Patent Publication Number: US-6342035-B1

Title: Hearing assistance device sensing otovibratory or otoacoustic emissions evoked by middle ear vibrations

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of Provisional Appln. 60/118,582 filed Feb. 5, 1999. 
     This application is related to co-pending, commonly assigned U.S. patent application entitled IMPLANTABLE HEARING SYSTEM HAVING MULTIPLE TRANSDUCERS, Ser. No. 08/693,430, filed on Aug. 7, 1996, and assigned to the assignee of the present application, and which is herein incorporated by reference. This application is also related to a co-pending, commonly assigned U.S. patent application entitled IMPLANTABLE HEARIG ASSISTANCE SYSTEM WITH CALIBRATION AND AUDITORY RESPONSE TESTING, Ser. No. 08/804,016, filed on Feb. 21, 1997, and assigned to the assignee of the present application, and which is herein incorporated by reference. 
    
    
     BACKGROUND OF INVENTION 
     1. Field of the Invention 
     This invention relates generally to auditory diagnosis and assistance and more particularly, but not by way of limitation, to an at least partially implantable hearing assistance system providing middle ear vibrations and sensing particularly based on evoked otovibratory and otoacoustic emissions. 
     2. Description of Related Art 
     Some types of partial middle ear implantable (P-MEI), total middle ear implantable (T-MEI), cochlear implant, or other hearing assistance systems utilize devices disposed within the middle ear or inner ear regions. Such devices might include an input transducer for receiving sound vibrations or an output stimulator for providing mechanical or electrical output stimuli corresponding to the received sound vibrations. 
     An example of such a device is disclosed in U.S. Pat. No. 4,729,366, issued to D. W. Schaefer on Mar. 8, 1988. In the &#39;366 patent, a mechanical-to-electrical piezoelectric input transducer is associated with the malleus, transducing mechanical energy into an electrical signal, which is amplified and further processed by an electronics unit. A resulting electrical signal is provided to an electrical-to-mechanical piezoelectric output transducer that generates a mechanical vibration coupled to an element of the ossicular chain or to the oval window or round window for assisting hearing. In the &#39;366 patent, the ossicular chain is interrupted by removal of the incus. Removal of the incus prevents the mechanical vibrations delivered by the piezoelectric output transducer from mechanically feeding back to the piezoelectric input transducer. 
     Introducing devices into the middle or inner ear regions typically involves intricate surgical procedures for positioning or affixing the devices and its components for communication or coupling to the desired auditory elements. The proper positioning and affixation for obtaining the best input signal and providing the best output stimuli is a often a difficult task. The patient is typically under general anesthesia, and is thus unable to provide the implanting physician with any human feedback or information regarding how well sound is being perceived. Thus, the implanting surgeon faces a difficult task that may yield uneven results in the proper positioning and affixation of components in the middle or inner ear regions in order to obtain proper sound perception. There is a need in the art to facilitate optimal positioning and affixing components in the middle or inner ear regions in order to obtain proper sound perception. After implantation, the physician would like to diagnose malfunctions of the hearing assistance system without performing further invasive procedures. It is possible for an implanted device or component to become dissociated from its corresponding auditory element (e.g., by a severe blow to the head or otherwise). Further, changes in one or more of the ossicular chain elements may result in the displacement and misalignment of the device or its components. For example, an output transducer initially positioned to be in contact with the stapes may later become dissociated from the stapes. There is, therefore, a need in the art to enable a physician to determine, without surgical intervention, whether or not the output transducer or other implanted component is still properly positioned. 
     Other complicating factors are also present. There may be a large variation between patients in the sound perception characteristics of their auditory systems. Moreover, there may be variations between hearing assistance systems, such as in their component characteristics. For example, the characteristics of the input transducer and output stimulator may well vary to some degree. Accordingly, there is a need for hearing assistance systems to provide diagnostic or calibration information to the physician, such as during or after the surgical implantation procedure, in order to ascertain efficacy and adjust therapy accordingly. There is a further need for self-calibration of such hearing assistance systems to increase their ease of use. 
     In the unrelated technological field of audiometric screening and diagnosis, numerous audiometric screening techniques have been developed to assess the state of a patient&#39;s auditory system. Some of these techniques are designed to provide diagnostic information without active participation by the patient. Such techniques are particularly useful for sleeping, anesthetized, unconscious patients or newborn infants who lack the cognitive ability to provide feedback to the physician. One such technique involves detection of transient evoked otoacoustic emissions, also referred to as Kemp echoes, cochlear echoes, and delayed evoked otoacoustic emissions. 
     In order to perform clinical diagnosis using otoacoustic emissions, a brief acoustic (i.e., sound pressure wave) stimulus is provided by an earphone that is introduced into the external auditory canal. Evoked otoacoustic emissions are sounds generated within the normal inner ear (cochlea) in response to the acoustic stimulus after a 5-20 millisecond latency period. Resulting sound pressure waves corresponding to the evoked otacoustic emissions are detected by a microphone introduced into the external auditory canal. Responses to several stimuli are averaged, amplified, and filtered. Transient evoked otoacoustic emissions are measurable in normal-hearing persons. However, if hearing loss exceeds 40-50 dB, an otoacoustic emission typically cannot be evoked in response to a transient stimulus. As a result, the presence or absence of transient evoked otoacoustic emissions can be used as an audiometric screening tool. 
     However, using transient evoked otoacoustic emission as a clinical diagnostic tool presents numerous difficulties. One such problem results from spontaneous otoacoustic emissions, which are internal sounds emitted by the human ear even in the absence of an external stimulus. The presence of such spontaneous otoacoustic emissions can make the transient evoked otoacoustic emissions more difficult to detect. Another problem is presence of noise in the introduced acoustic stimulus and the detected acoustic response. Such noise includes electronic noise (e.g., from the microphone, preamplifiers, receiver, filters, etc.), body noise (including spontaneous otoacoustic emissions), and environmental acoustic noise that enters the external auditory canal. This type of noise sources tend to mask the evoked otoacoustic emission, making it more difficult to detect. Thus, there is a need in the art to improve the sensitivity of detecting transient evoked otoacoustic emissions. For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need for calibration and diagnostic capability of PMEI, T-MEI or other hearing assistance systems, and there is a need in the unrelated technological field of audiometric screening and diagnosis for improved techniques of detecting cochlear emissions such as transient evoked otoacoustic emissions. 
