Patent Publication Number: US-7905824-B2

Title: Implantable hearing aid transducer with advanceable actuator to faciliate coupling with the auditory system

Description:
RELATED APPLICATIONS 
     This application claims priority as a Divisional Application to U.S. patent application Ser. No. 10/351,699, filed Jan. 27, 2003 now U.S. Pat. No. 7,278,963, entitled “IMPLANTABLE HEARING AID TRANSDUCER WITH ADVANCEABLE ACTUATOR TO FACILIATE COUPLING WITH THE AUDITORY SYSTEM”. 
    
    
     BACKGROUND OF THE INVENTION 
     Implantable hearing aids entail the subcutaneous positioning of some or all of various hearing augmentation componentry on or within a patient&#39;s skull, typically at locations proximate the mastoid process. Implantable hearing aids may be generally divided into two classes, semi-implantable and fully implantable. In a semi-implantable hearing aid, components such as a microphone, signal processor, and transmitter may be externally located to receive, process, and inductively transmit a processed audio signal to implanted components such as a receiver and transducer. In a fully-implantable hearing aid, typically all of the components, e.g., the microphone, signal processor, and transducer, are located subcutaneously. In either arrangement, a processed audio signal is provided to a transducer to stimulate a component of the auditory system 
     By way of example, one type of implantable transducer includes an electromechanical transducer having a magnetic coil that drives a vibratory actuator. The actuator is positioned to mechanically stimulate the ossicles via physical engagement. (See e.g., U.S. Pat. No. 5,702,342). In this regard, one or more bones of the ossicles are made to mechanically vibrate, causing the vibration to stimulate the cochlea through its natural input, the so-called oval window. An example of this transducer is included in the MET™ hearing aid of Otologics, LLC, in which a small electromechanical transducer is used to vibrate the incus (the 2nd of the 3 bones forming the ossicles), and thence produce the perception of sound. In this case, the vibratory actuator is coupled to the ossicles during mounting and positioning of the transducer within the patient. In one example, such coupling may occur via a small aperture formed in the incus bone. 
     As will be appreciated, coupling with the ossicles poses numerous challenges. For instance, during positioning of the transducer, it is often difficult for an audiologist or surgeon to determine the extent of the coupling. In other words, how well the actuator is attached to the ossicles. Additionally, due to the size of the transducer relative to the ossicles, it is difficult to determine if loading exists between the ossicles and transducer. In this regard, precise control of the engagement between the actuator of the transducer and the ossicles is of critical importance as the axial vibrations can only be effectively communicated when an appropriate interface or load condition exists between the transducer and the ossicles. Overloading or biasing of the actuator can result in damage or degraded performance of the biological aspect (movement of the ossicles) as well as degraded performance of the mechanical aspect (movement of the vibratory member). Additionally, an underloaded transducer, e.g., where the actuator is not fully connected to the ossicles, may result in reduced performance of the transducer. 
     Another difficulty with such coupling is that in some cases patients can experience a “drop-off” in hearing function after implantation. Such a drop off may be caused by changes in the physical engagement of the actuator, e.g., due to things such as tissue growth, or may be caused by a malfunction of the transducer or other componentry. After implantation, however, it is difficult to readily assess the performance and/or adjust an implanted transducer and interconnected componentry. For example, in the event of a “drop-off” in hearing function after implantation, it is difficult to determine the cause, e.g., over/under loading of the interface due to tissue growth or some other problem with the hearing aid, without invasive and potentially unnecessary surgery. In addition, once coupled for an extended period, the maintenance and/or replacement with a next generation transducer may be difficult. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, a primary object of the present invention is to simplify and improve implantation procedures for implantable hearing aid transducers. Another object of the present invention is to improve coupling of implantable transducers with a middle ear component, such as the ossicles. Another object of the present invention is to provide a means for achieving a proper interface, e.g., a low mechanical bias or no-load interface, between an implanted hearing aid transducer and a component of the auditory system. Another object of the present invention is to provide a hearing aid transducer with the ability to compensate in situ for undesirable interfaces, e.g., over or under loaded with respect to the component of the auditory system. In the context of the present invention, “in situ,” refers to in its proper position, e.g., in the context of the present transducer, as implanted in a patient and coupled to a middle ear component. A related object of the present invention is to provide an implantable hearing aid transducer with the ability to self compensate for undesirable interfaces both during implantation and subsequent to implantation. Another object of the present invention is to provide a means for removal, subsequent to implantation, of an implantable hearing aid transducer, e.g., for an upgrade and/or repair. 
     In relation to a transducer according to the present invention, each of the various aspects discussed in more detail below may include a transducer body preferably constructed from a biocompatible material that is implantable with in a patient. The transducer may also generally include an actuator associated with the transducer body to stimulate a component of the middle ear. The transducer may also include a driver to drive the actuator in response to transducer drive signals. The driver may be of any suitable design to drive the actuator and stimulate an associated middle ear component to produce or enhance the sensation of sound for a patient. For instance, some examples of the driver may include without limitation, an electrical, piezoelectric, electromechanical, and/or electromagnetic driver. 
