Patent Publication Number: US-9412347-B2

Title: Device for vibrating a stringed instrument

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. National Stage entry of International Application Number PCT/JP2014/003047 filed under the Patent Cooperation Treaty having a filing date of Jun. 6, 2014, which claims priority to Japanese Patent Application Number JP2013-121936 having a filing date of Jun. 10, 2013, the disclosures of both of which are hereby incorporated by reference herein in their entirety for all purposes. 
     TECHNICAL FIELD 
     The present invention relates to a device for vibrating a string instrument, and in particular a device for vibrating a string instrument suitable for using the string instrument as a loudspeaker. 
     BACKGROUND ART 
     A number of devices have been proposed over the past years for automatically playing musical instruments. Small music boxes are classical examples, and automatic pianos that play musical pieces according to electronically stored musical score data have come to be widely used. Attempts have been made to automatically play string instruments, but few practical solutions have been proposed because of the complex mechanisms such as robot arms that are required to properly pluck the strings. 
     It is known to season or age string instruments. When a string instrument is left alone without being played for a prolonged period of time, the instrument may become unable to produce the desired sound quality. Therefore, it is practiced to play a string instrument at a prescribed interval to maintain the string instrument in proper order, and this is called as “seasoning”. When a string instrument is freshly manufactured, it may also be unable to produce the intended sound quality. For this reason, the freshly manufactured string instrument is sometimes “aged” or played for a prescribed time period before it is delivered to the buyer of the string instrument. As the work of seasoning and aging is laborious, it has been proposed to cause the strings of string instruments to vibrate by using special powered vibrating devices for the purpose of aging or seasoning the string instruments. 
     For instance, Patent Document 1 discloses an arrangement in which a vibrating device is attached to a violin via a bridge cradle that can be detachably mounted on the bridge of the violin to vibrate the violin. It is also disclosed to interpose a vibrating device between the soundboard and the strings of a guitar to vibrate the guitar. However, because the force by which the vibrating device is attached to the string instrument is limited, only a low power vibration can be applied to the string instrument. If a high power vibration which is powerful enough to use the string instrument as a loudspeaker is applied to the string instrument, the vibrating device may be caused to rattle, and a desired vibration of the string instrument cannot be achieved. The vibrating device may even be detached from the string instrument during use. 
     The string instrument itself may be worked upon or modified so as to firmly attach the vibrating device to the string instrument, but this impairs the quality of the string instrument to such an extent as to render the string instrument incapable of producing the expected sound quality and damage the external appearance of the string instrument. Typically, such modification catastrophically depreciates the value of the string instrument. 
     Patent Document 2 proposes to use a violin as a loudspeaker by modifying the violin itself. The vibrating device is installed inside the violin in such a manner that the vibrating device is required to be installed during the manufacturing of the violin. Thus, the violin is not an ordinary violin from the beginning. A vibrating device could be installed in an existing violin with some effort, but no such undertaking is conceivable if the violin happens to be a costly one. 
     PRIOR ART REFERENCE(S) 
     Patent Document(s) 
     
         
         Patent Document 1: JP2009-505137A 
         Patent Document 2: JP2011-035851A 
       
    
     SUMMARY OF THE INVENTION 
     Task to be Accomplished by the Invention 
     In view of such problems of the prior art, a primary object of the present invention is to provide a device for vibrating a string instrument to allow the string instrument to be used as a loudspeaker. 
     A second object of the present invention is to provide a device for vibrating a string instrument that can be firmly attached to the string instrument without requiring a drastic or permanent work to be applied thereto for the purpose of using the string instrument as a loudspeaker. 
     Means to Accomplish the Task 
     Such objects of the present invention can be accomplished by providing a device ( 20 ,  100 ) for vibrating a string instrument ( 1 ) provided with a bridge ( 13 ), comprising: a base member ( 22 ,  102 ) provided with a load point member ( 24 ,  156 ) that engages the bridge ( 13 ); and a vibration generator ( 50 ,  140 ) mounted on the base member ( 22 ,  102 ) and configured to convert an electric signal into a mechanical vibration; wherein the base member ( 22 ,  102 ) includes a fulcrum member ( 30 ,  120 ) engaging an upper side of at least one string ( 9 ) of the string instrument ( 1 ), an anchor member ( 38 ,  130 ) engaging a lower side of the at least one string ( 9 ) at a point located between the load point member ( 24 ,  156 ) and the fulcrum member ( 30 ,  120 ) and a means ( 40 ,  132 ) for displacing at least one of the fulcrum member ( 30 ,  120 ) and the anchor member ( 38 ,  130 ) in a direction to urge the load point member ( 24 ,  156 ) against the bridge ( 13 ). 