     SUMMARY OF THE INVENTION 
     The present invention provides techniques for detecting cochlear emissions and performing audiometric, calibration, and diagnostic functions in an at least-partially implantable hearing assistance system. The present invention facilitates the optimal orientation, positioning and affixing of hearing assistance system devices and components in the middle or inner ear regions to ensure proper sound perception. According to one aspect of the present invention, a physician can determine, without surgical intervention, whether or not an already-implanted component is still properly positioned. Another advantage of the present invention allows improved sensitivity detection of cochlear emissions. 
     In one embodiment, the invention provides a transducer adapted for sensing mechanical vibrations produced by an inner ear. In another embodiment, the invention provides an apparatus comprising an output transducer and a first input transducer. The output transducer is adapted for coupling a mechanical vibration output stimulus to an inner ear in response to an electrical output signal. The first input transducer is adapted for receiving an emission (e.g., transient evoked otovibratory or otoacoustic emission) from the inner ear and generating an electrical first input signal in response to the emission. The output and first input transducers can be integrally or separately formed. 
     In one embodiment, the apparatus includes an electronics unit that is capable of adjusting the electrical output signal based on the received electrical first input signal. In another embodiment, the apparatus includes a second input transducer. In yet another embodiment, the apparatus further comprises an external transceiver, adapted for communication with the electronics unit. 
     Another aspect of the invention provides a method that includes disposing a transducer in the middle ear, stimulating the inner ear using the transducer disposed in the middle ear, and sensing emissions (e.g., transient evoked otovibratory or otoacoustic emissions) from the inner ear in response to stimulating the inner ear. 
     In one embodiment, the method also includes programming a hearing assistance device based on the sensed emissions from the inner ear. Another embodiment includes adjusting the stimulation of the inner ear based on the sensed emissions from the inner ear. In yet another embodiment, a data signal, based on the sensed emissions from the inner ear, is stored, or communicated from an implanted transmitter to an external receiver. A further embodiment includes repositioning the transducer (or adjusting a contact force between the transducer and an auditory element) based on the sensed emissions from the inner ear. The invention also allows programming of hearing assistance signal processing parameters of an implantable hearing assistance device based on the sensed emissions from the inner ear. 
     Another aspect of the invention provides a method that includes stimulating the inner ear, sensing emissions from the inner ear in response to stimulating the inner ear, and programming an implantable device (e.g., adjusting a gain or frequency response) based on the sensed emissions from the inner ear. 
     As described below, the present invention allows improved sensitivity detection of cochlear emissions, and provides easier implantation and subsequent calibration, diagnostic, and audiometric functions of an implantable hearing assistance device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, like numerals describe substantially similar components throughout the several views. 
     FIG. 1 illustrates generally a human auditory system. 
     FIG. 2 is a schematic/block diagram illustrating generally a hearing assistance system according to one embodiment of the present invention. 
     FIG. 3 is a schematic/block diagram illustrating generally a hearing assistance device according to another embodiment of the present invention. 
     FIG. 4 is a schematic/block diagram illustrating generally a hearing assistance device according to a further embodiment of the present invention. 
     FIG. 5 is a schematic/block diagram illustrating generally a hearing assistance device according to a partial middle-ear implantable (P-MEI) embodiment of the present invention. 
     FIG. 6 is a schematic/block diagram illustrating generally one embodiment of at least a portion of an electronics unit according to one aspect of the present invention. 
     FIG. 7 is a schematic/block diagram illustrating generally a further embodiment of at least a portion of an electronics unit according to another aspect of the present invention. 
     FIG. 8 is a flow chart illustrating generally one embodiment of a method of using the present invention for providing diagnostic information during implantation of portions of a hearing assistance device. 
     FIG. 9 is a flow chart illustrating generally a further embodiment of a method of using the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that the embodiments may be combined, or that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents. In the accompanying drawings, like numerals describe substantially similar components throughout the several views. 
     As described below, the present invention provides improved techniques for detecting transient evoked otoacoustic emissions by providing a mechanical vibration in the middle ear, rather than providing an external acoustic (sound pressure) stimulus. The present invention detects resulting transient evoked otovibratory or otoacoustic emissions, in response to the mechanical vibration stimulus. 
     Sensing the resulting transient evoked otoacoustic emission includes either directly sensing a mechanical sound vibration (defined herein as an “otovibratory emission”), or sensing a resulting sound pressure wave (defined herein as an otoacoustic emission”). In one embodiment, detection of otovibratory and otoacoustic emissions provides calibration and diagnostic functions for a middle ear implantable hearing system such as a partial middle ear implantable (P-MEI), total middle ear implantable (T-MEI), or other hearing system. A P-MEI or T-MEI hearing system assists the human auditory system in converting acoustic energy contained within sound waves into electrochemical signals delivered to the brain and interpreted as sound. 