     One or more of the above objectives and additional advantages may be realized by a first aspect of the present invention, which provides an implantable hearing aid transducer having an advanceable actuator. The transducer includes a transducer body having an aperture extending through at least a first side thereof, an actuator, and a driver to drive the actuator. According to this characterization, the actuator is advanceable through the aperture to couple with a middle ear component, e.g., the ossicles. It should be noted that in the context of the present invention, the coupling with the middle ear component may include a physical attachment or an adjacent positioning of the actuator relative the middle ear component. 
     Various refinements exist of the features noted in relation to the subject first aspect of the present invention. Further features may also be incorporated in the subject first aspect as well. These refinements and additional features may exist individually or in any combination. For instance, the aperture may also extend through a second side of the transducer body. In another instance, the actuator may be a separate structure from the transducer and be separately connectable to both the middle ear component and the transducer. In this regard, the transducer may also include a coupler for connecting the actuator to the transducer, e.g., within the aperture. In one example according to the present aspect, the coupler may be an adhesive, clamp or other means for connecting the actuator to the transducer. In another example according to the present aspect, the coupler may be selectively activatable between a coupled and uncoupled state to permit both connection of the actuator to the transducer and disconnection of the actuator from the transducer. For instance, the coupler may be constructed from a shape memory alloy activatable in response to a stimulus to connect and disconnect the actuator. In another example according to the present aspect, the coupler may be a material that is reshapeable in situ to permit compensating movements of the actuator to minimize loading between the middle ear component and transducer, e.g., such as may be caused by natural movement of the ossicles due to pressure changes, swallowing, etc. In this case, it is desirable that the reshapeable material be viscous enough at body temperature to permit gradual displacement of the actuator relative to the transducer but resistive to sudden movements to permit stimulation of the middle ear component in response to transducer drive signals. 
     In one example of an actuator according to the present aspect, the actuator may comprise a unitary elongated member that is both insertable into the aperture of the transducer body and advanceable relative thereto to couple with the middle ear component. In another example of an actuator according to the present aspect, the actuator may include first and second actuator members. In this case, one of the members may be connectable to the middle ear component, while the other member is advanceable relative to the transducer to couple with the member connected to the middle ear component. In this case, the actuator members may be coupled in any suitable manner whereby the coupled actuator members are sufficiently rigid for stimulation, e.g., through vibration of the middle ear component. It may be desirable, however, to provide a detachable coupler between the first and second actuator members, such as provided by the above described shape memory alloy. This provides the advantage of being able to uncouple the actuator members for removal of the transducer without disturbing the interface between the first actuator and the ossicles. 
     The actuator may be constructed from any material of sufficient rigidity for transmission of vibrations to the middle ear component. Some examples of the actuator include a wire, tube, pin etc., preferably formed from a biocompatible material. In this regard, it may be desirable that the length of the actuator be sufficiently longer than necessary for coupling with the middle ear component and transducer. In this case the coupling process may be facilitated, as the excess length is easier to work with during coupling and may be trimmed subsequent to connection to the transducer. 
     One or more of the above objectives and additional advantages may also be realized by a second aspect of the present invention, which provides an implantable hearing aid transducer having an actuator advanceable through a tube. In this case, the transducer includes a transducer body having an aperture extending through at least a first side thereof defined by the tube. According to this characterization, the actuator is advanceable through the tube, which in turn is connected to the transducer by a bellows member. Specifically, the bellows member may be connected between the first side of the transducer body and a first end of the tube. 
     Various refinements exist of the features noted in relation to the subject second aspect of the present invention. Further features may also be incorporated in the subject second aspect as well. These refinements and additional features may exist individually or in any combination. For instance, as with the above aspect the aperture may also extend through a second side of the transducer body. In this case, a second bellows member may be utilized to connect a second end of the tube to a second side of the transducer body to movably connect the tube to the transducer body. In this regard, the actuator may be a separate structure from the transducer that is separately connectable to both the middle ear component and the transducer, e.g., within the tube. According to this characterization, a driver of the transducer may be connected to the tube such that both the tube and the actuator are movable by the driver during stimulation of the middle ear component. 
     It will be appreciated that the transducer according to this aspect may be configured with either of the above-described actuators, e.g., a unitary actuator or two-piece actuator. Further, in this regard, the actuator may also be connected to the tube according to any of the above connection techniques. 
     One or more of the above objectives and additional advantages may also be realized by a third aspect of the present invention, which provides a method for implanting a hearing aid transducer within a patient. The method includes the steps of mounting/implanting a transducer body subcutaneously within the patient and aligning an aperture in at least a first side of the transducer body with a desired interface point on a middle ear component. According to this aspect, the transducer body may be initially loosely mounted within the patient to facilitate the step of aligning the transducer body with the desired interface on the middle ear component. In this regard, the method may further include securing the transducer body in the aligned position and advancing an actuator through the aperture toward the middle ear component for coupling to the same. 
     Various refinements exist of the features noted in relation to the subject third aspect of the present invention. Further features may also be incorporated in the subject third aspect as well. These refinements and additional features may exist individually or in any combination. For instance, the aligning step may include axially and laterally aligning the aperture with the desired interface. In this case, the method may further include the use of a guide, such as a laser sight to achieve a more precise alignment of the aperture with the desired interface. 
