Patent Application
20100272287
The present invention relates to the field of implantable hearing instruments, and in particular, to implantable electret microphones employable in fully- and semi-implantable hearing instrument systems.
Traditional hearing aids are placed in a user's ear canal. The devices function to receive and amplify acoustic signals within the ear canal to yield enhanced hearing. In some devices, “behind-the-ear” units have been utilized which comprise a microphone to transduce the acoustic input into an electrical signal, some type of signal processing circuitry to modify the signal appropriate to the individual hearing loss, an output transducer (commonly referred to in the field as a “receiver”) to transduce the processed electrical signal back into acoustic energy, and a battery to supply power to the electrical components.
Increasingly, a number of different types of fully- or semi-implantable hearing instruments have been developed. By way of example, implantable devices include instruments which employ implanted electromechanical transducers for stimulation of the ossicular chain and/or oval window, instruments which utilize implanted exciter coils to electromagnetically stimulate magnets fixed within the middle ear, and instruments which utilize an electrode array inserted into the cochlea to transmit electrical signals for sensing by the auditory nerve.
In these, as well as other implanted devices, acoustic signals are received by an implantable microphone, wherein the acoustic signal is converted to an electrical signal that is employed to generate a signal to drive an actuator that stimulates the ossicular chain and/or oval window or that is applied to selected electrodes of a cochlear electrode array. As may be appreciated, such implantable hearing instrument microphones must necessarily be positioned at a location that facilitates the receipt of acoustic signals and effective signal conversion/transmission. For such purposes, implantable microphones are most typically positioned in a surgical procedure between a patient's skull and skin, at a location rearward and upward of a patient's ear (e.g., in the mastoid region).
Given such positioning, the size and ease of installation of implantable hearing instrument microphones are primary considerations in the further development and acceptance of implantable hearing instrument systems. Further, it is important that a relatively high sensitivity and flat frequency response be provided to yield a high fidelity signal. Relatedly, the componentry cost of providing such a signal is of importance to achieving widespread use of implantable systems.
In view of the foregoing, a primary objective of the present invention is to provide an implantable microphone having a relatively small profile.
An additional objective of the present invention is to provide an implantable microphone that is reliable and cost effective.
Yet further objectives of the present invention are to provide an implantable microphone that provides high-sensitivity and relatively flat frequency response in acoustic signal conversion.
Yet another objective of the present invention is to provide an implantable microphone that provides directional sensitivity.
Yet another objective of the present invention is to provide an implantable microphone that provides a relatively higher gain at predetermined frequencies.
One or more of the above-noted objectives and additional advantages are realized by an implantable microphone of the present invention. The implantable microphone includes a hermetically-sealed, enclosed volume, and an electret member and back plate disposed with a space therebetween within the enclosed volume. The electret member and back plate are capacitively coupleable to provide an output signal indicative of acoustic signals incident upon at least one of the electret member and back plate. The electret arrangement yields a compact, and relatively low cost arrangement, while also providing a high quality output signal for use by an implantable hearing instrument.
As employed herein, an “electret member” is meant to refer to a microphone component having a dielectric material portion with a permanently-embedded static electric charge and an electrically-conductive material portion, or electrode. Further, a “back plate” is meant to refer to a microphone component having an electrically-conductive material portion, or electrode. When employed together in a microphone, the electret member and back plate may be disposed with the dielectric material portion of the electret member and the electrically-conductive material portion of the back plate located in opposing spaced relation and capacitively coupled, and with at least one of the electret member and back plate being moveable in response to acoustic signals incident thereupon, wherein electrical outputs from the electret member and back plate (e.g. from each of the electrodes) may be utilized to provide an electret output signal.
By way of example only, in a common source configuration, the electret member and back plate may be interconnected to a preamplifier (e.g., a FET) that is powered by a separate power source (e.g., an implantable, rechargeable battery). In turn, the preamplifier output may provide the electret output signal. The electret output signal may be processed and/or otherwise utilized to generate a drive signal applied to a transducer to stimulate a middle ear and/or inner ear component of a patient.
In one embodiment, the implantable microphone includes a hermetically-sealed, enclosed volume, and an electret member and back plate disposed with a space therebetween. The electret member and the back plate are capacitively coupleable to provide an output signal indicative of variations in the capacitive coupling across a lateral extent of the space in response to acoustic signals incident upon at least one of the electret member and the back plate. At least one of the electret member and the back plate includes a plurality of laterally offset portions located in corresponding spatial relation to a plurality of laterally offset regions comprising the lateral extent of the space. The output may be at least one of weighted and weightable in relation to the plurality of laterally offset portions.