     The vibrating device ( 20 ,  100 ) engages the string ( 9 ) at the fulcrum member ( 30 ,  120 ) and the anchor member ( 38 ,  130 ), and engages the bridge ( 13 ) at the load point member ( 24 ,  156 ) so that the vulnerable parts such as the soundboard of the string instrument ( 1 ) is avoided, and only the high strength part thereof is engaged. Therefore, the load point member ( 24 ,  156 ) can be pressed upon the bridge ( 13 ) with an adequate force so that the string instrument can be sounded with a large sound volume and a high sound quality. The term “bridge” means a member that is attached to the soundboard or the like to define an end of a string ( 9 ), and may also be called as “saddle”. The name of this part may vary depending on each particular kind of musical instruments. In the description and claims of this application, the term “bridge” should be interpreted in the broadest meaning as meaning a member that delimits an effective end of a string. 
     Preferably, the anchor member ( 38 ,  130 ), the load point member ( 24 ,  156 ) and the fulcrum member ( 30 ,  120 ) are located along a length of the string ( 9 ). Typically, the vibration generator ( 50 ,  140 ) and the load point member ( 24 ,  156 ) are located on one end part of the base member ( 22 ,  102 ), and the fulcrum member ( 30 ,  120 ) is provided on the other end part of the base member ( 22 ,  102 ). When the cam mechanism for lifting the anchor member ( 38 ,  130 ) upward is provided on the base member ( 22 ,  102 ), the load point member ( 24 ,  156 ) can be pushed against the bridge ( 13 ) by using a simple structure. 
     The load point member ( 24 ,  156 ) may consist of a single projection or a pair of projections arranged symmetrically about the center. In either case, the vibrating device ( 20 ,  100 ) can be supported on the musical instrument in a manner corresponding to the shape of the bridge ( 13 ) of the musical instrument in a stable manner. 
     The anchor member ( 38 ,  130 ) may comprise a rod member or a hook member engaging at least two strings ( 9 ) of the string instrument and extending along a direction perpendicular to an axial line connecting central parts of the load point member ( 24 ,  156 ) and the fulcrum member ( 30 ,  120 ) with each other. The rod member may be supported so as to be moveable toward and away from the musical instrument. The fulcrum member ( 30 ,  120 ) may comprise a rod member engaging at least two strings ( 9 ) of the string instrument and extending along a direction perpendicular to an axial line connecting central parts of the load point member ( 24 ,  156 ) and the fulcrum member ( 30 ,  120 ) with each other. 
     The base member ( 22 ) may comprise a locating portion ( 28 ) provided adjacent to the load point member ( 24 ), the locating portion ( 28 ) being configured to abut the bridge ( 13 ) from a side of the fulcrum member ( 30 ) in a lengthwise direction of the strings ( 9 ). Thereby, simply by sliding the vibrating device ( 20 ) along the strings ( 9 ), the axial positioning of the vibrating device ( 20 ) can be accomplished in a both simple and precise manner. 
     In order for a wide frequency range of sound to be reproduced, the vibration generator may comprise a pair of vibration generators ( 50 A,  50 B), one for high frequency range sound and the other for low frequency range sound, provided on either side of an axial line extending between centers of the load point member ( 24 ) and the fulcrum member ( 30 ). 
     Preferably, the base member ( 22 ) includes a pair of bifurcated parts ( 22 A,  22 B) that support the high frequency range vibration generator ( 50 A) and the low frequency vibration generator ( 50 B), respectively, and the load point member ( 24 ) is provided on each of the bifurcated parts ( 22 A,  22 B). 
