Patent Publication Number: US-10321217-B2

Title: Vibration transducer connector providing indication of worn state of device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 15/254,503, filed Sep. 1, 2016, which is hereby incorporated by reference in its entirety and for all purposes. 
    
    
     BACKGROUND 
     Wearable computing devices, such as head-wearable devices, ear-piece devices, smart watches, glasses-style and other head-mountable devices, body-worn health monitors, and smart headphones or headsets, are becoming increasingly common. 
     This application is a continuation of U.S. application Ser. No. 14/534,980, filed Nov. 6, 2014, which claims priority to U.S. Provisional Application No. 61/933,060, filed Jan. 29, 2014, both of which are hereby incorporated by reference in their entirety and for all purposes. 
     In some cases, a wearable device may include and/or couple to components that are used to provide audio to a wearer. Such components include ear buds, loudspeakers, and bone conduction speakers. 
     Additionally or alternatively, some wearable devices include sensory systems that allow a wearable device to determine whether or not it is being worn. Examples of such sensory systems include capacitive touch sensors to determine when the wearable is in contact with a wearer, proximity sensors to determine when the wearable device is near to or contacting the wearer, and inertial sensors to detect motion characteristic of the wearable device being worn. 
     SUMMARY 
     Described herein are embodiments that relate to or take the form of bone-conduction speaker (also referred to as a “vibration transducer” or “bone conduction transducer”), which is movably attached to a wearable device in a manner that provides an indication as to whether or not the device is being worn. In particular, a BCT may be attached to a wearable device by a movable member, which also includes a conductive pad. The conductive pad may be arranged opposite of an exposed terminal for an on-head detection (OHD) circuit arranged within the frame of the wearable device. The OHD circuit is configured as an open circuit, which can be completed when a conductor contacts the exposed terminal. Accordingly, the moveable member is arranged such that its conductive pad moves into contact with and completes the OHD circuit when the device is donned (i.e., worn), and is separated from the OHD circuit when the device is doffed (i.e., not worn). Accordingly, the state of the OHD circuit (either open or closed) may indicate whether or not the device is being worn. 
     In one aspect, an example apparatus includes: (a) a frame component for a wearable device, wherein the frame component comprises a contact feature for a circuit at least partially disposed in the frame component; (b) a member movably coupled to the frame component, wherein the member is also coupled to a vibration transducer; (c) at least one conductive pad coupled to the member and aligned with the contact feature in the frame component; and (d) a first spring and a second spring extending from the member, wherein the first and the second spring have a first and a second spring constant, respectively. The first spring and the second spring interface with the frame component, such that a difference between the first spring constant and the second spring constant results in a resting position of the member in which the conductive pad is separated from the contact feature, thereby opening the circuit. Further, when the wearable device is worn, the member is positioned so as to press the vibration transducer against the wearer and compress the first spring, thereby moving the conductive pad into contact with the contact feature and completing the circuit 
     In another aspect, an example apparatus includes: (a) a member coupled to a vibration transducer, wherein the member is also configured to couple to a frame component of a wearable device comprising a contact feature for a circuit; (b) at least one conductive pad coupled to the member and arranged to align with the contact feature in the frame component; and (c) a first spring and a second spring extending from the member, wherein the first and the second spring have a first and a second spring constant, respectively. The member is configured such that, when the member is coupled to the frame component, the first spring and the second spring interface with the frame component such that a difference between the first spring constant and the second spring constant results in a resting position of the member in which the conductive pad is separated from the contact feature, thereby opening the circuit. Further, when the wearable device is worn, the member presses the vibration transducer against the wearer and compresses the first spring, thereby moving the conductive pad into contact with the contact feature and completing the circuit. 
     In a further aspect, an example wearable device includes: (a) a frame comprising a contact feature for a circuit disposed therein; (b) a member movably coupled to the frame component; (c) a vibration transducer coupled to the member; (d) at least one conductive pad coupled to the member and aligned with the contact feature in the frame component; (e) a first spring and a second spring extending from the member, wherein the first and the second spring have a first and a second spring constant, respectively. The first spring and the second spring interface with the frame component such that a difference between the first spring constant and the second spring constant results in a resting position of the member in which the conductive pad is separated from the contact feature, thereby opening the circuit. Further, when the wearable device is worn, the member is positioned so as to press the vibration transducer against the wearer and compress the first spring, thereby moving the conductive pad into contact with the contact feature and completing the circuit. Additionally, the wearable device includes a control system (e.g., a processor and program instructions stored in memory) operable to determine when the circuit is closed, and to interpret a determination that the circuit is closed as an indication that the wearable device is being worn. 
     These as well as other aspects, advantages, and alternatives, will become apparent to those of ordinary skill in the art by reading the following detailed description, with reference where appropriate to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates a wearable computing device, according to an exemplary embodiment. 
         FIG. 1B  illustrates another wearable computing device, according to an exemplary embodiment. 
         FIGS. 2A to 2C  show another wearable computing device according to an example embodiment. 
         FIG. 3  is a block diagram showing components of a computing device and a wearable computing device, according to an example embodiment. 
         FIGS. 4A to 4C  are illustrations of a frame component of a wearable device, according to an example embodiment. 
         FIG. 5  is a view of the underside of s frame component to which an example member can be attached, according to an example embodiment. 
         FIG. 6  shows another configuration for a vibration-transducer member on a glasses-style wearable device, according to an example embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary methods and systems are described herein. It should be understood that the word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment or feature described herein as “exemplary” or as an “example” is not necessarily to be construed as preferred or advantageous over other embodiments or features. The exemplary embodiments described herein are not meant to be limiting. It will be readily understood that certain aspects of the disclosed systems and methods can be arranged and combined in a wide variety of different configurations, all of which are contemplated herein. 
     I. OVERVIEW 
     For various reasons, it may be desirable for a wearable computing device, such as an ear-piece device or headset, a glasses-style device, or a watch computing device, to have the ability to determine whether or not it is being worn. Since wearable devices are intended to be worn, the fact that a device is not being worn may serve as an indication that the device is not in use. Therefore, a wearable device may dynamically enable and disable certain power-hungry components and functionality according to whether or not the device is being worn. 