     Subsequent to mounting and aligning the transducer body, the method may further include using the aperture to form an interface on the middle ear component for the coupling of the actuator. According to this characterization, the method may further include inserting the actuator into the aperture prior to the advancing step, but subsequent to formation of the interface. Thereafter, the method may include coupling a distal end of the actuator to the middle ear component. It should be noted that according to the present method, the actuator may be a unitary actuator in which case the method may further include the step of coupling the other end of the actuator to the transducer. Alternatively, the actuator may be a two-piece actuator, in which case the method may include the steps of coupling a first actuator member to the middle ear component, advancing a second actuator member through the aperture, and connecting the first and second actuator members. In either case, the actuator may be detachably connected to the transducer to facilitate removal of the transducer without disturbing the coupling with the middle ear component. 
     One or more of the above objectives and additional advantages may also be realized by a fourth aspect of the present invention, which provides a method for implanting a hearing aid transducer within a patient. The method includes the steps of mounting/implanting a transducer body subcutaneously within the patient and aligning an aperture extending through a first and second side of the transducer body with a desired interface point on a middle ear component. As with the above aspect, the transducer body may be initially loosely mounted within the patient to facilitate the step of aligning the transducer body with the desired interface on the middle ear component. In this regard, the method further includes securing the transducer body in the aligned position and inserting an actuator through the aperture to couple with a middle ear component. Various refinements exist of the features noted in relation to the subject fourth aspect of the present invention. Further features may also be incorporated in the subject fourth aspect as well. These refinements and additional features may exist individually or in any combination. 
     One or more of the above objectives and additional advantages may also be realized by a fifth aspect of the present invention, which provides a method for operating an implantable transducer. The method includes the steps of receiving in a transducer, transducer drive signals, and processing the transducer drive signals to vibrate a tube movably connected to the transducer. In this regard, the method further includes, vibrating an actuator with the tube to stimulate a middle ear component. Various refinements exist of the features noted in relation to the subject fifth aspect of the present invention. Further features may also be incorporated in the subject fifth aspect as well. These refinements and additional features may exist individually or in any combination. 
     One or more of the above objectives and additional advantages may also be realized by a sixth aspect of the present invention, which provides a hearing aid that includes an acoustic signal receiver, signal processor, and implantable transducer. The acoustic signal receiver is operable to receive acoustic sound and generate acoustic response signals for the signal processor. The signal processor, in turn, is operable to process the acoustic response signals to generate transducer drive signals. The transducer includes a transducer body and actuator member that is advanceable relative to the transducer body. In this regard, the transducer may be any one of the above-described transducers, e.g., having a unitary or multiple actuator members. 
     Various refinements exist of the features noted in relation to the subject sixth aspect of the present invention. Further features may also be incorporated in the subject sixth aspect as well. These refinements and additional features may exist individually or in any combination. For instance, the present hearing aid may be a fully or semi-implantable hearing aid. In semi-implantable hearing aid applications, the acoustic sounds may be inductively coupled to the implanted transducer via an external transmitter and implanted receiver. In fully implantable applications, the acoustic sounds may be received by an implanted acoustic signal receiver e.g., an omni-directional microphone, and provided to an implanted signal processor for generation of the transducer drive signals. Additional aspects, advantages and applications of the present invention will be apparent to those skilled in the art upon consideration of the following. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a schematic view of a transducer for a semi-implantable or fully implantable hearing aid device; 
         FIG. 2  illustrates another example of a transducer for a semi-implantable or fully implantable hearing aid device; 
         FIG. 3  illustrates another example of a transducer for a semi-implantable or fully implantable hearing aid device; 
         FIG. 4  illustrates another example of a transducer for a semi-implantable or fully implantable hearing aid device; 
         FIG. 5  illustrates an example of a positioning system and protocol for implantation of a transducer for a semi-implantable or fully implantable hearing aid device; 
         FIG. 6  further illustrates the positioning system and protocol for implantation a transducer for a semi-implantable or fully implantable hearing aid device; 
         FIG. 7  illustrates another example of a transducer for a semi-implantable or fully implantable hearing aid device; 
         FIG. 8  illustrates another example of a transducer for a semi-implantable or fully implantable hearing aid device; 
         FIGS. 9   a  and  9   b  illustrate and bottom view of the transducer of  FIG. 8  for a semi-implantable or fully implantable hearing aid device; and 
         FIGS. 10 and 11  illustrate implantable and external componentry respectively, of a semi-implantable hearing aid device application of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made to the accompanying drawings, which at least assist in illustrating the various pertinent features of the present invention. In this regard, the following description is presented for purposes of illustration and description and is not intended to limit the invention to the form disclosed herein. Consequently, variations and modifications commensurate with the following teachings, and skill and knowledge of the relevant art, are within the scope of the present invention. The embodiments described herein are further intended to explain the best modes known 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. 
       FIG. 1  illustrates a schematic view of a transducer  100  according to the principles of the present invention. The transducer  100  may be employed with either a fully implantable hearing aid, wherein all of the components are located subcutaneously, or in conjunction with a semi-implantable hearing aid, wherein at least a portion of the hearing aid components, e.g., the microphone, are externally located relative to a patient. 
