Patent Publication Number: US-9432782-B2

Title: Electromagnetic transducer with air gap substitute

Description:
BACKGROUND 
     Hearing loss, which may be due to many different causes, is generally of two types: conductive and sensorineural. Sensorineural hearing loss is due to the absence or destruction of the hair cells in the cochlea that transduce sound signals into nerve impulses. Various hearing prostheses are commercially available to provide individuals suffering from sensorineural hearing loss with the ability to perceive sound. For example, cochlear implants use an electrode array implanted in the cochlea of a recipient to bypass the mechanisms of the ear. More specifically, an electrical stimulus is provided via the electrode array to the auditory nerve, thereby causing a hearing percept. 
     Conductive hearing loss occurs when the normal mechanical pathways that provide sound to hair cells in the cochlea are impeded, for example, by damage to the ossicular chain or the ear canal. Individuals suffering from conductive hearing loss may retain some form of residual hearing because the hair cells in the cochlea may remain undamaged. 
     Individuals suffering from conductive hearing loss typically receive an acoustic hearing aid. Hearing aids rely on principles of air conduction to transmit acoustic signals to the cochlea. In particular, a hearing aid typically uses an arrangement positioned in the recipient&#39;s ear canal or on the outer ear to amplify a sound received by the outer ear of the recipient. This amplified sound reaches the cochlea causing motion of the perilymph and stimulation of the auditory nerve. 
     In contrast to hearing aids, which rely primarily on the principles of air conduction, certain types of hearing prostheses commonly referred to as bone conduction devices, convert a received sound into vibrations. The vibrations are transferred through the skull to the cochlea causing generation of nerve impulses, which result in the perception of the received sound. Bone conduction devices are suitable to treat a variety of types of hearing loss and may be suitable for individuals who cannot derive sufficient benefit from acoustic hearing aids, cochlear implants, etc, or for individuals who suffer from stuttering problems. 
     SUMMARY 
     In accordance with one aspect, there is a balanced electromagnetic transducer, comprising first and second components connected together by a flexible component, at least a part of which flexes upon exposure of the transducer to energy, wherein the transducer is configured to generate a static magnetic flux that passes from the first component to the second component via the flexible component and travels across no more than two air gaps. 
     In accordance with another aspect, there is a device, comprising an electromagnetic transducer configured in at least one of a balanced or an unbalanced configuration, wherein only one air gap is present in an unbalanced configuration, and only two air gaps are present in a balanced configuration. 
     In accordance with another aspect, there is a method of transducing energy, comprising moving a first assembly relative to a second assembly in an oscillatory manner, wherein during the movement, there is interaction of a dynamic magnetic flux and a static magnetic flux, and directing the static magnetic flux along a closed circuit that in totality extends across one or more air gaps, all of the one or more air gaps having respective widths that vary while the static magnetic flux is so directed and interacting with the dynamic magnetic flux, wherein if more than one air gap is present in the closed circuit, a rate of change of variation of width of one of the air gaps of the closed circuit is different from that of at least one of the other air gaps of the closed circuit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Some embodiments are described below with reference to the attached drawings, in which: 
         FIG. 1A  is a perspective view of an exemplary bone conduction device in which at least some embodiments can be implemented; 
         FIG. 1B  is a perspective view of an alternate exemplary bone conduction device in which at least some embodiments can be implemented; 
         FIG. 2  is a schematic diagram conceptually illustrating a removable component of a percutaneous bone conduction device in accordance with at least some exemplary embodiments; 
         FIG. 3  is a schematic diagram conceptually illustrating a passive transcutaneous bone conduction device in accordance with at least some exemplary embodiments; 
         FIG. 4  is a schematic diagram conceptually illustrating an active transcutaneous bone conduction device in accordance with at least some exemplary embodiments; 
         FIG. 5  is a cross-sectional view of an example of a vibrating actuator-coupling assembly of the bone conduction device of  FIG. 2 ; 
         FIG. 6A  is a cross-sectional view of an embodiment of a vibrating actuator-coupling assembly of the bone conduction device of  FIG. 2 ; 
         FIG. 6B  is a cross-sectional view of the bobbin assembly of the vibrating actuator-coupling assembly of  FIG. 3A ; 
         FIG. 6C  is a cross-sectional view of the counterweight assembly of the vibrating actuator-coupling assembly of  FIG. 3A ; 
         FIG. 7  is a schematic diagram of a portion of the vibrating actuator-coupling assembly of  FIG. 6A ; 
         FIGS. 8A and 8B  are schematic diagrams detailing static and dynamic magnetic flux in the vibrating actuator-coupling assembly at the moment that the coils are energized when the bobbin assembly and the counterweight assembly are at a balance point with respect to magnetically induced relative movement between the two; 
         FIG. 9A  is a schematic diagram depicting movement of the counterweight assembly relative to the bobbin assembly of the vibrating actuator-coupling assembly of  FIG. 6A ; and 
         FIG. 9B  is a schematic diagram depicting movement of the counterweight assembly relative to the bobbin assembly of the vibrating actuator-coupling assembly of  FIG. 6A  in the opposite direction of that depicted in  FIG. 9A ; 
         FIG. 10  is a cross-sectional view of an alternate embodiment of a vibrating actuator-coupling assembly of the bone conduction device of  FIG. 2 ; 
         FIG. 11  is a cross-sectional view of an alternate embodiment of a vibrating actuator-coupling assembly of the bone conduction device of  FIG. 2 ; and 
         FIG. 12  is a cross-sectional view of an alternate embodiment of a vibrating actuator-coupling assembly of the bone conduction device of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1A  is a perspective view of a bone conduction device  100 A in which embodiments may be implemented. As shown, the recipient has an outer ear  101 , a middle ear  102  and an inner ear  103 . Elements of outer ear  101 , middle ear  102  and inner ear  103  are described below, followed by a description of bone conduction device  100 . 
     In a fully functional human hearing anatomy, outer ear  101  comprises an auricle  105  and an ear canal  106 . A sound wave or acoustic pressure  107  is collected by auricle  105  and channeled into and through ear canal  106 . Disposed across the distal end of ear canal  106  is a tympanic membrane  104  which vibrates in response to acoustic wave  107 . This vibration is coupled to oval window or fenestra ovalis  210  through three bones of middle ear  102 , collectively referred to as the ossicles  111  and comprising the malleus  112 , the incus  113  and the stapes  114 . The ossicles  111  of middle ear  102  serve to filter and amplify acoustic wave  107 , causing oval window  210  to vibrate. Such vibration sets up waves of fluid motion within cochlea  139 . Such fluid motion, in turn, activates hair cells (not shown) that line the inside of cochlea  139 . Activation of the hair cells causes appropriate nerve impulses to be transferred through the spiral ganglion cells and auditory nerve  116  to the brain (not shown), where they are perceived as sound. 
       FIG. 1A  also illustrates the positioning of bone conduction device  100 A relative to outer ear  101 , middle ear  102  and inner ear  103  of a recipient of device  100 . As shown, bone conduction device  100  is positioned behind outer ear  101  of the recipient and comprises a sound input element  126 A to receive sound signals. Sound input element may comprise, for example, a microphone, telecoil, etc. In an exemplary embodiment, sound input element  126 A may be located, for example, on or in bone conduction device  100 A, or on a cable extending from bone conduction device  100 A. 
     In an exemplary embodiment, bone conduction device  100 A comprises an operationally removable component and a bone conduction implant. The operationally removable component is operationally releasably coupled to the bone conduction implant. By operationally releasably coupled, it is meant that it is releasable in such a manner that the recipient can relatively easily attach and remove the operationally removable component during normal use of the bone conduction device  100 A. Such releasable coupling is accomplished via a coupling assembly of the operationally removable component and a corresponding mating apparatus of the bone conduction implant, as will be detailed below. This as contrasted with how the bone conduction implant is attached to the skull, as will also be detailed below. The operationally removable component includes a sound processor (not shown), a vibrating electromagnetic actuator and/or a vibrating piezoelectric actuator and/or other type of actuator (not shown—which are sometimes referred to herein as a species of the genus vibrator) and/or various other operational components, such as sound input device  126 A. In this regard, the operationally removable component is sometimes referred to herein as a vibrator unit. More particularly, sound input device  126 A (e.g., a microphone) converts received sound signals into electrical signals. These electrical signals are processed by the sound processor. The sound processor generates control signals which cause the actuator to vibrate. In other words, the actuator converts the electrical signals into mechanical motion to impart vibrations to the recipient&#39;s skull. 
     As illustrated, the operationally removable component of the bone conduction device  100 A further includes a coupling assembly  240  configured to operationally removably attach the operationally removable component to a bone conduction implant (also referred to as an anchor system and/or a fixation system) which is implanted in the recipient. In the embodiment of  FIG. 1 , coupling assembly  240  is coupled to the bone conduction implant (not shown) implanted in the recipient in a manner that is further detailed below with respect to exemplary embodiments of the bone conduction implant. Briefly, an exemplary bone conduction implant may include a percutaneous abutment attached to a bone fixture via a screw, the bone fixture being fixed to the recipient&#39;s skull bone  136 . The abutment extends from the bone fixture which is screwed into bone  136 , through muscle  134 , fat  128  and skin  232  so that the coupling assembly may be attached thereto. Such a percutaneous abutment provides an attachment location for the coupling assembly that facilitates efficient transmission of mechanical force. 
