very high. This may not be the first resonance of the system. The
most likely 1.sup.st mode may be the mass of the piezo/ref mass in
conjunction with the spring of the displacement amplifier or some
kind of bending mode. Narrow Ring (shown with displacement
amplifier) 700 Displacement per Volt w .DELTA.V = nd 31 ( r 0 h )
Stiffness F w = E 11 t r o ( h r o ) Capacitance C = n 2 0 _ 32 2
.pi.t ( r o h ) 1 st Mechanical Resonance ##EQU00008## Remember for
ring cases that F is a ring load (N/m) that will be summed by the
displacement amplifier. The appropriate 1.sup.st mechanical
resonance mode may not be clear. Likely the first resonance may
either be a bending type mode or a cos(2.theta.) mode. Wide Ring
Displacement per Volt w .DELTA.V = nd 31 ( b h ) Stiffness F w = E
11 t b ( b 2 - a 2 ) ( 1 + v ) a 2 + ( 1 - v ) b 2 Capacitance C =
n 2 0 _ 32 .pi. ( b 2 - a 2 ) h 1 st Mechanical Resonance
##EQU00009##
[0146] FIG. 10 shows an output transducer assembly comprising 1000
a cantilevered bimorph bender positioned on a support 1010 such
that the output transducer assembly is positioned over the lateral
process and away from the umbo when the support is placed on the
eardrum, suitable for incorporation with transducer assembly 30 as
described above. Many of the output transducers as described above
can be positioned on support 1010 so as to couple to the umbo of
the eardrum TM with the transducer positioned away from the umbo,
for example on the lateral process LP. The output transducer
positioned on the support 1010 so as to couple to the umbo with the
transducer positioned away from the umbo may comprise at least one
of a piezoelectric transducer, a rnagnetostrictive transducer, a
photostrictive transducer, a coil or a magnet. Support 1010 can be
made with known methods of molding to manufacture a support
customized to the ear of the user, for example as with the known
EarLens. The transducers as described above, for example simply
supported bimorph bender 400, cantilevered bimorph bender 500,
cantilevered bimorph bender 550, stacked piezo with mechanical
multiplier 600, ring piezo with mechanical multiplier 700 and ring
mass with bimorph piezoelectric transducer 800 can be positioned on
support 1010 so as to position the transducer at the desired
location on the eardrum when support 1010 is placed against
tympanic membrane TM. As shown in FIG. 10, the transducer may
comprise cantilevered bimorph bender 500 on support 1010 and
coupled to eardrum TM over the lateral process LP and away from the
umbo UM. Cantilevered bimorph bender 500 can be placed on the
support so as to align with malleus ML when the support is placed
against the eardrum. For example, support 530 of cantilevered
bimorph bender 500 can be positioned on support 1010 to conform to
the portion of the eardrum TM over the lateral process LP when
support 1010 is placed against the eardrum TM. In some embodiments,
support 530 can be placed directly on the eardrum without support
1010, for example directly over the lateral process LP. Mass 510 of
cantilevered bimorph bender 500 may be placed along the eardrum
away from the umbo U of the eardrum TM so as to decrease a
mechanical impedance of the support to sound transmitted with the
eardrum TM. Cantilever 520 has a first end coupled to mass 510 and
a second end coupled to support 530. Cantilever 520 may bend and
push against mass 510 and cause a force on support 530 which drives
the lateral process LP of the malleus ML to produce sensations of
sound.
[0147] FIGS. 10A and 10B show an output transducer assembly 1050
suitable for incorporation with transducer assembly 30 as described
above and comprising cantilevered bimorph bender 500 placed on a
support 1060 which may be made from a mold of the user's ear. The
output transducer positioned on the support 1060 may comprise at
least one of a piezoelectric transducer, a magnetostrictive
transducer, a photostrictive transducer, a coil or a magnet.
Support 530, mass 510 and the elongate member comprising bimorph
cantilever 520 of bimorph bender 500 are positioned on support 1060
such that mass 510 is positioned away from the umbo and the
elongate member is coupled to the umbo when support 1060 is placed
against eardrum TM. The elongate member, for example bimorph
cantilever 520, extends from the mass supported on the lateral
process to the umbo so as to couple to the motion of the transducer
to the eardrum at the umbo. This configuration has the advantage of
lowering the mechanical impedance with the mass positioned away
from the umbo while providing mechanical leverage with coupling at
the umbo.
