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 of a hearing aid device is presented for purposes of illustration and description . furthermore , the description is not intended to limit the invention to the form disclosed herein . consequently , variations and modifications commensurate with the 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 . fig1 and 2 illustrate one application of the present invention . as illustrated , the application comprises a fully implantable hearing instrument system . as will be appreciated , certain aspects of the present invention may be employed in conjunction with semi - implantable hearing instruments as well as fully implantable hearing instruments , and therefore the illustrated application is for purposes of illustration and not limitation . 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 is interconnected to a microphone assembly 130 via a signal wire 124 . the implant housing 100 may be utilized to house a number of components of the implantable hearing instrument . for instance , the implant housing 100 may house an energy storage device 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 . in the present arrangement , the signal processor within the implant housing 100 is electrically interconnected via a signal wire 106 to a transducer 108 . the transducer 108 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 108 includes a connection apparatus 112 for connecting the transducer 108 to the ossicles 120 of the patient . in a connected state , the connection apparatus 112 provides a communication path for acoustic stimulation of the ossicles 120 , e . g ., through transmission of vibrations to the incus 122 . the microphone assembly 130 is spaced from the implant housing 100 such that it is not mounted to the skull of a patient . such spacing facilitates vibration attenuation , as will be more fully discussed herein . the microphone assembly 130 includes a diaphragm 132 that is positioned to receive ambient acoustic signals through overlying tissue , a microphone transducer ( not shown ) for generating an output signal indicative of the received ambient acoustic signals , and a housing 134 for supporting the diaphragm 132 relative to the transducer . as shown , the microphone assembly 130 is mounted to soft tissue of the neck of the patient and the wire 124 interconnecting the implant housing 100 and the microphone assembly 130 is routed subcutaneously behind the ear of the patient . during normal operation , acoustic signals are received subcutaneously at the diaphragm 132 of the microphone assembly 130 . the microphone assembly 130 generates an output signal that is indicative of the received acoustic signals . the output signal is provided to the implant housing 100 via a signal wire 124 . upon receipt of the output signal , a signal processor within the implant housing 100 processes the signals to provide a processed audio drive signal via a signal wire 106 to the transducer 108 . 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 108 to transmit vibrations at acoustic frequencies to the connection apparatus 112 to effect the desired sound sensation via mechanical stimulation of the incus 122 of the patient . to power the fully implantable hearing instrument system of fig1 , an external charger ( not shown ) may be utilized to transcutaneously re - charge an energy storage device within the implant housing 100 . in this regard , the external charger may be configured for disposition behind the ear of the implant wearer in alignment with the implant housing 100 . the external charger and the implant housing 100 may each include one or more magnets 10 to facilitate retentive juxtaposed positioning . such an external charger may include a power source and a transmitter that is operative to transcutaneously transmit , for example , rf signals to the signal receiver 118 . as noted above , the microphone assembly 130 is spaced from the implant housing 100 such that it is not mounted on the skull of a patient . that is , by spacing the microphone assembly 130 from the skull , vibrations within the skull that may result from , for example , transducer feedback and / or biological sources ( e . g ., talking and / or chewing ) may be attenuated prior to reaching the microphone assembly 130 . stated otherwise , mounting the microphone assembly 130 relative to soft tissue of the patient substantially isolates the microphone assembly 130 from one or more sources of non - ambient vibrations ( e . g ., skull - borne vibrations ). as shown in fig2 , the microphone assembly 130 is mounted to the soft tissue in a patient &# 39 ; s neck in a triangular region 150 having a base bounded inferiorly by the clavicle ( not shown ), anteriorly by the sternocleidomastoid muscle 154 , and posteriorly by the trapezius muscle 152 . these two muscle structures 152 , 154 form an apex at the tip 156 of the mastoid process on the patient &# 39 ; s skull . such placement within this triangular region ( e . g ., between the muscle structures ) may facilitate implantation of the microphone assembly 130 . for instance , during an implant procedure an incision may be made in the mastoid process in order to interconnect the hearing instrument to the patient &# 39 ; s auditory system . positioning the microphone assembly 130 at a position proximate to the mastoid tip allows implantation of the microphone assembly 130 through an incision formed for the hearing instrument . that is , a surgeon may tunnel down from the hearing instrument incision and form a small pocket for the microphone assembly 130 beneath the skin of the patient &# 39 ; s neck . accordingly , the wire 124 interconnecting the implant housing 100 and the microphone assembly 130 may be routed during such a procedure . fig3 and 4 illustrate the receipt of non - ambient vibrations at the microphone assembly 130 at various mounting locations . specifically , fig3 illustrates