A bone conduction device comprising a multilayer piezoelectric element. The multilayer piezoelectric element comprises two stacked piezoelectric layers, and a flexible passive layer disposed between the piezoelectric layers. The device also comprises a mass component attached to the multilayer piezoelectric element; and a coupling attached to the multilayer piezoelectric element configured to transfer mechanical forces generated by the multilayer piezoelectric element and the mass component to a recipient's skull.
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14. A bone conduction device for converting received sound signals into a mechanical force for delivery to a recipient's skull, the device comprising:
a multilayer piezoelectric element comprising two stacked piezoelectric layers separated from each other by a non-conductive passive layer, wherein the piezoelectric layers have opposing directions of polarization such that application of electric signals, generated based on the sound signals, to both of the layers causes deflection of the piezoelectric element in a single direction and wherein the multilayer piezoelectric element comprises a plurality of adjacent segments configured to be actuated substantially independently;
a plurality of amplifiers configured to selectively generate electrical signals for application to the plurality of adjacent segments;
a mass component one or more mass components attached to the multilayer piezoelectric element so as to move in response to deformation of the piezoelectric element; and
a coupling configured to attach the device to the recipient so as to transfer mechanical forces generated by the multilayer piezoelectric element and the mass component to the recipient's skull.
1. A bone conduction device for converting received sounds signals into a mechanical force for delivery to a recipient's skull, the device comprising:
a plurality of separate, independently operable multilayer piezoelectric elements each comprising two stacked piezoelectric layers, and a passive layer disposed between and mounted to the piezoelectric layers so as to separate the piezoelectric layers from each other, wherein the piezoelectric layers are configured to deform in response to application thereto of electrical signals generated based on the received sound signals;
a mass component one or more mass components attached to one or more of the multilayer piezoelectric elements so as to move in response to deformation of the one or more piezoelectric elements; and
a coupling configured to attach the device to the recipient so as to transfer mechanical forces generated by the multilayer piezoelectric element and the mass component to the recipient's skull,
wherein the device is configured to apply an electric signal to a first of the plurality of multilayer piezoelectric elements in response to receipt of a high frequency sound signal by the device, and wherein the device is configured to apply an electric signal to a second of the plurality of multilayer piezoelectric elements in response to receipt of a low frequency sound signal by the device.
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a plurality of separate, independently operable multilayer piezoelectric elements.
25. The bone conduction device of
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The present application claims priority from German Patent Application No. 102009014770.5, filed Mar. 25, 2009, which is hereby incorporated by reference herein.
1. Field of the Invention
The present invention relates generally to bone conduction devices, and more particularly, to a bone conduction device having a multilayer piezoelectric element.
2. Related Art
Hearing loss, which may be due to many different causes, is generally of two types, conductive and sensorineural. Sensorineural hearing loss is due to the absence or destruction of the hair cells in the cochlea that transduce sound signals into nerve impulses. Various prosthetic hearing implants have been developed to provide individuals who suffer from sensorineural hearing loss with the ability to perceive sound. One such prosthetic hearing implant is referred to as a cochlear implant. Cochlear implants use an electrode array implanted in the cochlea of a recipient to bypass the mechanisms of the ear. More specifically, an electrical stimulus is provided via the electrode array directly to the auditory nerve, thereby causing a hearing sensation.
Conductive hearing loss occurs when the normal mechanical pathways that provide sound to hair cells in the cochlea are impeded, for example, by damage to the ossicular chain or ear canal. However, individuals suffering from conductive hearing loss may retain some form of residual hearing because the hair cells in the cochlea may remain undamaged.
Still other individuals suffer from mixed hearing losses, that is, conductive hearing loss in conjunction with sensorineural hearing. Such individuals may have damage to the outer or middle ear, as well as to the inner ear (cochlea).
Individuals suffering from conductive hearing loss are typically not candidates for a cochlear implant due to the irreversible nature of the cochlear implant. Specifically, insertion of the electrode assembly into a recipient's cochlea exposes the recipient to potential destruction of the majority of hair cells within the cochlea. Typically, destruction of the cochlea hair cells results in the loss of residual hearing in the portion of the cochlea in which the electrode assembly is implanted.