[0148] The mass can be positioned away from the umbo and/or aligned
with the malleus ML in many ways so as to reduce the input
impedance of the transducer assembly. For example, mass 510 can be
positioned on support 1060 such that mass 510 is supported with the
lateral process LP when support 1060 is placed against the ear.
Also cantilevered bimorph bender 500 and support 530 can be placed
directly on the eardrum TM such that mass 510 is aligned with
malleus ML, for example aligned with lateral process LP. As shown
in FIGS. 10A and 10B, mass 510 is placed on support 1060 over the
lateral process LP and support 530 is placed on support 1060 over
the umbo U when support 1060 is placed against the eardrum TM. The
elongate member comprising bimorph cantilever 520 has a first end
coupled to mass 510 and a second end coupled to support 530.
Cantilever 520 may bend and push against mass 510 and cause a force
on support 530 which drive the tip T of the malleus ML to produce
sensations of sound. The length of cantilever 520 may be provided
with a longer length such that cantilever 520 can provide more
mechanical leverage while reducing the input impedance of mass
510.
[0149] FIG. 11 shows two or more transducers positioned on a
support 1130 so as to rotate the malleus with hinged rotation at
low frequencies and twist the malleus at high frequencies and
suitable for incorporation with transducer assembly 30 as described
above. Many of the above described transducers can be placed on
support 1130. For example, embodiments of cantilevered bimorph
bender 550 and bimorph or wide ring piezo 800 may cause a twisting
motion on the eardrum TM and thus the malleus ML. Placement of two
or more output transducers, on different parts of the eardrum TM
can also produce a rotational or twisting motion on the eardrum TM
at the umbo and the malleus ML. The placed output transducers may
comprise, for example, at least one of simply supported biomorph
bender 400, cantilevered biomorph bender 500, stacked piezo with
mechanical multiplier 600, disk or narrow ring piezo with a
mechanical multiplier 700, and biomorph or wide ring piezo 800. For
example, FIGS. 11 and 11A show two cantilevered bimorph benders
500A and 5008B configured to couple to the umbo of the eardrum TM
on opposite lateral sides over the tip T of malleus ML.
Cantilevered bimorph benders 500A and 500B each comprise masses
510A and 510B, respectively, and bimorph cantilevers 520A and 520B,
respectively, and may both be supported with a common support 530
and/or support 1130 which also supports masses 510A and 510B. Each
of bimorph cantilevers 520A and 520B comprises an elongate member
that extends from the mass to the umbo to couple to the eardrum at
the umbo. A phase difference, as described above, between bimorphs
500A and 500B may cause malleus ML to twist. Masses 510A and 510B
are positioned on support 1130 such that masses 510A and 5108 are
supported with the lateral process when support 1130 is placed
against eardrum TM. Output transducers may be placed on other areas
of the eardrum TM as well, for example at additional locations away
from the umbo as described above. In some embodiments, support 530
can be coupled directly to eardrum TM, for example without support
1130.
[0150] Many of the above embodiments can be evaluated on an
empirical number of patients, for example 10 patients to optimize
the transducers, for example transducer mass, positioning, support
and circuitry. For example, experiments can be conducted on an
empirical number of ten patients to determine improved coupling of
sound with differential movement of the first transducer and second
transducer. In addition to testing with patients, the embodiments
can be tested with computer simulations and laboratory testing. The
below described experiments are merely examples of experiments that
can be performed, and a person of ordinary skill in the art will
recognize many variations and modifications that can be used to
improve and optimize the performance of the transducer devices
described herein.
[0151] IV. Experimental
[0152] For exemplary piezoelectric elements, five key
characteristics were looked at as a function of geometric
parameters. The five parameters were: 1) minimum manufacturable
layer thickness, 2) electrical capacitance, 3) 1.sup.st mechanical
resonant frequency (if available), 4) low frequency stiffness, and
5) maximum displacement achievable with a photodetector power
source. For each exemplary piezoelectric element, a contour plot of
the maximum displacement achievable at 2 kHz was made. FIG. 12
shows an exemplary contour map for an embodiment of a back-to-back
amplified stack piezoelectric elements, a PZT506 back-to-back stack
with displacement amplifier. Similar plots can be made for
additional embodiments comprising the simply supported bimorph
piezoelectric elements, for example a PZT506 simply supported
bimorph, a TRS singly crystal simply supported bimorph, and a PVDF
simply supported bimorph piezoelectric elements. FIG. 12 includes
combinations of different numbers of photodetectors used to power
the piezoelectric element and the width of the piezoelectric
element. The displacement shown accounts for the electrical
limitations of the photovoltaic power source as well as any
mismatch between the impedance of the umbo and the stiffness of the
driving piezo. Equation 1 and Table 6 below show the equation for
the maximum displacement and the parameter definitions.