     FIG. 1 illustrates generally a human auditory system. Sound waves are directed into an external auditory canal  20  by an outer ear (pinna)  25 . The frequency characteristics of the sound waves are slightly modified by the resonant characteristics of the external auditory canal  20 . These sound waves impinge upon the tympanic membrane (eardrum)  30 , interposed at the terminus of the external auditory canal  20 , between it and the tympanic cavity (middle ear)  35 . Variations in the sound waves produce tympanic vibrations. The mechanical energy of the tympanic vibrations is communicated to the inner ear, comprising cochlea  60 , vestibule  61 , and semicircular canals  62 , by a sequence of articulating bones located in the middle ear  35 . This sequence of articulating bones is referred to generally as the ossicular chain  37 . Thus, the tympanic membrane  30  and ossicular chain  37  transform acoustic energy in the external auditory canal  20  to mechanical energy at the cochlea  60 . 
     The ossicular chain  37  includes three ossicles: a malleus  40 , an incus  45 , and a stapes  50 . The malleus  40  includes manubrium and head portions. The manubrium of the malleus  40  attaches to the tympanic membrane  30 . The head of the malleus  40  articulates with one end of the incus  45 . The incus  45  normally couples mechanical energy from the vibrating malleus  40  to the stapes  50 . The stapes  50  includes a capitulum portion, comprising a head and a neck, connected to a footplate portion by means of a support crus comprising two crura. The stapes  50  is disposed in and against a membrane-covered opening on the cochlea  60 . This membrane-covered opening between the cochlea  60  and middle ear  35  is referred to as the oval window  55 . Oval window  55  is considered part of cochlea  60  in this patent application. The incus  45  articulates the capitulum of the stapes  50  to complete the mechanical transmission path. 
     Normally, prior to implantation of the invention, tympanic vibrations are mechanically conducted through the malleus  40 , incus  45 , and stapes  50 , to the oval window  55 . Vibrations at the oval window  55  are conducted into the fluid-filled cochlea  60 . These mechanical vibrations generate fluidic motion, thereby transmitting hydraulic energy within the cochlea  60 . Pressures generated in the cochlea  60  by fluidic motion are accommodated by a second membrane-covered opening on the cochlea  60 . This second membrane-covered opening between the cochlea  60  and middle ear  35  is referred to as the round window  65 . Round window  65  is considered part of cochlea  60  in this patent application. Receptor cells in the cochlea  60  translate the fluidic motion into neural impulses which are transmitted to the brain and perceived as sound. However, various disorders of the tympanic membrane  30 , ossicular chain  37 , and/or cochlea  60  can disrupt or impair normal hearing. 
     Hearing loss due to damage in the cochlea  60  is referred to as sensorineural hearing loss. Hearing loss due to an inability to conduct mechanical vibrations through the middle ear  35  is referred to as conductive hearing loss. Some patients have an ossicular chain  37  lacking sufficient resiliency to transmit mechanical vibrations between the tympanic membrane  30  and the oval window  55 . As a result, fluidic motion in the cochlea  60  is attenuated. Thus, receptor cells in the cochlea  60  do not receive adequate mechanical stimulation. Damaged elements of ossicular chain  37  may also interrupt transmission of mechanical vibrations between the tympanic membrane  30  and the oval window  55 . 
     Various techniques have been developed to remedy hearing loss resulting from conductive or sensorineural hearing disorder. For example, tympanoplasty is used to surgically reconstruct the tympanic membrane  30  and establish ossicular continuity from the tympanic membrane  30  to the oval window  55 . Various passive mechanical prostheses and implantation techniques have been developed in connection with reconstructive surgery of the middle ear  35  for patients with damaged elements of ossicular chain  37 . Two basic forms of prosthesis are available: total ossicular replacement prostheses (TORP), which is connected between the tympanic membrane  30  and the oval window  55 ; and partial ossicular replacement prostheses (PORP), which is positioned between the tympanic membrane  30  and the stapes  50 . 
     Various types of hearing aids have been developed to compensate for hearing disorders. A conventional “air conduction” hearing aid is sometimes used to overcome hearing loss due to sensorineural cochlear damage or mild conductive impediments to the ossicular chain  37 . Conventional hearing aids utilize a microphone, which transduces sound into an electrical signal. Amplification circuitry amplifies the electrical signal. A speaker transduces the amplified electrical signal into acoustic energy transmitted to the tympanic membrane  30 . However, some of the transmitted acoustic energy is typically detected by the microphone, resulting in a feedback signal which degrades sound quality. Conventional hearing aids also often suffer from a significant amount of signal distortion. 
     Implantable hearing systems have also been developed, utilizing various approaches to compensate for hearing disorders. For example, cochlear implant techniques implement an inner ear hearing system. Cochlear implants electrically stimulate auditory nerve fibers within the cochlea  60 . A typical cochlear implant system includes an external microphone, an external signal processor, and an external transmitter, as well as an implanted receiver and an implanted single channel or multichannel probe. A single channel probe has one electrode. A multichannel probe has an array of several electrodes. In the more advanced multichannel cochlear implant, a signal processor converts speech signals transduced by the microphone into a series of sequential electrical pulses corresponding to different frequency bands within a speech frequency spectrum. Electrical pulses corresponding to low frequency sounds are delivered to electrodes that are more apical in the cochlea  60 . Electrical pulses corresponding to high frequency sounds are delivered to electrodes that are more basal in the cochlea  60 . 
     The nerve fibers stimulated by the electrodes of the cochlear implant probe transmit neural impulses to the brain, where these neural impulses are interpreted as sound. 
     Other inner ear hearing systems have been developed to aid patients without an intact tympanic membrane  30 , upon which “air conduction” hearing aids depend. For example, temporal bone conduction hearing systems produce mechanical vibrations that are coupled to the cochlea  60  via a temporal bone in the skull. In such temporal bone conduction hearing systems, a vibrating element can be implemented percutaneously or subcutaneously. 
     A particularly interesting class of hearing systems includes those which are configured for disposition principally within the middle ear  35  space. In middle ear implantable (MEI) hearing assistance systems, an electrical-to-mechanical output transducer couples mechanical vibrations to the ossicular chain  37 , which is optionally interrupted to allow coupling of the mechanical vibrations thereto. Both electromagnetic and piezoelectric output transducers have been used to effect the mechanical vibrations upon the ossicular chain  37 . 