In a related aspect, the electret member may include the plurality of laterally offset portions which may be defined by at least one of a dielectric material disposed in a predetermined pattern and an electrically conductive material (e.g., charge pick-up members) disposed in a predetermined pattern. The pattern may be determined by a set of substantially orthogonal radial and angular functions. A useful set of such functions are the solutions to the differential equations of motion for a surface in cylindrical coordinates commonly known as Bessel functions.
In one embodiment, the plurality of laterally offset portions is defined by a predetermined pattern of a dielectric material. The pattern may include at least one of a plurality of spaced dielectric material patches and a dielectric material disposed in a complex-configuration pattern. The complex-configuration pattern may include a uniform pattern, the boundaries of which are the zeros of linear sums of substantially orthogonal radial and angular functions; a uniform pattern, the area of which provides a response proportional to the integral of the linear sums and placed within the boundary of the zeros; a uniform density interdigitated pattern with boundaries formed by the zeros; and a non-uniform density interdigitated pattern bound by the zeros, the density of which is proportional to the amplitude of the linear sums. The linear weighting of the functions may be chosen from the modes of the surface responsive to acoustic pressures response to a desired spectrum or direction of arrival.
In a related embodiment, the predetermined pattern of dielectric material includes a plurality of spaced dielectric material patches that are at least one of located and sized to weight the output in a predetermined manner. For example, the patches may be located in an array pattern selected from the group consisting of an interdigitated pattern bound by the zeros and connected by the sign of linear sums of substantially orthogonal radial and angular functions; and an interdigitated pattern bound by the zeros and connected by the sign of the linear sums of the functions, the relative area or density of which is determined by the amplitude of the linear sums, and the polarity of which is determined by the sign of the linear sums in the area bound by the zeros. The plurality of patches may also provide a plurality of outputs. In this regard, the microphone may further include at least one signal conditioner for conditioning at least one of the plurality of outputs to weight the output signal in a predetermined manner.
In another embodiment, the plurality of laterally offset portions is defined by a predetermined pattern of an electrically conductive material. The pattern may include at least one of a plurality of spaced electrically conductive material patches and an electrically conductive material disposed in a complex-configuration pattern. The complex-configuration pattern may include a uniform pattern, the boundaries of which are the zeros of linear sums of substantially orthogonal radial and angular functions; a uniform pattern, the area of which provides a response proportional to the integral of the linear sums and placed within the boundary of the zeros; a uniform density interdigitated pattern with boundaries formed by the zeros; and a non-uniform density interdigitated pattern bound by the zeros, the density of which is proportional to the amplitude of the linear sums. The linear weighting of the functions may be chosen from the modes of the surface responsive to acoustic pressures response to a desired spectrum or direction of arrival.
In a related embodiment, the predetermined pattern of electrically conductive material includes a plurality of spaced electrically conductive material patches that are at least one of located and sized to weight the output in a predetermined manner. For example, the patches may be located in an array pattern selected from the group consisting of an interdigitated pattern bound by the zeros and connected by the sign of linear sums of substantially orthogonal radial and angular functions; and an interdigitated pattern bound by the zeros and connected by the sign of the linear sums of the functions, the relative area or density of which is determined by the amplitude of the linear sums, and the polarity of which is determined by the sign of the linear sums in the area bound by the zeros. The plurality of patches may also provide a plurality of outputs. In this regard, the microphone may further include at least one signal conditioner for conditioning at least one of the plurality of outputs to weight the output signal in a predetermined manner.
In yet another embodiment, the back plate includes the plurality of laterally offset portions, which are defined by an electrically conductive material disposed in a predetermined pattern. The pattern may include at least one of a plurality of spaced electrically conductive material patches and an electrically conductive material disposed in a complex-configuration pattern. The complex-configuration pattern may include a uniform pattern, the boundaries of which are the zeros of linear sums of substantially orthogonal radial and angular functions; a uniform pattern, the area of which provides a response proportional to the integral of the linear sums and placed within the boundary of the zeros; a uniform density interdigitated pattern with boundaries formed by the zeros; and a non-uniform density interdigitated pattern bound by the zeros, the density of which is proportional to the amplitude of the linear sums. The linear weighting of the functions may be chosen from the modes of the surface responsive to acoustic pressures response to a desired spectrum or direction of arrival.