d m ax = ( d V ) R ( K pz K pz + R 2 Z umbo ) min ( N PD V ma x , (
I ma x N PD ) 2 .pi. f 1 C ) . EQUATION 1 ##EQU00010##
TABLE-US-00006 TABLE 6 EXEMPLARY TEST PARAMETERS Parameter Value
f.sub.max Maximum frequency of interest (10 kHz) f.sub.1 2 kHz -
frequency used to optimize design R Lever ratio K.sub.pz Low
frequency stiffness of piezo Z.sub.umbo Impedance of umbo at
f.sub.1 d Displacement per volt of a given design V N.sub.PD Number
of photocells in series V.sub.max Maximum voltage of single
photocell (0.4 V) I.sub.max Maximum current of single photocell
given the illumination constraints (224 uA) C Capacitance of a
given design min(x, y) Minimum function which takes the minimum of
the two arguments (x, y)
[0153] On top of the contour map shown, other parameters are shown
as "constraint lines". For example, the minimum manufacturable
thickness is represented as a line. Any design point falling below
or to the right of this line may be achievable. Any design point
falling above or to the left calls for a layer thickness that is
not currently available from any of the contacted vendors. Often,
only integer numbers of layers are possible. Similarly, the
capacitance is shown in a line. Any design falling below or to the
right of this line has less than the optimal capacitance for 2 kHz.
Any design above or to the left has a higher capacitance. At this
point, one must remember that the displacement contours are shown
at 2 kHz. At different frequencies, there will be a different
optimal capacitance. (Optimizing for higher frequencies will
require smaller capacitances.) Designs that have a mechanical
resonance of 10 kHz are shown as a line. Designs to the right have
higher resonant frequencies; designs to the left have lower
resonant frequencies. Designs that have a low frequency stiffness
equal to the umbo stiffness at 10 kHz are shown with a line.
Designs to the right have higher stiffnesses; designs to the left
have lower stiffnesses. In exemplary embodiments, piezoelectric
element parameters that are below and to the right of all the
constraint lines while at the same time maximizing location on the
displacement contour are chosen. Contour maps can be made for
embodiments of bimorph piezoelectric transducers using the
parameters set forth in Table 7.
TABLE-US-00007 TABLE 7 EXEMPLARY TEST PARAMETERS FOR BIMORPH
PIEZOELECTRICS TRS - Single Parameter PZT506 Crystal PVDF d.sub.11
64.5 GPa 11.6 GPa 3.0 GPa d.sub.33 225 pm/V 1000 pm/V 20 pm/V
.di-elect cons..sub.33 2250 7700 12 .rho. 8000 Kg/m.sup.3 7900
Kg/m.sup.3 1780 Kg/m.sup.3 Minimum layer 20 um 140 um 2 um
thickness Lever Ratio 1.0 1.0 1.0 L 5 mm 5 mm 5 mm
[0154] Contour maps can be made for embodiments of simply supported
bimorph piezoelectrics using the parameters set forth in Table 8.
The bimorph with the greatest displacement that meets all of the
constraints may be selected. Exemplary embodiments SSBM1, SSBM2,
SSBM3, SSBM4, SSBM5, SSBM6, SSBM7, SSBM8, SSBM12, SSBM15, and
SSBM18 give displacements greater than 0.1 um at 2 kHz.