     It is noted that while many of the details of the embodiments presented herein are described with respect to a percutaneous bone conduction device, some or all of the teachings disclosed herein may be utilized in transcutaneous bone conduction devices and/or other devices that utilize a vibrating electromagnetic actuator. For example, embodiments include active transcutaneous bone conduction systems utilizing the electromagnetic actuators disclosed herein and variations thereof where at least one active component (e.g. the electromagnetic actuator) is implanted beneath the skin. Embodiments also include passive transcutaneous bone conduction systems utilizing the electromagnetic actuators disclosed herein and variations thereof where no active component (e.g., the electromagnetic actuator) is implanted beneath the skin (it is instead located in an external device), and the implantable part is, for instance a magnetic pressure plate. Some embodiments of the passive transcutaneous bone conduction systems are configured for use where the vibrator (located in an external device) containing the electromagnetic actuator is held in place by pressing the vibrator against the skin of the recipient. In an exemplary embodiment, an implantable holding assembly is implanted in the recipient that is configured to press the bone conduction device against the skin of the recipient. In other embodiments, the vibrator is held against the skin via a magnetic coupling (magnetic material and/or magnets being implanted in the recipient and the vibrator having a magnet and/or magnetic material to complete the magnetic circuit, thereby coupling the vibrator to the recipient). 
     More specifically,  FIG. 1B  is a perspective view of a transcutaneous bone conduction device  100 B in which embodiments can be implemented. 
       FIG. 1A  also illustrates the positioning of bone conduction device  100 B relative to outer ear  101 , middle ear  102  and inner ear  103  of a recipient of device  100 . As shown, bone conduction device  100  is positioned behind outer ear  101  of the recipient. Bone conduction device  100 B comprises an external component  140 B and implantable component  150 . The bone conduction device  100 B includes a sound input element  126 B to receive sound signals. As with sound input element  126 A, sound input element  126 B may comprise, for example, a microphone, telecoil, etc. In an exemplary embodiment, sound input element  126 B may be located, for example, on or in bone conduction device  100 B, on a cable or tube extending from bone conduction device  100 B, etc. Alternatively, sound input element  126 B may be subcutaneously implanted in the recipient, or positioned in the recipient&#39;s ear. Sound input element  126 B may also be a component that receives an electronic signal indicative of sound, such as, for example, from an external audio device. For example, sound input element  126 B may receive a sound signal in the form of an electrical signal from an MP3 player electronically connected to sound input element  126 B. 
     Bone conduction device  100 B comprises a sound processor (not shown), an actuator (also not shown) and/or various other operational components. In operation, sound input device  126 B converts received sounds into electrical signals. These electrical signals are utilized by the sound processor to generate control signals that cause the actuator to vibrate. In other words, the actuator converts the electrical signals into mechanical vibrations for delivery to the recipient&#39;s skull. 
     In accordance with some embodiments, a fixation system  162  may be used to secure implantable component  150  to skull  136 . As described below, fixation system  162  may be a bone screw fixed to skull  136 , and also attached to implantable component  150 . 
     In one arrangement of  FIG. 1B , bone conduction device  100 B is a passive transcutaneous bone conduction device. That is, no active components, such as the actuator, are implanted beneath the recipient&#39;s skin  132 . In such an arrangement, the active actuator is located in external component  140 B, and implantable component  150  includes a magnetic plate, as will be discussed in greater detail below. The magnetic plate of the implantable component  150  vibrates in response to vibration transmitted through the skin, mechanically and/or via a magnetic field, that are generated by an external magnetic plate. 
     In another arrangement of  FIG. 1B , bone conduction device  100 B is an active transcutaneous bone conduction device where at least one active component, such as the actuator, is implanted beneath the recipient&#39;s skin  132  and is thus part of the implantable component  150 . As described below, in such an arrangement, external component  140 B may comprise a sound processor and transmitter, while implantable component  150  may comprise a signal receiver and/or various other electronic circuits/devices. 
       FIG. 2  is an embodiment of a bone conduction device  200  in accordance with an embodiment corresponding to that of  FIG. 1A , illustrating use of a percutaneous bone conduction device. Bone conduction device  200 , corresponding to, for example, element  100 A of  FIG. 1A , includes a housing  242 , a vibrating electromagnetic actuator  250 , a coupling assembly  240  that extends from housing  242  and is mechanically linked to vibrating electromagnetic actuator  250 . Collectively, vibrating electromagnetic actuator  250  and coupling assembly  240  form a vibrating actuator-coupling assembly  280 . Vibrating actuator-coupling assembly  280  is suspended in housing  242  by spring  244 . In an exemplary embodiment, spring  244  is connected to coupling assembly  240 , and vibrating electromagnetic actuator  250  is supported by coupling assembly  240 . 
       FIG. 3  depicts an exemplary embodiment of a transcutaneous bone conduction device  300  according to an embodiment that includes an external device  340  (corresponding to, for example, element  140 B of  FIG. 1B ) and an implantable component  350  (corresponding to, for example, element  150  of  FIG. 1B ). The transcutaneous bone conduction device  300  of  FIG. 3  is a passive transcutaneous bone conduction device in that a vibrating electromagnetic actuator  342  is located in the external device  340 . Vibrating electromagnetic actuator  342  is located in housing  344  of the external component, and is coupled to plate  346 . Plate  346  may be in the form of a permanent magnet and/or in another form that generates and/or is reactive to a magnetic field, or otherwise permits the establishment of magnetic attraction between the external device  340  and the implantable component  350  sufficient to hold the external device  340  against the skin of the recipient. 
     In an exemplary embodiment, the vibrating electromagnetic actuator  342  is a device that converts electrical signals into vibration. In operation, sound input element  126  converts sound into electrical signals. Specifically, the transcutaneous bone conduction device  300  provides these electrical signals to vibrating actuator  342 , or to a sound processor (not shown) that processes the electrical signals, and then provides those processed signals to vibrating electromagnetic actuator  342 . The vibrating electromagnetic actuator  342  converts the electrical signals (processed or unprocessed) into vibrations. Because vibrating electromagnetic actuator  342  is mechanically coupled to plate  346 , the vibrations are transferred from the vibrating actuator  342  to plate  346 . Implanted plate assembly  352  is part of the implantable component  350 , and is made of a ferromagnetic material that may be in the form of a permanent magnet, that generates and/or is reactive to a magnetic field, or otherwise permits the establishment of a magnetic attraction between the external device  340  and the implantable component  350  sufficient to hold the external device  340  against the skin of the recipient. Accordingly, vibrations produced by the vibrating electromagnetic actuator  342  of the external device  340  are transferred from plate  346  across the skin to plate  355  of plate assembly  352 . This can be accomplished as a result of mechanical conduction of the vibrations through the skin, resulting from the external device  340  being in direct contact with the skin and/or from the magnetic field between the two plates. These vibrations are transferred without penetrating the skin with a solid object such as an abutment as detailed herein with respect to a percutaneous bone conduction device. 
     As may be seen, the implanted plate assembly  352  is substantially rigidly attached to a bone fixture  341  in this embodiment. Plate screw  356  is used to secure plate assembly  352  to bone fixture  341 . The portions of plate screw  356  that interface with the bone fixture  341  substantially correspond to an abutment screw discussed in some additional detail below, thus permitting plate screw  356  to readily fit into an existing bone fixture used in a percutaneous bone conduction device. In an exemplary embodiment, plate screw  356  is configured so that the same tools and procedures that are used to install and/or remove an abutment screw (described below) from bone fixture  341  can be used to install and/or remove plate screw  356  from the bone fixture  341  (and thus the plate assembly  352 ). 
       FIG. 4  depicts an exemplary embodiment of a transcutaneous bone conduction device  400  according to another embodiment that includes an external device  440  (corresponding to, for example, element  140 B of  FIG. 1B ) and an implantable component  450  (corresponding to, for example, element  150  of  FIG. 1B ). The transcutaneous bone conduction device  400  of  FIG. 4  is an active transcutaneous bone conduction device in that the vibrating actuator  452  is located in the implantable component  450 . Specifically, a vibratory element in the form of vibrating actuator  452  is located in housing  454  of the implantable component  450 . In an exemplary embodiment, much like the vibrating actuator  342  described above with respect to transcutaneous bone conduction device  300 , the vibrating actuator  452  is a device that converts electrical signals into vibration. 
     External component  440  includes a sound input element  126  that converts sound into electrical signals. Specifically, the transcutaneous bone conduction device  400  provides these electrical signals to vibrating electromagnetic actuator  452 , or to a sound processor (not shown) that processes the electrical signals, and then provides those processed signals to the implantable component  450  through the skin of the recipient via a magnetic inductance link. In this regard, a transmitter coil  442  of the external component  440  transmits these signals to implanted receiver coil  456  located in housing  458  of the implantable component  450 . Components (not shown) in the housing  458 , such as, for example, a signal generator or an implanted sound processor, then generate electrical signals to be delivered to vibrating actuator  452  via electrical lead assembly  460 . The vibrating electromagnetic actuator  452  converts the electrical signals into vibrations. 
     The vibrating electromagnetic actuator  452  is mechanically coupled to the housing  454 . Housing  454  and vibrating actuator  452  collectively form a vibrating element  453 . The housing  454  is substantially rigidly attached to bone fixture  341 . 
     Some exemplary features of the vibrating electromagnetic actuator usable in some embodiments of the bone conduction devices detailed herein and/or variations thereof will now be described in terms of a vibrating electromagnetic actuator used in the context of the percutaneous bone conduction device of  FIG. 1A . It is noted that any and/or all of these features and/or variations thereof may be utilized in transcutaneous bone conduction devices such as those of  FIGS. 1B, 3 and 4  and/or other types of prostheses and/or medical devices and/or other devices, at least with respect to enabling utilitarian performance thereof. It is also noted that while the embodiments detailed herein are detailed with respect to an electromagnetic actuator, the teachings associated therewith are equally applicable to electromagnetic transducers that receive vibrations and output a signal indicative of the vibrations, at least unless otherwise noted. In this regard, it is noted that use of the term actuator herein also corresponds to transducer, and vice-versa, unless otherwise noted. 