     One example of a partial middle ear implantable (P-MEI) hearing system having an electromagnetic output transducer comprises: an external microphone transducing sound into electrical signals; external amplification and modulation circuitry; and an external radio frequency (RF) transmitter for transdermal RF communication of an electrical signal. An implanted receiver detects and rectifies the transmitted signal, driving an implanted coil in constant current mode. A resulting magnetic field from the implanted drive coil vibrates an implanted magnet that is permanently affixed only to the incus  45 . Such electromagnetic output transducers have relatively high power consumption requiring larger batteries, which limits their usefulness in total middle ear implantable (T-MEI) hearing systems. 
     A piezoelectric output transducer is also capable of effecting mechanical vibrations to the ossicular chain  37 . An example of such a device is disclosed in U.S. Pat. No. 4,729,366, issued to D. W. Schaefer on Mar. 8, 1988. In the &#39;366 patent, a mechanical-to-electrical piezoelectric input transducer is associated with the malleus  40 , transducing mechanical energy into an electrical signal, which is amplified and further processed by an electronics unit. A resulting electrical signal is provided to an electrical-to-mechanical piezoelectric output transducer that generates a mechanical vibration coupled to an element of the ossicular chain  37  or to the oval window  55  or round window  65 . In the &#39;366 patent, the ossicular chain  37  is interrupted by removal of the incus  45 . Removal of the incus  45  prevents the mechanical vibrations delivered by the piezoelectric output transducer from mechanically feeding back to the piezoelectric input transducer. 
     The present invention provides improved techniques for detecting transient evoked otovibratory and otoacoustic cochlear emissions emitted in response to a mechanical sound vibration stimulus, rather than in response to a conventionally introduced sound pressure wave stimulus. In this patent application, the terms cochlea  60  and inner ear  60  are used interchangeably. The term otovibratory emission is defined as a mechanical sound vibration emitted from the cochlea  60 . The term otoacoustic emission is defined as sound pressure wave (not a mechanical vibration) in a gaseous medium (e.g., air) emitted from the cochlea  60 . According to conventional techniques, otoacoustic emissions are sensed via a microphone placed in the external auditory canal  20 , and the otoacoustic emissions are generated by an acoustic (sound pressure wave) stimulus. According to one aspect of the present invention, a transient vibrational stimulus is used to evoke cochlear emissions. The transient vibrational stimulus may result in both transient evoked otovibratory and otoacoustic emissions. 
     FIG. 2 is a schematic/block diagram illustrating generally one embodiment of a hearing assistance system according to one embodiment of the present invention. This embodiment, by way of example, but not by way of limitation, includes total middle ear implantable (T-MEI) hearing assistance device  200  implanted in middle ear  35 . Portions of hearing assistance device  200  are optionally implanted in the mastoid  80  portion of the temporal bone. In this embodiment, incus  45  is removed. However, such removal of incus  45  is not required to practice the invention. This embodiment of hearing assistance device  200  includes electronics unit  205 , an input transducer  210 , and an integrally formed input/output transducer  215 . A carrier  220  is provided, such as for mounting portions of input transducer  210  and input/output transducer  215 . Though a unitary carrier  220  is shown, input transducer  210  and input/output transducer  215  are also affixable by separate carriers or by any other suitable technique. 
     The hearing assistance system also includes an external (i.e., not implanted) programmer  201 , which is communicatively coupled to an external or implantable portion of hearing assistance device  200 , such as electronics unit  205 . Programmer  201  includes hand-held, desktop, or a combination of hand-held and desktop embodiments, for use by a physician or the patient in which hearing assistance device  200  is implanted. 
     In one embodiment, each of programmer  201  and hearing assistance device  200  include an inductive element, such as a coil, for inductively-coupled bidirectional transdermal communication between programmer  201  and hearing assistance device  200 . Inductive coupling is just one way to communicatively couple programmer  201  and hearing assistance device  200 . Any other suitable technique of communicatively coupling programmer  201  and hearing assistance device  200  may also be used. In one embodiment, such communication includes programming of hearing assistance device  200  by programmer  201  for adjusting hearing assistance parameters in hearing assistance device  200 , and also provides data transmission from hearing assistance device  200  to programmer  201 , such as for parameter verification or diagnostic purposes. Programmable parameters include, but are not limited to: on/off, standby mode, type of noise filtering for a particular sound environment, frequency response, volume, delivery of a test stimulus on command, and any other adjustable parameter. 
     In a hearing assistance mode of operation, input transducer  210  senses the mechanical sound vibrations of an auditory element. In one embodiment, these mechanical sound vibrations are the result of external environmental sound pressure waves received in the external auditory canal  20 , and converted into mechanical vibrations by the tympanic membrane  30 . Input transducer  210  provides a resulting electrical input signal in response to the received mechanical sound vibrations of the auditory element. In the embodiment of FIG. 2, malleus  40  is illustrated, by way of example, as the auditory element from which vibrations are sensed, but other auditory elements are also capable of providing sound vibrations, including, but not limited to tympanic membrane  30 , incus  45  or other ossicle, or any prosthetic auditory element serving a similar function. 
     Input transducer  210  provides the resulting electrical input signal, such as through one or more lead wires at node  225 , to electronics unit  205 . Electronics unit  205  provides amplification, filtering, or other signal processing of the input signal, and provides a resulting electrical output signal, such as through one or more lead wires, illustrated generally by node  235 , to input/output transducer  215 . In this embodiment, by way of example, but not by way of limitation, input/output transducer  215  provides mechanical (e.g., vibratory) stimulation to oval window  55  of cochlea  60  through stapes  50 . 
     In one embodiment, input/output transducer  215  is also used to sense otovibratory emissions from cochlea  60  in response to an earlier-provided transient mechanical sound vibration stimulus. In this embodiment, input/output transducer  215  includes an integrally formed bidirectional transducer element (e.g., a piezoelectric element) for performing both electrical-to-mechanical and mechanical-to-electrical transduction. Input/output transducer  215  provides a vibrational stimulus to cochlea  60 , and also senses an otovibratory emission from cochlea  60  in response to the vibrational stimulus. Input/output transducer  215  provides a resulting input electrical signal through a lead wire at node  235  to electronics unit  205 . In another embodiment, input/output transducer  215  includes an electrical-to-mechanical transducer and a separately formed mechanical-to-electrical transducer, as described below. 
