Patent Publication Number: US-11050870-B2

Title: Bone conduction microphone, bone conduction headset, and communication device

Description:
TECHNICAL FIELD 
     The present disclosure relates to a bone conduction microphone configured to come into contact with a human body and collect vocal cord vibration, as well as a bone conduction headset and a communication device including the bone conduction microphone. 
     BACKGROUND ART 
     PTL 1 discloses a bone conduction microphone configured to be attached for use to a helmet, for example. The bone conduction microphone disclosed in PTL 1 includes a sound receiving plate provided on an outer wall surface of a housing of the bone conduction microphone, and a switch provided on another outer wall surface different from the outer wall surface provided with the sound receiving plate. When the bone conduction microphone is used to collect vocal cord vibration, a user has to press the sound receiving plate onto his or her chin or throat, as well as to separately press the switch. 
     CITATION LIST 
     Patent Literature 
     PTL 1: Unexamined Japanese Patent Publication No. 6-54387 
     SUMMARY OF THE INVENTION 
     The present disclosure provides a bone conduction microphone and other devices effective for collecting vocal cord vibration. 
     A bone conduction microphone according to the present disclosure is a bone conduction microphone configured to convert vocal cord vibration into a sound signal, and includes a vibration collection unit configured to come into contact with a human body and collect vibration in a predetermined direction, which is included in the vocal cord vibration, and a switch configured to switch whether collection of the vibration in the predetermined direction is enabled. The switch is disposed on a side of the vibration collection unit, which is opposite to a side configured to come into contact with the human body, to allow a direction of an operation of switching whether collection of the vibration in the predetermined direction is enabled to be parallel to the predetermined direction. 
     The bone conduction microphone according to the present disclosure can collect vocal cord vibration through a simple operation performed by a user, and is effective for collecting vocal cord vibration. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view illustrating a communication device including a bone conduction headset according to a first exemplary embodiment. 
         FIG. 2  is a perspective view illustrating an aspect of use of the bone conduction headset including a bone conduction microphone, according to the first exemplary embodiment. 
         FIG. 3  is a cross-sectional perspective view of the bone conduction microphone according to the first exemplary embodiment. 
         FIG. 4  is cross-sectional views of the bone conduction microphone according to the first exemplary embodiment, including a view illustrating a switch off state and a view illustrating a switch on state. 
         FIG. 5  is a block diagram illustrating a control configuration of the communication device according to the first exemplary embodiment. 
         FIG. 6  is a perspective view illustrating a communication device including a bone conduction headset according to a second exemplary embodiment. 
         FIG. 7  is a perspective view of the bone conduction headset in  FIG. 6 , when viewed differently in angle from  FIG. 6 . 
         FIG. 8  is a perspective view illustrating an aspect of use of the bone conduction headset according to the second exemplary embodiment. 
         FIG. 9  is a view illustrating a speaker circuit of the bone conduction headset according to the second exemplary embodiment. 
         FIG. 10  is a block diagram illustrating a control configuration of the communication device according to the second exemplary embodiment. 
         FIG. 11  is circuit diagrams relating to modification example 1 to the second exemplary embodiment, including a circuit diagram of a headset main body, a circuit diagram of a bone conduction microphone, and a circuit diagram of a sound microphone. 
         FIG. 12  is circuit diagrams relating to modification example 2 to the second exemplary embodiment, including a circuit diagram of a headset main body, a circuit diagram of a bone conduction microphone, and a circuit diagram of a sound microphone. 
         FIG. 13  is circuit diagrams relating to modification example 3 to the second exemplary embodiment, including a circuit diagram of a headset main body, a circuit diagram of a bone conduction microphone, and a circuit diagram of a sound microphone. 
         FIG. 14  is circuit diagrams relating to modification example 4 to the second exemplary embodiment, including a circuit diagram of a headset main body, a circuit diagram of a bone conduction microphone, and a circuit diagram of a sound microphone. 
         FIG. 15A  is views relating to modification example 4 to the second exemplary embodiment for describing an operation when the headset main body is coupled with the sound microphone and a type A transceiver. 
         FIG. 15B  is views relating to modification example 4 to the second exemplary embodiment for describing an operation when the headset main body is coupled with the bone conduction microphone and a type A transceiver. 
         FIG. 15C  is views relating to modification example 4 to the second exemplary embodiment for describing an operation when the headset main body is coupled with the sound microphone and a type B transceiver. 
         FIG. 15D  is views relating to modification example 4 to the second exemplary embodiment for describing an operation when the headset main body is coupled with the bone conduction microphone and a type B transceiver. 
         FIG. 15E  is views relating to modification example 4 to the second exemplary embodiment for describing an operation when the headset main body is coupled with the sound microphone and a smartphone type transceiver. 
         FIG. 15F  is views relating to the modification example 4 to the second exemplary embodiment for describing an operation when the headset main body is coupled with the bone conduction microphone and a smartphone type transceiver. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A bone conduction microphone according to the present disclosure is used, in a noise environment such as a construction site, to make communications, through wireless communications, with a partner in a remote location, for example. The bone conduction microphone is used by pressing a part of the bone conduction microphone onto a chin or a throat, for example, to collect, through bone conduction, vocal cord vibration generated from a human body. 
     Hereinafter, exemplary embodiments will be described in detail with reference to the drawings as appropriate. However, an excessively detailed description will not be given in some cases. For example, detailed descriptions of known matters and duplicated descriptions of substantially the same configurations will be sometimes skipped. This is to avoid the following description from being unnecessarily redundant and thus to help those skilled in the art to easily understand the description. 
     The accompanying drawings and the following description are only presented to help those skilled in the art fully understand the present disclosure. It is therefore not intended that subject matters described in the scope of the appended claims be limited to the drawings and the description herein. 
     First Exemplary Embodiment 
     Hereinafter, a first exemplary embodiment will be described with reference to  FIGS. 1 to 5 . 
     1-1. Overall Configuration of Communication Device 
       FIG. 1  is a perspective view illustrating communication device  9  including bone conduction headset  5 , according to the first exemplary embodiment.  FIG. 2  is a view illustrating an aspect of use of bone conduction headset  5  including bone conduction microphone  1 . 
     As illustrated in  FIG. 1 , communication device  9  includes bone conduction headset  5  including bone conduction microphone  1  and headset main body  50 , and transceiver  7 . Bone conduction microphone  1  is coupled to headset main body  50  via microphone cable  4 . Headset main body  50  includes ear hooks  52 . Ear hooks  52  are to be hooked to ears of a human body. Headset main body  50  is thus worn on a head. Headset main body  50  is coupled to transceiver  7  via headset cable  6 . Transceiver  7  is attached to a part of a garment, and is configured to perform communications with an external device possessed by a communication partner, for example. Bone conduction microphone  1  may be coupled to controller  55  of headset main body  50 , or may not be coupled to controller  55 , but may be coupled to transceiver  7  to directly enter a signal into transceiver  7 . 
     As illustrated in  FIG. 2 , bone conduction microphone  1  is attached to chin strap  3  of helmet  2  with metal fixture  26 . Bone conduction microphone  1  includes vibration collection unit  10  configured to come into contact with the human body and collect vocal cord vibration, and housing  21  configured to support vibration collection unit  10 . To enter voice into bone conduction microphone  1 , a user grips bone conduction microphone  1  and allows vibration collection unit  10  to come into contact with a chin or a throat. Therefore, bone conduction microphone  1  collects vocal cord vibration. When the user does not enter voice, bone conduction microphone  1  is suspended by chin strap  3 . At this time, vibration collection unit  10  is detached from the chin or the throat at a predetermined distance and therefore would be less likely to come into contact with the human body. 
     Bone conduction headset  5  includes sound microphone  57  configured to collect sound via air, and microphone holder  58  configured to support sound microphone  57 . For example, bone conduction microphone  1  is to be used under a noise environment, whereas sound microphone  57  is to be used under a non-noise environment. Bone conduction microphone  1  and sound microphone  57  are selectively switched and used. 
     In  FIG. 1 , an illustration of sound microphone  57  is omitted. In  FIG. 2 , an illustration of microphone cable  4  is omitted. 
     1-2. Configuration of Bone Conduction Microphone 
       FIG. 3  is a cross-sectional perspective view of bone conduction microphone  1 .  FIG. 4  is cross-sectional views of bone conduction microphone  1 . Part (a) illustrates a switch off state. Part (b) illustrates a switch on state. 
     As illustrated in  FIGS. 3 and 4 , bone conduction microphone  1  includes vibration collection unit  10  configured to collect vocal cord vibration, housing  21  configured to support vibration collection unit  10 , and switch  25  configured to switch whether collection of vocal cord vibration by vibration collection unit  10  is enabled. 