     For example, a wearable device can utilize knowledge of its donned or doffed state to extend the amount of time a wearable device can operate on a single charge of its battery (i.e., to extend its battery life). Specifically, when a wearable device determines that it is not being worn, the wearable device can turn off certain sensors and chipsets, and/or disable certain functions, which are considered unnecessary when the device is not in use. Note that taking such power-saving actions may be referred to as operating in “sleep” mode or a “low-power” mode. 
     As another example, a wearable device may enable security features when it determines it is not being worn. Specifically, if a device determines it is not being worn, this may be interpreted as an indication that the device&#39;s owner is not using, and perhaps is not in possession of, their device. As such, the wearable device may disable certain features and/or functions, and require a user enter authentication information (e.g., a passcode, fingerprint scan, etc.) before these features and/or functions can be utilized again. Note that taking such actions to secure a wearable device may be referred to as “locking” the wearable device. 
     Example embodiments may include or relate to a member having a vibration transducer, which attaches to a wearable device functions as a bone conduction speaker (also referred to as a bone conduction transducer or “BCT”). In addition to providing audio via the BCT, the member may be moveably attached to the wearable device, such that the positioning of the member provides an indication as to whether or not the device is donned (i.e., being worn) or doffed (i.e., not being worn). 
     More specifically, the BCT member may be a modular component, which can be attached to and detached from the frame of a wearable device. In particular, the BCT member may be moveably attached to the frame of the wearable device with a ball-and-socket joint, and may further include two springs that interface with the wearable frame at an attachment location. The springs may have differing spring constants, and may interface with the wearable&#39;s frame in a manner that biases the member to press the BCT against the wearer&#39;s body (and thereby provide audio to the wearer by vibrating the wearer&#39;s bone structure). The corresponding force which the wearer&#39;s body exerts on the BCT may compress the springs and thereby move the member from its natural resting position. 
     Further, the wearable device may include an on-head detection (OHD) circuit. The OHD circuit is a partial (i.e., incomplete) circuit disposed in the frame, which can be completed when a conductive material is brought into contact with its contact feature. Accordingly, an example BCT member may further include a conductive pad that is positioned opposite of the contact feature of the OHD circuit. The conductive pad may be arranged such that: (i) when the BCT is pressed against the wearer and the member moves from its resting position, the conductive pad is pressed against the contact feature, thereby completing the OHD circuit disposed in the frame, and (ii) when the wearable is not being worn and the BCT member returns to its resting position, the conductive pad is separated from the contact feature, such that the OHD circuit is opened. As such, the wearable device may interpret completion of the OHD circuit as an indication that the wearable device is being worn, and may interpret an open OHD circuit as an indication that the device is not being worn. 
     As a specific example, a modular “L-shaped” member may be attached to the side-arm of a glasses-style wearable device. This L-shaped member may be attached at a location on the side-arm that places the BCT behind the wearer&#39;s ear. The member may be removably attached to the wearable frame with a ball-and-socket joint allowing for one-degree of freedom, and may include springs to the front and rear of the joint (e.g., anterior and posterior of the joint). The rear spring may have a greater spring constant than the front spring, such that the member is biased to press the BCT against the back of the wearer&#39;s ear. Without this bias, the upper surface of the member could sit flush against or parallel to the lower surface of the BCT frame. However, because the springs bias the member towards the back of the ear, a rear portion of the member&#39;s upper surface may separate from the BCT frame when the wearable device is not being worn (and the member thus returns to its resting position). 
     Accordingly, a conductive pad may be placed on the rear portion of the member&#39;s upper surface, and an exposed terminal for an on-head detection (OHD) circuit may be located on a lower surface of the wearable device&#39;s frame, opposite of the conductive pad. With this arrangement, the conductive pad separates from the exposed terminal when the device is not being worn (leaving the OHD circuit open), but moves into contact with the exposed terminal when the device is worn (thus completing the OHD circuit). Accordingly, the wearable device may interpret completion of the OHD circuit as an indication that the wearable device is being worn, and vice versa. 
     Notably, the spring interface on an example BCT member may bias the member so as to provide a BCT having a comfortable but snug fit against the wearer. Thus, an example BCT member may help to balance the desire for high-quality audio quality with desire for an ergonomic fit. Advantageously, by adding the conductive pad and exposed contact feature for an open circuit in the wearable frame, the mechanics that provide a desirable fit for a BCT can also be utilized to obtain an on-head detection signal. 
     In a further aspect of some embodiments, the springs on a BCT member can also serve as part of an audio-signal path to the BCT. For example, the springs that provide the interface between the BCT member and the wearable frame may be connected to the input terminals of the BCT at one end of the member, and may contact audio terminals on the BCT frame at the other end of the member. Configured as such, the springs may relay an audio signal from the wearable device&#39;s audio source to the BCT. This arrangement may be particularly useful in a modular embodiment, since attaching and detaching the BCT member from the wearable from will also connect and disconnect the wearable device&#39;s audio source from the BCT. 
     In a further aspect, a wearable device, such as a glasses-style device, may have multiple attachment locations for a modular BCT member. These multiple attachment locations may all be configured to provide the same information regarding whether the device is being worn, and/or may all include audio terminals for relaying audio signals to the BCT via the BCT member&#39;s interfacing springs. By providing multiple attachment points, a wearable device may help users with differently shaped bodies achieve a better fit. 
     II. ILLUSTRATIVE WEARABLE COMPUTING DEVICES 
     Systems and devices in which exemplary embodiments may be implemented will now be described in greater detail. However, an exemplary system may also be implemented in or take the form of other devices, without departing from the scope of the invention. 
     An exemplary embodiment may be implemented in a wearable computing device that facilitates voice-based user interactions. However, embodiments related to wearable devices that do not facilitate voice-based user interactions are also possible. An illustrative wearable device may include an ear-piece with a bone-conduction speaker (e.g., a bone conduction transducer or “BCT”). A BCT may be arranged so as to contact the wearer and vibrate the wearer&#39;s bone structure when driven by an audio signal. The vibrations travel through the wearer&#39;s bone structure to the wearer&#39;s middle ear, such that the brain interprets the vibrations as sounds. The wearable device may take the form of an earpiece with a BCT, which can be tethered via a wired or wireless interface to a user&#39;s phone, or may be a standalone earpiece device with a BCT. Alternatively, the wearable device may be a glasses-style wearable device that includes one or more BCTs and has a form factor that is similar to traditional eyeglasses. Other types of wearable devices are also possible. 