     The transducer  100  includes a transducer body  102 , an actuator  104 , and a driver  108 . The transducer  100  may also include other conventional components such as transducer electronics etc., not shown on  FIG. 1  for clarity. The transducer body  102  is an implantable housing, preferably biocompatible and having a substantially central aperture  120  defined between a first end  116  and a second end  118 . The transducer body  102  may be constructed in various shapes, e.g., cylindrical or rectangular, as a matter of design choice. The transducer body  102  is mountable subcutaneously within the patient&#39;s mastoid process (e.g., via a hole drilled through the skull), in proximity to a desired coupling point with the auditory system, e.g., the ossicles. 
     The transducer  100  further includes a cylindrical tube  124  that defines the aperture  120  between the ends  116  and  118 . As will be further described below, the driver  108  is connected to the tube  124 , which in turn is movably connected to the transducer body  102 . This permits the driver  108  to axially vibrate the actuator  104  using the tube  124 . In this regard, the tube  124  is appropriately sized to receive the actuator  104  therein during implantation of the transducer  100 . Operationally, the actuator  104  is insertable through the aperture  120  such that a distal end  106  is positioned within the middle ear to stimulate the ossicles through selectively induced axial vibrations of the actuator  104 . These vibrations are in turn communicated to one of the bones of the ossicles, such as the incus bone, to yield enhanced hearing. 
     According to one embodiment of the present transducer  100 , the actuator  104  may be an elongated member that is separately connectable to the transducer body  102  and to the ossicles of the patient. According to this characterization, the actuator  104  is designed for insertion through the tube  124  where it may be attached to the ossicles of the patient prior to connection to the transducer body  102 . The actuator  104  may then be supportably connected within the tube  124  such that a minimal load is imposed on the ossicles during or subsequent to implantation by the transducer  100 . Specifically, the aperture  120  of the transducer  100  may be precisely aligned with the actuator  104  during implantation, such that when the actuator  104  and transducer  100  are coupled, any load imposed on the ossicles, such as by the weight of the actuator  104 , is substantially removed through support provided by the transducer  100  when the actuator  104  is coupled thereto. As will be further discussed below, the supportable connection between the actuator  104  and the transducer body  102  may be made in any suitable manner that permits transmission of axial vibrations from the transducer  100  to the ossicles of the patient. Some examples of connection alternatives include without limitation, adhesives, mechanical couplers, shape memory alloys, and materials that are reshapeable in situ. 
     To maintain isolation of the internal components of the transducer  100 , bellows  110  and  122  may be utilized to connect each end of the tube  124  to the transducer body  102 . The bellows,  110  and  122 , are hermetically interconnected to each end of the tube  124  and the transducer body  102  such that they form a seal with the tube  124  to isolate the internal components of the transducer  100  from the introduction of bodily fluids. As will become apparent from the following description, however, the interior of the tube  124  does not include sensitive transducer components and therefore may or may not be completely sealed as a matter of design choice. 
     The bellows,  110  and  122 , also permit a movable connection of the tube  124  relative to the transducer body  102 . Alternatively, as will be further described below, other means may be utilized to provide the movable connection and may or may not provide isolation of the internal components of the transducer  100 . In this regard, the bellows,  110  and  122 , each comprise a plurality of undulations that permit the bellows,  110  and  122 , to axially respond in an accordion-like fashion to axial vibrations of the tube  124  by the driver  108 . In this manner, when the actuator  104  is connected within the tube  124 , the driver  108  may induce vibration of the connected tube  124  and actuator  104  to stimulate the ossicles of the patient. The driver  108  may be any device operational to process transducer drive signals to produce axial vibration of the tube  124 , and in turn, the actuator  104 . Some examples, of the driver  108  include without limitation, a piezoelectric driver, and an electromagnetic driver. 
     Advantageously, the separate connection of the actuator  104  to the auditory system and the transducer  100  minimizes loading on the auditory system during implantation of the transducer  100 . Specifically, the separate attachment of the actuator  104  to the transducer  100  provides the advantage of allowing an audiologist or surgeon to implant the transducer body  102  within the patient such that the aperture  120  is aligned with a desired interface point on the ossicles. Subsequent to implantation and alignment of the transducer body  102 , the actuator  104  may be separately inserted through the aligned aperture  120  for connection with the ossicles. According to this characterization, the only load imposed on the ossicles is the load imposed by the weight of the actuator  104 , which is negligible compared to that of the transducer  100  as a whole. Furthermore, because the weight of the actuator  104  is relatively negligible, proper coupling with the ossicles is facilitated as an audiologist or surgeon is able to better sense when a proper couple is achieved. Finally, since the weight of the actuator  104  is relatively negligible, if a load is imposed on the ossicles during connection of the actuator  104 , the load is released when pressure applied during the connection is released, as the ossicles is able to move the connected actuator  104  to its equilibrium position prior to connection of the actuator  104  to the transducer  100 , e.g., within the tube  124 . 