     Preferably, a first vibration insulation member ( 108 ) for insulating vibrations between a vibration transmission member ( 152 ) of the vibration generator ( 140 ) and the base member ( 102 ) is provided between the vibration transmission member ( 152 ) and the base member ( 102 ). 
     Thereby, the vibration transmission member ( 152 ) is mounted on the base member ( 102 ) via the first vibration insulation member ( 108 ) so that the mechanical vibration of the vibration transmission member ( 152 ) is prevented from being transmitted to the base member ( 102 ). Thereby, the mechanical vibration of the vibration transmission member ( 152 ) is prevented from being transmitted to the fulcrum member ( 120 ) and the anchor member ( 130 ) via the base member ( 102 ) so that the mechanical vibration of the vibration transmission member ( 152 ) is prevented from being transmitted to the strings ( 9 ), and the sound is emitted strictly from the body ( 5 ). Therefore, the produced sound has a high quality, and in particular has a high clarity owing to the absence of noises in high frequency ranges. 
     Preferably, a second vibration insulation member ( 116 ) for insulating vibrations between the base member ( 102 ) and the fulcrum member ( 120 ) is provided between the base member ( 102 ) and the fulcrum member ( 120 ), and a third vibration insulation member ( 126 ) for insulating vibrations between the base member ( 102 ) and the anchor member ( 130 ) is provided between the base member ( 102 ) and the anchor member ( 130 ). 
     In this case, the mechanical vibration of the vibration transmission member ( 152 ) is prevented from being transmitted to the fulcrum member ( 120 ) and the anchor member ( 130 ) via the base member ( 102 ) so that an even higher quality sound can be achieved by the emission of sound from the body ( 5 ). 
     Effect of the Invention 
     Thus, the present invention provides a vibrating device for a string instrument that allows the string instrument to be sounded with a large sound volume and a high sound quality without requiring a drastic or permanent work to be applied thereto, and allows the string instrument to be favorably utilized as a loudspeaker. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a vibrating device for a string instrument given as a first embodiment of the present invention applied to a guitar; 
         FIG. 2  is a front view of the first embodiment; 
         FIG. 3  is a rear view of the first embodiment; 
         FIG. 4  is a side view of the first embodiment; 
         FIG. 5  is an end view of the first embodiment; 
         FIG. 6  is a vertical sectional view of a vibration generator for the first embodiment; 
         FIG. 7  is a front view of the spring member used in the vibration generator shown in  FIG. 6 ; 
         FIG. 8  is a view similar to  FIG. 4  showing a mode of operation of the first embodiment; 
         FIG. 9  is a view similar to  FIG. 4  showing a vibrating device for a string instrument given as a second embodiment of the present invention; 
         FIG. 10  is a front view showing a vibrating device for a string instrument given as a third embodiment of the present invention; 
         FIG. 11  is a rear view of the third embodiment; 
         FIG. 12  is a perspective view of a vibrating device for a string instrument given as a fourth embodiment of the present invention applied to a guitar; and 
         FIG. 13  is a vertical sectional view of the fourth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     Preferred embodiments of the present invention are described in the following with reference to the appended drawings. In the following description, the axial direction of the string instrument is defined as a line extending between a soundboard side and a head side of the string instrument. In regard to the soundboard located on the front side of the instrument, the direction directed toward the soundboard from the front side thereof is referred to as a downward direction or a backside direction, and the direction directed away from the soundboard is referred to as an upward direction or a front side direction. The term “bridge” as used in this description refers to a member attached to the soundboard or the like to define the corresponding effective end of the string, and may also be called by other names such as “saddle” depending on the kinds of the string instruments. In the description and claims of this application, the term “bridge” should be interpreted in the broadest meaning as a member that delimits an effective end of a string. 
     As shown in  FIG. 1 , a guitar  1  having a vibrating device  20  attached thereto is provided with a body  5  formed by a front board (soundboard)  3 , a sideboard (not shown in the drawing) and a back board (not shown in the drawing). The front board  3  is formed with a sound hole  7 . The guitar  1  has six strings  9 . 
     A bridge base member  11  consisting of a strip of plate is fixedly attached to the front board  3  by using an adhesive agent. A bridge (saddle)  13  extending perpendicularly to the lengthwise direction of the strings  9  is attached to the bridge base member  11 . 