       FIG. 1A  illustrates a wearable computing device  102 , according to an exemplary embodiment. In  FIG. 1A , the wearable computing device  102  takes the form of glasses-style wearable computing device. Note that wearable computing device  102  may also be considered an example of a head-mountable device (HMD), and thus may also be referred to as an HMD  102 . It should be understood, however, that exemplary systems and devices may take the form of or be implemented within or in association with other types of devices, without departing from the scope of the invention. As illustrated in  FIG. 1A , the wearable computing device  102  comprises frame elements including lens-frames  104 ,  106  and a center frame support  108 , lens elements  110 ,  112 , and extending side-arms  114 ,  116 . The center frame support  108  and the extending side-arms  114 ,  116  are configured to secure the wearable computing device  102  to a user&#39;s head via placement on a user&#39;s nose and ears, respectively. 
     Each of the frame elements  104 ,  106 , and  108  and the extending side-arms  114 ,  116  may be formed of a solid structure of plastic and/or metal, or may be formed of a hollow structure of similar material so as to allow wiring and component interconnects to be internally routed through the head-mounted device  102 . Other materials are possible as well. Each of the lens elements  110 ,  112  may also be sufficiently transparent to allow a user to see through the lens element. 
     The extending side-arms  114 ,  116  may each be projections that extend away from the lens-frames  104 ,  106 , respectively, and may be positioned behind a user&#39;s ears to secure the HMD  102  to the user&#39;s head. The extending side-arms  114 ,  116  may further secure the HMD  102  to the user by extending around a rear portion of the user&#39;s head. Additionally or alternatively, for example, the HMD  102  may connect to or be affixed within a head-mountable helmet structure. Other possibilities exist as well. 
     The HMD  102  may also include an on-board computing system  118  and at least one finger-operable touch pad  124 . The on-board computing system  118  is shown to be integrated in side-arm  114  of HMD  102 . However, an on-board computing system  118  may be provided on or within other parts of the head-mounted device  102  or may be positioned remotely from and communicatively coupled to a head-mountable component of a computing device (e.g., the on-board computing system  118  could be housed in a separate component that is not head wearable, and is wired or wirelessly connected to a component that is head wearable). The on-board computing system  118  may include a processor and memory, for example. Further, the on-board computing system  118  may be configured to receive and analyze data from a finger-operable touch pad  124  (and possibly from other sensory devices and/or user interface components). 
     In a further aspect, an HMD  102  may include various types of sensors and/or sensory components. For instance, HMD  102  could include an inertial measurement unit (IMU) (not explicitly shown in  FIG. 1A ), which provides an accelerometer, gyroscope, and/or magnetometer. In some embodiments, an HMD  102  could also include an accelerometer, a gyroscope, and/or a magnetometer that is not integrated in an IMU. 
     In a further aspect, HMD  102  may include sensors that facilitate a determination as to whether or not the HMD  102  is being worn. For instance, sensors such as an accelerometer, gyroscope, and/or magnetometer could be used to detect motion that is characteristic of the HMD being worn (e.g., motion that is characteristic of user walking about, turning their head, and so on), and/or used to determine that the HMD is in an orientation that is characteristic of the HMD being worn (e.g., upright, in a position that is typical when the HMD is worn over the ear). Accordingly, data from such sensors could be used as input to an on-head detection process. Additionally or alternatively, HMD  102  may include a capacitive sensor or another type of sensor that is arranged on a surface of the HMD  102  that typically contacts the wearer when the HMD  102  is worn. Accordingly data provided by such a sensor may be used to determine whether or not the HMD is being worn. Other sensors and/or other techniques may also be used to detect when the HMD is being worn. 
     HMD  102  also includes at least one microphone  146 , which may allow the HMD  102  to receive voice commands from a user. The microphone  146  may be a directional microphone or an omni-directional microphone. Further, in some embodiments, an HMD  102  may include a microphone array and/or multiple microphones arranged at various locations on the HMD. 
     In  FIG. 1A , touch pad  124  is shown as being arranged on side-arm  114  of the HMD  102 . However, the finger-operable touch pad  124  may be positioned on other parts of the HMD  102 . Also, more than one touch pad may be present on the head-mounted device  102 . For example, a second touchpad may be arranged on side-arm  116 . Additionally or alternatively, a touch pad may be arranged on a rear portion  127  of one or both side-arms  114  and  116 . In such an arrangement, the touch pad may arranged on an upper surface of the portion of the side-arm that curves around behind a wearer&#39;s ear (e.g., such that the touch pad is on a surface that generally faces towards the rear of the wearer, and is arranged on the surface opposing the surface that contacts the back of the wearer&#39;s ear). Other arrangements of one or more touch pads are also possible. 
     The touch pad  124  may sense the touch and/or movement of a user&#39;s finger on the touch pad via capacitive sensing, resistance sensing, or a surface acoustic wave process, among other possibilities. In some embodiments, touch pad  124  may be a one-dimensional or linear touchpad, which is capable of sensing touch at various points on the touch surface, and of sensing linear movement of a finger on the touch pad (e.g., movement forward or backward along the side-arm  124 ). In other embodiments, touch pad  124  may be a two-dimensional touch pad that is capable of sensing touch in any direction on the touch surface. Additionally, in some embodiments, touch pad  124  may be configured for near-touch sensing, such that the touch pad can sense when a user&#39;s finger is near to, but not in contact with, the touch pad. Further, in some embodiments, touch pad  124  may be capable of sensing a level of pressure applied to the pad surface. 