       FIG. 5  is a cross-sectional view of a vibrating actuator-coupling assembly  580 , which can correspond to vibrating actuator-coupling assembly  280  detailed above. The vibrating actuator-coupling assembly  580  includes a vibrating electromagnetic actuator  550  and a coupling assembly  540 . Coupling assembly  540  includes a coupling  541  mounted on coupling shaft  543 . Additional details pertaining to the coupling assembly are described further below with respect to the embodiment of  FIG. 6A . 
     As illustrated in  FIG. 5 , vibrating electromagnetic actuator  550  includes a bobbin assembly  554  and a counterweight assembly  555 . As illustrated, bobbin assembly  554  includes a bobbin  554 A and a coil  554 B that is wrapped around a core  554 C of bobbin  554 A. In the illustrated embodiment, bobbin assembly  554  is radially symmetrical. 
     Counterweight assembly  555  includes spring  556 , permanent magnets  558 A and  558 B, yokes  560 A,  560 B and  560 C, and spacer  562 . Spacer  562  provides a connective support between spring  556  and the other elements of counterweight assembly  555  just detailed. Spring  556  connects bobbin assembly  554  via spacer  524  to the rest of counterweight assembly  555 , and permits counterweight assembly  555  to move relative to bobbin assembly  554  upon interaction of a dynamic magnetic flux, produced by bobbin assembly  554 . 
     Coil  554 B, in particular, may be energized with an alternating current to create the dynamic magnetic flux about coil  554 B. Conversely, permanent magnets  558 A and  558 B generate a static magnetic flux. These permanent magnets  558 A and  558 B are part of counterweight assembly  555 , which also includes yokes  560 A,  560 B and  560 C. The yokes  560 A,  560 B and  560 C can be made of a soft iron in some embodiments. 
     As may be seen, vibrating electromagnetic actuator  550  includes two axial air gaps  570 A and  570 B that are located between bobbin assembly  554  and counterweight assembly  555 . With respect to a radially symmetrical bobbin assembly  554  and counterweight assembly  555 , such as that detailed in  FIG. 5 , air gaps  570 A and  570 B extend in the direction of relative movement between bobbin assembly  554  and counterweight assembly  555 , indicated by arrow  500 A. 
     Further as may be seen in  FIG. 5 , the vibrating electromagnetic actuator  550  includes two radial air gaps  572 A and  572 B that are located between bobbin assembly  554  and counterweight assembly  555 . With respect to a radially symmetrical bobbin assembly  554  and counterweight assembly  555 , the air gap extends about the direction of relative movement between bobbin assembly  554  and counterweight assembly  555 . As may be seen in  FIG. 5 , the permanent magnets  558 A and  558 B are arranged such that their respective south poles face each other and their respective north poles face away from each other. It is noted that in an alternate embodiment, the reverse can be the case (respective north poles face towards each other and respective south poles face away from each other). 
     In the electromagnetic actuator of  FIG. 5 , the radial air gaps  572 A and  572 B close static magnetic flux between the bobbin  554 A and the yokes  560 B and  560 C, respectively. Further, axial air gaps  570 A and  570 B close the static and dynamic magnetic flux between the bobbin  554 A and the yoke  560 A. Accordingly, in the radially symmetrical device of  FIG. 5 , there are a total of four (4) air gaps. 
     It is noted that the electromagnetic actuator of  FIG. 5  is a balanced actuator. In alternate configuration a balanced actuator can be achieved by adding additional axial air gaps above and below the outside of bobbin  554 B (and in some variations thereof, the radial air gaps are not present due to the addition of the additional axial air gaps). In such an alternate configuration, the yokes  560 B and  560 C are reconfigured to extend up and over the outside of bobbin  554 B (the geometry of the permanent magnets  558 A and  558 B and/or the yoke  560 A might also be reconfigured to achieve utility of the actuator). 
     Some embodiments of a balanced electromagnetic transducer will now be described that utilize fewer air gaps than the configuration of  FIG. 5  and the alternate variations as described above. In some exemplary embodiments, the electromagnetic actuator (balanced and/or unbalanced, as detailed below) is achieved by providing functionality to a resilient element, such as by way of example and not by way of limitation, a spring, beyond that which is normally associated therewith. Embodiments detailed herein are detailed with respect to a spring. It is noted, however, that in alternate embodiments of these embodiments and/or variations thereof, the disclosure of spring also corresponds to the disclosure of a resilient element. More particularly, not only does the spring provide resilient elasticity concomitant with the traditional use of the spring, but the spring also provides a conduit for magnetic flux (static and/or dynamic). In an exemplary embodiment utilizing a spring having such functionality, one or more of the above mentioned air gaps with respect to the embodiment of  FIG. 5  (e.g. the radial air gaps) are eliminated and/or one or more of the soft iron parts utilized in that embodiment are not utilized in this exemplary embodiment. 
     More particularly, it is noted that the balance electromagnetic actuator of  FIG. 5  relies on at least four air gaps (while the embodiment of  FIG. 5  is depicted as including two axial air gaps and two radial air gaps, other balance electromagnetic actuators utilize four axial air gaps). An exemplary embodiment includes a spring having dual functionality as a traditional spring, on the one hand, and a conduit for magnetic flux, on the other hand, such that at least one or two of the air gaps of the embodiment of  FIG. 5  can eliminated. Functionality according to a “traditional spring” includes, for example, an device that elastically deforms/moves from its unloaded position when pushed or pulled or pressed (i.e., subjected to load) and then returns to its original shape/returns to is unloaded position when the pushing, pulling or pressing is removed (load is removed). 
     In this regard, in some embodiments, there is an electromagnetic actuator that is balanced that has only two air gaps (both axial air gaps) owing to the fact that the spring(s) replaces two of the radial air gaps. That is, the magnetic flux is conducted through spring(s) instead of through air gaps. An exemplary embodiment of such will now be described, followed by some exemplary descriptions of some alternate embodiments. 
       FIG. 6A  is a cross-sectional view of a vibrating actuator-coupling assembly  680 , which can correspond to vibrating actuator-coupling assembly  280  detailed above. 
     Coupling assembly  640  includes a coupling  641  in the form of a snap coupling configured to “snap couple” to an anchor system on the recipient. As noted above with reference to  FIG. 1 , the anchor system may include an abutment that is attached to a fixture screw implanted into the recipient&#39;s skull and extending percutaneously through the skin so that snap coupling  341  can snap couple to a coupling of the abutment of the anchor system. In the embodiment depicted in  FIG. 6A , coupling  641  is located at a distal end—relative to housing  242  if vibrating actuator-coupling assembly  680  were installed in bone conduction device  200  of  FIG. 2  (i.e., element  680  being substituted for element  280  of  FIG. 2 )—of a coupling shaft  643  of coupling assembly  640 . In an embodiment, coupling  641  corresponds to coupling described in U.S. patent application Ser. No. 12/177,091 assigned to Cochlear Limited. In yet other embodiments, alternate couplings can be used. 
     Coupling assembly  640  is mechanically coupled to vibrating electromagnetic actuator  650  configured to convert electrical signals into vibrations. In an exemplary embodiment, vibrating electromagnetic actuator  650  (and/or any vibrating electromagnetic actuator detailed herein and/or variations thereof) corresponds to vibrating electromagnetic actuator  250  or vibrating electromechanical actuator  342  or vibrating electromechanical actuator  452  detailed above, and, accordingly, in some embodiments, the teachings detailed above and/or variations thereof with respect to such actuators are included in the genus of devices, genus of systems and/or genus of methods of utilizing the vibrating electromagnetic actuator  650  and/or any vibrating electromagnetic actuator detailed herein and/or variations thereof. This is further detailed below. 
     In operation, sound input element  126 A ( FIG. 1A ) converts sound into electrical signals. As noted above, the bone conduction device provides these electrical signals to a sound processor which processes the signals and provides the processed signals to the vibrating electromagnetic actuator  650  (and/or any other electromagnetic actuator detailed herein and/or variations thereof—it is noted that unless otherwise specified, any teaching herein concerning a given embodiment is applicable to any variation thereof and/or any other embodiment and/or variations thereof), which then converts the electrical signals (processed or unprocessed) into vibrations. Because vibrating electromagnetic actuator  650  is mechanically coupled to coupling assembly  640 , the vibrations are transferred from vibrating electromagnetic actuator  650  to coupling assembly  640  and then to the recipient via the anchor system (not shown). 
     As noted, the teachings detailed herein and/or variations thereof with respect to any given electromagnetic transducer are not only applicable to a percutaneous bone conduction device such as that according to the embodiment of  FIG. 2 , but also to a transcutaneous bone conduction device such as those according to embodiments of  FIG. 3  and  FIG. 4 . In this regard, the electromagnetic transducers detailed herein and/or variations thereof can be substituted for the vibrating actuator  342  of the embodiment of  FIG. 3  and the vibrating actuator  452  of the embodiment of  FIG. 4 . Accordingly, some embodiments include an active transcutaneous bone conduction device having the electromagnetic transducers detailed herein and/or variations thereof. Also, some embodiments include a passive transcutaneous bone conduction device having the electromagnetic transducers detailed herein and/or variations thereof. It is further again noted that other medical devices and/or other devices can utilize the electromagnetic transducers detailed herein and/or variations thereof. 
