Patent Publication Number: US-7722525-B2

Title: Lateral coupling of an implantable hearing aid actuator to an auditory component

Description:
FIELD OF THE INVENTION 
     The invention is related to the field of hearing aids, and in particular, to the contact interface between an implantable hearing aid transducer and a component of 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 contact. (See e.g., U.S. Pat. No. 5,702,342.) Generally, such a vibratory actuator is mechanically engaged (i.e., coupled) with 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 that is sized to receive a tip of the electromechanical transducer. In such an arrangement, the transducer tip may expansively contact the sides of the aperture, may be adhered within the aperture or tissue growth (e.g., osteointegration) may couple the transducer tip to the bone. One disadvantage of methods requiring a hole in the ossicle to facilitate attachment is that a surgical laser must be employed to ablate the ossicle&#39;s surface. The laser ablation procedure is burdensome and time consuming. Also, the required equipment is expensive and not present in every surgical setting. In other arrangements, clamps and/or clips are utilized to couple the vibratory actuator to an ossicle. However, such approaches can entail difficult implant procedures and yield sub-optimum coupling. 
     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, or 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. For example, precise control of the engagement between the actuator of the transducer and the ossicles is of critical importance as the axial 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 (e.g., movement of the ossicles) as well as degraded performance of the mechanical aspect (e.g., movement of the vibratory member). Additionally, an underloaded condition, i.e., one in which the actuator is not fully connected to the ossicles, may result in reduced performance of the transducer. In addition, once coupled for an extended period, the maintenance and/or replacement with a next generation transducer may be difficult. That is, in many coupling arrangements it may be difficult to de-couple a vibratory actuator/transducer. 
     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 devices, such as hearing aid transducers. Another object of the present invention is to allow for relative movement (e.g., lateral movement) between a component of the auditory system and an electromechanical transducer to account for physical variations of the auditory component caused by, for example, pressure changes, swallowing, etc. Another object is to provide auditory engagement means that allows for easily disengaging an auditory component. 
     One or more of the above objectives and additional advantages may be realized utilizing a contact or ‘force loading’ interface between an implantable transducer and a component of the auditory system. In this regard, a contact tip disposed at a distal end of a vibratory actuator (e.g., interconnected to an implantable transducer) may be laterally pressed against an auditory component (e.g., the ossicles) to provide a lateral load on the component. Tissue attached to the auditory component (e.g., ligaments) may maintain the actuator in contact with the auditory component for both positive and negative vibratory actuator displacement (e.g., axial displacement during operation of the implantable transducer.) In this regard, it has been determined that it is not necessary to physically attach the contact tip to the ossicle bone utilizing, for example, a hole drilled into the bone or by using a clip or clamp arrangement that extends around the ossicle bone to mount the transducer tip to the bone. That is, the lateral “force loading” of the ossicle bone provides the necessary contact for stimulation purposes. 
     In order to maintain the lateral force loading between the implantable transducer and an auditory component after an implant procedure it has been further recognized by the present inventors that it may be desirable to limit lateral movement of the auditory component relative to the vibratory actuator and/or to automatically reposition the vibratory actuator relative to the auditory component in conjunction with such lateral movement. In this regard, and by way of example, an ossicle bone may move laterally (e.g., in a direction transverse to a vibratory direction of the actuator) after an implant procedure as a result of pressure changes (e.g., changes in altitude) and/or physical movements of the patient (e.g., yawning). For purposes hereof, any such movement may be referred to as post-implantation auditory component movement. 
     In one aspect, an apparatus is provided that is employable with an implantable hearing aid transducer for mechanically stimulating an auditory component, wherein the apparatus comprises a vibratory actuator that is adapted for axial displacement in response to operation of an interconnected implantable hearing aid transducer, and a contact tip for directly contacting a lateral aspect of an auditory component, said contact tip being interconnected to a distal end of the vibratory actuator for axial displacement therewith. Of note, at least a portion of the vibratory actuator may be laterally deflectable, wherein the contact tip may be laterally displaceable upon lateral deflection of the vibratory actuator to apply a lateral loading force to an auditory component. In turn, enhanced contact maintenance between the contact tip and an auditory component may be realized. 