     First, vibration collection unit  10  will be described. Vibration collection unit  10  includes contact member  12  configured to come into contact with the human body, vocal cord sensor  11  supported by contact member  12 , and pressing member  13  configured to transmit a pressing force from contact member  12  to switch  25 . 
     Contact member  12  is a member configured to come into contact with the human body to transmit vocal cord vibration being collected to vocal cord sensor  11 . Contact member  12  has a bottomed cylindrical shape, and includes side surface part  12   b , opening part  12   c  opening at an end of side surface part  12   b , and contact part  12   a  provided at the other end of side surface part  12   b  to come into contact with the human body. In  FIG. 3 , contact part  12   a  is provided to face a positive side in a Z direction of side surface part  12   b , while opening part  12   c  is provided to face a negative side in the Z direction of side surface part  12   b . Side surface part  12   b  is partially curved outward to have a structure configured to bend and deform to easily absorb vibration noise. 
     Contact member  12  is an elastic body softer than housing  21 , and is made of a resin material such as silicone rubber. A term “soft” denotes both a case in which a material being used is soft and a case in which a structure is soft (e.g., thin or wavy for easy deformation). It is preferable that contact member  12  be made of such a material that provides a comfortable touch feel. 
     Vocal cord sensor  11  is a detection element configured to detect vibration in a predetermined direction (Z direction), which is included in vocal cord vibration transmitted via contact member  12 . Vocal cord sensor  11  is a piezoelectric element having a flat plate shape and configured to allow thickness vibration to occur, for example. Vocal cord sensor  11  is attached to an inner wall of contact part  12   a  of contact member  12  to be able to deform in the Z direction to allow thickness vibration to occur. Vocal cord sensor  11  is configured to convert vibration detected in the Z direction into an electric signal, and to enter the electric signal into headset main body  50  or transceiver  7 . In  FIG. 3 , an illustration of wire related to vocal cord sensor  11  is omitted. However, a sensor amplifier for vocal cord sensor  11  may be provided in housing  21 . The sensor amplifier may be used to amplify an electric signal. The signal may be entered into headset main body  50  or transceiver  7 . 
     Pressing member  13  has a plate shape, and provided on the end of side surface part  12   b  to cover opening part  12   c  of contact member  12 . Pressing member  13  is made of a resin material or a metal material harder than contact member  12 . Below a center of pressing member  13  (adjacent to housing  21 ), switch  25  described above is disposed. With pressing member  13  made of a material harder than contact member  12 , a pressing force received by contact member  12  when a user comes into contact with contact member  12  can be securely transmitted to switch  25 . 
     Pressing member  13  is provided with diaphragm  30  having an annular shape. Specifically, an outer circumference region on a lower surface (surface adjacent to housing  21 ) of pressing member  13  is adhered with an inner circumference region of upper surface  30   b  of diaphragm  30 . Diaphragm  30  is an elastic body softer than contact member  12 , and can easily absorb vibration noise. Diaphragm  30  can more easily deform than contact member  12 . A term “easily deform” denotes both a case in which a material that can easily deform is used and a case in which a structure that can easily deform is used. For example, diaphragm  30  may be made from resin film (e.g., polyethylene terephthalate film) or metal film having a thin plate shape to be able to easily deform. Diaphragm  30  made from an elastic body softer than contact member  12  for easy deformation prevents, when contact member  12  receives a pressing force, contact member  12  from being crushed before pressing member  13  presses and turns on switch  25 . 
     Next, housing  21  and switch  25  will be described. Housing  21  is made of a resin material harder than contact member  12 . Housing  21  has a cylindrical shape, and includes base  21   a  provided at an end of the cylindrical shape, and pillar  21   b  having an annular shape protruding toward the other end from base  21   a  around an outer circumference of base  21   a . Below (opposite to pillar  21   b ) base  21   a , metal fixture  26  described above is provided. 
     Cover  22  having a cylindrical shape is attached above housing  21 . Cover  22  has opening  22   a  greater than contact member  12 . With contact part  12   a  of contact member  12  being protruded and exposed from opening  22   a , base  21   a  and pillar  21   b  of housing  21  are covered with cover  22 . A predetermined gap is provided between opening  22   a  of cover  22  and side surface part  12   b  of contact member  12 , suppressing cover  22  and contact member  12  to come into contact with each other. 
     On end face  21   c  of pillar  21   b  of housing  21 , diaphragm  30  and vibration collection unit  10  described above are disposed. Diaphragm  30  is disposed to allow an outer circumference region of lower surface  30   a  to overlap with end face  21   c  of pillar  21   b . On an outer circumference region of upper surface  30   b  of diaphragm  30 , packing  23  made of synthetic rubber and having an annular shape is disposed. As cover  22  is to be attached to housing  21 , packing  23  presses diaphragm  30  against pillar  21   b . Therefore, the outer circumference region of diaphragm  30  is pinched by packing  23  and pillar  21   b.    
     In other words, diaphragm  30  is positioned between vibration collection unit  10  and housing  21 . Vibration collection unit  10  is supported by housing  21  via diaphragm  30 . With diaphragm  30  being deformed, vibration collection unit  10  is supported by housing  21  to allow position displacement to occur in the Z direction. 
     Housing  21  includes switch fixing part  21   d  configured to attach switch  25 . Switch fixing part  21   d  protrudes from base  21   a , and is provided inside pillar  21   b.    
     Switch  25  is provided on switch fixing part  21   d . Switch  25  is disposed to allow an on-off operation direction to be parallel to the Z direction, i.e., to be parallel to a direction of vibration to be detected by vocal cord sensor  11 . 
     More specifically, switch  25  is disposed on switch fixing part  21   d  to allow a central axis extending in the Z direction of switch  25  and a central axis extending in the Z direction of vibration collection unit  10  to align with each other. Therefore, a pressing force applied onto vibration collection unit  10  can efficiently transmit to switch  25 , improving ease of operation for a user. 
     Switch  25  is a tactile switch, for example. Switch  25  is kept an on state while being pressed, and an off state when released. The tactile switch includes a spring for easy absorption of vibration noise. Stroke s 1  in the Z direction of operation unit  25   a  configured to perform switching between on and off is 0.2 mm, for example (see part (b) of  FIG. 4 ). Operation unit  25   a  of switch  25  is provided to have, while switched off, a gap ranging from 0.1 mm to 0.2 mm inclusive with respect to pressing member  13 . The gap may not always be provided. The lower surface of pressing member  13  may be configured to come into contact with operation unit  25   a  of switch  25 . 
     In bone conduction microphone  1  according to the exemplary embodiment, switch  25  is disposed, as illustrated in part (a) of  FIG. 4 , in housing  21  in a direction of position displacement (negative side in the Z direction) of vibration collection unit  10 . As illustrated in part (b) of  FIG. 4 , when position displacement occurs on vibration collection unit  10 , vibration collection unit  10  presses switch  25 . As a result, switch  25  is turned on. As switch  25  is turned on, vocal cord sensor  11  of vibration collection unit  10  can collect vocal cord vibration. 
     A description based on an operation by the user will be given. As the user grips bone conduction microphone  1 , allows vibration collection unit  10  to come into contact with the chin or the throat, and gently presses vibration collection unit  10  onto the chin or the throat, switch  25  is turned on. As the user moves vibration collection unit  10  away from the chin or the throat, switch  25  is turned off. 
     1-3. Configuration of Bone Conduction Headset 
     Next, a configuration of bone conduction headset  5  will be described with reference to  FIG. 1 . 
     Bone conduction headset  5  includes bone conduction microphone  1  and headset main body  50 . 
     Headset main body  50  includes support body  54  and a pair of speakers  51 . Support body  54  has a U-shape, and includes both ends (end  54   b , end  54   c ) facing each other, and central part  54   a  positioned between both the ends (end  54   b , end  54   c ). Central part  54   a  of support body  54  denotes a part around a center when support body  54  is viewed along the U-shape. The pair of speakers  51  are respectively supported by both the ends (end  54   b , end  54   c ) to face each other. On one of the ends of support body  54 , i.e., end  54   b , bone conduction microphone  1  is coupled via microphone cable  4 . As illustrated in  FIG. 2 , on the one of the ends, i.e., end  54   b , sound microphone  57  is also coupled via microphone holder  58 . 
     Support body  54  is mainly made of a resin material, and is internally provided with a wire aggregate having elasticity. Support body  54  is internally provided with wires used to couple bone conduction microphone  1 , sound microphone  57 , controller  55 , and speakers  51 , for example. Both the ends (end  54   b , end  54   c ) of support body  54  each have a pillar shape extending upward and downward (Z direction). The pair of speakers  51  are respectively provided on upper sides (positive side in the Z direction) of both the ends (end  54   b , end  54   c ). Both the ends (end  54   b , end  54   c ) are respectively provided with ear hooks  52 . At central part  54   a  of support body  54 , controller  55  is incorporated. 