     In a further aspect, earpiece  140  and  141  are attached to side-arms  114  and  116 , respectively. Earpieces  140  and  141  can each include a BCT  142  and  143 , respectively. Each earpiece  140 ,  141  may be arranged such that when the HMD  102  is worn, each BCT  142 ,  143  is positioned to the posterior of a wearer&#39;s ear. For instance, in an exemplary embodiment, an earpiece  140 ,  141  may be arranged such that a respective BCT  142 ,  143  can contact the auricle of both of the wearer&#39;s ear. Other arrangements of earpieces  140 ,  141  are also possible. Further, embodiments with a single earpiece  140  or  141  are also possible. 
     In an exemplary embodiment, a BCT, such as BCT  142  and/or BCT  143 , may operate as a bone-conduction speaker. For instance, a BCT may be implemented with a vibration transducer that is configured to receive an audio signal and to vibrate a wearer&#39;s bone structure in accordance with the audio signal. More generally, it should be understood that any component that is arranged to vibrate a wearer&#39;s bone structure may be incorporated as a bone-conduction speaker, without departing from the scope of the invention. 
     In a further aspect, HMD  102  may include at least one audio source (not shown) that is configured to provide an audio signal that drives BCT  142  and/or BCT  143 . For instance, in an exemplary embodiment, an HMD  102  may include an internal audio playback device such as an on-board computing system  118  that is configured to play digital audio files. Additionally or alternatively, an HMD  102  may include an audio interface to an auxiliary audio playback device (not shown), such as a portable digital audio player, a smartphone, a home stereo, a car stereo, and/or a personal computer, among other possibilities. In some embodiments, an application or software-based interface may allow for the HMD  102  to receive an audio signal that is streamed from another computing device, such as the user&#39;s mobile phone. An interface to an auxiliary audio playback device could additionally or alternatively be a tip, ring, sleeve (TRS) connector, or may take another form. Other audio sources and/or audio interfaces are also possible. 
     Further, in an embodiment with two ear-pieces  140  and  141 , which both include BCTs, the ear-pieces  140  and  141  may be configured to provide stereo audio. However, non-stereo audio is also possible in devices that include two ear-pieces. 
     Note that in the example shown in  FIG. 1A , HMD  102  does not include a graphical display.  FIG. 1B  shows another wearable computing device  152  according to an example embodiment, which is similar to the HMD shown in  FIG. 1B  but includes a graphical display. In particular, the wearable computing device shown in  FIG. 1B  takes the form of a glasses-style HMD  152  with a near-eye display  158 . As shown, HMD  152  may include BCTs  162  that is configured and functions similarly to BCTs  142  and  143 , an onboard computing system  158  that is configured and functions similarly to onboard computing system  118 , and a microphone  176  that is configured and functions similarly to microphone  146 . HMD  152  may additionally or alternatively include other components, which are not shown in  FIG. 1B . 
     HMD  152  includes a single graphical display  158 , which may be coupled to the on-board computing system  158 , to a standalone graphical processing system, and/or to other components of HMD  152 . The display  158  may be formed on one of the lens elements of the HMD  152 , such as a lens element described with respect to  FIG. 1A , and may be configured to overlay computer-generated graphics in the wearer&#39;s field of view, while also allowing the user to see through the lens element and concurrently view at least some of their real-world environment. (Note that in other embodiments, a virtual reality display that substantially obscures the user&#39;s view of the physical world around them is also possible.) The display  158  is shown to be provided in a center of a lens of the HMD  152 , however, the display  158  may be provided in other positions, and may also vary in size and shape. The display  158  may be controllable via the computing system  154  that is coupled to the display  158  via an optical waveguide  160 . 
     Other types of near-eye displays are also possible. For example, a glasses-style HMD may include one or more projectors (not shown) that are configured to project graphics onto a display on an inside surface of one or both of the lens elements of HMD. In such a configuration, the lens element(s) of the HMD may act as a combiner in a light projection system and may include a coating that reflects the light projected onto them from the projectors, towards the eye or eyes of the wearer. In other embodiments, a reflective coating may not be used (e.g., when the one or more projectors take the form of one or more scanning laser devices). 
     As another example of a near-eye display, one or both lens elements of a glasses-style HMD could include a transparent or semi-transparent matrix display, such as an electroluminescent display or a liquid crystal display, one or more waveguides for delivering an image to the user&#39;s eyes, or other optical elements capable of delivering an in focus near-to-eye image to the user. A corresponding display driver may be disposed within the frame of the HMD for driving such a matrix display. Alternatively or additionally, a laser or LED source and scanning system could be used to draw a raster display directly onto the retina of one or more of the user&#39;s eyes. Other types of near-eye displays are also possible. 
     Generally, it should be understood that an HMD and other types of wearable devices may include other types of sensors and components, in addition or in the alternative to those described herein. Further, variations on the arrangements of sensory systems and components of an HMD described herein, and different arrangements altogether, are also possible. 
       FIGS. 2A to 2C  show another wearable computing device according to an example embodiment. More specifically,  FIGS. 2A to 2C  shows an earpiece device  200 , which includes a frame  202  and a behind-ear housing  204 . As shown in  FIG. 2B , the frame  202  is curved, and is shaped so as to hook over a wearer&#39;s ear  250 . When hooked over the wearer&#39;s ear  250 , the behind-ear housing  204  is located behind the wearer&#39;s ear, For example, in the illustrated configuration, the behind-ear housing  204  is located behind the auricle, such that a surface  252  of the behind-ear housing  204  contacts the wearer on the back of the auricle. 
     Note that the behind-ear housing  204  may be partially or completely hidden from view, when the wearer of earpiece device  200  is viewed from the side. As such, an earpiece device  200  may be worn more discreetly than other bulkier and/or more visible wearable computing devices. 
     Referring back to  FIG. 2A , the behind-ear housing  204  may include a BCT  225 . Note that BCT  225  is provided as an example of a BCT generally. While the BCT configuration shown in  FIGS. 2A to 2C  differs from those described later in reference to  FIGS. 4A to 6 , it should be understood that the BCT functionality described in reference to BCT  225  may apply equally to BCTs configured as shown in  FIGS. 4A to 6 , and to other BCT configurations as well. 