     Advantageously, the separate connection of the actuator  104  also facilitates alignment of the transducer  100  with the desired component of the auditory system, e.g., the incus bone. For instance, if after connection of the actuator  104  to the ossicles, it is noticed that the alignment is not perfect, the transducer body  102  may be loosened from its secure position and further aligned as necessary with the actuator  104 . In this case, the actuator  104  may serve as a guide for the finite alignment of the transducer body  102  with the ossicles. Furthermore, the aperture  120  also provides additional advantages during preparation of the ossicles for attachment of the actuator  104 . Specifically, the aperture  120  may be used to align a device for forming an interface on the ossicles for connection of the actuator  104 . For instance, a laser drill or other instrumentation may be inserted through the aligned aperture to form an aperture in the ossicles that may be utilized to couple the actuator  104 . In this case, the aperture  120  also provides a convenient conduit by which excess material from the operation may be removed from the patient. Still yet another advantage of the separate structure of the actuator  104  is that in the event a loading condition develops in the patient subsequent to implantation, e.g., due to events such as tissue growth and/or other changes in biological conditions, the actuator  104  may be separated from the transducer body  102  and the body  102  realigned in the proper position without disconnection of the actuator  104  from the ossicles. It should be noted that this would most likely require a small operation to access the implanted transducer  100 , but the evasiveness of such a procedure is minimized as the interface between the actuator  104  and middle ear component is not disturbed. 
       FIG. 2  illustrates an example of the transducer  100 , namely transducer  200 . The transducer  200  is an electromagnetic transducer that includes an electromagnetic driver having a coil  202  and magnet  204 . The coil  202  may be electrically interconnected to a signal processor (not shown), which provides transducer drive signals that induce desired magnetic fields across the magnet  204 , to affect a desired movement of the actuator  104 . In this regard, the magnet  204  may be multiple magnets connected to the tube  124  or may be a single cylindrical magnet connected to and circumscribing the tube  124  as a matter of design choice. 
     The transducer  200  is substantially similar to the transducer  100  except that it includes an annular coupler  206  to connect the actuator  104  to the tube  124 . The coupler  206  may be any apparatus suitable for providing a secure connection between the actuator  104  and the tube  124 . Preferably, however, the coupler  206  forms a detachable connection therebetween as such a connection facilitates removal and/or adjustment of the transducer  200 . According to this characterization, one example of the coupler  206  is a shape memory alloy including without limitation, NiTinol (trade name for the standard alloy Nickel-Titanium). Such alloys are known for their ability to take on a predetermined shape in response to a stimulus such as a temperature change. Specifically, shape memory alloys, such as NiTinol, undergo a phase transformation when cooled from their high temperature form, Austenite, to their low temperature form, Martensite. When such alloys are in the Martensite form, they are easily deformed to a new shape. When the alloy is heated, however, it recovers its previous shape, hence the name shape memory alloy. Advantageously, for alloys such as NiTinol, the temperature at which the alloy returns to its original shape may be adjusted, typically between the range of 100 degrees Celsius to negative 100 degrees Celsius. 
     In one example according to this characterization, the coupler  206  may be preformed (its original shape) in a connected state relative to the actuator  104 . In other words, in its original shape, before a stimulus such as heat is applied, the actuator  104  is coupled within the tube  124 . In this case, to achieve the connection with the ossicles, the coupler  206  may be heated so that the actuator  104  may be removed from the transducer body  102 . The transducer body  102  may then be implanted within the mastoid process of the patient and the aperture  120  aligned with the ossicles, e.g., the incus  212 . Subsequent to preparation of the incus, e.g., formation of a small interface or hole  112 , the actuator  104  may be inserted through the aperture  120  and connected to the interface  112 . Further alignment as necessary of the transducer body  102  may then be performed before the coupler  206  is returned to its original shape to couple the actuator  104  to the tube  124 . 
       FIG. 3  illustrates another example of the transducer  100 , namely transducer  300 . Similar to the transducer  200 , the transducer  300  is an electromagnetic transducer that includes an electromagnetic driver having a coil  202  and magnet  204 . Also similar to the transducer  200 , the transducer  300  includes the actuator  104  that is separately connectable to the transducer body  102  and the ossicles, e.g., the incus  212 . In contrast, however, the transducer  300  includes a coupler  302  extending substantially along the length of aperture  120 . In this case, the coupler  302  comprises a material that is reshapeable in situ at body temperature disposed within the tube  124  around the actuator  104 . According to this characterization, the coupler  302  is configured to relax under light constant loading, to permit gradual axial movement of the actuator  104  relative to the tube  124 . Such gradual movement of the actuator  104  relaxes load forces between the incuse  212  and actuator  104 . For instance, such load forces may result from the natural movement of the ossicles during pressure changes because of a patient significantly changing altitudes, e.g., during a visit to the mountains or ride in an un-pressurized airplane. 
     In this regard, the coupler  302  should comprise a material viscous enough at body temperature, e.g., in the range of 94° to 108°, to be resistive to sudden movements, but also reshapeable in response to light constant loading to permit gradual displacement of the actuator  104  relative to the tube  124 . This permits efficient mechanical energy transfer at audible frequencies, while allowing gradual load compensating displacements to occur. Although it will be appreciated that numerous materials (currently in existence and that will be available in the future) exhibiting the above-described properties may be utilized, some examples of the coupler  302  include without limitation, wax based materials, elastomer based materials, and/or silicon based materials. Those skilled in the art, however, will appreciate numerous other materials that may be utilized according to the principles of the present invention. 