TABLE-US-00008 TABLE 8 DISPLACEMENT MEASUREMENTS FOR EXEMPLARY
BIMORPH PIEZOELECTRIC EMBODIMENTS Beam Number of Beam 1/2 Number of
Layer Maximum Embodiment Material width photodetectors thickness
layers thickness displacement SSBM1 PZT506 0.5 mm 1 120 um 6 20 um
0.15 um SSBM2 PZT506 0.5 mm 2 120 um 4 30 um 0.16 um SSBM3 PZT506
0.5 mm 3 120 um 3 40 um 0.15 um SSBM4 PZT506 1.0 mm 1 100 um 4 25
um 0.15 um SSBM5 PZT506 1.0 mm 2 100 um 2 50 um 0.15 um SSBM6
PZT506 1.0 mm 3 100 um 1 100 um 0.12 um SSBM7 PZT506 1.5 mm 1 100
um 3 33 um 0.12 um SSBM8 PZT506 1.5 mm 2 100 um 2 50 um 0.14 um
SSBM9 PZT506 1.5 mm 3 100 um 1 100 um 0.09 um SSBM10 TRS-SC 0.5 mm
1 280 um 2 140 um 0.045 um SSBM11 TRS-SC 0.5 mm 2 280 um 2 140 um
0.09 um SSBM12 TRS-SC 0.5 mm 3 280 um 2 140 um 0.13 um SSBM13
TRS-SC 1.0 mm 1 280 um 2 140 um 0.05 um SSBM14 TRS-SC 1.0 mm 2 280
um 2 140 um 0.09 um SSBM15 TRS-SC 1.0 mm 3 230 um 1 230 um 0.10 um
SSBM16 TRS-SC 1.5 mm 1 280 um 2 140 um 0.045 um SSBM17 TRS-SC 1.5
mm 2 230 um 1 230 um 0.07 um SSBM18 TRS-SC 1.5 mm 3 230 um 1 230 um
0.10 um SSBM19 PVDF 2.0 mm 2 210 um 34 6.2 um 0.045 um SSBM20 PVDF
2.0 mm 3 210 um 16 13.1 um 0.045 um SSBM21 PVDF 3.0 mm 2 210 um 27
7.8 um 0.04 um SSBM22 PVDF 3.0 mm 3 210 um 14 15 um 0.04 um
[0155] The PZT506 material appears to be the suitable for making
the bimorph. Its combination of thin layer thicknesses, high
piezoelectric constants and moderate permittivity provides a
suitable best output. Also, it appears that a wide range of beams
all produce roughly the same output, 0.15 um. Choosing between
these options can be based on tradeoffs of manufacturing. For
example, layers in the biomorph can be traded-off against
segmenting the photodetector.
[0156] Contour maps can be made for embodiments of back-to-back
amplified stack piezoelectric elements, a TRS single crystal
back-to-back stack with displacement amplifier, respectively. A
displacement amplified stack piezoelectric elements may comprise a
scissor jack with two stacks placed back-to-back pushing outwards.
In this configuration, the centerline of the assembly does not
move. Therefore, the maximum stack length to consider for
displacement purposes is 2.5 mm or half of the maximum allowable
dimension. However, the effective capacitance may be needed to
account for both stacks. The lever ratio may be limited to be
between 1 and 15. In between those limits, the stiffness of the
stack can be matched to the impedance of the umbo at 10 kHz. Since
the number of layers in a stack is high, the thickness of the
glue/electrodes between layers may need to be considered. For
example, a glue/electrode layer thickness of 16 um may be used.
Like with simply supported bimorph piezoelectric elements above,
amplified stack piezoelectric elements were analyzed at a variety
of thicknesses and assuming various numbers of photodetectors in
series. Neither the stiffness nor the 1.sup.st resonance of the
stack was a limiting factor while layer thickness, capacitance and
length may be limiting factors.
[0157] Table 9 below shows some exemplary ranges of parameters for
embodiments of back-to-back amplified stack piezoelectric
elements.
TABLE-US-00009 TABLE 9 EXEMPLARY TEST PARAMETERS FOR BACK- TO-BACK
STACK PIEZOELECTRICS TRS - Single Parameter PZT506 Crystal E.sub.11
64.5 GPa 11.6 GPa d.sub.33 545 pm/V 1900 pm/V .di-elect
cons..sub.33 2250 7700 .rho. 8000 Kg/m.sup.3 7900 Kg/m.sup.3
Minimum layer 20 um 140 um thickness Lever Ratio 1.0 to 15.0 1.0 to
15 L 2.5 mm 2.5 mm
[0158] Table 10 below shows parameters for several embodiments of
back-to-back amplified stack piezoelectric elements Both the single
crystal material and the PZT506 material appear to have maximum
outputs near 0.3 um. Several embodiments of back-to-back amplified
stack piezoelectric elements produce similar amounts of
displacement. Thus, there may be flexibility in manufacturing.