       FIG. 5  is a block diagram illustrating a control configuration of communication device  9  including bone conduction headset  5 . 
     As illustrated in  FIG. 5 , communication device  9  includes bone conduction headset  5  and transceiver  7 . 
     Headset main body  50  includes controller  55  and speakers  51 . Controller  55  includes a central processing unit (CPU), a random access memory (RAM), and a read only memory (ROM), for example. Speakers  51  are bone conduction speakers, for example, and are coupled to controller  55 . Bone conduction microphone  1  including vocal cord sensor  11  and switch  25  is coupled to controller  55 . Sound microphone  57  is coupled to controller  55 . Controller  55  of headset main body  50  is coupled to transceiver  7 . 
     Communication device  9  is configured to perform wireless communications, via transceiver  7 , with an external device possessed by a communication partner. Specifically, signals output from vocal cord sensor  11  and sound microphone  57  enter, via headset main body  50 , into transceiver  7 . The signals are further sent, via transceiver  7 , to the external device possessed by the communication partner. However, while switch  25  of bone conduction microphone  1  is turned on, signals sent from sound microphone  57  do not undergo processing, but only signals sent from vocal cord sensor  11  undergo processing in transceiver  7 . On the other hand, transceiver  7  receives signals sent from the external device. Speakers  51  then output the signals via controller  55  of headset main body  50 . In a communication method for transceiver  7 , a frequency band such as 422 MHz band or 440 MHz band is used. 
     A signal output from bone conduction microphone  1  may not once enter into controller  55  of headset main body  50 , but may directly enter into transceiver  7 . In the exemplary embodiment, bone conduction microphone  1 , headset main body  50 , and transceiver  7  are wire-coupled with each other. However the present disclosure is not limited to the example. The components may be wireless-coupled by using a frequency band such as 2.4 GHz band used in Bluetooth (registered trademark), for example. 
     1-4. Effects and Other Benefits 
     As described above, in the exemplary embodiment, bone conduction microphone  1  configured to convert vocal cord vibration into a sound signal includes vibration collection unit  10  configured to come into contact with a human body and collect vibration in the predetermined direction (Z direction in  FIGS. 1 to 3 ), which is included in the vocal cord vibration, and switch  25  configured to switch whether collection of vibration in the predetermined direction is enabled. Switch  25  is disposed on a side of the vibration collection unit, which is opposite to a side configured to come into contact with the human body, to allow the direction of the operation of switching whether collection of the vibration in the predetermined direction is enabled to be parallel to the predetermined direction. 
     Therefore, when switch  25  is operated in the predetermined direction, vibration collection unit  10  can easily collect vocal cord vibration in the predetermined direction. Therefore, bone conduction microphone  1  can easily collect vocal cord vibration with a simple operation. 
     In the exemplary embodiment, when vibration collection unit  10  is pressed onto a human body, switch  25  of bone conduction microphone  1  is turned on. When vibration collection unit  10  is detached from the human body, switch  25  is turned off. When switch  25  is in an on state, vibration collection unit  10  collects vibration in the predetermined direction. When switch  25  is in an off state, vibration collection unit  10  does not collect vibration in the predetermined direction. 
     Therefore, as vibration collection unit  10  is pressed onto or detached from a human body, switch  25  switches whether collection of vocal cord vibration is enabled. Therefore, bone conduction microphone  1  can easily collect vocal cord vibration with a simple operation. In particular, the bone conduction microphone is supposed to be used during work under a noise environment such as building site, construction site, factory, and distribution warehouse. Bone conduction microphone  1  according to the exemplary embodiment can collect vocal cord vibration with a simple operation. Therefore, bone conduction microphone  1  does not hinder the user at work, achieving higher ease of operation. 
     In the exemplary embodiment, vibration collection unit  10  includes contact member  12  configured to come into contact with a human body, and vocal cord sensor  11  configured to detect vibration in the predetermined direction via contact member  12 . Bone conduction microphone  1  further includes housing  21  configured to support contact member  12  and switch  25 . Contact member  12  is an elastic body softer than housing  21 . 
     Vocal cord sensor  11  is supported by housing  21  via contact member  12  that is soft. Therefore, vocal cord sensor  11  would be less likely to accept external vibration noise transmitted to housing  21  and vibration noise generated in housing  21 . Therefore, bone conduction microphone  1  can easily collect vocal cord vibration. 
     In the exemplary embodiment, bone conduction microphone  1  further includes diaphragm  30  positioned between vibration collection unit  10  and housing  21 . Vibration collection unit  10  is supported by housing  21  via diaphragm  30 . 
     Vocal cord sensor  11  of vibration collection unit  10  is supported by housing  21  via diaphragm  30 . Therefore, vocal cord sensor  11  would be less likely to accept external vibration noise transmitted to housing  21  and vibration noise generated in housing  21 . Therefore, bone conduction microphone  1  can easily collect vocal cord vibration. 
     In the exemplary embodiment, diaphragm  30  is an elastic body softer than contact member  12 . 
     Therefore, external vibration noise transmitted to housing  21  and vibration noise generated in housing  21  are absorbed by soft diaphragm  30 , and would be less likely to enter into vocal cord sensor  11 . Therefore, bone conduction microphone  1  can easily collect vocal cord vibration. 
     In the exemplary embodiment, housing  21  has a tubular shape. 
     Vibration collection unit  10  is supported by housing  21  via diaphragm  30  to allow position displacement to occur in the operation direction of switch  25 . Switch  25  is disposed in housing  21  in the direction of position displacement of vibration collection unit  10 . When position displacement occurs on vibration collection unit  10 , vibration collection unit  10  presses switch  25 . As a result, switch  25  is turned on. Vibration collection unit  10  then collects vibration in the predetermined direction (Z direction) described above. 
     Therefore, as switch  25  is operated in the predetermined direction, vibration collection unit  10  is ready to collect vocal cord vibration in the predetermined direction. Therefore, bone conduction microphone  1  can easily collect vocal cord vibration with a simple operation. 
     In the exemplary embodiment, vibration collection unit  10  and switch  25  are disposed in housing  21  to allow the central axes extending in the direction of position displacement (Z direction) to align with each other. 
     Therefore, a pressing force applied onto vibration collection unit  10  can efficiently transmit to switch  25 , improving ease of operation for a user. 
     In the exemplary embodiment, vocal cord sensor  11  is a piezoelectric element configured to provide thickness vibration. A thickness direction of the piezoelectric element is identical to the predetermined direction (Z direction) described above. 
     Therefore, vocal cord sensor  11  can easily collect vibration in the predetermined direction, which is included in vocal cord vibration. 
     In the exemplary embodiment, bone conduction headset  5  includes bone conduction microphone  1  and speakers  51 . 
     With bone conduction headset  5  equipped with bone conduction microphone  1 , bone conduction headset  5  can easily collect vocal cord vibration with a simple operation. 
     In the exemplary embodiment, communication device  9  includes bone conduction headset  5 , and transceiver  7  coupled to bone conduction headset  5  to perform communications with an external device. 
     With communication device  9  equipped with bone conduction headset  5  described above, communication device  9  can easily collect vocal cord vibration with a simple operation, achieving easy communications. 
     In the exemplary embodiment, communication device  9  includes bone conduction microphone  1 , and transceiver  7  coupled to bone conduction microphone  1  to perform communications with an external device. 
     With communication device  9  equipped with bone conduction microphone  1 , communication device  9  can easily collect vocal cord vibration with a simple operation, achieving easy communications. 
     Second Exemplary Embodiment 
     Bone conduction headset  5 A and communication device  9 A according to a second exemplary embodiment will be described below with reference to  FIGS. 6 to 10 . 
     2-1. Overall Configuration of Communication Device 
       FIG. 6  is a perspective view illustrating communication device  9 A including bone conduction headset  5 A.  FIG. 7  is a perspective view of bone conduction headset  5 A, when viewed differently in angle from  FIG. 6 .  FIG. 8  is a perspective view illustrating an aspect of use of bone conduction headset  5 A. 
     As illustrated in  FIGS. 6 and 7 , communication device  9 A includes bone conduction headset  5 A including sound microphone  57  and headset main body  50 , and transceiver  7 . Sound microphone  57  is coupled to headset main body  50  via microphone holder  58 . Headset main body  50  includes a pair of speakers  51  and a pair of ear hooks  52 . Ear hooks  52  are to be hooked to ears of a human body. Headset main body  50  is thus worn on a head. Speakers  51  are wire-coupled to transceiver  7  via headset cable  6 . Transceiver  7  is attached to a part of a garment, and is configured to perform communications with an external device possessed by a communication partner, for example. Sound microphone  57  may be coupled to controller  55  of headset main body  50  or may not be coupled to controller  55 , but may be coupled to transceiver  7  to directly enter a signal into transceiver  7 . 