     To maintain isolation of the internal components and prevent seepage of the coupler material  302 , the ends of the tube  124  may include annular sleeves  304  and  306 . In this regard, according to one example of the implantation procedure for the transducer  300 , the sleeve  306  may be permanently connected, e.g., such as by welding, to the end of the tube  124 . Alternatively, the end of the tube  124  may be of a stepped-in cylindrical configuration such that it forms an integral sleeve for containment of the coupler material  302 . Subsequent to implanting and alignment of the transducer body  102  with the desired interface point  112 , the actuator  104  may be inserted through the aperture  120  and connected to the incus  212 . It should be noted, that at this point in the implant procedure, the bellows  122  is not connected to the transducer body  102 . Further alignment of the transducer body  102  and actuator  104  may then be performed as necessary before the reshapeable material of the coupler  302  is injected around the actuator  104 . Following introduction of the coupler material  302 , the aperture  120  is sealed at the proximal end by the sleeve  304 . In one example, of such a configuration, the sleeve  304  may be secured in place via an overlapping electrodeposited layer  308  (e.g., comprising a biocompatible material such as gold) disposed across and about the abutment region for interconnection and sealing purposes. Subsequent to securing the sleeve  304  in position on the tube  124 , the bellows  122  is connected to the transducer body as illustrated in  FIG. 3 . According to this characterization, the bellows  122  may be connected by any appropriate means, with one example, including electrodeposited layer  310  disposed over the joint between the transducer body  102  and the bellows  122 . 
       FIG. 4  illustrates another example of the transducer  100 , namely the transducer  400 . The transducer  400  is substantially similar to the transducers,  200  and  300 , in that includes a transducer body  102  and an electromagnetic driver including the coil  202  and magnet  204 . In contrast, however, the transducer  400  includes an actuator member comprising a first member  404  and a second member  406 . As with the above embodiments, the members,  404  and  406 , may be any structure of sufficient rigidity to transmit vibrations, with some examples including without limitation, a pin, a tube, a wire, etc. preferably formed from a biocompatible material such as, titanium, a titanium alloy, platinum, a platinum alloy, or gold-plated stainless steel. 
     The member  406  includes the distal end  106  made of, or coated with, a ceramic or other suitable material to facilitate coupling with the incus  212 . The member  404 , on the other hand, is an elongated member designed for coupling with the member  406 . In this regard, at least one of the members,  404  and  406 , in this case member  406 , includes a coupling apparatus  408 . The coupling apparatus  408  could be any mechanism capable of joining the members,  404  and  406 , such that vibrations may be transmitted to the incus  212  from the transducer  400 . In one preferred example of the transducer  400 , the coupling apparatus  408  may comprise a shape memory alloy as described above. Advantageously, this permits the members,  404  and  406 , to be easily separated without disturbing the connection between the interface  112  and member  406 . 
     As with the transducers,  200  and  300 , the actuator may be separately connected to the transducer  100  and the incus  212  during the implantation procedure. According to this characterization, the implantation procedure may involve connecting the member  406  to the incus  212 . Advantageously, this may be performed prior to implanting and aligning the transducer body  102  or subsequent to implanting and aligning the transducer body  102  as a matter of choice. It should be noted, however, that each of these approaches provides its own advantages. For instance, where the member  406  is connected to the incus  212  prior to implantation of the transducer body  102  it will be appreciated that better visibility and spatial conditions exist for the surgeon or audiologist. Additionally, the member  406  may provide a target for alignment of the aperture  120  during the implantation. Alternatively, however, where the member  406  is connected to the incus  212  subsequent to implantation the transducer body  102 , the transducer body  102  may be utilized to form an interface, e.g.,  112  and align the member  406  with the interface  112  during connection. 
     In either case, subsequent to positioning of the transducer body  102 , the member  404  may be inserted through the aperture  120  and coupled to the member  406 . As with the above examples, the additional step of further aligning the transducer body  102  with the member  406  may precede the coupling step. Once the members,  404  and  406 , are coupled, the member  404  may be connected within the tube  124  by either of the above-described methods, e.g., the coupler  302  or coupler  206 . Alternatively, as with the above embodiments, any other suitable method, e.g., an adhesive or mechanical clamp, may also be utilized to make the connection as a matter of design choice. 
       FIG. 5  illustrates an example of a transducer positioning system  500  that may be utilized to facilitate the implantation and alignment of the above-described transducers, e.g.,  100 . The positioning system  500  includes a carrier assembly  502 , a swivel assembly  504 , and a mounting apparatus  506 , e.g., bone anchor. Such assemblies may be readily interconnected as illustrated on  FIG. 5  to cooperate in a manner that allows for selective three-dimensional positioning of the transducer  100  at a desired location within the patient&#39;s skull. 
     In this regard, the transducer  100  is supportably connected to a first end  508  of the carrier assembly  502 . In turn, the carrier assembly  502  is supportably received in an opening  510  provided in the swivel assembly  504 . The assembled carrier assembly  502  and swivel assembly  504  is supportably interconnected to the mounting apparatus  506 . Swivel assembly  504  includes opposing, top and bottom plate members  512  and  514 , respectively, which are interconnected to capture a rotatable ball member  516  therebetween. The rotatable ball member  516  also includes an aperture defining a portion of the opening  510  for receiving the carrier assembly  502 . 