Rather, individuals suffering from conductive hearing loss typically receive an acoustic hearing aid, referred to as a hearing aid herein. Hearing aids rely on principles of air conduction to transmit acoustic signals to the cochlea. In particular, a hearing aid typically uses an arrangement positioned in the recipient's ear canal or on the outer ear to amplify a sound received by the outer ear of the recipient. This amplified sound reaches the cochlea causing motion of the perilymph and stimulation of the auditory nerve.
Unfortunately, not all individuals who suffer from conductive hearing loss are able to derive suitable benefit from hearing aids. For example, some individuals are prone to chronic inflammation or infection of the ear canal thereby eliminating hearing aids as a potential solution. Other individuals have malformed or absent outer ear and/or ear canals resulting from a birth defect, or as a result of medical conditions such as Treacher Collins syndrome or Microtia. Furthermore, hearing aids are typically unsuitable for individuals who suffer from single-sided deafness (total hearing loss only in one ear). Hearing aids commonly referred to as “cross aids” have been developed for single sided deaf individuals. These devices receive the sound from the deaf side with one hearing aid and present this signal (either via a direct electrical connection or wirelessly) to a hearing aid which is worn on the opposite side. Unfortunately, this requires the recipient to wear two hearing aids. Additionally, in order to prevent acoustic feedback problems, hearing aids generally require that the ear canal be plugged, resulting in unnecessary pressure, discomfort, or other problems such as eczema.
As noted above, hearing aids rely primarily on the principles of air conduction. However, other types of devices commonly referred to as bone conducting hearing aids or bone conduction devices, function by converting a received sound into a mechanical force. This force is transferred through the bones of the skull to the cochlea and causes motion of the cochlea fluid. Hair cells inside the cochlea are responsive to this motion of the cochlea fluid and generate nerve impulses which result in the perception of the received sound. Bone conduction devices have been found suitable to treat a variety of types of hearing loss and may be suitable for individuals who cannot derive sufficient benefit from acoustic hearing aids, cochlear implants, etc, or for individuals who suffer from stuttering problems.
In one aspect of the present invention, a bone conduction device for converting received acoustic signals into a mechanical force for delivery to a recipient's skull is provided. The bone conduction device comprises: a multilayer piezoelectric element comprising two stacked piezoelectric layers, and a flexible passive layer disposed between and mounted to the piezoelectric layers, wherein the piezoelectric layers are configured to deform in response to application thereto of electrical signals generated based on the received sound signals; a mass component attached to the multilayer piezoelectric element so as to move in response to deformation of the piezoelectric element; and a coupling configured to attach the device to the recipient so as to transfer mechanical forces generated by the multilayer piezoelectric element and the mass component to the recipient's skull.
In another aspect of the present invention, a bone conduction device for converting received acoustic signals into a mechanical force for delivery to a recipient's skull is provided. The bone conduction device comprises: a multilayer piezoelectric element comprising two stacked piezoelectric layers separated by a substantially flexible passive layer, wherein the piezoelectric layers have opposing directions of polarization such that application of electric signals, generated based on the sound signals, to both of the layers causes deflection of the piezoelectric element in a single direction; a mass component attached to the multilayer piezoelectric element so as to move in response to deformation of the piezoelectric element; and a coupling configured to attach the device to the recipient so as to transfer mechanical forces generated by the multilayer piezoelectric element and the mass component to the recipient's skull.
Embodiments of the present invention are described below with reference to the attached drawings, in which:
Embodiments of the present invention are generally directed to a bone conduction device for converting a received sound signal into a mechanical force for delivery to a recipient's skull. The bone conduction device comprises a multilayer piezoelectric element having two or more stacked piezoelectric layers, and a flexible passive layer disposed between the piezoelectric layers. The piezoelectric layers are configured to deform in response to application thereto of electrical signals generated based on the received sound signals The bone conduction device also includes a mass component attached to the multilayer piezoelectric element so as to move in response to deformation of the piezoelectric element, and a coupling configured to attach the device to the recipient. The coupling transfers mechanical forces generated by the multilayer piezoelectric element and the mass component to the recipient's skull.
The voltage of an electric field or electrical signal utilized to actuate a multilayer element may be lower than the voltage utilized in to actuate a single layer piezoelectric device. That is, a higher voltage electric field is required to generate a desired deflection of a single piezoelectric element than is required to generate the same desired deflection of a multilayer piezoelectric element. As such, bone conduction devices having a multilayer piezoelectric element in accordance with embodiments of the present invention have the advantage of requiring less power lower to produce desired mechanical force for delivery to a recipient's skull.