     Bone conduction headset  5 A includes bone conduction microphone  1  configured to collect vocal cord vibration through bone conduction, and microphone cable  4  used to couple bone conduction microphone  1  to headset main body  50 . For example, bone conduction microphone  1  is to be used under a noise environment, whereas sound microphone  57  is to be used under a non-noise environment. Bone conduction microphone  1  and sound microphone  57  are selectively switched and used. 
     2-2. Configuration of Bone Conduction Headset 
     Bone conduction headset  5 A includes sound microphone  57  configured to collect sound via air, bone conduction microphone  1 , and headset main body  50 . A configuration of bone conduction microphone  1  is similar to the configuration described in the first exemplary embodiment. Therefore, a detailed description is omitted. 
     Headset main body  50  includes support body  54  and a pair of speakers  51 . Specifically, speakers  51  are bone conduction speakers configured to transmit sound information through bone conduction to a brain without drum membranes being interposed. Support body  54  has a U-shape, and includes both ends (end  54   b , end  54   c ) facing each other, and central part  54   a  positioned between both the ends (end  54   b , end  54   c ). Central part  54   a  of support body  54  denotes a part around a center when support body  54  is viewed along the U-shape. The pair of speakers  51  are respectively supported by both the ends (end  54   b , end  54   c ) to face each other. 
     On one end of support body  54 , i.e., end  54   b , sound microphone  57  is coupled via microphone holder  58 , as well as bone conduction microphone  1  is coupled via microphone cable  4 . On the other end of support body  54 , i.e., end  54   c , transceiver  7  is coupled via headset cable  6 . A connector may be used as coupler  59  configured to couple headset cable  6  and end  54   c  to allow headset cable  6  to be attached to and detached from end  54   c.    
     Support body  54  is mainly made of a resin material, and is internally provided with a wire aggregate having elasticity. Support body  54  is internally provided with wires used to couple sound microphone  57 , bone conduction microphone  1 , controller  55 , and speakers  51 , as well as PTT switch  62  and mute switch  64  described later, for example. Both the ends (end  54   b , end  54   c ) of support body  54  each have a pillar shape extending upward and downward (Z direction). The pair of speakers  51  are respectively provided on upper sides (positive side in the Z direction) of both the ends (end  54   b , end  54   c ). Both the ends (end  54   b , end  54   c ) are respectively provided with ear hooks  52 . At central part  54   a  of support body  54 , controller  55  is incorporated. 
     Support body  54  has elasticity. Parts other than central part  54   a  can thus easily deform. Specifically, support body  54  has a structure allowing the parts other than central part  54   a  to deform to change a distance between both the ends (end  54   b , end  54   c ) facing each other. An elastic force of support body  54  is adjusted to allow, when headset main body  50  is worn on the head, pressing force P 1  to be appropriately applied to sides of the head without allowing speakers  51  to detach from skin on areas in front of the ears, as well as to press the skin excessively. Support body  54  is formed, when headset main body  50  is worn, to extend from both the ends (end  54   b , end  54   c ), through lower sides of the ears, to central part  54   a  lying on a rear side of the head. As the lower sides of the ears are bypassed, a pair of eyeglasses can be easily worn. With the form extending to central part  54   a  lying on the rear side of the head, a helmet or a cap can be easily worn. 
     Bone conduction headset  5 A according to the exemplary embodiment includes push to talk (PTT) switch  62  used to make communications with a communication partner holding an external device, and mute switch  64  used to lower sound entering from the external device. 
     PTT switch  62  is provided to end  54   b  without being coupled with headset cable  6 . Specifically, PTT switch  62  is provided to outside surface  54   b   1  of end  54   b . PTT switch  62  is turned on when a button is pressed in a direction vertical to outside surface  54   b   1 , i.e., toward a left side surface of a face. When PTT switch  62  is turned on, the user can make communications with the communication partner. It is preferable that PTT switch  62  be provided to face the positive side in the Z direction from a center of outside surface  54   b   1 . Further, it is more preferable that PTT switch  62  be provided on a rear surface of corresponding one of speakers  51 . This prevents headset main body  50  from moving from the head even when the user presses the button. 
     Mute switch  64  is provided to end  54   c  coupled with headset cable  6 . In other words, mute switch  64  is provided to end  54   c  opposite to end  54   b  provided with PTT switch  62 . Mute switch  64  is inserted and coupled to a wire that couples coupler  59  and speaker  51  on end  54   b , as well as inserted and coupled to a wire that couples coupler  59  and speaker  51  on end  54   c . Mute switch  64  according to the exemplary embodiment includes an operation unit (button) configured to accept an operation by a user, as well as includes a resistor and a contact (switch) provided in a speaker circuit described later. 
     Mute switch  64  is provided to outside surface  54   c   1  of end  54   c . Mute switch  64  operates when the button is pressed in a direction vertical to outside surface  54   c   1 , i.e., toward a right side surface of the face. Similar to PTT switch  62 , it is preferable that mute switch  64  be provided to face the positive side in the Z direction from a center of outside surface  54   c   1  to prevent the headset main body from moving from the head even when the button is pressed. It is more preferable that mute switch  64  be provided to outside surface  54   c   1  of end  54   c , i.e., on a rear surface of corresponding one of speakers  51 . While mute switch  64  is pressed, volume of sound signals from transceiver  7  lowers. As mute switch  64  is released, volume of sound signals from transceiver  7  returns to its original degree. 
     A pressing force required to operate mute switch  64  is set to approximately ½ to ¼ inclusive of pressing force P 1  that each of the sides of the head receives when headset main body  50  is worn (see  FIG. 8 ). That is, with the set force smaller than pressing force P 1 , headset main body  50  is prevented from moving from the head even when mute switch  64  is pressed. 
       FIG. 9  is a circuit diagram illustrating the speaker circuit of bone conduction headset  5 A according to the second exemplary embodiment. 
     In the speaker circuit according to the exemplary embodiment, the resistor and mute switch  64  are bypass-inserted between a positive side wire and a ground side wire for speakers  51 . As the user presses the button of mute switch  64 , the contact closes. Therefore, the resistor is coupled to the speaker circuit, lowering a level of sound to be output from speakers  51 . 
       FIG. 10  is a block diagram illustrating a control configuration of communication device  9 A including bone conduction headset  5 A. 
     As illustrated in  FIG. 10 , headset main body  50  includes controller  55  and speakers  51 . Controller  55  includes a central processing unit (CPU), a random access memory (RAM), and a read only memory (ROM), for example. Specifically, speakers  51  are bone conduction speakers, and are coupled to transceiver  7  via mute switch  64 . 
     Sound microphone  57  and bone conduction microphone  1  are coupled to controller  55 . PTT switch  62  is coupled to controller  55 . Controller  55  is coupled to transceiver  7  via signal line  71 . Mute switch  64  is provided on a signal line distinct from signal line  71 , i.e., provided on sound line  72  configured to accept outputs from transceiver  7 . Sound line  72  of headset main body  50  is coupled with input unit  73  configured to accept sound signals from transceiver  7 . Input unit  73  is provided to end  54   c , similar to mute switch  64 . A sound signal entered into input unit  73  enters into bone conduction speakers  51 . 
     Communication device  9 A performs wireless communications, via transceiver  7 , with an external device possessed by a communication partner. Specifically, signals output from sound microphone  57  and bone conduction microphone  1  enter transceiver  7  via headset main body  50 . Further, the signals are sent, via transceiver  7 , to the external device possessed by the communication partner. On the other hand, a signal sent from the external device is received by transceiver  7 , and is then analog-converted. Further, the signal is output, via headset cable  6  and mute switch  64 , from speakers  51 . In a communication method for transceiver  7 , a frequency band such as 422 MHz band or 440 MHz band is used. Bone conduction headset  5 A may perform communications with a plurality of external communication apparatuses via transceiver  7 . 
     By pressing PTT switch  62 , the user can make communications with the communication partner. The user can press mute switch  64  to lower sound from the communication partner. 
     2-3. Effects and Other Benefits 
     As described above, in the exemplary embodiment, bone conduction headset  5 A includes support body  54  having a U-shape, the pair of bone conduction speakers  51  respectively provided to one of ends of support body  54 , i.e., first end  54   b , and another one of the ends, which lies opposite to first end  54   b , i.e., second end  54   c , sound microphone  57  coupled to first end  54   b , and mute switch  64  provided to either of first end  54   b  or second end  54   c , and configured to control bone conduction speakers  51  to lower volume. 