     Further this regard, the vibratory actuator may be laterally deflectable to laterally displace the contact tip in a first direction and/or a second direction (e.g., opposite to the first direction) within a predetermined displacement range (i.e., in either direction) that is greater than a predetermined maximum for post-implantation auditory component movement, thereby facilitating the maintenance of lateral loading contact post-implantation. In particular, a vibratory actuator may be provided which, in a deflected state, yields a predetermined displacement range with a maximum value of about 1 millimeters (i.e., lateral displacement of the contact tip) in either direction relative to an undeflected state. 
     Relatedly, the vibratory actuator may be provided so that the contact tip applies a lateral loading force within a predetermined force range when the contact tip is displaced at any position across a predetermined displacement range. In one embodiment, such predetermined displacement range may be 0.1 millimeters to 1 millimeters, with a corresponding predetermined force range of about 0.056 gf (grams of force) to 2.08 gf. In another embodiment, the predetermined displacement of range may be 0.3 millimeters to 1 millimeters, with a corresponding predetermined force range of about 0.168 gf to 2.08 gf. 
     Further, the vibratory actuator and interconnected transducer may be provided so that the lateral loading force applied by the contact tip to an auditory component is maintained at a magnitude which is greater than the magnitude of an axial load force applied by the contact tip to the auditory component. That is, the vibratory actuator and implantable transducer may be provided so that, in a deflected state, the contact tip may apply a lateral loading force that is maintained at a magnitude that is greater than the magnitude of axial load force applied by the contact tip upon initial placement as well as during axial displacement in response to operation of an implantable transducer to yield auditory component stimulation. Even more particularly, the vibratory actuator and transducer may be provided to yield a lateral loading force on an auditory component by the contact tip that is at least two times greater than the axial load force applied thereto by the contact tip. 
     In one approach, a deflectable portion of the vibratory actuator may be of a compliant nature so as to flex (e.g., elastically deform) and thereby accommodate lateral displacement of a contact tip and otherwise yield a desired lateral loading force at the contact tip. In another approach, a distal end of a vibratory actuator may be pivotable relative to a proximal end of the vibratory actuator so as to accommodate lateral displacement of the contact tip, wherein an external force means (e.g., a magnetic field defined at an implantable transducer) to act upon the proximal end to yield a lateral loading force at the contact tip. As may be appreciated, the noted approaches may be implemented separately or together. 
     In yet another aspect, a contact tip may comprise a convex surface portion for directly contacting a lateral aspect of the auditory component. The provision of the convex surface portion facilitates relative contact movement between the contact tip and an auditory component. In one arrangement, the contact tip may be of a rounded configuration (e.g. a ball-end configuration.) 
     An inventive method is also provided for use in connection with the mechanical stimulation of an auditory component by an implantable hearing aid transducer. The method includes the step of contacting a contact tip with a lateral aspect of an auditory component, wherein the contact tip is interconnected to a distal end of a vibratory actuator that is axially displaceable in response to operation of an interconnected implantable hearing aid transducer. The method further includes the steps of moving the contact tip relative to the auditory component while maintaining the contact therewith, and displacing the contact tip to an initial loaded position in response to the moving step, wherein the contact tip applies an initial lateral loading force to the lateral aspect of the auditory component. 
     The method may further include the step of automatically displacing the contact tip to another loaded position, after the moving step, in response to post-implantation auditory component, wherein the contact tip remains in contact with and applies another lateral loading force to the lateral aspect of the auditory component. In this regard, the initial loaded position and the another loaded position may each be within a predetermined displacement range for the contact tip that is provided by the vibratory actuator and/or the transducer. Further, the initial loading force and the another loading force may each be within a predetermined force range that is provided on the vibratory actuator and/or the transducer. By way of example, a predetermined displacement range provided that is about 0.1 millimeters to 1 millimeters, and a corresponding predetermined force range may be provided that is about 0.056 gf to 2.08 gf. 
     In conjunction with the inventive method, the displacing step may include a step of deflecting at least a portion of the vibratory actuator. In turn, the deflecting step may entail flexing said portion of the vibratory actuator and/or pivoting a distal end of the vibratory actuator relative to a proximal end thereof. 