     FIG. 3 is a schematic/block diagram, similar to FIG. 2, illustrating generally a hearing assistance device  200  according to another embodiment of the present invention. However, in FIG. 3, input/output transducer  215  includes a separately formed input transducer element  215   a  and output transducer element  215   b.  By way of example, but not by way of limitation, input transducer element  215   a  includes a piezoelectric transducer element for sensing otovibratory emissions from cochlea  60 , and output transducer element  215   b  includes an electromagnetic transducer comprising a coil  300  and permanent magnet  305  that is electromagnetically driven by coil  300 . Output transducer element  215   b  provides mechanical vibrations to cochlea  60  both for assisting hearing and for stimulating evoked otovibratory and otoacoustic emissions. 
     Output element  215   b  is implemented as any type of electrical-to-mechanical transducer, including, but not limited to a piezoelectric transducer, electromagnetic transducer, or inductor type. Input transducer element  215   a  is implemented as any type of mechanical-to-electrical transducer, including, but not limited to a piezoelectric transducer, electromagnetic transducer, a capacitive transducer, an accelerometer and microphone (described below). Alternatively, input transducer element  215   a  is omitted, and otovibratory or otoacoustic emissions are sensed by input transducer  210 , particularly when ossicular chain  37  is intact and functional. During a hearing assistance mode of operation, input transducer  210  senses mechanical vibrations resulting from environmental sounds, rather than from transient evoked otovibratory or otoacoustic emissions. 
     FIG. 4 is a schematic/block diagram illustrating generally a hearing assistance device  200  according to another embodiment of the present invention. In FIG. 4, stapes  50  is removed and input/output transducer  215  is mechanically coupled to cochlea  60  either directly, or via an intermediate coupling element  400 . By way of example, but not by way of limitation, intermediate coupling element  400  can include a stiff rod or wire. Input/output transducer  215  provides mechanical vibrations to cochlea  60  both for assisting hearing and for stimulating evoked otovibratory or otoacoustic emissions. Input/output transducer element  215  also senses the resulting evoked otovibratory emissions from cochlea  60 , providing a resulting electrical input signal through a lead wire at node  235  to electronics unit  225 . Alternatively, otoacoustic emissions are sensed by microphonic input transducer  210 , particularly when ossicular chain  37  is intact and functional. During a hearing assistance mode of operation, microphonic input transducer  210  senses environmental sounds, rather than transient evoked otoacoustic emissions. 
     FIG. 5 is a schematic/block diagram, similar to FIG. 2, illustrating generally a hearing assistance device  200  according to a partial middle-ear implantable (P-MEI) embodiment of the present invention. FIG. 5 also illustrates, by way of example, but not by way of limitation, an embodiment in which incus  45  is present and ossicular chain  37  is intact. Also by way of example, but not by way of limitation in this embodiment, electronics unit  205  is not implanted, but is instead worn externally, such as behind pinna  25 . Input transducer  210  includes an external microphone disposed in external auditory canal  20  or elsewhere, for transducing acoustic sound pressure waves into an electrical input signal. Input/output transducer  215  is mechanically coupled to incus  45 , stapes  50 , or directly to cochlea  60 , as described above, providing mechanical vibrations for hearing assistance and stimulation of evoked otovibratory or otoacoustic emissions. In one embodiment, input/output transducer  215  also senses the resulting evoked otovibratory cochlear emissions. In another embodiment, input/output transducer  215  provides mechanical vibrations in middle ear  35  for stimulating resulting evoked otoacoustic emissions that are sensed by microphone  210  in external auditory canal  20 . Alternatively, input/output transducer  215  is replaced by an output-only transducer (e.g., an electrical-to-mechanical transducer, as described above) for providing mechanical vibrations in middle ear  35  that stimulate resulting evoked otoacoustic emissions sensed by microphone  210  in external auditory canal  20 . 
     FIG. 6 is a schematic/block diagram illustrating generally one embodiment of at least a portion of electronics unit  205  according to one aspect of the present invention. In the embodiment of FIG. 6, electronics unit  205  includes a signal processing unit  600 , an input amplifier  605 , and an output amplifier  610 . Input amplifier  605  and output amplifier  610  are each electrically coupled between signal processing unit  600  and input/output transducer  215  through one or more shared or separate lead wires illustrated generally by node  235  in FIGS. 2-5. 
     Output amplifier  610  receives an output electrical signal at node  615  from signal processing unit  600 , and provides, in response thereto, a buffered or amplified electrical output signal for driving input/output transducer  215  and producing a mechanical vibration stimulus that is directly or indirectly coupled to cochlea  60 . Input amplifier  605  receives an input electrical signal from input/output transducer  215  that is transduced from otovibratory or otoacoustic emissions from cochlea  60  that are evoked in response to an earlier-provided mechanical vibration stimulus thereto. In response to the input electrical signal received from input/output transducer  215 , input amplifier  605  provides at node  620  a buffered or amplified input electrical signal to signal processing unit  600 . 
     According to one aspect of the present invention, hearing assistance device  200  provides a middle ear  35  mechanical vibration stimulus to cochlea  60 , rather than providing an external acoustic sound pressure wave stimulus. This is particularly advantageous when incus  45  is disarticulated (removed), or when sound pressure waves cannot be received by tympanic membrane  30  and transmitted as mechanical vibrations through ossicular chain  37  without interruption or attenuation. 
     According to another aspect of the present invention, hearing assistance device  200  is capable of efficient, high sensitivity detection of an evoked cochlear response. In this embodiment, otovibratory emissions are directly sensed, rather than indirectly sensing the resulting otoacoustic emission sound pressure waves in external auditory canal  20 . Otovibratory emissions from cochlea  60  are likely communicated through ossicular chain  37 , thereby driving tympanic membrane  30  to produce the otoacoustic emissions. The otoacoustic emissions are likely attenuated from the otovibratory emissions, and the otoacoustic emissions may be completely absent due to ossicular interruption or malfunction. Moreover, the frequency of otovibratory and otoacoustic emissions may differ. Otovibratory emissions likely allow more sensitive monitoring of cochlear response. The present invention allows the detection of both otovibratory and otoacoustic emissions from cochlea  60  to be used as a clinical audiometric diagnostic tool, or to be used in providing calibration and diagnostic functions in hearing assistance device  200 . 