     Therefore, a user can operate mute switch  64  provided to bone conduction headset  5 A to lower volume on bone conduction speakers  51 . For example, while the user wearing bone conduction headset  5 A is making conversations with an adjacent partner, if the user hears other communications via bone conduction speakers  51  from transceiver  7 , the user faces difficulty in making conversations with the adjacent partner. In this case, the user can operate mute switch  64  to lower volume on bone conduction speakers  51  to continue smooth conversations. 
     In the exemplary embodiment, the pair of bone conduction speakers  51  include the speaker circuit. Mute switch  64  includes the button configured to accept an operation by the user, the resistor configured to be coupled with the speaker circuit, and the switch configured to couple the resistor to the speaker circuit. When the button is operated, the switch closes. The resistor is coupled to the speaker circuit. Volume on bone conduction speakers  51  thus lowers. 
     As described above, bone conduction headset  5 A can lower volume on bone conduction speakers  51  without fully silencing sound. If sound is fully silenced, the user cannot respond to an instruction given from the communication partner to complete a task or cannot answer the communication partner. However, by lowering volume without fully silencing sound, the user can respond to the communication partner as required. 
     In the exemplary embodiment, first end  54   b  or second end  54   c  is not provided with mute switch  64 , but is provided with PTT switch  62  configured to switch on or off of an input of sound microphone  57 . 
     PTT switch  62  and mute switch  64  are respectively provided to ends  54   b ,  54   c  distinct from each other. Therefore, PTT switch  62  and mute switch  64  would be less likely to be unintentionally pressed. 
     In the exemplary embodiment, bone conduction headset  5 A includes coupler  59  and headset cable  6  both used to couple transceiver  7 , and is configured to perform communications with a plurality of external communication apparatuses via transceiver  7 . 
     Therefore, bone conduction headset  5 A can perform communications with the plurality of external communication apparatuses. In the situation, even when the user hears from transceiver  7  communications that are not directed to the user, the user can operate mute switch  64  to lower volume on bone conduction speakers  51 . By lowering volume of communications that are not directed to the user, the user can smoothly make conversations with an adjacent partner, and, further, can concentrate the user&#39;s task. 
     In the exemplary embodiment, bone conduction headset  5 A includes support body  54  having a U-shape, speakers  51  respectively provided to one end of support body  54 , i.e., end  54   b , and the other end, i.e., end  54   c , headset cable  6  for accepting sound from an external device, and mute switch  64  configured to lower sound entering from the external device. Headset cable  6  and mute switch  64  are both provided to either of the ends, i.e., end  54   b  and end  54   c.    
     In the exemplary embodiment, second end  54   c  includes input unit  73  configured to accept a sound signal entering from transceiver  7 . Mute switch  64  is also provided to second end  54   c.    
     Therefore, wiring inside support body  54  can be simplified. If headset cable  6  and input unit  73  are provided to end  54   b , and mute switch  64  is provided to end  54   c , a wire in end  54   b  coupled with headset cable  6  and input unit  73  needs to be inserted into support body  54 , and coupled to mute switch  64  on end  54   c . The wire then needs to be folded, inserted into support body  54 , and coupled to speaker  51  on end  54   b . In the exemplary embodiment, headset cable  6 , input unit  73 , and mute switch  64  are all provided to one of the ends of support body  54 . Therefore, a wire does not need to be folded, shortening a wire length. Therefore, wiring inside bone conduction headset  5 A can be simplified. 
     In the exemplary embodiment, a pressing force required to operate mute switch  64  ranges from ½ to ¼ inclusive of pressing force P 1  to be applied to each of the sides of the head when headset main body  50  is worn. 
     Therefore, even when mute switch  64  is pressed, bone conduction headset  5 A can be easily prevented from moving from the head. 
     In the exemplary embodiment, the operation unit (button) of mute switch  64  is disposed on outside surface  54   b   1  of first end  54   b  or outside surface  54   c   1  of second end  54   c , in other words, on an upper side above the center of outside surface  54   b   1  or outside surface  54   c   1 , i.e., disposed to face the positive side in the Z direction. 
     Therefore, even when mute switch  64  is pressed, bone conduction headset  5 A can be easily prevented from moving from the head. 
     2-4. Modification Examples 
     In the second exemplary embodiment, one of the ends of support body  54 , i.e., end  54   b , is coupled with sound microphone  57  via microphone holder  58 , as well as is coupled with bone conduction microphone  1  via microphone cable  4 . 
     Here is described, as modification examples to the second exemplary embodiment, cases where bone conduction microphone  1  and sound microphone  57  are detachably and replaceably coupled to headset main body  50 . 
     First, a coupler including connector  170  is provided to end  54   b  of headset main body  50 . Connector  180  is used at an end of microphone cable  4 , which is to be coupled to bone conduction microphone  1 , i.e., to be coupled to headset main body  50 . Connector  190  is used at an end of microphone holder  58  to be coupled to sound microphone  57 , i.e., to be coupled to bone conduction headset  5 A. With this configuration, bone conduction microphone  1  and sound microphone  57  are detachable and replaceable with respect to headset main body  50 . 
     At this time, when the coupler at end  54   b  is coupled with sound microphone  57 , communications with a communication partner may be possible when PTT switch  62  is in an on state. When the coupler at end  54   b  is coupled with bone conduction microphone  1 , communications with a communication partner may be possible when switch  25  is in an on state. 
     How to operate PTT switch  62  provided to headset main body  50  and switch  25  provided to bone conduction microphone  1  will be described below with reference to  FIGS. 11, 12 . 
       FIG. 11  is circuit diagrams relating to modification example 1 to the second exemplary embodiment. Part (a) is a circuit diagram of headset main body  50 . Part (b) is a circuit diagram of bone conduction microphone  1 . Part (c) is a circuit diagram of sound microphone  57 . 
     As illustrated in part (a) of  FIG. 11 , connector  170  of the coupler at end  54   b  is a female stereo jack (three-polar jack). Chip  171  (Lch) of connector  170  is coupled to controller  55  via PTT switch  62 . Ring  172  (Rch) of connector  170  is directly coupled to controller  55 . Sleeve  173  (GND) of connector  170  is coupled to GND. 
     As illustrated in part (b) of  FIG. 11 , connector  180  of bone conduction microphone  1  is a male stereo jack (three-polar jack). A signal picked by vocal cord sensor  11  is output from ring  182  (Rch) of connector  180 . Switch  25  is inserted between vocal cord sensor  11  and ring  182  (Rch). The details on switch  25  have been described in the first exemplary embodiment. 
     As illustrated in part (c) of  FIG. 11 , connector  190  of sound microphone  57  is a male stereo jack (three-polar jack). A signal picked by sound microphone  57  is output from chip  191  (Lch) of connector  190 . 
     With the configuration described above, when bone conduction microphone  1  is coupled to headset main body  50 , connector  180  is inserted into connector  170 . Therefore, conversations can be controlled with switch  25  provided to bone conduction microphone  1 . On the other hand, when headset main body  50  is coupled to sound microphone  57 , connector  190  is inserted into connector  170 . Therefore, conversations can be controlled with PTT switch  62  provided to end  54   b  of bone conduction headset  5 A. 
       FIG. 12  is circuit diagrams relating to modification example 2 to the second exemplary embodiment. Part (a) is a circuit diagram of headset main body  50 . Part (b) is a circuit diagram of bone conduction microphone  1 . Part (c) is a circuit diagram of sound microphone  57 . 
     In the circuit diagram of modification example 1 described in  FIG. 11 , the stereo jack (three-polar jack) has been used as connector  190  of sound microphone  57 . However, monaural jacks (bipolar jacks) are often used in an ordinary sound microphone. If a monaural jack connector is used in the circuit diagram of modification example 1, ring  172  (Rch) of connector  170  reaches GND. Therefore, a current cannot sometimes flow into chip  171  (Lch). 
     In view of this fact, modification example 2 will describe a circuit diagram where sound microphone  57  has connector  195  that is a monaural jack. 
     The circuit illustrated in  FIG. 12  differs in configuration from the circuit illustrated in  FIG. 11  in terms of two points described below. First, one of the two points is that connector  195  of sound microphone  57  is a monaural jack (bipolar jack). Further, the other of the two points is that a circuit including transistor  174  and transistor  175  is provided between ring  172  (Rch) of connector  170  of headset main body  50  and controller  55 . 
     How the circuit illustrated in  FIG. 12  operates will be described below. 