     In yet another aspect, the contacting step and/or moving step may entail linearly advancing the contact tip relative to the auditory component. Alternatively or additionally the contacting step and/or moving step may include advancing the contact tip along an arcuate path relative to an auditory component. 
     In yet a further aspect, the inventive method may include a step of operating the implantable transducer to successively advance and retract the vibratory actuator and contact tip relative to an auditory component, wherein an axial force is applied to the auditory component. In turn, the method may provide for maintaining the lateral loading force applied by the contact tip to the auditory component at a magnitude greater than the axial force applied by the contact tip during operation of the transducer. In this regard, it may be preferable to maintain the lateral loading force at least two times greater than the axial force. 
     Additional aspects and advantages relating to the present invention may be apparent to those skilled in the art upon consideration of the further description that follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a fully implantable hearing instrument as implanted in a wearer&#39;s skull. 
         FIG. 2A  illustrates one embodiment of the present invention in operative contact with an auditory component. 
         FIG. 2B  illustrates an enlarged portion of the Fig. A. 
         FIG. 3A  illustrates a top view of another embodiment of the present invention. 
         FIG. 3B  illustrates a side cross-sectional view of the embodiment shown in  FIG. 3A , as taken along the section cut line AA shown in  FIG. 3A . 
         FIG. 4A  illustrates a side view of the embodiment of  FIG. 3A . 
         FIG. 4B  illustrates a top cross-sectional view of the embodiment of  FIG. 3A , as taken along the section cut line BB shown in  FIG. 4A , wherein a vibratory actuator is in a deflected state. 
         FIG. 5A  illustrates a perspective view of another embodiment of the present invention, wherein a vibratory actuator tip is in an undeflected state. 
         FIG. 5B  illustrates a perspective view of the embodiment shown in  FIG. 5A , wherein the vibratory actuator is in a deflected state. 
         FIG. 6A  illustrates a top view of the embodiment shown in  FIG. 5A . 
         FIG. 6B  illustrates a side cross-sectional view of the embodiment of  FIG. 5A , as taken along the section cut line AA shown in  FIG. 6A . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates one application of the present invention. As illustrated, the application comprises a fully implantable hearing instrument system. As will be appreciated, aspects of the present invention may be employed in conjunction with semi-implantable hearing instruments as well. 
     In the illustrated system, a biocompatible implant housing  100  is located subcutaneously on a patient&#39;s skull. The implant housing  100  includes a signal receiver  118  (e.g., comprising a coil element) and a microphone  130  that is positioned to receive acoustic signals through overlying tissue. The signal receiver  118  may be utilized for transcutaneously re-charging an energy storage device within the implant housing  100  as well as for receiving program instructions for the hearing instrument system. 
     The implant housing  100  may be utilized to house a number of components of the fully implantable hearing instrument. For instance, the implant housing  100  may house an energy storage device, a microphone transducer, and a signal processor. Various additional processing logic and/or circuitry components may also be included in the implant housing  100  as a matter of design choice. Typically, the signal processor within the implant housing  100  is electrically interconnected via wire  106  to an electromechanical transducer  140 . 
     The transducer  140  is supportably connected to a positioning system  110 , which in turn, is connected to a bone anchor  116  mounted within the patient&#39;s mastoid process (e.g., via a hole drilled through the skull). The transducer  140  includes a vibratory actuator  112  for operatively interfacing the transducer  140  to the ossicles  120  of the patient. In an operative state, the vibratory actuator  112  provides a communication path for acoustic stimulation of the ossicles  120 , e.g., through transmission of vibrations to the incus  122 . As will be more fully discussed herein, the vibratory actuator may form a lateral contact interface between the transducer  140  and the ossicles. 
     During normal operation, acoustic signals are received subcutaneously at the microphone  130 . Upon receipt of the acoustic signals, a signal processor within the implant housing  100  processes the signals to provide a processed audio drive signal (e.g., a transducer drive signal) via wire  106  to the transducer  140 . As will be appreciated, the signal processor may utilize digital processing techniques to provide frequency shaping, amplification, compression, and other signal conditioning, including conditioning based on patient-specific fitting parameters. The audio drive signal causes the transducer  140  to transmit vibrations at acoustic frequencies to the vibratory actuator  112  to effect the desired sound sensation via mechanical stimulation of the incus  122  of the patient. These vibrations are then transmitted from the incus  122  to the stapes  124 , effecting a stimulation of the cochlea  126 . 