     As will be appreciated, when carrier assembly  502  is positioned through opening  510 , the carrier assembly  502  is movable in a first dimension, e.g., axially or vertically in the direction (A) relative to the incus  212  to position the transducer  100  proximate the incus  212 . Similarly, when carrier assembly  502  is initially positioned through opening  510 , the ball member  516  is loosely constrained between the top and bottom plates,  512  and  514 , to permit lateral positioning along arc (B) of the transducer  100 . Specifically the axial and lateral alignment of the transducer  100  is to achieve alignment of the aperture  120  with a desired interface point, e.g., for the formation of an interface, such as  112 , on the incus  212 . In other words, the tube  124  may be utilized during positioning of the transducer  100  to align the transducer  100  with the desired interface point, as well as to provide the positional relationship between the actuator  104  and transducer body  102  when the actuator  104  is inserted therein. During such positioning, it may also be desirable to utilize a guide such as guide  520 , inserted through the aperture  120  to precisely locate the desired interface point on the incus  212 . 
     Once the transducer body  102  is positioned, e.g., alignment of the aperture  120  with the interface point, a locking nut  518  is rotatably securable within the mounting apparatus  506  to secure the ball member  516 , which in turn secures the carrier assembly  502  and fixes the position of the transducer body  102 . Once the transducer body  102  is positioned, the aperture  120  may again be utilized as a guide for a drill or other instrument for forming the interface  112  on the incus  212 . Advantageously, according to this characterization, the tube  124  is further utilized to form the interface  112  in the incus  212 , as well as to locate the desired interface point, and position the transducer body  102  relative to the interface point. 
     Referring to  FIG. 6 , subsequent to preparation of the incus  212 , the actuator  104  is inserted through the positioning system  500  and the aperture  120  where it is connected to the interface  112  in a conventional manner. It should be noted in this regard, that substantially no load is applied on the incus  212  during the connection, as the weight of the actuator  104  is substantially inconsequential. Additionally, connection of the actuator  104  is simplified as the surgeon or audiologist is able to sense or feel when the actuator  104  is completely seated within the interface  112 . Furthermore, when pressure applied during connection of the actuator  104  is released, the incus  212  is able to compensate for loading through movement of the actuator  104  to an equilibrium position prior to connection of the actuator  104  to the transducer body  102 . Subsequent to connecting the actuator  104  to the incus  212 , the locking nut  518  may again be loosened to permit further alignment of the transducer  100  relative to the connected actuator  104  as necessary. When final positioning of the transducer  100  is achieved, the actuator  104  is coupled within the tube  124  to complete the implantation process. 
     It should be noted that the above-described operation would be similar with regard to the transducer  400  except that the operation would require the additional step of connecting the actuator members,  404  and  406 , prior to connection of the member  404  to the transducer body  102 . 
       FIG. 7  illustrates another example of a method for implanting a transducer, such as transducer  100 , within a patient. In this case, however, the transducer  100  and positioning system  500  are configured such that the transducer  100  may be positionally retained within the ball member  516 . This in turn permits lateral alignment of the aperture  120 , along arc B, with a desired interface point on the incus  212 . As with the above embodiment, the transducer  100  may initially be loosely constrained within the positioning system  500  and a guide such as a laser sight utilized to align the aperture  120  with the interface point on the incus  212 . 
     Once the transducer  100  is laterally positioned, the locking nut  518  may be utilized to secure the ball member  516  around the transducer  100 , which in turn secures the transducer  100  in a fixed position relative to the positioning system  500 . It will also be appreciated that as with the above embodiment, the aperture  120  may be utilized, following the positioning, as a guide for a drill or other instrument to form the interface  112  on the incus  212 . Once positioned, the actuator  104  may be inserted through the aperture  120  and connected to the incus  212  and transducer  100  as described above. 
     According to the present example, the length of the actuator  104  controls the vertical relationship between the transducer  100  and incus  212 . Thus, it may be desirable to utilize actuator members of various lengths as the exact distance between the mounted transducer  100  and the interface  112  may vary slightly from patient to patient. Alternatively, however, a sufficiently long actuator may be utilized and the excess length trimmed substantially flush with the top of the transducer  100  following connection with the incus  212  and transducer body  102 . 
     Advantageously, this method provides a simple means of implanting and positioning the transducer  100  within a patient. Furthermore, it will be appreciated that the present method eliminates the use of the carrier assembly  502 , as the length of the actuator  104  may be varied to achieve the vertical relationship between the transducer  100  and incus  212 . This in turn simplifies implantation and positioning as well as reducing foreign objects introduced to the patient. 