     BCT  225  may be, for example, a vibration transducer or an electro-acoustic transducer that produces sound in response to an electrical audio signal input. As such, BCT  225  may function as a bone-conduction speaker that plays audio to the wearer by vibrating the wearer&#39;s bone structure. Other types of BCTs are also possible. Generally, a BCT may be any structure that is operable to directly or indirectly vibrate the bone structure of the user. 
     As shown in  FIG. 2C , BCT  225  may be arranged on or within the behind-ear housing  204  such that when the earpiece device  200  is worn, BCT  225  is positioned posterior to the wearer&#39;s ear, in order to vibrate the wearer&#39;s bone structure. More specifically, BCT  225  may form at least part of, or may be vibrationally coupled to the material that forms, surface  252  of behind-ear housing  204 . Further, earpiece device  200  may be configured such that when the device is worn, surface  252  is pressed against or contacts the back of the wearer&#39;s ear. As such, BCT  225  may transfer vibrations to the wearer&#39;s bone structure via surface  252 . Other arrangements of a BCT on an earpiece device are also possible, including but not limited to those described in greater detail in reference to  FIGS. 4A to 6B . 
     As further shown in  FIGS. 2A to 2C , the earpiece device  200  also includes a touch pad  210 . The touch pad  210  may arranged on a surface of the behind-ear housing  204  that curves around behind a wearer&#39;s ear (e.g., such that the touch pad is generally faces towards the wearer&#39;s posterior when the earpiece device is worn). Other arrangements are also possible. 
     In some embodiments, touch pad  210  may be a one-dimensional or linear touchpad, which is capable of sensing touch at various points on the touch surface, and of sensing linear movement of a finger on the touch pad (e.g., movement upward or downward on the back of the behind-ear housing  204 ). In other embodiments, touch pad  210  may be a two-dimensional touch pad that is capable of sensing touch in any direction on the touch surface. Additionally, in some embodiments, touch pad  210  may be configured for near-touch sensing, such that the touch pad can sense when a user&#39;s finger is near to, but not in contact with, the touch pad. Further, in some embodiments, touch pad  210  may be capable of sensing a level of pressure applied to the pad surface. 
     In the illustrated embodiment, earpiece device  200  also includes a microphone arm  215 , which may extend towards a wearer&#39;s mouth, as shown in  FIG. 2B . Microphone arm  215  may include a microphone  216  that is distal from the earpiece. Microphone  216  may be an omni-directional microphone or a directional microphone. Further, an array of microphones could be implemented on a microphone arm  215 . Alternatively, a bone conduction microphone (BCM), could be implemented on a microphone arm  215 . In such an embodiment, the arm  215  may be operable to locate and/or press a BCM against the wearer&#39;s face near or on the wearer&#39;s jaw, such that the BCM vibrates in response to vibrations of the wearer&#39;s jaw that occur when they speak. Note that the microphone arm is  215  is optional, and that other configurations for a microphone are also possible. Further, in some embodiments, ear bud  215  may be a removable component, which can be attached and detached from the earpiece device by the user. 
     In some embodiments, a wearable device may include two types of microphones: one or more microphones arranged specifically to detect speech by the wearer of the device, and one or more microphones that are arranged to detect sounds in the wearer&#39;s environment (perhaps in addition to the wearer&#39;s voice). Such an arrangement may facilitate intelligent processing based on whether or not audio includes the wearer&#39;s speech. 
     In some embodiments, a wearable device may include an ear bud (not shown), which may function as a typical speaker and vibrate the surrounding air to project sound from the speaker. Thus, when inserted in the wearer&#39;s ear, the wearer may hear sounds in a discrete manner. Such an ear bud is optional, and may be implemented a removable (e.g., modular) component, which can be attached and detached from the earpiece device by the user. 
     III. ILLUSTRATIVE COMPUTING DEVICES 
       FIG. 3  is a block diagram showing basic components of a computing device  310  and a wearable computing device  330 , according to an example embodiment. In an example configuration, computing device  310  and wearable computing device  330  are operable to communicate via a communication link  320  (e.g., a wired or wireless connection). Computing device  310  may be any type of device that can receive data and display information corresponding to or associated with the data. For example, the computing device  310  may be a mobile phone, a tablet computer, a laptop computer, a desktop computer, or an in-car computer, among other possibilities. Wearable computing device  330  may be a wearable computing device such as those described in reference to  FIGS. 1A, 1B, 2A, 2B, and 2C , a variation on these wearable computing devices, or another type of wearable computing device altogether. 
     The wearable computing device  330  and computing device  310  include hardware and/or software to enable communication with one another via the communication link  320 , such as processors, transmitters, receivers, antennas, etc. In the illustrated example, computing device  310  includes one or more communication interfaces  311 , and wearable computing device  330  includes one or more communication interfaces  331 . As such, the wearable computing device  330  may be tethered to the computing device  310  via a wired or wireless connection. Note that such a wired or wireless connection between computing device  310  and wearable computing device  330  may be established directly (e.g., via Bluetooth), or indirectly (e.g., via the Internet or a private data network). 
     In a further aspect, note that while computing device  310  includes a graphic display system  316 , the wearable computing device  330  does not include a graphic display. In such a configuration, wearable computing device  330  may be configured as a wearable audio device, which allows for advanced voice control and interaction with applications running on another computing device  310  to which it is tethered. 
     Communication link  320  may be a wired link, such as a universal serial bus or a parallel bus, or an Ethernet connection via an Ethernet port. A wired link may also be established using a proprietary wired communication protocol and/or using proprietary types of communication interfaces. The communication link  320  may also be a wireless connection using, e.g., Bluetooth® radio technology, communication protocols described in IEEE 802.11 (including any IEEE 802.11 revisions), Cellular technology (such as GSM, CDMA, UMTS, EV-DO, WiMAX, or LTE), or Zigbee® technology, among other possibilities. 
     As noted above, to communicate via communication link  320 , computing device  310  and wearable computing device  330  may each include one or more communication interface(s)  311  and  331  respectively. The type or types of communication interface(s) included may vary according to the type of communication link  320  that is utilized for communications between the computing device  310  and the wearable computing device  330 . As such, communication interface(s)  311  and  331  may include hardware and/or software that facilitates wired communication using various different wired communication protocols, and/or hardware and/or software that facilitates wireless communications using various different wired communication protocols. 