     FIG. 7 is a schematic/block diagram illustrating generally, by way of example, but not by way of limitation, a further embodiment of at least a portion of electronics unit  205  according to one embodiment of the present invention. In the embodiment of FIG. 7, electronics unit  205  also includes battery  700 , memory  705 , a transmitter such as transceiver  710 , and analog multiplexers  715  and  720 . FIG. 7 also illustrates external programmer  201 , included in one embodiment of the hearing assistance system of the present invention, which includes a receiver or transceiver that is adapted to be communicatively coupled to electronics unit  205 , as described above. Battery  700  provides power to the various electrical components of electronics unit  205 . 
     In one embodiment, analog multiplexer  720  allows the electrical output signal provided by output amplifier  610 , and the electrical input signal resulting from the evoked otovibratory response to share common lead wires at node  235  for electrical coupling to input/output transducer  215 . In another embodiment, multiplexer  720  is omitted, and separate lead wires are provided, illustrated generally by node  235 , for separately communicating the electrical output signal from output amplifier  610  and the electrical input signal from input/output transducer  215 . In yet another embodiment, in which otovibratory or otoacoustic emissions are sensed via input transducer  210 , rather than sensing otovibratory emissions through input/output transducer  215 , analog multiplexers  715  and  720  are omitted. 
     In one embodiment, analog multiplexer  715  allows shared use (e.g., time multiplexed) of input amplifier  605  for amplification of both the input electrical signal provided by input transducer  210  (during hearing assistance mode) as well as the input electrical signal provided by input/output transducer  215  in response to the a evoked otovibratory emission from cochlea  60  (during diagnostic mode). In another embodiment, analog multiplexer  715  is omitted, and input amplifier  605  is separately implemented as two input amplifiers for respectively amplifying the input electrical signal provided by input transducer  210  and the input electrical signal provided by input/output transducer  215  in response to the evoked otovibratory emission from cochlea  60 . 
     In one embodiment, signal processing unit  600  includes circuits for filtering and other signal processing, analog-to-digital conversion, and a microprocessor or other microcontroller. In this embodiment, signal processing unit  600  is electrically coupled to memory  705  and transceiver  710 , such as by bus  730 . In one embodiment,memory  705  is integrally formed on a monolithic integrated circuit together with signal processing unit  600 . Memory  705  is capable of storing data, such as data based on the electrical input signal received from input/output transducer  215  in response to sensed evoked otovibratory or otoacoustic emissions from cochlea  60 , or data based on the electrical input signal received from input transducer  210  (e.g., piezoelectric bimorph or microphone) in response to sensed evoked otovibratory or otoacoustic emissions from cochlea  60 . Transceiver  710  is capable of transmitting to external programmer  201 , or other external transceiver, data based on sensed evoked otovibratory or otoacoustic emissions from cochlea  60 . 
     In one embodiment, transceiver  710  is also capable of receiving data from programmer  201  and communicating the received data to memory  705  for storage or to signal processing unit  600 . 
     According to one aspect of the present invention, the detection of otovibratory or otoacoustic emissions from cochlea  60  is used as a clinical diagnostic tool during surgical implantation of portions of hearing assistance device  200 . In one embodiment, input/output transducer  215  (or output transducer  215 B) is positioned by the implanting physician for directly or indirectly stimulating cochlea  60  in response to environmental sounds sensed by input transducer  210 . In this embodiment, the presence of otovibratory or otoacoustic emissions can indicate proper positioning of input/output transducer  215  (or output transducer  215 B). 
     FIG. 8 is a flow chart illustrating generally one embodiment of a method of using the present invention for providing diagnostic information during implantation of portions of hearing assistance device  200 . First, an access hole  85  is created, as described above, for disposing components of hearing assistance device  200  in middle ear  35 . At logic step  800 , a transducer, such as input/output transducer  215 , is disposed in middle ear  35 . The transducer is communicatively coupled to electronics unit  205 . In one embodiment, for example, input/output transducer  215  is electrically coupled to electronics unit  205 , such as through one or more lead wires at node  235 . 
     At logic step  805 , cochlea  60  is directly or indirectly stimulated. In one embodiment, input/output transducer  215  (or output transducer  215 B) provides a mechanical vibration stimulus in middle ear  35  that is coupled to oval window  55  of cochlea  60  through stapes  50 . 
     At logic step  810 , an otovibratory or otoacoustic emission, evoked in response to the stimulus of logic step  805 , is sensed by input/output transducer  215  or input transducer  210 . The resulting electrical input signal is converted into a digital data signal, such as by an analog-to-digital (A/D) converter included in signal processing unit  600 . Subsequently, the program logic checks to see if there is sufficient data for a response under decision step  812 . If the response to the query is in the affirmative, the program logic proceeds to logic step  815 . In the alternate, if the response is negative, the program logic reverts into a subroutine and goes back to logic step  810 . After the program logic proceeds to logic step  815  data signal based on the sensed otovibratory or otoacoustic emissions is communicated at logic step  815  from an implanted transmitter, such as transceiver  710 , to an external receiver, such as within programmer  201 . Subsequently, the program logic checks to see if data transfer is completed under decision block  818 . If the data is completed the program logic proceeds to logic step  820  where the transducer is repositioned or the contact force adjusted. In the alternate, if the data transfer is not completed, the program logic enters a subroutine and reverts back to logic step  815 . After logic step  820 , the program logic proceeds to decision block  822  where the need for further adjustments, if any, is checked. In the event there is such a need, the program logic goes into a subroutine and reverts back to logic step  805 . In the alternate, if no other adjustments are required, the program logic advances to logic step  824  and the operation is completed. 