       FIGS. 8 and 9  illustrate another example of a transducer  100  according to the present invention, namely transducer  800 . Similar to transducer  100 , the transducer  800  includes a driver, e.g., coil  202  and magnet  204 , which drives an internally mounted tube  124  to transmit vibrational energy to the actuator  104 . In contrast, however, the transducer body  802  is configured in the shape of the ball member  516 . In other words, the transducer body  802  is configured for rotational movement within a mounting apparatus, e.g., bone anchor  804 , to align the transducer  800  for connection with the incus  212 . Specifically, the transducer body  802  replaces the ball member  516  of the positioning system  500 , such that the aperture  120  is aligned with the incus  212  through rotational movements of the transducer body  802  within the bone anchor  804 . Once properly aligned, the locking nut  518  is tightened down to secure the transducer between the top plate  512  and a bottom lip  806  of the bone anchor  804 . 
     As with the above embodiment, the length of the actuator  104  controls the vertical relationship between the transducer  800  and incus  212 . Thus, it may be desirable to utilize actuator members of various lengths as the exact distance between the mounted transducer  800  and the interface  112  may vary slightly from patient to patient. Alternatively, however, a sufficiently long actuator may be utilized and the excess length trimmed substantially flush with the top  116  of the transducer  800  following connection with the incus  212  and transducer body  802 . 
     It will also be appreciated that the transducer  800  does not include the bellows members  110  and  122 . Rather, the tube  124  of the transducer  100  may be movably connected in a substantially flush relation to the ends  116  and  118  of the transducer  800 . According to this characterization, the tube  124  may be connected to the transducer body  802  using a spring washer  902  fixed to the end  118  such as by welding or electrodeposition. Tube  124  may connect to spring washer  902  by any suitable means, with one example including flange  906 . Flange  906  sandwiches spring washer  902  between the flange  906  and the end of the tube  124 . 
     To permit movement of the tube  124  relative to the transducer body  802 , the spring washer  902  includes helical compression leafs  904 . At its opposing end  116 , however, the tube  124  may be slidably engaged within an aperture formed in the top  900  of the transducer body  802  such that the tube  124  is axially movable therein relative to the transducer  800 . Alternatively, a second spring washer  902  may be utilized to connect the tube  124  to the top of the transducer body  802 . It will be appreciated that according to this characterization, spring washer  902  and top  900  may not provide a sealing function at the ends  116  and  118  of the transducer  800 . Accordingly, it may be desirable to seal the magnet  204  to the tube  124  during construction of the transducer  800 . For instance, the magnet  204  may be sealed using plating, such as gold or titanium, or may even be coated with other materials, preferably biocompatible, to protect the magnet during the introduction of bodily fluids within the interior of the transducer body  802 . 
       FIGS. 10 and 11  illustrate one application of the present invention in a semi-implantable hearing aid device. The illustrated application comprises a semi-implantable hearing aid device having implanted components shown in  FIG. 10 , and external components shown in  FIG. 11 . As will be appreciated, the present invention may also be employed in conjunction with fully implantable systems, wherein all components of a hearing aid system are located subcutaneously. 
     In the illustrated device, an implanted biocompatible housing  700  is located subcutaneously on the patient&#39;s skull. The housing  700  includes an RF signal receiver  718  (e.g., comprising a coil element) and a signal processor  704  (e.g., comprising processing circuitry and/or a microprocessor). The signal processor  704  is electrically interconnected via wire  706  to the transducer  100 . As will be appreciated various processing logic and/or circuitry may also be included in the housing  700  as a matter of design choice. 
     The transducer  100  is supportably connected to the transducer positioning system  500  which in turn, is mounted within the patient&#39;s mastoid process (e.g., via a hole drilled through the skull). Referring to  FIG. 11 , the semi-implantable system further includes an external housing  800  comprising a microphone  808  and internal speech signal processing (SSP) circuitry (not shown). The SSP unit is electrically interconnected via wire  802  to an RF signal transmitter  804  (e.g., comprising a coil element). The external housing  800  is configured for disposition around the rearward aspect of the patient&#39;s ear. The external transmitter  804  and implanted receiver  718  each include magnets,  806  and  702  respectively, to facilitate retentive juxtaposed positioning. 
     During normal operation, acoustic signals are received at the microphone  808  and processed by the SSP unit within external housing  800 . As will be appreciated, the SSP unit may utilize digital processing to provide frequency shaping, amplification, compression, and other signal conditioning, including conditioning based on patient-specific fitting parameters. In turn, the SSP unit via wire  802  provides RF signals to the transmitter  804 . Such RF signals may comprise carrier and processed acoustic drive signal portions. The RF signals are transcutaneously transmitted by the external transmitter  804  to the implanted receiver  718 . As noted, the external transmitter  804  and implanted receiver  718  may each comprise coils for inductive coupling signals therebetween. 
     Upon receipt of the RF signal, the implanted signal processor  704  processes the signals (e.g., via envelope detection circuitry) to provide a processed drive signal via wire  706  to the transducer  100 . The drive signals cause the actuator  104  to axially vibrate at acoustic frequencies to effect the desired sound sensation via mechanical stimulation of the ossicles of the patient. More particularly, the modulating drive signals yield a changing magnetic field at transducer  100 , thereby effecting movement of the actuator  104 . 
     Those skilled in the art will appreciate variations of the above-described embodiments that fall within the scope of the invention. As a result, the invention is not limited to the specific examples and illustrations discussed above, but only by the following claims and their equivalents.