     Computing device  310  and wearable computing device  330  include respective processing systems  314  and  324 . Processors  314  and  324  may be any type of processor, such as a micro-processor or a digital signal processor, for example. Note that computing device  310  and wearable computing device  330  may have different types of processors, or the same type of processor. Further, one or both of computing device  310  and a wearable computing device  330  may include multiple processors. 
     Computing device  310  and a wearable computing device  330  further include respective on-board data storage, such as memory  318  and memory  328 . Processors  314  and  324  are communicatively coupled to memory  318  and memory  328 , respectively. Memory  318  and/or memory  328  (any other data storage or memory described herein) may be computer-readable storage media, which can include volatile and/or non-volatile storage components, such as optical, magnetic, organic or other memory or disc storage. Such data storage can be separate from, or integrated in whole or in part with one or more processor(s) (e.g., in a chipset). In some implementations, the data storage  104  can be implemented using a single physical device (e.g., one optical, magnetic, organic or other memory or disc storage unit), while in other implementations, the data storage  104  can be implemented using two or more physical devices. 
     Memory  318  can store machine-readable program instructions that can be accessed and executed by the processor  314 . Similarly, memory  328  can store machine-readable program instructions that can be accessed and executed by the processor  324 . 
     In a further aspect, a communication interface  311  of the computing device  310  may be operable to receive a communication from the wearable audio device that is indicative of whether or not the wearable audio device is being worn. Such a communication may be based on sensor data generated by at least one sensor of the wearable audio device. As such, memory  318  may include program instructions providing an on-head detection module. Such program instructions may to: (i) analyze sensor data generated by a sensor or sensors on the wearable audio device to determine whether or not the wearable audio device is being worn; and (ii) in response to a determination that the wearable audio device is not being worn, lock the wearable audio device (e.g., by sending a lock instruction to the wearable audio device) and/or take other responsive actions. 
     IV. ILLUSTRATIVE VIBRATION-TRANSDUCER MEMBERS 
     As noted above, example embodiments may include or take the form of a vibration-transducer member or BCT member, which can be removably or permanently attached a BCT to the frame of a wearable device, and which is configured to provide an electrical and/or mechanical indication as to whether the device is being worn. 
       FIGS. 4A to 4C  illustrate a vibration-transducer member  400  according to an example embodiment. The frame component  401  shown in  FIGS. 4A to 4C  may be part of a wearable device such as those illustrated in  FIGS. 1A to 2C . For instance, frame component  401  may be a side arm of a glasses-style wearable device, such as those shown in  FIGS. 1A and 1B . Member  400  can also be coupled to components of other head wearable devices, or to a wearable device configured to be worn on other parts of the body. 
       FIGS. 4A and 4B  are side-view illustrations of a vibration-transducer member  400  coupled to a frame component  401  of a wearable device, according to an example embodiment.  FIG. 4C  is a simplified illustration of the underside of the same frame component  401 , for which  FIGS. 4A and 4B  show a side view. As such,  FIG. 4C  provides a more direct view of the features of the frame component  401  that couple the frame component to member  400 . 
       FIG. 4A  illustrates a resting position of the member  400  in which an on-head detection (OHD) circuit  422  disposed in the frame component  401  is open (i.e., an incomplete circuit). Herein, the resting position should of the member should be understood to be a position the member returns to when coupled to the frame component, and no object other than those coupling the member to the frame of the wearable device, is applying force to the member. 
     Conversely,  FIG. 4B  illustrates a position of member  400  in which the OHD circuit disposed in the frame component  401  is completed by conductive pad of member  400 . 
     As further shown in  FIG. 4B , when the wearable device is worn, the wearer&#39;s ear  430  may contact BCT  402  and push member  400  into a position so as to complete the OHD circuit, thereby providing an indication that the wearable device is being worn. Further, when the wearable device is not being worn, member  400  may be configured to return to the resting position shown in  FIG. 4A  and open the OHD circuit, thereby providing an indication that the wearable device is not being worn. 
     A. On-Head Detection 
     Referring to  FIG. 4A  in greater detail, member  400  includes or is coupled to a vibration transducer  402 , which may be configured as a bone conduction transducer (BCT). Further, member  400  includes a male connector  418  that is adapted to connect to a female connector  408  of the frame component  401 . In the illustrated example, male connector  418  and female connector  408  provide a ball-and-socket type joint, which allows for movement with one degree of freedom. Configured as such, the member can pivot between the resting position shown in  FIG. 4A  and the position shown in  FIG. 4B . Note that the member  400  may or may not be able to rotate past the positions shown in  FIGS. 4A and 4B , depending upon the particular implementation. 
     It should be understood that male connector  418  is but one example of a connector feature for a BCT member. Other types of connector features for coupling a BCT member to a wearable device are also possible. For instance, in an alternative arrangement, a male connector  418  may be arranged on the frame of the wearable device, and a corresponding female connector may be arranged on the BCT member. Furthermore, the connector feature is not limited to ball-and-socket type joints; other types of joints and connectors may also be utilized to moveably couple the member to the frame of a wearable device. Additionally, connecting features between a BCT member and a wearable frame may allow the member to move with more than one degree of freedom, without departing from the scope of the invention. 
     Member  400  also includes a conductive pad  420 , which is arranged opposite a contact feature  410  of the OHD circuit  422  disposed within frame component  401 . The contact feature may be arranged so as to interrupt (i.e., open) the OHD circuit when not in contact with the conductive pad  420  of member  400 . Correspondingly, the OHD circuit  422  is completed when conductive pad  420  is moved into contact with the contact feature  410  of the OHD circuit  422 . 
     The conductive pad  420  may be implemented in various ways. For instance, the conductive pad  420  may be a carbon pad, conductive foam, or another soft and/or flexible conductive material. However, more rigid conductive materials may also be utilized. Further, while  FIGS. 4A and 4B  show the conductive pad  420  arranged on piece extending from an upper surface of “L-shaped” member  400 , conductive pad could also be arranged on or within the upper surface of L-shaped member  400 . More generally, the size, shape, and/or arrangement of the conductive pad on a vibration-transducer member may vary, depending upon the particular implementation. 