     As illustrated in  FIG. 6A , vibrating electromagnetic actuator  650  includes a bobbin assembly  654 , a counterweight assembly  655  and coupling assembly  640 . For ease of visualization,  FIG. 6B  depicts bobbin assembly  654  separately. As illustrated, bobbin assembly  654  includes a bobbin  654 A and a coil  654 B that is wrapped around a core  654 C of bobbin  654 A. In the illustrated embodiment, bobbin assembly  654  is radially symmetrical (i.e., symmetrical about the longitudinal axis  699 . 
       FIG. 6C  illustrates counterweight assembly  655  separately, for ease of visualization. As illustrated, counterweight assembly  655  includes springs  656  and  657 , permanent magnets  658 A and  658 B, yoke  660 A, and counterweight mass  670 . Springs  656  and  657  connect bobbin assembly  654  to the rest of counterweight assembly  655 , and permit counterweight assembly  655  to move relative to bobbin assembly  654  upon interaction of a dynamic magnetic flux, produced by bobbin assembly  654 . In this regard, with reference back to  FIG. 6A , spring  656  includes a flexible section  690  that is not directly connected to any component of the bobbin assembly  654  or to any component of the counterweight assembly  655  that flexes, as will be further detailed below. Along these lines, spring  656  can be directly adhesively bonded, riveted, bolted, welded, etc., directly to the bobbin assembly  654  and/or to any component of the counterweight assembly  655  so as to hold the components together/in contact with one another such that embodiments detailed herein and/or variations thereof can be practiced. Any device, system or method that can be utilized to connect the components of the vibrating actuator-coupling assembly can be utilized in at least some of the embodiments detailed herein and/or variations thereof. 
     As can be seen, the two permanent magnets  658 A and  658 B respectively directly contact the springs  656  and  657 . That is, there is no yoke or other component (e.g., in the form of a ring) interposed between the magnets and the springs. Accordingly, the magnetic flux generated by the magnets flows directly into the springs without passing through an intermediary component or without passing through a gap. However, it is noted that in an alternate embodiment, there can be an intermediary component, such as a yoke or the like. Further, in some embodiments, there can be a gap between the magnets and the springs. 
     The dynamic magnetic flux is produced by energizing coil  654 B with an alternating current. The static magnetic flux is produced by permanent magnets  658 A and  658 B of counterweight assembly  655 , as will be described in greater detail below. In this regard, counterweight assembly  655  is a static magnetic field generator and bobbin assembly  654  is a dynamic magnetic field generator. As may be seen in  FIGS. 6A and 6C , hole  664  in spring  656  provides a feature that permits coupling assembly  641  to be rigidly connected to bobbin assembly  654 . 
     It is noted that while embodiments presented herein are described with respect to a bone conduction device where counterweight assembly  655  includes permanent magnets  658 A and  658 B that surround coil  654   b  and moves relative to coupling assembly  640  during vibration of vibrating electromagnetic actuator  650 , in other embodiments, the coil may be located on the counterweight assembly  655  as well, thus adding weight to the counterweight assembly  655  (the additional weight being the weight of the coil). 
     As noted, bobbin assembly  654  is configured to generate a dynamic magnetic flux when energized by an electric current. In this exemplary embodiment, bobbin  654 A is made of a soft iron. Coil  654 B may be energized with an alternating current to create the dynamic magnetic flux about coil  654 B. The iron of bobbin  654 A is conducive to the establishment of a magnetic conduction path for the dynamic magnetic flux. Conversely, counterweight assembly  655 , as a result of permanent magnets  658 A and  658 B, in combination with yoke  660 A and springs  656  (this feature being described in greater detail below), at least the yoke, in some embodiments, being made from soft iron, generate, due to the permanent magnets, a static magnetic flux. The soft iron of the bobbin and yokes may be of a type that increases the magnetic coupling of the respective magnetic fields, thereby providing a magnetic conduction path for the respective magnetic fields. 
       FIG. 7  depicts a portion of  FIG. 6A . As may be seen, vibrating electromagnetic actuator  650  includes two axial air gaps  770 A and  770 B that are located between bobbin assembly  654  and counterweight assembly  655 . As used herein, the phrase “axial air gap” refers to an air gap that has at least a component that extends on a plane normal to the direction of primary relative movement (represented by arrow  600 A in  FIG. 6A —more on this below) between bobbin assembly  654  and counterweight assembly  655  such that the air gap is bounded by the bobbin assembly  654  and counterweight assembly  655  in the direction of relative movement between the two. 
     Accordingly, the phrase “axial air gap” is not limited to an annular air gap, and encompasses air gaps that are formed by straight walls of the components (which may be present in embodiments utilizing bar magnets and bobbins that have a non-circular (e.g. square) core surface). With respect to a radially symmetrical bobbin assembly  654  and counterweight assembly  655 , cross-sections of which are depicted in  FIGS. 6A-7 , air gaps  770 A and  770 B extend in the direction of relative movement between bobbin assembly  654  and counterweight assembly  655 , air gaps  770 A and  770 B are bounded as detailed above in the “axial” direction. With respect to  FIG. 7 , the boundaries of axial air gap  770 B are defined by surface  754 B of bobbin  654 A and surface  760 B of yoke  660 A. 
     It is noted that the primary direction of relative motion of the counterweight assembly of the electromagnetic transducer is parallel to the longitudinal direction of the electromagnetic transducer, and with respect to utilization of the transducers in a bone conduction device, normal to the tangent of the surface of the bone  136  (or, more accurately, an extrapolated surface of the bone  136 ) local to the bone fixtures. It is noted that by “primary direction of relative motion,” it is recognized that the counterweight assembly may move inward towards the longitudinal axis of the electromagnetic actuator owing to the flexing of the springs (providing, at least, that the spring does not stretch outward, in which case it may move outward or not move in this dimension at all), but that most of the movement is normal to this direction. 
     Further as may be seen in  FIG. 7 , in contrast to the device of  FIG. 5 , the vibrating electromagnetic actuator  650  includes no radial air gaps located, for example, between bobbin assembly  654  and counterweight assembly  655 . As used herein, the phrase “radial air gap” refers to an air gap that has at least a component that extends on a plane normal to the direction of relative movement between bobbin assembly  654  and counterweight assembly  655  such that the air gap is bounded by bobbin assembly  654  and counterweight assembly  655  in a direction normal to the primary direction of relative movement between the two (represented by arrow  600 A in  FIG. 6A ). Accordingly, in some exemplary embodiments, due to the feature of the conductive springs  656  and  657 , the radial air gaps of the configuration of  FIG. 5  are not utilized in the embodiment of  FIG. 6A  and variations thereof, and, in some embodiments and variations thereof, there are no additional axial air gaps than those depicted in  FIG. 6A . 
     As can be seen in  FIG. 7 , the permanent magnets  658 A and  658 B are arranged such that their respective south poles face each other and their respective north poles face away from each other. It is noted that in other embodiments, the respective south poles may face away from each other and the respective north poles may face each other. 
       FIG. 8A  is a schematic diagram detailing the respective static magnetic flux  880  and static magnetic flux  884  of permanent magnets  658 A and  658 B, and dynamic magnetic flux  882  of coil  654 B in vibrating actuator-coupling assembly  680  when coil  654 B is energized according to a first current direction and when bobbin assembly  654  and counterweight assembly  655  are at a balance point with respect to magnetically induced relative movement between the two (hereinafter, the “balance point”). That is, while it is to be understood that the counterweight assembly  655  moves in an oscillatory manner relative to the bobbin assembly  654  when the coil  654 B is energized, there is an equilibrium point at the fixed location corresponding to the balance point at which the counterweight assembly  654  returns to relative to the bobbin assembly  654  when the coil  654 B is not energized. 
       FIG. 8B  is a schematic diagram detailing the respective static magnetic flux  880  and static magnetic flux  884  of permanent magnets  658 A and  658 B, and dynamic magnetic flux  886  of coil  654 B in vibrating actuator-coupling assembly  680  when coil  654 B is energized according to a second current direction (a direction opposite the first current direction) and when bobbin assembly  654  and counterweight assembly  655  are at a balance point with respect to magnetically induced relative movement between the two. 
     It is noted that  FIGS. 8A and 8B  do not depict the magnitude/scale of the magnetic fluxes. In this regard, it is noted that in some embodiments, at the moment that coil  654 B is energized and when bobbin assembly  654  and counterweight assembly  655  are at the balance point, relatively little, if any, static magnetic flux flows through the core  654 C of the bobbin  654 A/the space  654 D (see  FIG. 6B ) in the coil  654 B (the space  654 D being formed as a result of the coil  654 B being wound about, and at least partially filled by, the core  654 C of the bobbin  654 A). Accordingly,  FIGS. 8A and 8B  depict this fact. However, during operation, the amount of static magnetic flux that flows through the core increases as the bobbin assembly  654  travels away from the balance point (both downward and upward away from the balance point) and decreases as the bobbin assembly  654  travels towards the balance point (both downward and upward towards the balance point). Still, the amount that travels through the core is minimal compared to the amount the travels through the respective air gaps. In this regard, static magnetic flux circuits  880  and  884  as depicted in  FIG. 8A  represent an ideal static magnetic flux path, where it is to be understood that magnetic flux, albeit relatively limited quantities, can also travel outside this ideal path. 
     As can be seen from  FIGS. 8A and 8B , the static magnetic flux and the dynamic magnetic flux all cross the same air gaps, and there are no air gaps crossed by the static magnetic flux that are not cross by the dynamic magnetic flux, at least with respect to the ideal paths of the static magnetic flux and the dynamic magnetic flux. 
     It is noted that the directions and paths of the static magnetic flux and dynamic magnetic flux are representative of some exemplary embodiments, and in other embodiments, the directions and/or paths of the fluxes can vary from those depicted. 