     When connector  195  (monaural jack) of sound microphone  57  is inserted into connector  170  of headset main body  50 , ring  172  (Rch) of connector  170  reaches GND. A base of transistor  174  reaches 0 V. A collector of transistor  174  attains High. A gate of transistor  175  attains High. Transistor  175  is thus turned OFF. Therefore, no current flows into ring  172  (Rch) of connector  170 . However, when PTT switch  62  of headset main body  50  is turned on, a current flows into chip  171  (Lch) of connector  170 . 
     On the other hand, when connector  180  of bone conduction microphone  1  is inserted into connector  170  of headset main body  50 , ring  172  (Rch) does not reach GND. Therefore, a voltage is applied to the base of transistor  174 . The base of transistor  174  attains High. An emitter of transistor  174  attains Low. As a result, the collector of transistor  174  attains Low. A gate of transistor  175  then attains Low. Transistor  175  is turned ON. As a result, a current flows into ring  172  (Rch) of connector  170 . 
     Next, circuits will be described with reference to  FIGS. 13, 14  in a case in which controller  55  of headset main body  50  sends sound collected with a microphone to transceiver  7 , and a case in which controller  55  outputs the sound received from transceiver  7  to bone conduction speakers  51 . 
       FIG. 13  is circuit diagrams relating to modification example 3 to the second exemplary embodiment. Part (a) is a circuit diagram of headset main body  50 . Part (b) is a circuit diagram of bone conduction microphone  1 . Part (c) is a circuit diagram of sound microphone  57 . 
     In modification example 3 illustrated in  FIG. 13 , sound microphone  57  and bone conduction microphone  1  are selectively coupled to connector  220  of headset main body  50 . Transceiver  7  is coupled to connector  200  of headset main body  50 . Connector  200  lies at a tip of headset cable  6 . As an example, connector  220  to the microphone is a three-polar jack (female), while connector  200  to transceiver  7  is a four-pole plug (male). Here, it is supposed that transceiver  7  to be coupled to headset main body  50  is such a type of a transceiver (hereinafter referred to as type A transceiver) that is configured to detect that the PTT switch is pressed, through a voltage drop (e.g. from 3 V to 2 V) at sleeve  204  of connector  200 . 
     As illustrated in part (a) of  FIG. 13 , chip  221  (Lch) of connector  220  is coupled to sleeve  204  (Mic) of connector  200  via PTT switch  230 . Ring  222  (Rch) of connector  220  is coupled to sleeve  204  of connector  200 . Sleeve  223  (GND) of connector  220  is coupled to ring  1 _ 203  (GND) of connector  200 . Ring  2 _ 202  (sound−) and chip  201  (sound+) of connector  200  are both coupled to speaker  211  (Lch) and speaker  212  (Rch). 
     The circuit diagram of the bone conduction microphone in part (b) of  FIG. 13  and the circuit of sound microphone  57  in part (c) of  FIG. 13  are respectively similar to the circuit diagrams in parts (b), (c) of  FIG. 11 . Therefore, descriptions are omitted in here. 
     Next, operations when two kinds of microphones are each combined with a type A transceiver will be described. 
     Combination of Sound Microphone and Type A Transceiver 
     When sound microphone  57  is used in headset main body  50 , PTT switch  230  of headset main body  50  is used to achieve a PTT function. Sleeve  204  of connector  200  is coupled, via chip  221  of connector  220 , chip  191  of connector  190 , sound microphone  57 , sleeve  193  of connector  190 , and sleeve  223  of connector  220 , to GND (ring  1 _ 203  of connector  200 ). Therefore, when PTT switch  230  is pressed, a voltage drop occurs. Transceiver  7  detects the voltage drop at sleeve  204  of connector  200  to detect that PTT switch  230  is pressed. 
     Combination of Bone Conduction Microphone and Type A Transceiver 
     When bone conduction microphone  1  is used in headset main body  50 , switch  25  of bone conduction microphone  1  is used to achieve a PTT function. Sleeve  204  of connector  200  is coupled, via ring  222  of connector  220 , ring  182  of bone conduction microphone  1 , switch  25 , vocal cord sensor  11 , sleeve  183  of bone conduction microphone  1 , and sleeve  223  of connector  220 , to GND (ring  1 _ 203  of connector  200 ). Therefore, when switch  25  of bone conduction microphone  1  is pressed, a voltage drop occurs. Transceiver  7  detects the voltage drop at sleeve  204  of connector  200  to detect that the PTT switch is pressed. 
     As described above, in modification example 3, transceiver  7  can detect that PTT switch  230  is pressed, regardless of a kind of a microphone. 
     Next, modification example 4 to the second exemplary embodiment will be described below with reference to  FIGS. 14 and 15A to 15F .  FIG. 14  is circuit diagrams relating to modification example 4. Part (a) is a circuit diagram of headset main body  50 . Part (b) is a circuit diagram of bone conduction microphone  1 . Part (c) is a circuit diagram of sound microphone  57 . 
     In modification example 4, sound microphone  57  and bone conduction microphone  1  illustrated in  FIG. 14  are selectively coupled to connector  320  of headset main body  50 . Transceiver  7  is coupled to connector  300  of headset main body  50 . Connector  300  lies at a tip of headset cable  6 . As an example, connector  320  to the microphone is a three-polar jack (female), while connector  300  to transceiver  7  is a four-pole plug (male). 
     In modification example 4, transceiver  7  to be coupled to headset main body  50  varies in kind. That is, three kinds of transceivers are available, such as type B transceiver and smartphone type transceiver, in addition to type A transceiver described above. A type B transceiver denotes a type of a transceiver configured to detect the PTT switch through a voltage drop (e.g. from 3 V to 0 V) at ring  2 _ 302  of connector  300 . 
     A smartphone type transceiver denotes a smartphone having a transceiver function configured to always turn a microphone on without detecting a PTT switch. 
     As illustrated in part (a) of  FIG. 14 , in headset main body  50 , chip  321  (Lch) of connector  320  on a microphone side is coupled, via ring  2 _ 302  of connector  300  on a transceiver side and PTT switch  340 , to ring  1 _ 303  of connector  300 . Ring  322  (Rch) of connector  320  is coupled to ring  1 _ 303  (GND) of connector  300 . Sleeve  323  (GND) of connector  320  is coupled to sleeve  304  (Mic) of connector  300 . Ring  1 _ 303  and chip  301  of connector  300  are both coupled to left speaker  331  and right speaker  332 . 
     As illustrated in part (b) of  FIG. 14 , connector  360  of bone conduction microphone  1  is a male stereo jack (three-polar jack). A signal picked by vocal cord sensor  11  is output, via chip  361  (Lch) of connector  360  and PTT switch  370 , from ring  362  (Rch). 
     The circuit of the sound microphone in part (c) of  FIG. 14  is similar to the circuit of the sound microphone illustrated in part (c) of  FIG. 11 . Therefore, here omits its description. 
     Next, operations when two kinds of microphones and three kinds of transceivers are respectively combined with each other will be described. 
     Combination of Sound Microphone and Type A Transceiver 
       FIG. 15A  is views for describing an operation when headset main body  50  is coupled with sound microphone  57  and transceiver  7  that is a type A transceiver. 
     When sound microphone  57  is used in headset main body  50 , PTT switch  340  of headset main body  50  illustrated in part (a) is used to achieve a PTT function. Sleeve  304  of connector  300  is coupled, via sleeve  323  of connector  320 , sleeve  193  of sound microphone  57 , chip  191  of sound microphone  57 , and PTT switch  340 , to GND  310 . Therefore, when PTT switch  340  is pressed, a voltage drop occurs. Transceiver  7  can detect the voltage drop at sleeve  304  of connector  300  to detect that PTT switch  340  is pressed. The configuration and the function of PTT switch  340  are similar to the configuration and the function of mute switch  64  in the second exemplary embodiment. 
     Combination of Bone Conduction Microphone and Type A Transceiver 
       FIG. 15B  is views for describing an operation when headset main body  50  is coupled with bone conduction microphone  1  and transceiver  7  that is a type A transceiver. 
     When bone conduction microphone  1  is used in headset main body  50 , PTT switch  370  of bone conduction microphone  1  illustrated in part (b) is used to achieve a PTT function. Sleeve  304  of connector  300  is coupled, via sleeve  323  of connector  320 , sleeve  363  of bone conduction microphone  1 , PTT switch  370 , and ring  362  of bone conduction microphone  1 , to GND  310 . Therefore, when PTT switch  370  of bone conduction microphone  1  is pressed, a voltage drop occurs. Transceiver  7  can detect the voltage drop at sleeve  304  of connector  300  to detect that PTT switch  370  is pressed. The configuration and the function of PTT switch  370  are similar to the configuration and the function of switch  25  in the first exemplary embodiment. 