     In an example embodiment, the contact feature  410  may take the form of a resistive copper button pattern, which is exposed to the exterior of the frame component (e.g., on an underside of the side-arm of a glasses-style wearable device). Alternatively, contact feature  410  could be implemented using various types of mechanical, electrical, and/or electromechanical buttons or switches. As yet another alternative, contact feature could be implemented using various types of sensors, such as a proximity sensor or capacitive touch sensor that detects when conductive pad  420  is close to or contacting the frame component. Other implementations of a contact feature for an OHD circuit are also possible. 
     Member  400  is also coupled to a first spring  414  and a second spring  416 . Due to their relative positioning in the illustrated embodiment, springs  414  and  416  may also be referred to as a posterior spring  414  and an anterior spring  416 , respectively. However, this characterization should not be considered limiting. 
     In the illustrated configuration, springs  414  and  416  interface with frame component  401  of the wearable device. That is, springs  414  and  416  make contact with frame component  401  when member  400  is in its resting position (shown in  FIG. 4A ), and remain in contact with the frame component  401  when contact with the wearer&#39;s ear moves member  400  into the position shown in  FIG. 4B . However, in other embodiments, it is possible that one or both springs could separate from the frame component when the member is moved into certain positions. 
     In a further aspect, the posterior spring  414  has a larger spring constant than anterior spring  416 . This difference in spring constants biases member  400  to press vibration transducer  402  against the back of the wearer&#39;s ear, and results in a resting position in which the conductive pad  420  is separated from contact feature  410  of the OHD circuit  422 , as shown in  FIG. 4A . Since the resting position of member  400  separates the conductive pad  420  from contact feature  410 , and since conductive pad  420  is pressed against contact  410  when the wearable device is worn (as shown in  FIG. 4B ), the wearable device interprets completion of the OHD circuit as an indication that the device is being worn. 
     B. Dual Function of Springs as Audio Relays 
     In some embodiments, springs  414  and  416  may be formed from a conductive material, and may be used to transmit audio signals to the BCT. In such embodiments, the frame component  401  may include spring contact terminals  404 ,  406 . The spring contact terminals  404 ,  406  may be formed from or include a conductive material, and may serve to electrically couple the springs  414 ,  416  to an audio source (not shown) via audio signal lines  424 . For instance, spring contact terminals  404  and  406  may be configured as a positive (+) terminal and a negative (−) terminal to a circuit (e.g., audio line  424 ) that carries a signal from an integrated audio source of the wearable device. As such, the wearable device may output an audio signal that drives the vibration transducer  402  via spring contact terminals  404  and  406  and springs  414  and  416 . 
     In some embodiments, spring contact terminals  404 ,  406  may be recessed within detents of a wearable device&#39;s frame. Such detents may be sized and shaped to accept springs  414  and  416 , respectively. Alternatively, spring contact terminals  404 ,  406  may be flush with the surface of the wearable device&#39;s frame. Other configurations of spring contact terminals are also possible. 
     C. PCB Configuration 
     In an example embodiment, spring contact terminals  404  and  406 , contact feature  410 , OHD circuit  422 , and/or audio line  424  may be disposed on a printed circuit board (PCB). Further, in some embodiments, a flexible PCB may be utilized. The PCB may be arranged within a frame component  401  of a wearable device; or more specifically, within a housing that forms an outer shell of the frame component. For example, the PCB may be disposed in a plastic or metal side-arm of a glasses-style wearable device. Such a frame-component housing may have one or more cavities that expose spring contact terminals  404  and  406 , such that the spring contact terminals  404  and  406  can electrically couple to springs  414  and  416  of member  400 . Additionally or alternatively, a frame-component housing may have one or more cavities that expose contact feature  410 , such that conductive pad  420  can come into contact with and/or electrically couple with contact feature  410  to complete the OHD circuit. 
     D. Modular Vibration-Transducer Members 
     In a further aspect, male connector  418  and female connector  408  may be sized and shaped such that the member  400  can be removably attached to the frame component  401 . Configured as such, member  400  can be a modular component of a wearable device, which the user can attach and remove as they see fit. 
     In a modular configuration, a wearable device may include two or more attachment locations. The inclusion of multiple attachment locations allows different users to customize the fit of a BCT to better suit their needs. For example, when member  400  is implemented on a glasses-style wearable device, and BCT  402  is designed to contact the posterior of the wearer&#39;s ear, a single location for attachment of the member  400  may be insufficient to properly locate the BCT for all users. However, if multiple attachment locations are provided on the same side-arm of the glasses-style device, each user can attach the member at a location that better fits the size of their head. For example, users with differently sized and/or shaped heads can attach the member at different locations on the side-arm to achieve a similar fit (e.g., with the BCT firmly, but not uncomfortably, pressed against the back of their ear by member  400 ). 
       FIG. 5  is a view of the underside of another frame component  501  to which member  400  can be attached, according to an example embodiment. Frame component  501  is similar to frame component  401 , except that frame component  501  provides multiple locations for attaching a vibration-transducer member  400 . 
     Frame component  501  provides a first attachment location  503   a  and a second attachment location  503   b . The first attachment location  503   a  includes female connector feature  508   a , as well as spring contact features  504   a  and  506   a . The second attachment location  503   b  includes female connector feature  508   b , as well as spring contact features  504   b  and  506   b . Additionally, a frame component adapted for multiple attachment locations may include multiple contact features for an OHD circuit. For instance, the frame component  501  illustrated in  FIG. 5  includes a first contact feature  510   a , which corresponds to the first attachment location  503   a , and a second contact feature  510   b , which corresponds to attachment location  503   b.    
     The first and second attachment locations  503   a  and  503   b  are configured such that member  400  can be coupled to either attachment location, and can be moved back and forth between attachment locations as the user sees fit. More specifically, member  400  can be attached at the first attachment location  503   a  by coupling the member&#39;s male connector  418  to female connector  503   a , or can be attached at the second attachment location  503   b  by coupling the member&#39;s male connector  418  to female connector  503   b.    