       FIGS. 2A and 2B  each illustrate a contact tip  302  interconnected to the transducer  140  via the vibratory actuator  112 , as disposed (e.g., by the positioning system  110  and bone anchor  116 ) proximate to a lateral aspect of the incus  122 , in both an initial contact position A and in a superimposed, advanced position B. In this regard, and as previously noted, it has been determined that adequate transfer of mechanical energy (e.g., vibrations) from the transducer  140  to the incus  122  may be achieved by a lateral contact loading of the contact tip  302  of the transducer  140  to the incus  122 , or other ossicle bone as the case may be. For such purposes, at least a portion of the vibratory actuator  112  may be laterally deflectable. In turn, during implant procedures the transducer  140  may be advanced so that the contact tip  302  contacts the incus  122  (e.g., position A in  FIGS. 2A and 2B ), and then the transducer  140  may be further advanced so that the contact tip  302  may be laterally displaced and the vibratory actuator  112  may be correspondingly deflected (e.g., position B in  FIGS. 2A and 2B ), wherein a predetermined force is applied to the lateral aspect of the incus  122 . 
     In this regard, it should be noted that ligaments (not shown) are connected to the ossicular chain. These ligaments counteract the lateral loading force applied by the contact tip  302 . Stated otherwise, the ligaments pull the incus towards its unloaded or static location and thereby against the contact tip  302 . 
     Of further note, when the transducer  140  is operated during use to displace the transducer tip  302  (e.g., axially), the transducer tip  302  may be axially advanced relative to the incus  122 . Accordingly, the incus  122  may be displaced (i.e., to the right as shown in  FIG. 2 ). In contrast, when the transducer tip  302  is retracted relative to the incus  122 , the ligaments interconnected to the incus  122  may pull the incus back towards its static location as the transducer tip  302  retracts (i.e., to the right in  FIG. 2 ). By virtue of the initial loading of the incus  122 , the incus  122  may be operative to move in contact with the contact tip  302  for both positive and negative transducer tip displacements. 
     As may be appreciated from the foregoing description, it has been determined that it is not necessary to physically attach the contact tip  302  to the ossicle bone utilizing, for example, a hole drilled into the bone or by using a clip or clamp arrangement that extends around the ossicle bone to mount the transducer tip to the bone. That is, the lateral “force loading” of the ossicle bone provides the necessary contact for sustained stimulation purposes. 
     As previously noted, an auditory component, such as the incus  122 , may move laterally after an implant procedure (e.g., after initial placement of contact tip  302 .) Such movement may be the result of pressure changes (e.g., changes in altitude) affecting the ossicular chain and/or physical movements of the patient (e.g., yawning). In such instances of post-implantation auditory movement, it has been determined that the maintenance of a contact relationship may be facilitated by use of a vibratory actuator  112  having a deflectable portion that works to allow the contact tip  302  to laterally deflect across a continuum of positions within a predetermined range. In turn, the contact tip  302  may maintain contact with an auditory component upon initial placement, as well as during and subsequent to post-implantation auditory component movement. 
     More particularly, a deflectable portion of the vibratory actuator  112  may be provided so that the contact tip  302  may be displaced in either a first direction or a second direction to an initial loaded position within a predetermined range upon initial placement, and so that the contact tip  302  may automatically move to one or more other loaded position(s) within the predetermined range after initial placement (e.g. upon further deflection or reduced deflection of vibratory actuator  112 .) In this regard, the predetermined range may be established so that the resultant contact yields a lateral loading force on an auditory component within a desired force range at all positions across the predetermined range. 
     Reference is now made to  FIGS. 3A ,  3 B,  4 A and  4 B which illustrate an embodiment of implantable transducer  400  physically interconnected to a positioning system  110  and electrically interconnected to a wire  106  (e.g., for interconnection with an implant housing  100 .) The positioning system  110  may be selectively, physically interconnected to a bone anchor  116 , of the type shown in  FIG. 1 . 