     Combination of Sound Microphone and Type B Transceiver 
       FIG. 15C  is views for describing an operation when headset main body  50  is coupled with sound microphone  57  and transceiver  7  that is a type B transceiver. 
     When sound microphone  57  is used in headset main body  50 , PTT switch  340  of headset main body  50  illustrated in part (a) is used to achieve a PTT function. While PTT switch  340  of headset main body  50  is not pressed, a voltage is supplied from transceiver  7  to sleeve  304  (Mic) of connector  300 . The voltage is further supplied, via sleeve  323  of connector  320 , sound microphone  57 , and chip  321  of connector  320 , to ring  2 _ 302  (PTT through) of connector  300 . On the other hand, when PTT switch  340  of headset main body  50  is pressed, ring  2 _ 302  of connector  300  is coupled, via PTT switch  340 , to GND  310 . As a result, a voltage drop occurs. Transceiver  7  can detect the voltage drop at ring  2 _ 302  of connector  300  to detect that the PTT switch is pressed. 
     Combination of Bone Conduction Microphone and Type B Transceiver 
       FIG. 15D  is views for describing an operation when headset main body  50  is coupled with bone conduction microphone  1  and transceiver  7  that is a type B transceiver. 
     When bone conduction microphone  1  is used in headset main body  50 , PTT switch  370  of bone conduction microphone  1  illustrated in part (b) is used to achieve a PTT function. While PTT switch  370  of bone conduction microphone  1  is not pressed, a voltage is supplied from transceiver  7  to sleeve  304  of connector  300 . The voltage is further supplied, via sleeve  323  of connector  320 , sound microphone  57 , and chip  321  of connector  320 , to ring  2 _ 302  (PTT through) of connector  300 . On the other hand, when PTT switch  370  of bone conduction microphone  1  is pressed, ring  2 _ 302  of connector  300  is coupled, via chip  361  of bone conduction microphone  1 , PTT switch  370 , and ring  362  of bone conduction microphone  1 , to GND  310 . As a result, a voltage drop occurs. Transceiver  7  detects the voltage drop at ring  2 _ 302  of connector  300  to detect that the PTT switch is pressed. 
     Combination of Sound Microphone and Smartphone Type Transceiver 
       FIG. 15E  is views for describing an operation when headset main body  50  is coupled with sound microphone  57  and transceiver  7  that is a smartphone type transceiver. 
     To couple transceiver  7  that is a smartphone type transceiver to headset main body  50 , a part (not illustrated) configured to short-circuit ring  1 _ 303  and ring  2 _ 302  of connector  300  illustrated in part (a) is to be inserted between connector  300  and transceiver  7 . Below will be described an operation under a supposition that the part is inserted, and thus ring  1 _ 303  and ring  2 _ 302  of connector  300  are short-circuited. 
     Ring  2 _ 302  of connector  300  is short-circuited with ring  1 _ 303  of connector  300 , and thus reaches GND. Chip  321  of connector  320  also reaches GND. At this time, chip  191  of connector  190  of sound microphone  57  illustrated in part (b) also reaches GND. As a result, sound microphone  57  attains a normally operating state. Therefore, even when a user does not press PTT switch  340  of headset main body  50 , the user can use sound microphone  57  to make communications. 
     Combination of Bone Conduction Microphone and Smartphone Type Transceiver 
       FIG. 15F  is views for describing an operation when headset main body  50  is coupled with bone conduction microphone  1  and transceiver  7  that is a smartphone type transceiver. 
     To couple a smartphone type transceiver to headset main body  50 , a part (not illustrated) configured to short-circuit ring  1 _ 303  and ring  2 _ 302  of connector  300  illustrated in part (a) is to be inserted between connector  300  and transceiver  7 . Herein will describe an operation under a supposition that the part is inserted, and thus ring  1 _ 303  and ring  2 _ 302  of connector  300  are short-circuited. 
     Ring  2 _ 302  of connector  300  is short-circuited with ring  1 _ 303  of connector  300 , and thus reaches GND. Chip  321  of connector  320  also reaches GND. At this time, chip  361  of connector  360  of bone conduction microphone  1  illustrated in part (b) also reaches GND. As a result, bone conduction microphone  1  attains a normally operating state. Therefore, even when a user does not press PTT switch  370  of bone conduction microphone  1 , the user can use bone conduction microphone  1  to make communications. 
     As described above, headset main body  50  according to modification example 4 can operate in any of the combinations of the two kinds of microphones and the three kinds of transceivers. 
     Effects and Other Benefits of Modification Example 4 
     As described above, modification example 4 is a bone conduction headset system, i.e., a sound input and output device, including headset main body  50  and a microphone device. Headset main body  50  includes PTT switch  340  serving as a communication switch, the bone conduction speakers, connector  320  serving as a first connector to be coupled with the microphone ( 1 ,  57 ), and connector  300  serving as a second connector to be coupled with transceiver  7 . Connector  320  includes the three contacts of sleeve  323 , ring  322 , and chip  321  arranged in this order. Connector  300  includes the four contacts of sleeve  304 , ring  1 _ 303 , ring  2 _ 302 , and chip  301  arranged in this order. Sleeve  304  of connector  320  is coupled to sleeve  323  of connector  300 . Ring  322  of connector  320  is coupled to a ground. Chip  321  of connector  320  is coupled to ring  2 _ 302  of connector  300 , as well as is coupled, via PTT switch  340 , to the ground. The microphone device includes the microphone ( 1 ,  57 ), and the connector ( 360 ,  190 ) serving as a third connector configured to couple the microphone ( 1 ,  57 ) to headset main body  50 . The connector ( 360 ,  190 ) includes the three contacts of the chip ( 361 ,  191 ), the ring ( 362 ), and the sleeve ( 363 ,  193 ) arranged in this order. The sleeve ( 363 ,  193 ) of the connector ( 360 ,  190 ) is coupled to one of terminals of the microphone ( 1 ,  57 ). The chip ( 361 ,  191 ) of the connector ( 360 ,  190 ) is coupled to another one of the terminals of the microphone ( 1 ,  57 ). The connector ( 360 ,  190 ) is coupled to connector  320  of headset main body  50 . 
     Therefore, the bone conduction headset system can detect that PTT switch  340  is pressed even when a transceiver coupled to connector  300  is either of type A and type B. 
     In the bone conduction headset system according to modification example 4, connector  320  is the three-polar jack including the three contacts of sleeve  323 , ring  322 , and chip  321  arranged in this order from a plug insertion port. Connector  300  is the four-polar jack including the four contacts of sleeve  304 , ring  1 _ 303 , ring  2 _ 302 , and chip  301  arranged in this order from a plug insertion port. The connector ( 360 ,  190 ) is the three-pole plug including the three contacts of the chip ( 361 ,  191 ), the ring ( 362 ), and the sleeve ( 363 ,  193 ) arranged in this order from a tip. When the connector ( 360 ,  190 ) that is the three-pole plug is inserted into the connector ( 320 ) that is the three-polar jack, the microphone ( 1 ,  57 ) is coupled to headset main body  50 . 
     Therefore, the bone conduction headset system can detect that PTT switch  340  is pressed even when a transceiver coupled to connector  300  is either of type A and type B. 
     Modification example 4 is a bone conduction headset system including headset main body  50  and bone conduction microphone  1 . Headset main body  50  includes PTT switch  340 , the bone conduction speakers, connector  320  coupled with bone conduction microphone  1 , and connector  300  coupled with transceiver  7 . Connector  320  includes the three contacts of sleeve  323 , ring  322 , and chip  321  arranged in this order. Connector  300  includes the four contacts of sleeve  304 , ring  1 _ 303 , ring  2 _ 302 , and chip  301  arranged in this order. Sleeve  304  of connector  320  is coupled to sleeve  323  of connector  300 . Ring  322  of connector  320  is coupled to the ground. Chip  321  of connector  320  is coupled to ring  2 _ 302  of connector  300 , as well as is coupled, via PTT switch  340 , to the ground. The microphone device includes bone conduction microphone  1 , connector  360  configured to couple bone conduction microphone  1  to headset main body  50 , and PTT switch  370 . Connector  360  includes the three contacts of chip  361 , ring  362 , and sleeve  363  arranged in this order. Sleeve  363  is coupled to a positive side terminal of bone conduction microphone  1 . Chip  361  is coupled to a negative side terminal of bone conduction microphone  1 . Ring  362  is coupled, via PTT switch  370 , to the negative side terminal of bone conduction microphone  1 . 
     Therefore, the bone conduction headset system can detect that PTT switch  340  is pressed even when a transceiver coupled to connector  300  is either of type A and type B. Further, when bone conduction microphone  1  is coupled to connector  300 , PTT switch  370  of bone conduction microphone  1  can be used to make communications. 