     As may be seen from  FIGS. 8A and 8B , axial air gaps  770 A and  770 B close static magnetic flux circuits  880  and  884 . It is noted that the phrase “air gap” refers to a gap between the component that produces a static magnetic field and a component that produces a dynamic magnetic field where there is a relatively high reluctance but magnetic flux still flows through the gap. The air gap closes the magnetic field. In an exemplary embodiment, the air gaps are gaps in which little to no material having substantial magnetic aspects is located in the air gap. Accordingly, an air gap is not limited to a gap that is filled by air. 
     Still with reference to  FIGS. 8A and 8B , it is noted that static magnetic flux circuits  880  and  884  each constitute closed flux paths/closed circuits. These paths/circuits are considered herein to be “local circuits” in that they are local to the individual permanent magnets that generate the circuit. As can be seen, each closed static magnetic flux path depicted in  FIGS. 8A and 8B  travels across no more than one air gap. That said, it is noted that in some embodiments or in potentially all embodiments, there is a static magnetic flux that travels across both air gaps. Such a scenario can exist in the case of trace flux and/or in the case of movement of the counterweight assembly  655  from the balance point, where some of the flux from one magnet travels through one air gap and some flux travels through another air gap. Without being bound by theory, such can exist in the scenario where the static magnetic flux also travels through the core of the bobbin. Still, even in such a scenario, there is a closed static magnetic flux path that travels across only one air gap. The path, however, is considered herein to be a “global” circuit as it extends outside the local circuit owing to, for example, its travels through the core of the bobbin. 
       FIGS. 8A and 8B  clearly depict that the static magnetic flux generated by the counterweight assembly  655  travels across only two air gaps. This is as contrasted to the embodiment of  FIG. 5 , where the generated static magnetic flux crosses four air gaps. In this regard, an exemplary embodiment includes a balanced electromagnetic transducer where only two air gaps are present. 
     As can be seen from the figures, the dynamic magnetic flux also crosses both air gaps. In an exemplary embodiment, neither the dynamic magnetic flux nor the static magnetic flux crosses an air gap at the other does not cross. 
     Referring now to  FIG. 9A , the depicted magnetic fluxes  880 ,  882  and  884  of  FIG. 8A  will magnetically induce movement of counterweight assembly  655  downward (represented by the direction of arrow  900   a  in  FIG. 9A ) relative to bobbin assembly  654  so that vibrating actuator-coupling assembly  680  will ultimately correspond to the configuration depicted in  FIG. 9A . More specifically, vibrating electromagnetic actuator  650  of  FIG. 6A  is configured such that during operation of vibrating electromagnetic actuator  650  (and thus operation of bone conduction device  200 ), an effective amount of the dynamic magnetic flux  882  and an effective amount of the static magnetic flux (flux  880 , flux  884  and/or a combination of flux  880  and  884 ) flow through at least one of axial air gaps  770 A and  770 B sufficient to generate substantial relative movement between counterweight assembly  655  and bobbin assembly  654 . 
     As used herein, the phrase “effective amount of flux” refers to a flux that produces a magnetic force that impacts the performance of vibrating electromagnetic actuator  650 , as opposed to trace flux, which may be capable of detection by sensitive equipment but has no substantial impact (e.g., the efficiency is minimally impacted) on the performance of the vibrating electromagnetic actuator. That is, the trace flux will typically not result in vibrations being generated by the electromagnetic actuators detailed herein and/or typically will not result in the generation electrical signals in the absence of vibration inputted into the transducer. 
     Further, as may be seen in  FIGS. 8A and 8B , the static magnetic fluxes enter bobbin  654 A substantially only at locations lying on and parallel to a tangent line of the path of the dynamic magnetic fluxes  882 . 
     As may be seen from  FIGS. 8A and 8B , the dynamic magnetic flux is directed to flow within the area sandwiched by the springs  656  and  657 . In particular, no substantial amount of the dynamic magnetic flux  882  or  886  passes through or into springs  656 . Further, no substantial amount of the dynamic magnetic flux  882  or  886  passes through the two permanent magnets  658 A and  658 B of counterweight assembly  655 . Moreover, as may be seen from the FIGs., the static magnetic fluxes ( 880 ,  884  and/or a combination of the two) is produced by no more than two permanent magnets  658 A and  658 B. 
     It is noted that the schematics of  FIGS. 8A and 8B  represent respective instantaneous snapshots while the counterweight assembly  655  is moving in opposite directions ( FIG. 8A  being downward movement,  FIG. 8B  being upward movement), but both when the bobbin assembly  654  and counterweight assembly  655  are at the balance point. 
     As counterweight assembly  655  moves downward relative to bobbin assembly  654 , as depicted in  FIG. 9A , the span of axial air gap  770 A increases and the span of axial air gap  770 B decreases. This has the effect of substantially reducing the amount of effective static magnetic flux through axial air gap  770 A and increasing the amount of effective static magnetic flux through axial air gap  770 B. However, in some embodiments, the amount of effective static magnetic flux through springs  656  and  657  collectively substantially remains about the same as compared to the flux when counterweight assembly  655  and bobbin assembly  654  are at the balance point. (Conversely, as detailed below, in other embodiments the amount is different.) Without being limited by theory, this is believed to be the case because the deflection of the springs  656  and  657  is within parameters that do not result in a significant change in spring orientation that substantially impacts the amount of effective static magnetic flux through the springs. That is, the springs do not substantially impact the flow of magnetic flux. 
     Upon reversal of the direction of the dynamic magnetic flux, the dynamic magnetic flux will flow in the opposite direction about coil  654 B. However, the general directions of the static magnetic flux will not change. Accordingly, such reversal will magnetically induce movement of counterweight assembly  655  upward (represented by the direction of arrow  900 B in  FIG. 9B ) relative to bobbin assembly  654  so that vibrating actuator-coupling assembly  680  will ultimately correspond to the configuration depicted in  FIG. 9B . As counterweight assembly  655  moves upward relative to bobbin assembly  654 , the span of axial air gap  770 B increases and the span of axial air gap  770 A decreases. This has the effect of reducing the amount of effective static magnetic flux through axial air gap  770 B and increasing the amount of effective static magnetic flux through axial air gap  770 A. However, the amount of effective static magnetic flux through the springs  656  does not change due to a change in the span of the axial air gaps as a result of the displacement of the counterweight assembly  655  relative to the bobbin assembly  654  for the reasons detailed above with respect to downward movement of counterweight assembly  655  relative to bobbin assembly  654 . 
     As can be seen from  FIGS. 9A and 9B , the springs  656  and  657  deform with transduction of the transducer (e.g., actuation of the actuator). Accordingly, at least a portion of the static magnetic flux flows through solid material that deforms during transduction by the electromagnetic transducer. This as contrasted to the flow of static magnetic flux through, for example, the yokes of the embodiment of  FIG. 5 , where the yokes do not deform during actuation (transduction). 
     Referring back to  FIG. 5 , it can be seen that the embodiments thereof utilizes yokes  560 B and  560 C to establish the radial air gaps between the yokes and the bobbin assembly  354 . That is, the embodiment of  FIG. 5  utilizes three separate yokes (including yoke  560 A). Conversely, the embodiment of  FIG. 6A  utilizes only one yoke (it is noted that the depictions of  FIGS. 6A to 6C  are cross-sectional views of a rotationally symmetric vibrating electromagnetic actuator, and thus yoke  660 A is in the form of a ring). Note further that in the case of a balanced actuator that utilizes only axial air gaps, it has been heretofore known to utilize yokes that extend above and below (with respect to the orientation of  FIG. 5 ) the bobbin assembly. Accordingly, an exemplary embodiment provides for a balance electromagnetic actuator having fewer yokes. 
     Note further that the reduction of such components can have utility in that manufacturing tolerance buildup is not as significant of a factor as it might otherwise have been. That is, in the embodiment of  FIG. 6A , tolerance buildup affecting the axial air gaps could be limited to the tolerances of the permanent magnet  658 B (or permanent magnet  658 A) and the yoke  600 A. This can have utility in that the size of the axial air gaps can be reduced relative to that which would be utilized to account for tolerance buildup with respect to the embodiment of  FIG. 5 . This is because there would be less tolerance uncertainty in the embodiment of  FIG. 6A . 
     In some embodiments of the embodiment of  FIG. 6A , it is relatively easier to align the various components of the actuator as compared to the implementation of embodiments according to  FIG. 5 . The potential for tilting of the counterweight assembly components relative to the bobbin assembly components and/or vice-versa is lower relative to that associated with embodiments according to  FIG. 5 . Such tilting can cause the air gaps, especially the radial air gaps, to collapse or otherwise be reduced in width, such that a deleterious effect on the performance of the actuator results. Along these lines, embodiments according to  FIG. 6A  need not account for as much tilt relative to one another as embodiments corresponding to  FIG. 5  to avoid contact (such as contact while the actuators are vibrating). Still further, because of the reduced span of the flexible portion of the springs relative to embodiments corresponding to  FIG. 5 , the assemblies are less likely to tilt relative to one another/the assemblies are more resistant to tilting (i.e., for a given force that causes tilting, the embodiment of  FIG. 6A  tilts less than the embodiment of  FIG. 5 ). Accordingly, the axial air gaps can be less wide in embodiments corresponding to  FIG. 6A  than in the embodiments corresponding to  FIG. 5 , all other things being equal. This can have utility in that the relative efficiency of the actuator can be greater than it otherwise might have been. 
     Accordingly, in an exemplary embodiment, there is an electromagnetic transducer that is configured such that an angle of tilt between the bobbin assembly and the counterweight assembly is about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95% and/or any value or range of values therebetween in about 1% increments (e.g., about 56%, about 88% to about 94%, etc.) for a given tilt force, of that which would be present in an electromagnetic transducer according to the embodiment of  FIG. 5  and variations thereof, all other things being equal. 