     An end of each string  9  is passed above the bridge  13  and is secured to a bridge pin  15  which is in turn fixedly secured to the bridge base member  11 . The string  9  is placed under tension by a tension adjusting mechanism (not shown in the drawing) which is connected to the other end of the string  9  so that the string  9  is pressed against the upper side of the bridge  13  and the bridge  13  defines an effective end of the string  9 . 
     A vibrating device  20  given as a first embodiment of the present invention is described in the following with reference to  FIGS. 2 to 5 . The vibrating device  20  includes a base member  22  consisting of a substantially rectangular plate member elongated in the lengthwise direction of the strings  9 . 
     The lower surface of the base member  22  facing the guitar  1  is fitted with or formed with a vibration transmission member  26  in a lengthwise end part of the base member  22 , and the vibration transmission member  26  is centrally provided with a load point member  24  in the form of a projection. The vibration transmission member  26  is further provided with a locating projection  28  in a part thereof slightly offset from the load point member  24  toward the other end with respect to the lengthwise direction. The locating projection  28  projects slightly further than the load point member  24 . The side of the load point member  24  facing away from the locating projection  28  is formed with a guide slope  24 A that facilitates the mounting of this device as will be described hereinafter. 
     The other lengthwise end of the base member  22  is fitted with or formed with a fulcrum member  30  consisting of a rod shaped member extending perpendicularly to the lengthwise direction of the strings  9  on the lower surface thereof facing the guitar  1 . The lower surface of the fulcrum member  30  is formed with a large number of grooves  30 A extending in the lengthwise direction of the base member  22 . These grooves  30 A prevent slippage between the strings  9  and the fulcrum member  30  when the device is in operation. A laterally central part of the fulcrum member  30  is provided with a projection  32  which serves as a guide member when sliding the vibrating device  20  over the strings  9  in the lengthwise direction into an operating position by being fitted between the two central strings  9 . 
     A lengthwise middle part of the base member  22  is centrally provided with a support hole  34  passed (vertically) through the thickness of the base member  22 . The support hole  34  receives a support member  36  in a both rotatable and vertically slidable manner, and a lower end of the support member  36  projecting below the base member  22  is fitted with an anchor member  38 . The anchor member  38  consists of a rod member extending perpendicularly to the lengthwise direction of the strings  9  between the vibration transmission member  26  (load point member  24 ) and the fulcrum member  30 . The upper surface of the anchor member  38  is formed with a large number of grooves  38 A ( FIG. 1 ) extending in the lengthwise direction of the base member  22  in a similar manner as the lower surface of the fulcrum member  30 . 
     A lever cam  40  is provided on the base member  22 . The lever cam  40  consists of an L-shaped member including an arm  40 A and a cam  40 B extending perpendicularly from each other and having a pivot pin  42  passed through the junction of these two parts as will be discussed hereinafter. A slot  40 C extends from the free end of the cam  40 B to the junction between the two parts. The slot  40 C receives the upper end of the support member  36 , and the pivot pin  42  is passed through the junction of the lever cam  40  and through the upper end of the support member  36  across the slot  40 C so that the lever cam  40  is pivotally connected to the support member  36  via the pivot pin  42 . 
     A mushroom pin  44  projects upward from the upper surface of the base member  22  at a part thereof adjoining the support member  36  from the side of the fulcrum member  30 . The pivotal movement of the lever cam  40  around the pivot pin  42  is permitted by the mushroom pin  44  being received by the slot  40 C, and the range of the pivotal movement of the lever cam  40  is delimited by the arm  40 A or the cam  40 B of the lever cam  40  being engaged by an enlarged head  44 A of the mushroom pin  44 . 
     In this support structure, when the arm  40 A of the lever cam  40  is placed in the horizontal posture illustrated in  FIG. 4 , the cam  40 B is in the upright position so that the anchor member  38  is placed in a raised position. When the arm  40 A of the lever cam  40  is pivoted into the upright posture as shown in  FIG. 8A , the cam  40 B is laid flat on the base member  22  so that the anchor member  38  is placed in a lowered position. 