TABLE-US-00010 TABLE 10 DISPLACEMENT MEASUREMENTS FOR EXEMPLARY
BACK- TO-BACK STACK PIEZOELECTRIC EMBODIMENTS Number of Stack
photode- Number of Layer Material width tectors layers thickness
Maximum PZT506 0.5 mm 1 65 20 um 0.2 um PZT506 0.5 mm 2 45 40 um
0.23 um PZT506 0.5 mm 4 25 90 um 0.28 um PZT506 0.75 mm 1 58 30 um
0.15 um PZT506 0.75 mm 2 32 65 um 0.18 um PZT506 0.75 mm 4 16 135
um 0.20 um PZT506 1.0 mm 1 45 40 um 0.13 um PZT506 1.0 mm 2 25 70
um 0.15 um PZT506 1.0 mm 4 12 180 um 0.16 um TRS-SC 0.5 mm 1 17 140
um 0.1 um TRS-SC 0.5 mm 2 17 140 um 0.2 um TRS-SC 0.5 mm 4 14 170
um 0.31 um TRS-SC 0.75 mm 1 17 140 um 0.14 um TRS-SC 0.75 mm 2 17
140 um 0.28 um TRS-SC 0.75 mm 4 9 260 um 0.31 um TRS-SC 1.0 mm 1 17
140 um 0.15 um TRS-SC 1.0 mm 2 14 175 um 0.25 um TRS-SC 1.0 mm 4 7
350 um 0.28 um
[0159] Embodiments of piezoelectric elements were also tested using
a laser vibrometer to measure the velocity (and hence the
displacement) of a target. Data was analyzed to yield displacement
per volt and plotted versus frequency. Data was determined using
the equations mentioned above and plotted alongside the test
data.
[0160] A single Morgan stacked as shown in FIG. 13A was tested. The
parameters for the single Morgan stack piezo are shown in Table 11
below. A plot of the test data, including displacement versus
voltage, is shown in FIG. 13B.
TABLE-US-00011 TABLE 11 EXEMPLARY PARAMETERS FOR MORGAN STACKED
PIEZO Parameter Value Material Morgan PZT506 Piezo Dimensions 1
.times. 1 .times. 1.8 mm Layer Thickness 20 .mu.m Number of Layers
50 E11 6.45e10.sup. d33 545e-12 d31 -225e-12 Density 8000 Relative
Permittivity 2250 Kp (coupling factor) 0.70 Input Voltage 1 V Input
Frequency range 100-20000 Hz Measured capacitance 52 nF Calculated
capacitance 49.8 nF
[0161] A Steiner and Martins cofired Piezo series bimorph as shown
in FIG. 14A was tested. The parameters for the single Morgan stack
are shown in Table 12 below. A plot of the test data, including
displacement versus voltage, is shown in FIG. 14B. Affixing the
piezo using a flexible material increased the vibrational
displacement by a few dB.
TABLE-US-00012 TABLE 12 EXEMPLARY PARAMETERS FOR STEINER AND
MARTINS COFIRED PIEZO - SERIES BIMORPH Parameter Value Material
STEMInc SMQA Piezo Dimensions 7 mm .times. 7 mm Layer Thickness 200
.mu.m E11 8.6e10.sup. d33 310e-12 d31 -140e-12 Density 7900
Relative Permittivity 1400 Kp (coupling factor) 0.58 Input Voltage
1 V Input Frequency range 100-20000 Hz Measured capacitance 1.4 nF
Calculated capacitance 1.4 nF
[0162] A TRS Single Crystal Bimorph Cantilever as shown in FIG. 15A
was tested. The parameters for the single Morgan stack are shown in
Table 13 below. The parameters may comprise known parameters and
can be measured by one of ordinary skill in the art. A plot of the
test data, including displacement versus voltage, is shown in FIG.
15B.
TABLE-US-00013 TABLE 13 EXEMPLARY PARAMETERS FOR TRS SINGLE CRYSTAL
BIMORPH CANTILEVER Parameter Value Material TRS single crystal
Piezo Dimensions 6 mm .times. 6 mm Layer Thickness 140 .mu.m E11
1.16e10.sup. d33 1900e-12 d31 -1000e-12 Density 7900 Relative
Permittivity 7700 Input Voltage 1 V Input Frequency range 100-20000
Hz Measured capacitance nF Calculated capacitance 35 nF
[0163] A TRS Single Crystal Bimorph on a washer as shown in FIG.
16A was tested. The parameters for the single Morgan stack are
shown in Table 14 below. A plot of the test data, including
displacement versus voltage, is shown in FIG. 16B In this test, the
resonance is in the predicted frequency but the magnitude is off by
nearly 20 dB. The capacitance is also off, so the piezo may be
damaged.