In a related embodiment, the predetermined pattern of electrically conductive material includes a plurality of spaced electrically conductive material patches that are at least one of located and sized to weight the output in a predetermined manner. For example, the patches may be located in an array pattern selected from the group consisting of an interdigitated pattern bound by the zeros and connected by the sign of linear sums of substantially orthogonal radial and angular functions; and an interdigitated pattern bound by the zeros and connected by the sign of the linear sums of the functions, the relative area or density of which is determined by the amplitude of the linear sums, and the polarity of which is determined by the sign of the linear sums in the area bound by the zeros. The plurality of patches may also provide a plurality of outputs. In this regard, the microphone may further include at least one signal conditioner for conditioning at least one of the plurality of outputs to weight the output signal in a predetermined manner.
In another embodiment, the electret member of the microphone may include a plurality of laterally offset portions that may include at least one positively charged dielectric material portion and at least one negatively charged dielectric material portion. Further, the plurality of laterally offset portions may be disposed in a predetermined pattern.
In a related aspect, the at least one positively charged dielectric material portion and the at least one negatively charged dielectric material portion may be at least one of located and sized to weight an output signal in a predetermined matter. Further, the at least one positively charged dielectric material portion may provide at least a first output within the enclosed volume and the at least one negatively charged dielectric material portion may provide at least a second output within the enclosed volume, wherein the first output and the second output are employable to generate an output signal.
In another embodiment, the plurality of laterally offset portions may provide a plurality of outputs that are employable to generate the output signal, wherein the output signal reflects a predetermined directional sensitivity to acoustic signals. In this regard, the plurality of laterally offset portions may be at least one of located and sized to provide the predetermined directional sensitivity. Further, the microphone may include at least one signal conditioner for conditioning at least one of the plurality of outputs in a predetermined manner to provide the predetermined directional sensitivity. The predetermined directional sensitivity may be based, at least in part, upon physical attributes of a patient (e.g., the direction dependent frequency shaping of a patient's pinna).
In a related aspect, at least one of the electret member and the back plate may be flexible and tensioned along at least a first tension axis that extends across the at least one of the electret member and back plate. Further, the plurality of portions may be located a predetermined spatial relation to the at least a first tension axis to provide, at least in part, a predetermined directional sensitivity.
Additional aspects and corresponding advantages will be apparent to those skilled it the art upon consideration of the further description that follows.
As shown in
By way of example only, in a common source configuration, the electret member 10 and back plate of the diaphragm 20 may each be electrically interconnected to a preamplifier (e.g., a FET) that is powered by a separate power source (e.g., an implantable, rechargeable battery). In turn, the preamplifier output may provide an electret output signal. In turn, such output signal may be utilized to generate a drive signal for an implanted hearing aid instrument (e.g., an electromechanical or electromagnetic transducer for middle ear stimulation or a cochlear electrode array).
The electret member 10 may be of a non-flexible construction and disposed in fixed relation to the housing 30. Further, the electret member 10 may be electrically insulated from the housing 30 and back plate of the flexible diaphragm 20 by one or more peripheral insulating member(s) 32. Such peripheral member(s) 32, or other components, may also be disposed to engage and thereby facilitate positioning and tensioning of the diaphragm 20 at a desired distance h from the electret member 10, as shown in
The electret member 10 may comprise a charged dielectric material layer 12 and an electrode 14 (e.g., a metal plate or metallized support member). By way of example, the dielectric material layer 12 may comprise a permanently-charged, halocarbon polymer such as polyfluoroethylenepropylene. The diaphragm 20 may comprise an electrically-conductive material, e.g., a biocompatible metal such as titanium, wherein the diaphragm 20 may integrally define the back plate. In other arrangements, a separate metal layer defining the electrode of the back plate may be provided on an internal side of the diaphragm 20.
A plurality of spaced, electrically-conductive members 70, i.e., electrical pick-up members, are included. In this regard, electrically-conductive members 70 may be combinatively employed to provide a first electrical output from electret member 10 that is employed with a second electrical output from the back plate of diaphragm 20 to provide an electret output signal. By way of example, the electrically-conductive members 70 may be electrically interconnected in parallel, wherein the electrical output of each of the electrically-conductive members 70 will reflect a corresponding measure of capacitive coupling between the electret member 10 and back plate of diaphragm 20 in the corresponding spatial regions of the dielectric layer 12 that adjacently oppose the electrically-conductive members 70. In turn, the electrically-conductive members 70 may be located in corresponding relation to a predetermined plurality of acoustic vibration frequency ranges that correspond with differing distance ranges relative to a center axis of the microphone, thereby facilitating the provision of an improved electret output signal.