     Still further, it is noted that the substitution of the springs for the air gaps also reduces or otherwise eliminates any need to control or otherwise adjusts the size of those air gaps during manufacturing, if only because those air gaps are no longer present. In this regard, with respect to  FIG. 5 , it is clear that a high degree of concentricity must exist with respect to the bobbin assembly and the counterweight assembly with respect to the radial air gaps. Tolerance buildups alone create difficulty in manufacturing the actuator. Further, there is a high degree of precision required to fit the bobbin assembly into the counterweight assembly. With respect to actuators that utilize four axial air gaps, the tolerance buildups create difficulty in manufacturing the actuator. Because of the reduction in the number of air gaps according to the embodiment of  FIG. 6  as compared to that of  FIG. 5  and the variations thereof, the number of “controlled dimensions” that impact performance of the actuator are reduced, at least as compared to an actuator having four air gaps, all other things being equal. 
     Additionally, it is noted that in some embodiments utilizing a spring to close the static magnetic flux, larger axial air gaps can be utilized than those of the embodiment of  FIG. 5 , all other things being equal. In an exemplary embodiment, this can enable a larger tilt angle between the counterweight assembly and the bobbin assembly without having one component contact the other component as compared to that according to the embodiment of  FIG. 5 , all other things being equal. More specifically, in an exemplary embodiment, there is an electromagnetic transducer that is configured such that an angle of tilt between the bobbin assembly and the counterweight assembly resulting in contact between the two components, as referenced from the same relative positions (e.g., at the balance point, the top of the transduction motion, the bottom of the transduction motion, etc.) is about 105%, 110%, 115%, 120%, 125%, 130%, 135%, 140%, 145% or 150% and/or any value or range of values therebetween in about 1% increments (e.g., about 116%, about 121% to about 138%, etc.) of that which would be present in an electromagnetic transducer according to the embodiment of  FIG. 5  and variations thereof, all other things being equal. 
     The embodiments of  FIGS. 6A-9B  detailed above include the use of two separate springs  656  and  657  as conduits of the static magnetic flux and no radial air gaps. In an alternate embodiment, only one spring is used (either the top or the bottom spring) as a conduit of static magnetic flux (but two or more springs may be present—the additional springs being utilized for their traditional resilient purposes), and in the place of the other spring, a radial air gap located between bobbin assembly  654  and counterweight assembly  655  is utilized to close the static magnetic flux. It is noted that in an alternate embodiment, two or more springs can be utilized as conduits for static magnetic flux along with one or two or more radial air gaps. 
     More particularly,  FIG. 10  depicts an alternate embodiment of a vibrating actuator-coupling assembly  1080 , that utilizes both a spring  656  and a radial air gap  1072 A to close the static magnetic flux, where like reference numbers correspond to the components detailed above. As can be seen, bobbin assembly  1054  includes a bobbin that has arms  1054 A and  1054 B that are different from one another, with arm  1054 B corresponding to the bottom arm of the bobbin  654 A of  FIG. 6A . However, arm  1054 A extends further in the lateral direction than arm  1054 B, and arm  1054 A is “thicker” in the longitudinal direction than arm  1054 B, at least with respect to the portions closest to counterweight assembly  1055 . 
     As can be seen, permanent magnets  1058 A and  1058 B are of a different geometry than the permanent magnets of the embodiment of  FIG. 6A . More particularly, in the embodiment depicted in  FIG. 10 , the permanent magnets  1058 A and  1058 A are shorter than the permanent magnets of  FIG. 6A . Also, the permanent magnets  1058 A and  1058 B are of the same configuration, although in other embodiments, different configurations can be utilized. In this regard, depending on the path of the magnetic fluxes, different sized permanent magnets (i.e., magnets of different strength) can be utilized to obtain a balanced vibrating actuator. 
     Referring still to  FIG. 10 , it can be seen that yokes  1060 B and  1060 C have been added in addition to yoke  1060 A (which corresponds to yoke  660 A of  FIG. 6A ). The magnetic flux generated by permanent magnet  1058 B flows through yoke  1060 A and bobbin assembly  1054  and spring  656  in a manner substantially the same as that detailed above with respect to the embodiment of  FIGS. 6A-9B , with the exception that the flux also flows through yoke  1060 C. With regard to the flow of flux through yoke  1060 C, the flux flows in a substantially linear manner therethrough (i.e., vertically into and out of yoke  1060 C). Conversely, the magnetic flux generated by permanent magnet  1058 A flows through yoke  1060 B and bobbin assembly  1054 A in a manner more akin to the flux of permanent magnet  558 A of  FIG. 5 . In at least general terms, the flux enters yoke  1060 B in a vertical direction, and then arcs to a generally horizontal direction to leave the yoke  1060 B and enter arm  1054 A of bobbin assembly  1054  across radial air gap  1072 A. In this regard, radial air gap  1072 A generally corresponds to the radial air gap between yoke  560 B and bobbin  554 A of  FIG. 5 . The flux then arcs from the horizontal direction to the vertical direction to flow into yoke  1060 A across axial air gap  470 A. (It is noted that the just described flux flows would be reversed for magnets having an opposite polarity than that which would result in the just described flow. In some embodiments any direction of magnetic flux flow can be utilized, providing that the teachings detailed herein and/or variations thereof can be practiced.) 
     It is noted that in the embodiment of  FIG. 10 , a number of the components are depicted as being symmetrical and/or are identical to one another (albeit some are reversed). However, in other embodiments the configurations of the components can be varied. By way of example only and not by way of limitation, because of the presence of radial air gap  1072 A at the “top” of the actuator and the absence of such an air gap at the “bottom” of the actuator (while there is a gap, the gap is relatively much larger than the radial air gap  1072 A at the top (although in other embodiments, this is not the case) and little to no magnetic flux flows through that gap (instead the flux flows through the spring), and thus it is not an air gap), there may be utilitarian value in utilizing a permanent magnet  1058 A that is stronger than permanent magnet  1058 B and/or utilizing a yoke  1060 B that is different from yoke  1060 C, etc., at least if such results in a balanced actuator. Indeed, in some embodiments, the bottom yoke  1060 C might be eliminated, and an elongated permanent magnet  1058 B and/or the geometry of yoke  1060 A being substituted in its place. With regard to the latter scenario, while the embodiment of yoke  1060 A is depicted as being symmetrical, other embodiments can include a yoke that is not symmetrical, at least in order to compensate for any flux path discrepancies resulting from utilizing the spring  656  on the bottom and the radial air gap  1072 A on the top. 
     It is noted that the distance spanning the radial air gap  1060 B can be set during design so as to result in a utilitarian balanced actuator. Alternatively, or in addition to this, the properties of the spring  656  can be set during design to achieve such a balanced actuator. (Exemplary properties of the spring  656  that can be set during design are described below.) In this regard, owing to the fact that there is no corresponding radial air gap at the bottom of the actuator, in an exemplary embodiment, there is a relationship between the distance of the air gap  1072 A and the thickness of the spring  656  that exists such that with respect to other parameters, a balance actuator is achieved. 
     While the embodiment of  FIG. 10  includes a radial air gap located at the top but not at the bottom, in an alternative embodiment the radial air gap and the corresponding componentry is located at the bottom instead of the top (and the spring and corresponding componentry is located at the top). 
     As noted above, the embodiment of  FIG. 10  utilizes yokes positioned at both the north and south Poles of the permanent magnets, as opposed to the embodiment of  FIG. 6A , which utilizes a yoke only at the north or south poles of the permanent magnets. In an exemplary embodiment, yokes can be positioned on both sides of the permanent magnets (i.e., interposed between the permanent magnets and the respective springs, along with a yoke (or more than one yoke) interposed between the two permanent magnets. Any configuration and/or flux path flow that can be utilized to practice embodiments detailed herein and/or variations thereof can be utilized in some embodiments. 
     Referring back to  FIG. 6A , because of the elimination of corresponding air gaps via use of springs  656  and  657  to close the static magnetic flux, the tendency of such eliminated air gaps to collapse is correspondingly effectively eliminated, and, in an exemplary embodiment, the spring constant need not be as high as might be the case in embodiments that utilize four axial air gaps, such as that detailed above with respect to  FIG. 5  and variations thereof. 
     As can be seen from the embodiments illustrated in the figures, all permanent magnets of counterweight assembly  655  that are configured to generate the static magnetic fluxes  880  and  884  are located to the sides of the bobbin assembly  655 . Along these lines, such permanent magnets may be annular permanent magnets with respective interior diameters that are greater than the maximum outer diameter of the bobbin  654 A, when measured on the plane normal to the direction (represented by arrow  900 A in  FIG. 9A ) of the generated substantial relative movement of the counterweight assembly  655  relative to the bobbin assembly  654 , as illustrated in  FIGS. 9A and 9B . Conversely, in an alternate embodiment, some or all of the permanent magnets of counterweight assembly  655  that are configured to generate the static magnetic fluxes are located above and/or below the bobbin assembly  655 . 
     In some embodiments, the configuration of the counterweight assembly  655  reduces or eliminates the inaccuracy of the distance (span) between faces of the components forming the air gaps that exists due to the permissible tolerances of the dimensions of the permanent magnets. In this regard, in some embodiments, the respective spans of the axial air gaps  770 A and  770 B, when measured when the bobbin assembly  654  and the counterweight assembly  655  are at the balance point, are not dependent on the thicknesses of the permanent magnets  658 A and  658 B as compared to the embodiment of  FIG. 5  and/or variations thereof, all other things being equal. 