     The data received by programmer  201  is displayed for the implanting physician on any type of display device, including but not limited to a screen display or a quartz readout. The displayed data allows the implanting physician to determine the amplitude of any detected otovibratory or otoacoustic emissions. If no otovibratory or otoacoustic emission is sensed, or inadequate amplitude is obtained, the implanting physician optionally reposition the transducer (e.g., input/output transducer  215  or output transducer  215 B) at logic step  820 . Logic steps  805  through  820  are optionally repeated until an adequate otovibratory or otoacoustic emission signal is obtained. In other words, the detection of otovibratory or otoacoustic emissions is used as a feedback signal to enable the physician to correctly position the implant so that adequate signals will be produced. In one embodiment, otovibratory or otoacoustic responses resulting from several stimulations of cochlea  60  are averaged to provide the resulting data signal communicated from transceiver  710 . 
     Thus, according to one aspect of the invention, otovibratory or otoacoustic emissions are used to provide diagnostic information to assist the implanting physician in positioning components of a hearing assistance device  200 , such as an electrical-to-mechanical output transducer in a P-MEI or T-MEI hearing assistance device. 
     According to another aspect of the invention, otovibratory or otoacoustic emissions are used to provide diagnostic information to optimize a force between input/output transducer  215  (or output transducer  215 B) and a corresponding auditory element that it contacts (e.g., stapes  50 ). In one embodiment, for example, the contact force is selected based on the desired output vibration frequency. In yet another embodiment, for example, multiple output transducers, each having a different frequency response, optimize an overall frequency response of vibrations delivered to cochlea  60 , as described in a co-pending U.S. patent application to Kroll et al. entitled IMPLANTABLE HEARING SYSTEM HAVING MULTIPLE TRANSDUCERS, Ser. No. 08/693,430, filed on Aug. 7, 1996, and assigned to the assignee of the present application, and which is herein incorporated by reference. 
     According to one aspect of the present invention, a vibration is provided, at logic step  805 , within (e.g., near the center of the passband) the particular output transducer&#39;s frequency range. The contact force between the output transducer and its corresponding auditory element (e.g., stapes  50 ) is adjusted at logic step  820  to maximize the amplitude of the resulting otovibratory or otoacoustic emission sensed at step  810 . In one example, a tighter connection is provided for an output transducer vibrating at higher frequencies (e.g., frequencies that are greater than 1 kHz) and a looser connection is provided for a different output transducer vibrating at lower frequencies (e.g., frequencies that are lower than 1 kHz). 
     According to another aspect of the invention, otovibratory or otoacoustic emissions are used to noninvasively provide diagnostic information in a newly or chronically implanted hearing assistance device, for example hearing assistance device  200 . By executing logic steps  805 ,  810 , and  815  on an already-implanted hearing assistance device  200 , the physician can determine whether input/output transducer  215  (or output transducer  215 B) remains in proper contact with a corresponding auditory element (e.g., stapes  50 ) for directly or indirectly vibrating cochlea  60 . 
     In one embodiment, for example, a piezoelectric bimorph input/output transducer  215  is mounted such that it contacts stapes  60  for delivering mechanical vibrations to cochlea  60  through stapes  50 . However, input/output transducer  215  may become dissociated from stapes  50  (e.g., by a severe blow to the patient&#39;s head or otherwise). Also, fibrous ingrowth may change the interface characteristics (such as interfacial force) between input/output transducer  215  and stapes  50 . If otovibratory or otoacoustic emissions were present immediately after hearing assistance device  200  was implanted, data communication indicating the absence of such otovibratory or otoacoustic emissions at a subsequent follow-up patient examination may noninvasively indicate inadequate stimulation by input/output transducer  215 . 
     In another embodiment, the otovibratory or otoacoustic emission data communicated by hearing assistance device  200  to programmer  201  is used in conjunction with other auditory response testing techniques, including, but not limited to: electric response audiometry (ERA), auditory brain-stem response (ABR), cortical electric response, electrocochleography, or other known audiometric techniques. Examples of auditory response testing techniques are described in a copending U.S. patent application to Kroll et al. entitled IMPLANTABLE HEARING ASSISTANCE SYSTEM WITH CALIBRATION AND AUDITORY RESPONSE TESTING, Ser. No. 08/804,016, filed on Feb. 21, 1997, and assigned to the assignee of the present application, and which is herein incorporated by reference. One aspect of the present invention allows the physician to differentiate between cochlear and neural problems. For example, if hearing assistance device  200  indicates the presence of otovibratory or otoacoustic emissions, but accompanying ABR tests fail to obtain a response signal, the origin of the hearing disfunction is likely neural, not cochlear. 
     FIG. 9 is a flow chart, similar to FIG. 8, illustrating generally a further embodiment of a method of using the present invention in which signal processing unit  600  provides an automated sequence of stimulation logic step  805  and otovibratory or otoacoustic sensing logic step  810 . The method of FIG. 9 further provides intermediate parameter readjustment at logic step  900 , as described below. Parameter adjustment at step logic step  900  includes, but is not limited to, adjustment of vibrational stimulation amplitude and frequency. 
     In one embodiment, for example, tone burst vibrational stimulations are provided at 500 Hz, 1 kHz, 2 kHz, 4 kHz, followed by a wideband click (e.g., containing frequency content substantially throughout the range between 500 Hz and 4 kHz). At each such frequency content setting, the amplitude of the vibrational stimulation may also be varied, such as by incrementally increasing the amplitude of the vibrational stimulation from 40 dB SPL to 100 dB SPL at 20 dB SPL increments. These frequencies and amplitudes are enumerated above by way of example only, and not by way of limitation. Other sequences of the frequency and amplitude of the vibrational stimulation may also be used. 
     In another embodiment, for example, where the patient&#39;s degree of hearing loss is already known, such information is provided to hearing assistance device  200  by the physician via programmer  201 , and the parameter readjustment at logic step  900  is tailored accordingly. For example, but not by way of limitation, for a patient having a hearing loss of approximately 40 dB at frequencies less than 1 kHz, and a hearing loss of approximately 60 dB at frequencies greater than 1 kHz, vibrational stimuli are sequentially delivered according to Table 1. For other patients having different hearing losses, frequencies and amplitudes different from those in Table 1 are used. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Patient with 40 dB loss &lt; I kHz and 60 dB loss &gt; I kHz 
               