     The bone anchor  116  may be of a type as taught in U.S. Pat. No. 6,293,903 entitled “APPARATUS AND METHOD FOR MOUNTING IMPLANTABLE HEARING AID DEVICE”, issued Sep. 25, 2001, the entirety of which is hereby incorporated by reference. Further, the positioning system  110  may be of the type as generally taught by U.S. Pat. No. 6,491,622 entitled “APPARATUS AND METHOD FOR POSITIONING AN IMPLANTABLE HEARING AID DEVICE” issued Dec. 10, 2002, the entirety of which is hereby incorporated by reference. 
     In short, the positioning system  110  may include a carrier assembly  20  and a swivel assembly  40  that allow for selective three-dimensional positioning of the transducer  400  and interconnected contact tip  402  at a desired location within a patient. In this regard, the transducer  400  may be supportively connected to a first end  22  of the carrier assembly  20 . In turn, the carrier assembly  20  may be supportively received and selectively secured in an opening defined through a ball member  42  that is captured between plates  44  of the swivel assembly  40 . The interface between the carrier assembly  20  and swivel assembly  40  provides for pivotable, lateral positioning of the first end  22  of the carrier assembly  20  and of the transducer  400  interconnected thereto. That is, the carrier assembly  20  may pivot upon rotation of the ball member  42 , thereby allowing the contact tip  402  to be moved along an arcuate path to a desired position. In turn, the interconnected plates  44  may be selectively secured to a bone anchor  116  maintain a select pivotal orientation. Further, the carrier assembly  20  may be selectively secured along a continuum positions within the opening of the swivel assembly  40 , thereby facilitating linear advancement/retraction of the carrier assembly  20  and interconnected transducer  400  and contact tip  402  in a depth dimension. Additionally, the carrier assembly  20  may be defined so that its first end  22  may be selectively advanced and retracted in the depth of dimension relative to an outer support member  24  thereof (e.g., by utilizing a lead screw arrangement), thereby further facilitating selective linear positioning of the transducer  400  and contact tip  402 . 
     As may be appreciated, in relation to an implementation as shown in  FIGS. 2A and 2B , the positioning system  110  may be employed to move (e.g., advance or retract) the contact tip  402  toward an auditory component by moving the carrier assembly  20  relative to the swivel assembly  40 , by moving the first end  22  of the carrier assembly  20  relative to the support member  24  thereof and/or by pivoting the carrier assembly  20  relative to the plates  44  of the swivel assembly  40 . 
     As shown, the contact tip  402  of transducer  40 , may be interconnected to a distal end of the axially displaceable vibratory actuator  404 , wherein axial displacement of the vibratory actuator  404  may be utilized to effect contact stimulation of an auditory component. In additional to being axially displaceable, the vibratory actuator  404  may be further provided to allow for lateral deflection or displacement of the contact tip  402 . That is, as illustrated in  FIG. 3B , at least a portion the vibratory actuator may be laterally deflectable so that the contact tip  402  may be displaced in either a first direction within a predetermined range and/or in a second direction within a predetermined range relative to a center axis of contact between the contact tip  402  and an auditory component. For example, the contact center axis coincidental within center axis of the vibratory actuator  404 . 
     In the embodiment illustrated in  FIGS. 3A ,  3 B,  4 A and  4 B the transducer  400  may comprise a transducer housing  420  that houses a magnetic coil  410 , and stacked magnetic members  412 , each of which extend about a leaf member  414 , wherein the magnetic coil  410  and magnetic members  412  may be electrically driven to a generate a magnetic field to induce vibratory movement of the leaf member  414  at desired acoustic frequencies. The leaf member  414  may be interconnected to a drive pin  416  as shown. 
     Further in this regard, the drive pin  416  may be disposed to pass through a first plug member  418  that is proximally interconnected to the transducer housing  420  (e.g., via laser welding to yield a hermetic seal), a bellows member  422  that is proximally interconnected to a distal end of the first plug member  418  (e.g., via laser welding to yield a hermetic seal), and a second plug member  424  that is proximally interconnected to a distal end of the bellows member  422  (e.g., via laser welding to yield a hermetic seal.) The second plug member  424  may be distally interconnected to a distal end of the drive pin  416  via an intermediate plug member  426  (e.g., via laser welding to yield a hermetic seal), wherein the second plug member  424  may be axially displaceable with the drive pin  416 . In this regard the bellows member  422  may be provided with undulations that facilitate movement of drive pin  416  and the second plug member  424  relative to the transducer housing  420 , while allowing the first plug member  418  to maintain a fixed position relative to the transducer housing  420 . Further, the undulations of the bellows member  422  accommodate flexure of the drive pin  116  in connection with deflected displacement of the contact tip  402  during use, as shown in  FIG. 3B . 