The electrically-conductive members 70 may be provided in the form of three spaced rings 70a, 70b and 70c, as shown in
Of note, while the embodiment shown in
Referring now to
Another embodiment of the present invention is illustrated in
In the embodiment shown in
The processing stages 76-78 shown may be used to finely tune the frequency response of the microphone 1. For example, the electrically conductive members 70 may be sized and/or located to provide a relatively flat frequency response across a desirable range of frequencies. However, it may be difficult to achieve the optimum response by sizing and locating the members 70 alone. This may be due to mechanical variations, individual patient physical variations, individual patient frequency sensitivity, or other issues. Thus, the processing stages 76-78 may be used to selectively amplify the output signals to provide a better performing microphone 1 for an individual patient.
As can be appreciated, the tension axes 272 function to partition the surface of the diaphragm 20 into a plurality of laterally offset regions. In this regard, each region may serve as an element in an array of acoustic sensors, such that the response of the diaphragm 20 due to acoustic signals may be controlled to provide desirable properties, such as directional sensitivity, a predetermined frequency response, improved sensitivity, or other characteristics. In one embodiment, at least one of the tension axes 272 and the spaced, electrically-conductive members 270a-d are designed to provide directional sensitivity that corresponds to a physical characteristic of a patient (e.g., the direction dependent frequency response resulting from the shape of a patient's pinna).
As discussed above, the tension axes 272 operate to divide the diaphragm 20 into partitions (e.g., an array of acoustic sensors) that may be utilized to provide directional sensitivity by using, for example, beamforming techniques. Generally, beamforming (e.g., a phased array) takes advantage of the fact that the distance from an acoustic source and each element in the array is slightly different. This results in the acoustic signals arriving at each element at slightly different times, such that the output signals from each element are phase shifted relative to each other. Various mathematical techniques may be used to determine the direction of an acoustic source by analyzing the plurality of phase-shifted signals. For example, the microphone 1 may be designed so that acoustic signals that originate directly in front of a patient are amplified to a greater extent than signals from behind the patient, such that the patient may more clearly hear a conversation with another person.
In addition to directional sensitivity, the array of acoustic sensors may be used to simulate a physical characteristic of a patient. For example, the array may be designed to simulate the function of a patient's pinna. In addition to collecting sound, the pinna functions to filter the sound in a way that adds directional information. Specifically, the filtering process preferentially amplifies sounds in the frequency range of human speech. Thus, the array may be designed to model the human pinna to achieve the same desirable frequency response. Additionally, the pinna and surrounding structures filter sounds in a directionally dependent way, so that a given direction corresponds to a specific frequency shaping. The array may be designed so as to produce the frequency shaping corresponding to a given direction (e.g. its direction of greatest sensitivity).
To achieve the aforementioned beamforming functionality, tension axes may be provided in any desirable quantity and position. Further, electrically-conductive members may be sized and/or located to provide the desired response. Additionally or alternatively, the functionality may be achieved using various signal processing techniques. For example, the plurality of output signals from the plurality of electrically-conductive members may be processed in the time domain (e.g., using “delay and sum”) or frequency domain (e.g., using FFT or a filter bank).
In this embodiment, the electrically-conductive member 70a may be coupled to the positively charged dielectric material portion 212a, to provide a first output within the enclosed volume of the microphone 1. Similarly, the electrically conductive member 70b may be coupled to the negatively charged dielectric material portion 212b, to provide a second output within the enclosed volume. In this regard, the first output and the second output may be employed to generate an output signal of the microphone 1. As can be appreciated, this configuration may provide an electret output signal entirely from a single side of the electret member 10 (e.g., within the volume 44), which may reduce the volume requirements and the complexity of the design for the microphone 1 by not requiring any electrical connections on the back plate 20.
The foregoing description of the present invention has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit the invention to the form disclosed herein. Consequently, variations and modifications commensurate with the above teachings, and skill and knowledge of the relevant art, are within the scope of the present invention. The embodiments described hereinabove are further intended to explain known modes of practicing the invention and to enable others skilled in the art to utilize the invention in such or other embodiments and with various modifications required by the particular application(s) or use(s) of the present invention. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art.
This application claims priority to U.S. Provisional Application Ser. No. 61/173,275, filed Apr. 28, 2009, entitled “PATTERNED IMPLANTABLE ELECTRET MICROPHONE”, the entirety of which is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61173275 | Apr 2009 | US |