            
           
           
               
               
               
            
               
                   
                 Frequency 
                 Amplitude 
               
               
                   
                 (Hz) 
                 (dB SPL at stapes) 
               
               
                   
                   
               
               
                   
                  500 
                 40, 60, 80, 100 
               
               
                   
                 1000 
                 40, 60, 80, 100 
               
               
                   
                 2000 
                    60, 80, 100 
               
               
                   
                 4000 
                    60, 80, 100 
               
               
                   
                 Wideband 
                 40, 60, 80, 100 
               
               
                   
                 (e.g., 500 Hz-4000 Hz) 
               
               
                   
                   
               
            
           
         
       
     
     After the automated sequence of stimulation logic steps  805 , otovibratory or otoacoustic sensing logic steps  810 , and parameter readjustment logic steps  900 , the data is optionally communicated to the physician at logic step  815 . In one embodiment, such as during implantation of portions of hearing assistance device  200 , the physician then repositions input/output transducer  215  or adjusts the contact force at logic step  820 . Signal processing unit  600  is capable of adjusting an electrical output signal to input/output transducer  215 , such as based on the received electrical first input signal from input/output transducer  215 . In one embodiment, signal processing unit  600  self-programs hearing assistance device  200 , adjusting certain hearing assistance signal processing parameters (e.g., gain, frequency response, noise filtering) at step  905 , based on the otovibratory or otoacoustic emission data sensed at step  810 . Alternatively, the physician intervenes and manually programs such hearing assistance signal processing parameters at step  910  based on the data communicated at step  815 . Thus, programming the hearing assistance device  200  can be either with or without physician intervention. Looking at FIG. 9 in more detail, The program is initiated under logic step  800  by disposing the transducer in the middle ear. Consequently, the cochlea is stimulated under logic step  805 . The program logic proceeds to logic step  810  where the vibrations (otovibratory or otoacoustic emission) are sensed. Under the subsequent decision block  812 , the program logic checks to verify if there is sufficient data for a response. In the vent it is found that the data is not sufficient the program logic goes into a subroutine and reverts back to logic step  805 . In the alternate, if the data is found to be sufficient, the program logic proceeds to logic step  813  where the data destination is set or selected. Decision block  814  confirms the selection of data destination. If no selections are available, the program logic goes into a subroutine and reverts back to logic step  813 . In the event that at least one data destination is selected, the program logic proceeds to logic step  815  where data transfer to one of the selected channels is executed. Accordingly, data may be transferred to modify signal processing parameters under logic step  905 , reposition transducer/ adjust contact force under logic step  820  and enable the physician to program signal processing parameters under logic step  910 . Subsequently, the program logic proceeds to decision block  912  to check if there is a need for other adjustments. In the event there is a need to modify or make adjustments, the program logic enters a subroutine and reverts back to logic step  805 . In the alternate, if no other adjustments are needed or indicated, the program logic proceeds to logic step  914  where the session is terminated. 
     Accordingly, the present invention provides a transient middle ear mechanical vibration stimulus, and senses an evoked otovibratory or otoacoustic emission from the cochlea. Based on the sensed emissions, diagnostic information is provided to the physician, allowing easier positioning and coupling of an electrical-to-mechanical output transducer. In other words, the detection of otovibratory or otoacoustic emissions is used as a feedback signal to enable the physician to correctly position the implant so that adequate signals will be produced. Diagnosis of auditory system or hearing assistance system malfunctions is easier using the data communicated from the implantable hearing assistance device. Signal processing parameters are adjusted based on the sensed cochlear emissions. Cochlear emissions are also more likely to be detected with improved sensitivity. 
     It is to be understood that the above description is intended to be illustrative, and not restrictive. Combinations of the above-described embodiments are also included within the scope of the present invention. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.