     To help the user more easily move the vibration-transducer member  400  between different attachment locations, the OHD circuit  522  may be designed such that it is open when none of the contact features are in contact with a conductive material, and such that the OHDC circuit can be completed by contacting any one of the contact features with a conductive material. Configured as such, OHD functionality may be provided regardless of which attachment location is used, without requiring any user input to indicate which attachment location is being used. 
     For instance, in frame component  501 , contact features  510   a  and  510   b  are connected in parallel to OHD circuit  522 . Thus, if conductive pad  420  is separated from both contact features  510   a  and  510   b , OHD circuit  522  will be open. Accordingly, the open circuit may be detected and interpreted as an indication that the wearable device is not being worn. And, when conductive pad  420  contacts either the first contact feature  510   a  or the second contact feature  510   b , the OHD circuit  522  will be completed. Therefore, the closed circuit may be detected and interpreted as an indication that the wearable device is being worn. 
     Additionally or alternatively, audio connections (e.g., spring contact points) may be provided at each attachment location, such that the same audio source can drive vibration transducer, regardless of which attachment location the vibration-transducer member is attached to. For example, as shown in  FIG. 5 , spring contact features  504   a ,  506   a  and spring contact features  504   a ,  506   a  provide parallel connections to audio line  524 . More specifically, when member  400  is attached at the first attachment location  503   a  (e.g., by coupling male connector  418  to female connector  508   a ), springs  414  and  416  may be coupled to spring contact features  504   a  and  506   a , thereby connecting vibration transducer  402  to audio circuit  524  via springs  414  and  416 . And, when member  400  is attached at the second attachment location  503   b , springs  414  and  416  may be coupled to spring contact features  504   b  and  506   b , which also connects vibration transducer  402  to audio circuit  524  via springs  414  and  416 . 
     In practice, frame component  501  could be part of a side-arm of glasses-style wearable device, such as that shown in  FIG. 1A . The multiple attachment locations could be implemented along a rear portion of a side-arm, thus allowing different users to attach a modular BCT member at different locations that better fit the respective size and shape of each of their bodies. In some embodiments, modular attachment locations could be provide along both side-arms of a BCT, allowing for connection of two BCT members, and perhaps stereo audio via two BCTs attached thereto. 
     More generally, it should be understood that other arrangements of attachment locations for a modular BCT member are also possible, both on a glasses-style wearable device and on other types of wearable devices. Further, while  FIG. 5  only shows two attachment locations on the same wearable device, wearable devices with more than two attachment locations for a BCT member are also possible. 
     E. Alternative Arrangements of a Vibration-Transducer Member 
     It should be understood that many variations on the embodiments illustrated herein, and other embodiments altogether, are possible. 
     As just one example,  FIG. 6  shows another configuration for a vibration-transducer member  600  on a glasses-style wearable device  601 , according to an example embodiment. Vibration-transducer member  600  includes a BCT  602 , a connector feature  618 , springs  614  and  616 , and a conductive pad  620 . 
     Further, when coupled to the side-arm of device  601 , member  600  is positioned so as to press BCT  602  against the temple of wearer  603 . To do so, BCT  602 , connector feature  618 , springs  614  and  616 , and conductive pad  620  may function in the same or a similar manner as BCT  402 , connector feature  418 , springs  414  and  416 , and conductive pad  420 , respectively. However, the arrangement of member  600  differs from that of member  400  in that springs  614  and  616  bias the member  600  to press BCT  602  against the wearer&#39;s temple, rather than against the back of the wearer&#39;s ear. 
     More specifically, member  600  may attach to the side-arm of device  601  at a location in front of the ear and adjacent to the temple of wearer  603 . Additionally, the orientation of member  600  and its components (e.g., BCT  602 , connector feature  618 , springs  614  and  616 , and conductive pad  620 ) with respect to the side-arm may differ by approximately ninety degrees from the orientation of member  400  with respect to frame component  401 . In this arrangement, spring  616  functions as an inner spring that is closer to the temple than spring  614 , and spring  614  functions as an outer spring that is closer to the right shoulder of wearer  603  than spring  616 . Further, in order to bias member  600  to press BCT  602  against the temple, spring  614  has a greater spring constant than spring  616 . 
     As further shown in  FIG. 6 , when wearable device  601  is worn and BCT  602  contacts the temple of wearer  603 , conductive pad  620  moves into contact with the contact feature  610  for an OHD circuit of device  601 . Further, the difference between the spring constants of spring  614  and  616  is such that conductive pad  620  separates from the contact feature  610  when wearer  603  remove devices  601  from their head (thereby returning member  600  to its resting position. While the OHD circuit of device  601  is not shown explicitly in  FIG. 6 , it should be understood that contact feature  610  may be part of an OHD circuit that operates in a similar manner as the OHD circuit of device  401 . As such, the movement of the conductive pad  620  into and out of contact with contact feature  610  may indicate whether the device  601  is donned or doffed, respectively. 
     F. Other Aspects 
     Using information from multiple sensors and systems when determining whether a wearable device is being worn provides redundancy and can help to reduce errors in the determined donned and/or doffed status of the device. Accordingly, in some embodiments, a variety of sensors and/or systems may be used to determine whether or not a wearable device is being worn. In such implementations, an indication from an OHD circuit, such as those described in reference to  FIGS. 4A to 6 , may combined with other sensor information in order to make the ultimate determination as to whether or not a wearable device is being worn. 
     For example, a proximity sensor may be located on a wearable device such that it is near to a wearer&#39;s body when the device is being worn, and will typically be exposed when the device is not being worn. As such, when the proximity sensor indicates an object within some threshold distance from the sensor, this may be interpreted as an indication that the device is being worn. As another example, an inertial measurement unit (IMU) may be utilized to detect positioning and/or movement of a wearable device that is characteristic of the device being worn. And, as yet another example, a capacitive touch sensor may be located on a wearable device such that it contacts a wearer&#39;s body when the device is being worn. Other mechanisms for obtaining information indicative of whether a device is being worn are also possible. Further, one or more of such additional indications may be combined with the indication provided by a vibration-transducer member according to an example embodiment. 
     V. CONCLUSION 
     While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.