     In the bone conduction headset system according to modification example 4, the bone conduction speakers include left speaker  331  and right speaker  332 . Ring  1 _ 303  of connector  300  is coupled to one of left speaker  331  and right speaker  332 . Chip  301  of connector  300  is coupled to the other of left speaker  331  and right speaker  332 . 
     Therefore, the bone conduction headset system can output, from left speaker  331  and right speaker  332 , sound entered through transceiver  7  coupled to connector  300 . 
     In the bone conduction headset system according to modification example 4, when connector  300  is coupled to transceiver  7  that is a smartphone type transceiver, ring  1 _ 303  and ring  2 _ 302  of connector  300  are short-circuited. For example, a part configured to short-circuit ring  1 _ 303  and ring  2 _ 302  may be inserted between connector  300  and transceiver  7 . 
     Therefore, ring  2 _ 302  of connector  300  is short-circuited with ring  1 _ 303  of connector  300 , and thus reaches the ground. Chip  321  of connector  320  also reaches the ground. In this case, chip  361  of connector  360  coupled to connector  320  also reaches the ground. As a result, bone conduction microphone  1  attains a normally operating state. Chip  191  of connector  190  coupled to connector  320  also reaches the ground. As a result, sound microphone  57  attains a normally operating state. Therefore, even when PTT switch  340  and PTT switch  370  are not pressed, communications are possible. As described above, the bone conduction headset system normally operates even when a transceiver coupled to connector  300  is a smartphone type transceiver. 
     Modification example 4 is headset main body  50  including PTT switch  340 , the bone conduction speakers, connector  320  coupled with a microphone, and connector  300  coupled with transceiver  7 . Connector  320  includes the three contacts of sleeve  323 , ring  322 , and chip  321  arranged in this order. Connector  300  includes the four contacts of sleeve  304 , ring  1 _ 303 , ring  2 _ 302 , and chip  301  arranged in this order. Sleeve  304  of connector  320  is coupled to sleeve  323  of connector  300 . Ring  322  of connector  320  is coupled to the ground. Chip  321  of connector  320  is coupled to ring  2 _ 302  of connector  300 , as well as is coupled, via PTT switch  340 , to the ground. 
     Therefore, headset main body  50  can detect that PTT switch  340  is pressed even when a transceiver coupled to connector  300  is either type A or type B. 
     In headset main body  50  according to modification example 4, connector  320  is the three-polar jack including the three contacts of sleeve  323 , ring  322 , and chip  321  arranged in this order from a plug insertion port. Connector  300  is the four-polar jack including the four contacts of sleeve  304 , ring  1 _ 303 , ring  2 _ 302 , and chip  301  arranged in this order from a plug insertion port. 
     Therefore, headset main body  50  can detect that PTT switch  340  is pressed even when a transceiver coupled to connector  300  is either type A or type B. 
     In headset main body  50  according to modification example 4, the bone conduction speakers include left speaker  331  and right speaker  332 . Ring  1 _ 303  of connector  300  is coupled to one of left speaker  331  and right speaker  332 . Chip  301  of connector  300  is coupled to the other of left speaker  331  and right speaker  332 . 
     Therefore, headset main body  50  can output, from left speaker  331  and right speaker  332 , sound entered through transceiver  7  coupled to connector  300 . 
     In headset main body  50  according to modification example 4, when connector  300  is coupled with transceiver  7  that is a smartphone type transceiver, ring  1 _ 303  and ring  2 _ 302  of connector  300  are short-circuited. For example, a part configured to short-circuit ring  1 _ 303  and ring  2 _ 302  may be inserted between connector  300  and transceiver  7 . 
     Therefore, ring  2 _ 302  of connector  300  is short-circuited with ring  1 _ 303  of connector  300 , and thus reaches the ground. Chip  321  of connector  320  also reaches the ground. In this case, chip  361  of connector  360  coupled to connector  320  also reaches the ground. As a result, bone conduction microphone  1  attains a normally operating state. Chip  191  of connector  190  coupled to connector  320  also reaches the ground. As a result, sound microphone  57  attains a normally operating state. Therefore, even when PTT switch  340  and PTT switch  370  are not pressed, conversations are possible. As described above, headset main body  50  normally operates even when a transceiver coupled to connector  300  is a smartphone type transceiver. 
     Other Exemplary Embodiments 
     As described above, the exemplary embodiments and the modification examples have been described as examples of the technique in the present disclosure. For that purpose, the accompanying drawings and the detailed description have been provided. 
     The components illustrated in the accompanying drawings and described in the detailed description can include components essential for solving the problems, as well as components that are not essential for solving the problems but required to describe the above techniques as an example. For this reason, it should not be immediately recognized that those unnecessary components are necessary just because those unnecessary components are described in the accompanying drawings and the detailed description. 
     The above exemplary embodiments and the modification examples are provided to exemplify the technique according to the present disclosure, and various changes, replacements, additions, omissions, and the like can be made within the scope of the claims and equivalents thereof. 
     For example, vocal cord sensor  11  is not limited to a piezoelectric element, but may be a vibration detection element such as acceleration pickup gauge or differential transformer. 
     For example, contact member  12 , housing  21 , and cover  22  may not each have a cylindrical shape, but may each have a rectangular tubular shape. 
     For example, the second exemplary embodiment has illustrated an example where, when bone conduction headset  5 A is worn, central part  54   a  of support body  54  is arranged behind the head. However, the present disclosure is not limited to the example. Such a structure may be applicable that central part  54   a  is to be arranged on the head. 
     The second exemplary embodiment has illustrated an example where, when bone conduction headset  5 A is worn, support body  54  being formed bypasses the lower sides of the ears. However, the present disclosure is not limited to the example. Such a structure may be applicable that support body  54  has a shape extending along upper sides of the ears, and support body  54  can be hooked on the ears. 
     The second exemplary embodiment has illustrated an example where, while mute switch  64  is pressed, volume of sound signals sent from transceiver  7  lowers, whereas, when mute switch  64  is released, the volume of sound signals sent from transceiver  7  returns to its original degree. However, the present disclosure is not limited to the configuration. Such a configuration may be applicable that, when mute switch  64  is pressed once, volume lowers, and, when mute switch  64  is pressed again, the volume returns to its original degree. 
     Modification example 4 to the exemplary embodiment has explained that connector  320  of headset main body  50  is a three-polar jack (female), whereas connector  300  is a four-pole plug (male). However, this is merely an example. The present disclosure is not limited to the example. Such jacks and plugs may be applicable that conform to shapes of connector  190  of sound microphone  57 , connector  360  of bone conduction microphone  1 , and the connector of transceiver  7 , which are to be coupled to headset main body  50 . For example, connector  320  may be a three-pole plug, whereas connector  300  may be a four-polar jack. 
     INDUSTRIAL APPLICABILITY 
     The present disclosure is applicable to a bone conduction microphone configured to come into contact with a human body and collect vocal cord vibration. The present disclosure is also applicable to a sound input and output device used when a construction site helmet, a motorcycle helmet, a headphone, or an intercommunication (in-com) device, for example, is worn on the head to make communications with a communication partner. 
     REFERENCE MARKS IN THE DRAWINGS 
     
         
           1 : bone conduction microphone (microphone) 
           2 : helmet 
           3 : chin strap 
           4 : microphone cable 
           5 ,  5 A: bone conduction headset 
           6 : headset cable 
           7 : transceiver 
           9 ,  9 A: communication device 
           10 : vibration collection unit 
           11 : vocal cord sensor 
           12 : contact member 
           12   a : contact part 
           12   b : side surface part 
           12   c : opening part 
           13 : pressing member 
           21 : housing 
           21   a : base 
           21   b : pillar 
           21   c : end face 
           21   d : switch fixing part 
           22 : cover 
           22   a : opening 
           23 : packing 
           25 : switch 
           25   a : operation unit 
           26 : metal fixture 
           30 : diaphragm 
           30   a : lower surface 
           30   b : upper surface 
           50 : headset main body (sound input and output device) 
           51 : speaker (bone conduction speaker) 
           52 : ear hook 
           54 : support body 
           54   a : central part 
           54   b : end (first end) 
           54   c : end (second end) 
           54   b   1 ,  54   c   1 : outside surface 
           55 : controller 
           57 : sound microphone (microphone) 
           58 : microphone holder 
           59 : coupler 
           62 ,  230 ,  340 ,  370 : PTT switch (communication switch) 
           64 : mute switch 
           71 : signal line 
           72 : sound line 
           73 : input unit 
           190 ,  360 : connector (third connector) 
           300 : connector (second connector) 
           320 : connector (first connector) 
         P 1 : pressing force 
         s 1 : stroke