     It is noted that while the surfaces creating the radial air gap of  FIG. 10  are depicted as uniformly flat, in other embodiments, the surfaces may be partitioned into a number of smaller mating surfaces. It is further noted that the use of radial air gap  1072 A permits relative ease of inspection of the radial air gaps from the outside of the vibrating electromagnetic actuator  650 , in comparison to, for example absence of the radial air gap. 
       FIG. 11  depicts an exemplary alternate embodiment of a vibrating actuator, one that is unbalanced, as will now be described. 
       FIG. 11  is a cross-sectional view of a vibrating actuator-coupling assembly  1180 , which can correspond to vibrating actuator-coupling assembly  280  detailed above. Like reference numbers corresponding to elements detailed above will not be addressed. 
     As illustrated in  FIG. 11 , vibrating electromagnetic actuator  1150  includes a bobbin assembly  1154  connected to coupling assembly  640  via spring  656 . Reference numeral  1190  indicates the flexible section of the spring  656 , a section of the spring which flexes because, in this embodiment, it is not directly connected to any component of the bobbin assembly or to any component of the yoke  1160 . It is noted that in some embodiments, yoke  1160  can flex to a certain degree, and thus those sections of spring  655  that are connected to the flexing portions of yoke  1160  also flex. Accordingly, section  1190  can extend into the section attached to yoke  1160  in some embodiments. It can be seen that mass  670  is attached to bobbin  1154 A of bobbin assembly  1154 . In the embedment of  FIG. 11 , the bobbin assembly  1154  also functionally serves as a counterweight assembly. (It is noted that the embodiments detailed above likewise can be configured in alternate variations such that the bobbin assembly, or at least portions thereof, functionally correspond to the counterweight.) 
     Spring  656  permits the bobbin assembly  1154  and mass  670  to move relative to yoke  1160  and coupling assembly  640 , which is connected thereto, upon interaction of a dynamic magnetic flux, produced by bobbin assembly  1154  upon energizement of coils  1154 B. More particularly, a dynamic magnetic flux is produced by energizing coil  1154 B with an alternating current. The dynamic magnetic flux is not shown, but it parallels the static magnetic flux  1180  produced by permanent magnet  1158 A of the bobbin assembly. That is, in an exemplary embodiment, the dynamic magnetic flux, if depicted, would be located at the same place as the depicted static magnetic flux  1180 , with the exception that the arrow heads would change direction depending on the alternation of the current. 
     In this regard, bobbin assembly  1154  is both a static magnetic field generator and a dynamic magnetic field generator. 
     The functionality and configuration of the elements of the embodiment of  FIG. 11  (and  FIG. 12  detailed below) can correspond to that of the corresponding functional elements of one or more or all of the other embodiments detailed herein. 
     Vibrating electromagnetic actuator  1150  includes a single axial air gap  1170  that is located between bobbin assembly  1154  and yoke  1160 . In this regard, the spring  656  is utilized to close both the static and dynamic magnetic flux, and both fluxes are closed through the same air gap  1170  (and thus a single air gap  1170 ). 
     It is noted that the directions and paths of the static magnetic fluxes (and thus by description above, the dynamic magnetic fluxes) are representative of some exemplary embodiments, and in other embodiments, the directions and/or paths of the fluxes can vary from those depicted. 
     As noted above, coupling assembly  640  is attached (either directly or indirectly) to yoke  1160 . Without being bound by theory, yoke  1160 , in some embodiments, channels the fluxes into and/or out of (depending on the alternation of the current and/or the polarity direction of the permanent magnet  1158 A) the bobbin assembly so as to achieve utilitarian functionality of the vibrating electromagnetic actuator  1150 . It is noted that in an alternate embodiment, yoke  1160  is not present (i.e., the fluxes enter and/or exit or at least substantially enter and/or exit the spring  656  from/to the bobbin assembly  1154 ). 
     As can be seen, the flux enters and/or exits magnet  1158 A directly from or to spring  656 . Conversely in an alternate embodiment this is not the case. In this regard,  FIG. 12  depicts an alternate embodiment of a vibrating electromagnetic actuator  1250  of a vibrating actuator-coupling assembly  1280 , where the fluxes enter and/or exit a further axial air gap  1171 . Reference numeral  1290  indicates the flexible section of the spring  655 , corresponding to flexible section  1190  detailed above. 
     Still with reference to  FIG. 12 , it can be seen that the gap between the yoke  1160  and the bobbin  1254  is smaller than the gap between spring  656  and permanent magnet  1258 A. This is done to account for tilting of the bobbin assembly/counterweight assembly relative to the coupling assembly  640 . In this regard, the distance moved as a result of relative tilting between the assemblies of the vibrating actuator-coupling assembly  1280  will typically be greater with increasing distance away from the longitudinal axis. In this regard, the larger gap between the permanent magnet  1258 A and spring  656  as compared to the gap between the yoke  1160  and the bobbin  1254  accounts for this phenomenon, thus reducing and/or eliminating the likelihood that these components contact each other during tilting. In some exemplary embodiments, in an un-energized actuator, the gap between the yoke  1160  and the bobbin  1254  is about 60 microns, and the gap between the spring  656  and the permanent magnet  1258 A is about 250 microns. That said, in an alternate embodiment, because of the resilient nature of the spring  656 , in an exemplary embodiment, the width of the gaps may be equal. Without being bound by theory, in an exemplary embodiment, the resiliency of the spring  656  reduces and/or eliminates potential deleterious effects of contact between the spring and the permanent magnet. Of course, with respect to the embodiment of  FIG. 11 , where the permanent magnet  1158 A is secured to spring  656 , there is no gap between these two components at all. Accordingly, in an exemplary embodiment, there is a transducer where there is no meaningful discrepancy between the widths of the air gaps during operation thereof. 
     In view of the above, embodiments detailed herein and or variations thereof can enable a method of transducing energy. In an exemplary embodiment of this method there is the action of moving the counterweight assembly  655  relative to the bobbin assembly  654 A in an oscillatory manner. This action is such that during the movement of the two assemblies relative to one another, there is interaction of a dynamic magnetic flux and a static magnetic flux (e.g. at the air gaps). An exemplary method further includes the action of directing the static magnetic flux along a closed circuit that in its totality extends across one or more air gaps. In an exemplary embodiment, this action is such that all of the one or more air gaps have respective widths that vary while the static magnetic flux is so directed and interacting with the dynamic magnetic flux. This action is further qualified by the fact that if there is more than one air gap present in the closed-circuit (e.g., the embodiment of  FIG. 12 , as compared to for example the embodiment of  FIG. 6A  or the embodiment of  FIG. 11 ), a rate of change of variation of the width of one of the air gaps of the closed-circuit is different from that of at least one of the other air gaps of the closed-circuit. Along these lines, it can be seen from  FIG. 12  that the air gap between the spring and the permanent magnet will vary in width at a different rate than that of the air gap between the yoke and the bobbin. This is in contrast to, for example, the embodiment of  FIG. 5 , where the closed static magnetic flux crosses two air gaps, where the width of one of the air gaps (i.e. the radial air gap) does not vary while the static magnetic flux interacts with the dynamic magnetic flux. Further, in an exemplary embodiment, the amount of width variation of the air gap between the spring and the permanent magnet will vary by a different amount than that of the air gap between the yoke and the bobbin. 
     At least some embodiments detailed herein and/or variations thereof enable a method to be practiced where static magnetic flux is directed along a path that extends through a solid body while the solid body flexes (e.g., the embodiment of  FIGS. 6A, 10, 11 and 12 ). 
     It is noted that some exemplary embodiments include any device, system and/or method where static and/or magnetic flux travels through a spring in a manner that eliminates an air gap due to the use of the spring in such a manner. Along these lines, it is noted that unless otherwise specified, any of the specific teachings detailed herein and/or variations thereof can be applicable to any of the embodiments detailed herein and/or variations thereof unless otherwise specified. 
     The elimination of some or all of the radial and/or axial air gaps via the use of, for example, a spring to close the magnetic flux, can make the actuator more efficient as compared to other actuators that instead utilize corresponding radial and/or axial air gaps. In this regard, air gaps can present substantial magnetic reluctances. The relative reduction and/or elimination of such magnetic reluctance to make the actuator more efficient relative to an actuator utilizing such air gaps. In an exemplary embodiment, this can permit smaller permanent magnets to be used/weaker permanent magnets to be used while obtaining the same efficacy as an actuator utilizing such air gaps, all other things being equal. In an exemplary embodiment, the mass of the permanent magnets and/or strength of the permanent magnets, all other things being equal, is about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or about 95%, and/or is about any value or range of values therebetween in about 1% increments (e.g., 61%, 66% to 94%, etc.) of that for an actuator utilizing such air gaps, all other things being equal. 
     Different performance parameters can be obtained by varying design parameters of a given actuator, and thus obtaining an actuator having such design parameters. For example, varying the mechanical stiffness of the springs (k) varies the resonance frequency of the actuator. Varying the magnetic flux conductive properties of the springs varying the amount of magnetic flux that can be conducted by the springs. In some exemplary embodiments of balance electromagnetic actuators detailed herein and/or variations thereof, one or more or all of the springs only effectively conduct static magnetic flux. That is, little to no dynamic magnetic flux is conducted by the spring(s) (any dynamic magnetic flux conducted by the springs only amounts to trace amounts of flux). In an exemplary embodiment, the springs are made of a material that have a high saturation flux density, and the magnetic permeability of the material is generally unspecified (e.g. it can be within a range from and including low to high permeability, at least providing that the spring has a sufficiently high saturation flux density to accept the static magnetic flux, which does not vary, in contrast to the dynamic magnetic flux). 