     As further illustrated, an adapter member  428  may be interconnected to a distal end of the second plug member  424  and may include a slotted portion for receiving an elongate member  430  interconnected to the contact tip  402  (e.g. integrally formed therewith.) More particularly, the elongate member  430  may be inserted into the slotted portion of the adapter member  428 , wherein an outside surface of the slotted portion of the adapter member  428  may be crimped to maintain the contact tip  402  at desired fixed position relative to the adapter member  428 . 
     Referring now to  FIGS. 5A ,  5 B and  6 , another embodiment of a transducer  500  with a laterally displaceable tip member  502  is illustrated. In the position shown in  FIG. 5A , the contact tip  502  is disposed co-axially with a vibratory actuator  504 .  FIG. 5B  illustrates the contact tip  502  in a displaced position and the vibratory actuator  504  in a deflected state. As may be appreciated, such a deflected state may be realized when the contact tip  502  is advanced after initial contact with a lateral aspect of an auditory component (e.g. in a manner analogous to that shown in relation to the contact tip  402  in  FIG. 4 .) In this embodiment, the deflection of tip member  502  may be provided by virtue of a compliant, elongate member  506  interconnected to the contact tip  502  (e.g. integrally formed therewith.) 
     With particular reference to  FIG. 6 , the transducer  500  includes a transducer housing  520  physically interconnected to a positioning system  110 . In turn, the positioning system  110  may be interconnected to a bone anchor  116 , in a manner analogous to the arrangement shown in  FIG. 1 . 
     In this embodiment, the transducer housing  520  houses a variable reluctance motor arrangement. The principles of operation of such an arrangement is taught by U.S. Pat. No. 7,166,069 entitled VARIABLE RELUCTANCE MOTOR, issued Jan. 23, 2007, the entirety of which is hereby incorporated by reference. 
     The transducer  500  includes a drive pin  516  that is interconnected to a sealed canister  522  which houses an armature member  534 . The canister  522  and interconnected drive pin  516  are moveably positioned within an H-shaped magnetic housing  524  that is fixedly interconnected to the transducer housing  520 . Wafer spring members  526  may be provided at each end of the canister  522 , wherein the wafer spring members  526  are interconnected to the canister  522  at an inner periphery thereof, and wherein an outer periphery of the wafer spring members  526  may be interconnected to the housing  524 . Such an arrangement provides for centered support of the canister  522  within housing  524 , yet allows for relative axial movement between the canister  522 /drive pin  516  and the housing  524 . 
     As further illustrated, a back iron member  530  may be positioned about the magnetic housing  524 . In turn, a fixed, ring-shaped magnet  532  (e.g., a permanent magnet) may be located within the back iron member  530  and about the housing  524  and canister  522  disposed therewith. 
     Further, a ring-shaped magnetic coil assembly  538  may be disposed within the back iron member  530  adjacent to a proximal end of the housing  524 . As may be appreciated, the magnetic coil assembly  538  permanent magnet  532  and back iron member  530  may collectively define a stator member. 
     The drive pin  516  may be interconnected to an adapter member  536  having distal slotted portion for slideably receiving the elongate member  506 . The slotted portion of adapter member  536  may be secured to the elongate member  506 , (e.g., via crimping, welding, etc.) In operation, armature member  534  may be linearly displaced by varying the magnitude of a current applied to the magnetic coil assembly  538 . In turn, the canister  522  and drive pin  516  may be linearly advanced/retracted at acoustic frequencies to stimulate an auditory component via vibratory actuator  504  and contact tip  502 . 
     The above-noted embodiments are provided for purposes of illustration. Numerous modifications, adaptations and extensions are contemplated and are intended to be within the scope of the present invention.