As noted above, bone conduction devices have been found suitable to treat a variety of types of hearing loss and may suitable for individuals who cannot derive suitable benefit from acoustic hearing aids, cochlear implants, etc.
In a fully functional human hearing anatomy, outer ear 101 comprises an auricle 105 and an ear canal 106. A sound wave or acoustic pressure 107 is collected by auricle 105 and channeled into and through ear canal 106. Disposed across the distal end of ear canal 106 is a tympanic membrane 104 which vibrates in response to acoustic wave 107. This vibration is coupled to oval window or fenestra ovalis 110 through three bones of middle ear 102, collectively referred to as the ossicles 111 and comprising the malleus 112, the incus 113 and the stapes 114. Bones 112, 113 and 114 of middle ear 102 serve to filter and amplify acoustic wave 107, causing oval window 110 to articulate, or vibrate. Such vibration sets up waves of fluid motion within cochlea 115. Such fluid motion, in turn, activates tiny hair cells (not shown) that line the inside of cochlea 115. Activation of the hair cells causes appropriate nerve impulses to be transferred through the spiral ganglion cells and auditory nerve 116 to the brain (not shown), where they are perceived as sound.
Bone conduction device 100 further includes a coupling 140 configured to attach the device to the recipient. In the specific embodiments of
It would be appreciated that embodiments of the present invention may be implemented with other types of couplings and anchor systems. Exemplary couplings and anchor systems that may be implemented in accordance with embodiments of the present invention include those described in the following commonly owned and co-pending U.S. patent application Ser. No. 12/167,796, entitled “SNAP-LOCK COUPLING SYSTEM FOR A PROSTHETIC DEVICE,” U.S. patent application Ser. No. 12/167,851, entitled “TANGENTIAL FORCE RESISTANT COUPLING SYSTEM FOR A PROSTHETIC DEVICE,” U.S. patent application Ser. No. 12/167,871, entitled “MECHANICAL FIXATION SYSTEM FOR A PROSTHETIC DEVICE,” U.S. patent application Ser. No. 12/167,825, entitled, “TISSUE INJECTION FIXATION SYSTEM FOR A PROSTHETIC DEVICE,” U.S. patent application Ser. No. 12/168,636, entitled “TRANSCUTANEOUS MAGNETIC BONE CONDUCTION DEVICE,” U.S. patent application Ser. No. 12/168,603, entitled “HEARING DEVICE HAVING ONE OR MORE IN-THE-CANAL VIBRATING EXTENSIONS,” and U.S. patent application Ser. No. 12/168,620, entitled “PIERCING CONDUCTED BONE CONDUCTION DEVICE.” The contents of these applications are hereby incorporated by reference herein. Additional couplings and/or anchor systems which may be implemented are described in U.S. Pat. No. 3,594,514, U.S. Patent Publication No. 2005/0020873, U.S. Patent Publication No. 2007/0191673, U.S. Patent Publication No. 2007/0156011, U.S. Patent Publication No. 2004/0032962, U.S. Patent Publication No. 2006/0116743 and International Application No. PCT/SE2008/000336. The contents of these applications are hereby incorporated by reference herein.
As noted, a bone conduction device, such as bone conduction device 100, utilizes a vibrator or actuator to generate a mechanical force for transmission to the recipient's skull. As described below, embodiments of the present invention utilize a multilayer piezoelectric element to generate the desired force. Specifically, the multilayer piezoelectric element comprises two or more active piezoelectric layers each mounted to a passive layer. The piezoelectric layers mechanically deform (i.e. expand or contract) in response to application of the electrical signal thereto. This deformation (vibration) causes motion of a mass component attached to the piezoelectric element. The deformation of the piezoelectric element and the motion of the mass component generate a mechanical force that is transferred to the recipient's skull. The direction and magnitude of deformation of a piezoelectric element in response to an applied electrical signal depends on material properties of the layers, orientation of the electric field with respect to the polarization direction of the layers, geometry of the layers, etc. As such, modifying the chemical composition of the piezoelectric layer or the manufacturing process may impact the deformation response of the piezoelectric element. It would be appreciated that various materials have piezoelectric properties and may implemented in embodiments of the present invention. One commonly used piezoelectric material is lead zirconate titanate, commonly referred to as (PZT).