acceleration data for three different mounting locations where a source of skull - borne vibration initiates an acceleration in the patient &# 39 ; s tissue that may be received by the microphone assembly 130 . the data corresponds with locations directly above the pinna 160 , the mastoid tip 170 , and a soft tissue mount 180 in the neck that is 25 mm below the mastoid tip . as will be appreciated , the pinna 160 and mastoid tip 170 mounting locations are proximate the skull of the patient . accordingly , these skull mount locations 160 , 170 are more directly subjected to acceleration caused by skull - borne vibrations . as shown , the acceleration level at the soft tissue mount 180 in the neck is 10 to 20 db lower than at the skull - mounted locations 160 , 170 for frequencies above 2 khz . fig4 illustrates feedback gain caused by operation of the transducer 108 of the hearing instrument . that is , actuation of the transducer results in the generation of skull - borne vibrations that may be received and amplified by the microphone assembly 130 . fig4 illustrates the received feedback ( e . g ., vibration ) for two separate microphone assembling mounting locations , namely a skull mount location 190 that is 8 mm above the pinna and a soft tissue mount 200 located 25 mm below the mastoid tip . as with the acceleration data above , the feedback gain measurements made at the soft tissue mount 200 in the neck show a pronounced improvement . for instance , over the range of 1 khz to 6 khz , the feedback gain at the soft tissue mount 200 was 10 to 35 db lower than at the skull mount 190 above the pinna . fig5 illustrates another embodiment where the microphone assembly 130 is mounted to the soft tissue of a patient &# 39 ; s chest . more specifically , fig5 illustrates a sub - clavicle mounting where the microphone assembly 130 is positioned beneath the patient &# 39 ; s clavicle . in such an arrangement , the signal wire 124 extending between the microphone 130 and the implant housing 100 , or other portion of the hearing instrument disposed proximate to the skull ( not shown ), may need to be considerably longer than the signal wire utilized for mounting the microphone to soft tissue in the patient &# 39 ; s neck . for instance , the signal wire 124 may require of length greater than 15 cm , greater than 20 cm or even greater than 30 cm . fig6 illustrates a further embodiment where an implant housing 100 is co - located with the microphone assembly 130 . in a further arrangement , the microphone assembly may be incorporated into the implant housing ( not shown ). implantation of the microphone assembly 130 at increased distances from the skull mounted portion of the implantable hearing instrument may require that the signal wire 124 be detachably connectable to one or both of microphone assembly 130 and the skull mounted portion of the implantable hearing instrument . in this regard , one or both ends of the wire 124 may include a detachable connector . one detachable connector that may be utilized is illustrated in u . s . pat . no . 6 , 517 , 476 , entitled : “ connector for implantable hearing aid ” having an issue date of feb . 11 , 2003 , the contents of which are incorporated herein by reference . implantation of the microphone assembly at increased distances from a skull - mounted portion of the hearing instrument may require separate incisions . for example , in reference to fig5 , the implant housing 100 and an associated auditory stimulation device ( e . g ., mechanical transducer , electrode array , etc ) may be implanted via a first incision and the microphone assembly 130 may be implanted via a second incision at , for example , a sub - clavicle location . the wire 124 may then be routed using , for example , a flexible catheter , a trocar , cannula , etc ., that is inserted in one of the incisions and routed beneath the skin of the patient to the other incision . in either of the above - noted arrangements , the microphone assembly 130 is preferably disposed over soft tissue . that is , the microphone assembly is not in direct contact with a bone surface as such a surface is highly effective in transferring vibrations to the microphone assembly . typically , it is desirable that at least 2 mm . of soft tissue be disposed between the microphone assembly and any underlying bone . in order to maintain the position of the assembly 130 relative to the soft tissue , the assembly may be sutured to such soft tissue . the soft tissue mount allows for attenuating and / or eliminating the transfer of skull borne vibrations to the microphone assembly 130 . however , it will be noted that movement of the microphone assembly may result in the enhancement or introduction of other sources of non - ambient sound . for instance , sub - clavicle mounting of the microphone assembly may result in the application of cardio - pulmonary signals to the assembly . accordingly , it may be desirable to process the microphone output signal ( s ) to reduce the effect of such non - ambient sound . one arrangement that may be utilized to reduce the effects of non - ambient sound is described in u . s . patent application ser . no . 11 / 330 , 788 entitled : “ active vibration attenuation for implantable microphone ,” having a filing date of jan . 11 , 2006 , the entire contents of which are incorporated herein by reference . the foregoing description of the present invention has been presented for purposes of illustration and description . furthermore , the description is not intended to limit the invention to the form disclosed herein . consequently , variations and modifications commensurate with the above teachings , and skill and knowledge of the relevant art , are within the scope of the present invention . the embodiments described hereinabove are further intended to explain 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 . it is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art .