TABLE-US-00014 TABLE 14 EXEMPLARY PARAMETERS FOR TRS SINGLE CRYSTAL
ON WASHER Parameter Value Material TRS single crystal Piezo
Dimensions 1 mm .times. 5 mm Layer Thickness 140 .mu.m E11
1.16e10.sup. d33 1900e-12 d31 -1000e-12 Density 7900 Relative
Permittivity 7700 Input Voltage 1 V Input Frequency range 100-20000
Hz Measured capacitance 3.6 nF Calculated capacitance 4.2 nF
[0164] A stacked piezo pair with V-jack type displacement
amplification as shown in FIG. 17A was tested. The parameters for
the single Morgan stack are shown in Table 15 below. A plot of the
test data, including displacement versus voltage, is shown in FIGS.
17B and 17C. In this test, an additional resonance appears which
may most likely a resonance in the mechanical lever.
TABLE-US-00015 TABLE 15 EXEMPLARY PARAMETERS FOR STACKED PIEZO PAIR
WITH V-JACK DISPLACEMENT AMPLIFICATION Parameter Value Material
Morgan PZT506 Piezo Dimensions 1 .times. 1 .times. 3.6 mm Lever
angle, lever ratio 3.5.degree., 16X Layer Thickness 20 .mu.m Number
of Layers 100 E11 6.45e10.sup. d33 545e-12 d31 -225e-12 Density
8000 Relative Permittivity 2250 Kp (coupling factor) 0.70 Input
Voltage 1 V Input Frequency range 100-20000 Hz Measured capacitance
104 nF Calculated capacitance 99.6 nF
[0165] Embodiments of output transducers which were placed on a
subject's eardrum were tested. The transducer was wire driven,
connected directly to the audiometer to determine the acoustic
threshold. In order to reduce the effect of the wires, 48 AWG wire
was used between the transducer and a location just outside the ear
canal. The position of the transducer was verified by a physician
using a video otoscope.
[0166] Once in place, the audiometer driven transducer was
energized across a 12 k.OMEGA. load and the audiometer setting
adjusted to reach threshold. The threshold was recorded at each
frequency tested. After the testing was complete and the transducer
removed from the subject's ear, the transducer was reconnected to
the audiometer and the voltage measured. Often, the audiometer
setting was increased by 40 dB to make a reliable measurement.
[0167] The data collected was converted to pressure equivalent
using Minimum Audible Pressure curves and plotted against the
specifications, bench-top data and average electromagnetic or EM
system output. In all cases, the assumption is that the input to
the transducer is 0.4V peak and 75 mW. The bench-top data was
determined by measuring the unloaded displacement and comparing to
the known displacement of the umbo at each frequency plotted.
[0168] In addition to the threshold measurements, the feedback
pressure was measured at two locations: at the umbo and at the
entrance to the ear canal. Often, the transducer was driven by a
laptop running SYSid, and operated at 1V peak, with the feedback
measured with an ER-7c microphone. The resulting data gives a
measure of the gain margin for each transducer design/location if
the microphone is located either deep in the canal or at the canal
entrance.
[0169] FIGS. 18A-20B show peak power output and feedback for the
tested embodiments of output transducers. Although an idealized
target peak power output of 106 dB is shown for purposes of
comparison, peak power outputs of less than 106 dB, for example 80
or 90 dB at 10 kHz, can provide improved hearing for many patients.
FIGS. 18A and 18B show peak power output and feedback,
respectively, of a TRS single crystal bimorph placed on the umbo.
The on ear results match the bench top predictions up to 2 kHz,
then diverge, with the on-ear results remaining flat up to 12 kHz.
The umbo located transducer used a different piezo than the center
of pressure located transducer.
[0170] FIGS. 19A and 19B show peak power output and feedback,
respectively, of a TRS single crystal bimorph placed on the center
of pressure of the eardrum. The on ear results match the bench top
predictions up to 2 kHz, then diverge, with the on-ear results
remaining flat up to 12 kHz. Employing feedback cancellers or other
feedback handling techniques, or moving the microphone location can
improve the power output and feedback profiles.
[0171] FIGS. 20A and 20B show peak power output and feedback,
respectively, of a stacked piezo pair with V-jack type displacement
amplification placed on the center of pressure of the eardrum. The
100 nF piezo load causes the PV system to be current limited
starting at a low frequency. The overall equivalent pressure per
volt (when not current limited) is better than the bimorph case by
about 20 dB.
[0172] While the above is a complete description of the preferred
embodiments of the invention, various alternatives, modifications,
and equivalents may be used. Therefore, the above description
should not be taken as limiting in scope of the invention which is
defined by the appended claims.
* * * * *