Unimorph piezoelectric element 200 comprises a piezoelectric layer 202 mounted to a passive layer 204. It would be appreciated that layer 204 may be any one or more of a number of different materials. In one embodiment, layer 204 is a metal layer. In the exemplary configuration of
Unimorph piezoelectric element 200 is shown as having a piezoelectric strip layer 202 having a generally rectangular geometry. However, piezoelectric layers 202 may comprise, for example, piezoelectric disks or piezoelectric plates. Additionally, layers 202 and 204 are shown having a planar configuration prior to application of an electric field to layer 202. However, it would be appreciated that layers 202 and 204 may have a concave shape prior to application of the electric field.
Bimorph piezoelectric element 300 comprises first and second piezoelectric layers 302 separated by a flexible passive layer 304. Each piezoelectric layer 302 is mounted to opposing sides of passive layer 304. It would be appreciated that passive layer 304 may be any one or more of a number of different materials. In one embodiment, layer 304 is a metal layer, and more specifically, a metal foil layer. In the illustrative arrangement of
In the exemplary configuration of
In the embodiments of
Additionally,
Multilayer-bimorph piezoelectric element 400 comprise two pairs 450 of piezoelectric layers 402 each having, in the exemplary configuration of
When an electric field is applied to piezoelectric layers 402, layers 402A and 402B expand longitudinally as illustrated by arrows 408, while layers 402C and 402D contract longitudinally as illustrated by arrows 406. Due to the opposing expansion and contraction, the centers of layers 402 and 404 deflect in the direction illustrated by arrow 405. As described elsewhere herein, the deflection of layers 402, 404 is used to output a mechanical force that generates vibration of the recipient's skull.
In the embodiments of
Additionally,
As noted above,
Additionally, as noted above,
In the embodiments of
The determination of which segments 570 to actuate may be based on a number of factors. In one specific embodiment, amplifier 572, and thus segment 570B, is activated in response to receipt by the device of high frequency signals, while amplifier 574, and thus segments 570A and 570C, is activated in response to low frequency signals. In such specific embodiments, the force generated by the deflection of segment 570B causes perception of high frequency sound signals, while deflection of segments 570A and 570C result in perception of low frequency sound signals.
As noted above, in order to generate sufficient force to vibrate a recipient's skull, at least one mass component is mechanically attached to the piezoelectric element.
Similar to the embodiments described above, coupling 680 is utilized to transfer the mechanical force generated by piezoelectric actuator 620 to the recipient's skull. In certain embodiments, coupling 680 may comprise a bayonet coupling, a snap-in or on coupling, a magnetic coupling, etc.
In embodiments of the present invention, mass 684 is piece of material such as tungsten, tungsten alloy, brass, etc, and may have a variety of shapes. Additionally, the shape, size, configuration, orientation, etc., of mass 684 may be selected to optimize the transmission of the mechanical force from piezoelectric actuator 620 to the recipient's skull. In specific embodiments, mass 684 has a weight between approximately 3 g and approximately 50 g. Furthermore, the material forming mass 684 may have a density between approximately 6000 kg/m3 and approximately 22000 kg/m3.
As shown, piezoelectric element 700 is also attached to coupling 780 which is utilized to transfer the mechanical force generated by piezoelectric actuator 720 to the recipient's skull. In certain embodiments, coupling 780 may comprise a bayonet coupling, a snap-in or on coupling, a magnetic coupling, etc.
In the exemplary arrangement of
As noted,
In the embodiments described above, the maximum deflection of the piezoelectric elements may be the same axis as the combined center of the mass components and/or along the axis of the coupling to the skull. Such a configuration results in a balanced device.
Additionally, a piezoelectric actuator for use in a direct bone conduction device may have one or more resonant peaks within the range of approximately 300 to approximately 12000 Hz. In a specific arrangement, a piezoelectric actuator may have two resonance peaks where one peak is at less than approximately 1000 Hz, and the other peak is within the range of approximately 4000 to approximately 12000 Hz.
In a still other specific example, a piezoelectric actuator may have a resonant peak at less than approximately 300 Hz. Such an actuator may be used to transmit a tactile sensation to a recipient, rather than an audio sensation.
While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. All patents and publications discussed herein are incorporated in their entirety by reference thereto.
Andersson, Marcus, Asnes, Kristian, Bervoets, Wim, Holgersson, Erik, Stromsten, Patrik W.
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