     Without being bound by theory, it is believed that in at least some exemplary embodiments, embodiments of the electromagnetic transducers utilizing springs as flux conduits detailed herein and/or variations thereof can be designed based on an understanding that while the spring(s) constitute bottlenecks for the static magnetic flux, these are bottlenecks that do not change with performance of the transducer. That is, designing the actuators can be optimized and rendered more efficient than those of, for example, the embodiment of  FIG. 5  and variations thereof, provided that this understanding is taken into account. Along these lines, because a given flux saturation of the spring does not vary with movement of the counterweight assembly (i.e. changing widths of the axial air gaps), once the amount of expected static magnetic flux is determined, the spring can be designed to account for the static magnetic flux, with the knowledge that the expected static magnetic flux will not vary with respect to operational extremes of the transducer. Put another way, the static magnetic flux generated by the permanent magnets is constant. It is the fact that the path has variables that vary with operation of the transducer (i.e., the air gaps) that impart uncertainty into expected static magnetic flux values. By replacing at least some of the air gaps with the springs, this uncertainty is reduced. That is, the amount of static magnetic flux that a given spring of a given geometry can accept and still enable the transducer to operate in a utilitarian manner is fixed. It does not change with operation of the transducer. Accordingly, any need to address this “uncertainty” during the design process is not present with respect to transducers utilizing springs to close the static magnetic flux. Additionally, without being bound by theory, by saturating the springs with static magnetic flux, dynamic magnetic flux is less likely to travel therethrough, and this it is more likely to retained sandwiched between the springs. 
     Moreover, the use of springs as conduits of the static magnetic flux avoid the possibility of “air gap collapse” because there is no air gaps to collapse. In this regard, the magnetic reluctance through a spring is generally constant, and, in contrast, the reluctance across an air gap varies with the width of the air gap. Still further, with respect to radial air gaps that have widths that do not vary, there is still a change in the reluctance across such gaps (e.g., due to imperfections in the alignment of the counterweight assembly and the bobbin assembly, movement away from the alignment during movement of the counterweight assembly upward and/or downward relative to the bobbin assembly, etc.). Accordingly, the reluctance across a spring does not change as much as the change reluctance across even a radial air gap. 
     In some exemplary embodiments, the effective spring thickness and/or the effective spring radius are varied during design so as to obtain utilitarian spring stiffnesses and utilitarian spring magnetic flux property. By effective spring thickness, it is meant the thickness of a cross-section of the flexible portion of the spring lying on a plane parallel to and lying on the longitudinal axis of the actuator (i.e., the axis aligned with the direction of movement of the bobbin assembly (counterweight assembly) relative to the bobbin assembly). By effective spring radius, it is meant the distance from the longitudinal axis to the location at which the spring contacts structure of the bobbin/counterweight assembly (where it no longer flexes), adjusted for the fact that the area around the longitudinal axis does not flex (due to, for example, the coupling  640  and/or the yoke  1160 ). That is, the term “effective” addresses the fact that there are portions of the spring that are present but do not flex during energizement of the actuator. By varying the effective spring thickness and the effective spring radius, a wide range of spring stiffnesses can be achieved for a wide range of magnetic fluxes that travel through the spring. In this regard, if a spring thickness of, for example 0.3 mm is utilitarian to achieve a utilitarian magnetic flux therethrough, the effective radius of the spring can be varied (e.g., by varying the distance of the flexible section  1190  during design to obtain a utilitarian spring stiffness for that thickness without substantially impacting the utilitarian nature of the magnetic flux, and visa-versa. 
     It is noted at this time that in an exemplary embodiment, the thicknesses of the springs of the embodiments detailed herein and/or variations thereof can be about 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm or about 0.4 mm or any value or range of values between these values in 0.01 mm increments (e.g., about 0.22 mm, about 0.17 mm to about 0.33 mm, etc.). Any spring thickness that can enable the teachings detailed herein and or variations thereof to be practiced can be utilized in some embodiments. Further in this regard any spring geometry can be utilized as well. Along these lines, while a spring having a circular circumference has been the focus of the embodiments detailed herein, springs having a square circumference, a rectangular circumference, or an oval circumference etc., can be utilized in some embodiments. 
     It is noted that in an exemplary embodiment, the diameters of the electromagnetic transducers according to the embodiments herein and/or variations thereof can be about 8 mm with respect to the balance transducers and about 11 mm with respect to the unbalanced transducers. In some exemplary embodiments, the diameters of the electromagnetic transducers can be about 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm or about 13 mm in length and/or a length of any value or range of values therebetween in about 0.1 mm increments (e.g., about 7.8 mm, 6.7 mm to about 11.2 mm, etc.). 
     It further noted that in an exemplary embodiment, the seismic mass of the transducers detailed herein and or variations thereof, totals about 6 g, and the amount of that mass made up by the permanent magnets corresponds to about 0.3 g. By seismic mass, it is meant the mass of the components that move relative to the portions of the transducer that are fixed to the much more massive object into which were from which the vibrations travel. Accordingly in an exemplary embodiment, the ratio of the mass of the permanent magnets to the total seismic mass of the transducer is about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or about 0.10 or any value or range of values therebetween in about 0.002 increments (e.g., about 0.053, about 0.041 to about 0.064, etc.). 
     Without being bound by theory, in an exemplary embodiment, utilization of the springs as a conduit for the magnetic flux enables the permanent magnets to be made smaller, as the flux generated by those permanent magnets is more efficiently conducted through the components of the transducer. In this regard, air gaps present a feature that frustrates, to an extent, the efficient conduction of the flux through the transducer. The elimination of the air gaps by replacement thereof by the springs enables smaller (e.g., less powerful magnets to be used) as compared to the transducer that utilizes air gaps instead of springs to close the magnetic field, all other things being. 
     An exemplary embodiment includes placing holes through one or more or all of the springs of the actuator to “fine-tune” the stiffness and/or magnetic flux properties of the spring(s). Accordingly, an exemplary embodiment includes springs having holes (circular, oval, arcuate etc.) therethrough. Some embodiments of these exemplary embodiments include through holes while other embodiments of these exemplary embodiments include tools that do not pass all the way through the spring. Accordingly by varying the depth of these holes, the stiffness and/or magnetic flux properties can be further fine-tuned. It is therefore noted that a method of manufacture of the actuators detailed herein and/or variations thereof includes fine-tuning the stiffness and/or magnetic flux properties of a spring along these lines. 
     In at least some exemplary embodiments, the actuators in general, and the springs in particular, are configured such that during all operating conditions (e.g., such as those conditions pertaining to the operation of a bone conduction device to talk a hearing percept), the springs remain magnetically saturated. In an exemplary embodiment, this enables the magnetic flux passing through the springs to be substantially if not completely independent of the respective magnetic field. Accordingly, an exemplary embodiment is such that the magnetic flux through the springs does not substantially vary with variations in the axial air gap size during operation (e.g., during utilization of the actuator in a bone conduction device to invoke a hearing percept). In an exemplary embodiment, this provides utility in that the risk of air gap collapse is reduced as compared to actuators that do not have such features, where air gap collapse can occur when the magnetic force is stronger than the restoring mechanical spring force. 
     In an exemplary embodiment, the spring is made out of materials that have a relatively high yield strength or otherwise can withstand the stresses exposed to the spring during normal operation of the vibrating actuators (e.g. such as utilization of the actuators in a bone conduction device to invoke a hearing percept), and also a relatively high magnetic induction. By way of example only and not by way of limitation, materials having yield stresses of about 400, 450, 475, 500, 515, 525, 530, 535, 540, 545, 550, 555, 560, 565, 570, 575, 580, 600, 625, 650 and/or about 700 MPa and or any value or range of values therebetween in at least 0.1 MPa increments (e.g., 523.7 MPa, 515-585 MPa, etc.) can be used for the spring. Also by way of example only and not by way of limitation, materials having magnetic flux saturation of about 0.5 T, 0.6 T, 0.7 T, 0.8 T, 0.9 T, 1.0 T, 1.1 T, 1.2 T, 1.3 T, 1.4 T, 1.5 T, 1.6 T, 1.7 T, 1.8 T, 1.9 T, 2.0 T, 2.1 T, 2.2 T, 2.3 T, 2.4 T and/or 2.5 T and/or any value or range of values therebetween in at least 0.01 T increments can be used for the spring. An exemplary material is Hiperco® Alloy 27. 
     It is noted that in some embodiments, the static flux through the springs  656  and/or  657  is substantially constant (including constant) through the range of movements of the counterweight assembly  655  relative to the bobbin assembly  654 . Without being bound by theory, it is believed that this is due to magnetic flux saturation, where by limiting the flux density, the magnetic force is correspondingly limited. This can prevent and/or otherwise reduce the risk of axial air gap collapse relative to a transducer utilizing air gaps to close the static magnetic flux, all other things being equal. 
     In an exemplary embodiment, the springs are configured and dimensioned such that the reluctance across one spring is effectively the same as the reluctance across the other spring through the range of movements of the counterweight assembly relative to the bobbin assembly. In an exemplary embodiment utilizing a spring and a radial air gap (e.g., according to the embodiment of  FIG. 10 ), the spring and the radial air gap are configured and dimensioned such that the reluctance across the spring is effectively the same as the reluctance across the air gap through the range of movements of the counterweight assembly relative to the bobbin assembly. Accordingly, to the extent that reluctance varies in some embodiments, in some embodiments, as reluctance varies in one spring, the reluctance will vary in the same way at the other spring. Also accordingly, to the extent that reluctance varies in some embodiments, in some embodiments, as reluctance varies in one spring, the reluctance will vary in the same way at the radial air gap, and visa-versa. 
     While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.