     The free end of the cam  40 B is formed as a flat end in the illustrated embodiment, but may also be formed in different configurations as long as the cam  40 B is enabled to perform the function thereof. 
     A vibration generator  50  is mounted on a front surface of the base member  22  facing away from the guitar  1  at a lengthwise end portion thereof. As shown in  FIG. 6 , the vibration generator  50  includes a solid cylindrical permanent magnet  52 , a yoke member  56  extending from a part thereof connected to an axial end of the permanent magnet  52  to a part thereof surrounding the outer circumferential surface of the other axial end of the permanent magnet  52  at a prescribed magnetic gap  54  and a voice coil  60  resiliently supported by a spring member  58  so as to be positioned in the magnetic gap  54 . A disk  62  made of plastic material is fixed to the voice coil  60  as an output end. The yoke member  56  is surrounded by an appropriate case which is not shown in the drawing. 
     As shown in  FIG. 7 , the spring member  68  is made by cutting a sheet spring into a prescribed shape, and integrally includes an inner annular portion  58 A fixedly attached to the disk  62  in the center, an outer annular portion  58 B disposed coaxially with respect to the inner annular portion  58 A, a pair of concentric intermediate annular portions  58 C and a plurality of bridge portions  58 D connecting adjoining annular portions  55 A,  55 B and  55 C at an angular interval of 90 degrees. 
     When the vibration generator  50  receives a supply of electric current corresponding a sound signal, the voice coil  60  causes a vibratory movement of the disk  62 . Therefore, any object that is directly or indirectly attached to the disk  62  which in this case consists of the vibration transmission member  26  is caused to vibrate. 
     The mode of operation of the vibrating device  20  is described in the following with reference to  FIG. 8 . 
     First of all, as shown in  FIG. 8A , the arm  40 A of the lever cam  40  is lifted until the support member  36  is caused to project downward from the base member  22  to the maximum extent. By suitably turning the base member  22  so as to be perpendicular to the strings  9 , the rod-shaped anchor member  38  can be passed through the gap between the adjoining strings  9  in the center and positioned below the strings  9 . The vibration transmission member  26  is then slid along the upper side of the strings  9  toward the bridge  13  until the locating projection  28  abuts the bridge  13 . During this process, the vibration transmission member  26  is favorably guided by the strings  9  so that the load point member  24  of the vibration transmission member  26  can favorably ride onto the bridge  13  owing to the sliding movement of the guide slope  24 A over the bridge  13  as the load point member  24  is forced against the bridge  13 . The relative position between the locating projection  28  and the load point member  24  is determined such that the load point member  24  is correctly engaged by the upper surface of the bridge  13  as a result of this process. 
     When the arm  40 A of the lever cam  40  is pushed down under this condition as shown in  FIG. 8B , owing to the camming action between the cam  40 B of the lever cam  40  and the corresponding part of the base member  22 , the anchor member  38  along with the support member  36  is raised. This upward motion of the anchor member  38  causes the anchor member  38  to be pushed against the lower side of the strings  9 . As a result, the base member  22  creates a third class lever including the fulcrum formed by the contact between the fulcrum member  30  and the strings  9 , the effort point formed by the contact between the anchor member  38  and the strings  9 , and the load point formed by the contact between the load point member  24  such that the load point member  24  of the vibration transmission member  26  is pushed against the upper surface of the bridge  13 . In particular, when the anchor member  38  is pushed firmly against the lower side of the strings  9  against the elastic force produced by the strings  9 , the load point member  24  of the vibration transmission member  26  is pressed against the bridge in a correspondingly firm manner with the fulcrum member  30  acting as the fulcrum. 
     The magnitude of this pressing force can be freely selected by appropriately determining the dimensions and the configurations of the lever cam  40 . The magnitude of the pressing force can also be adjusted by changing the tension of the strings  9  on which the vibrating device  20  is mounted. The grooves  30 A and  38 A formed in the fulcrum member  30  and the anchor member  38  perform the function of preventing the strings  9  from slipping sideways, and contribute to supporting the vibrating device  20  on the string instrument in a stable manner. Alternatively or additionally to the grooves  30 A and  38 A formed in the fulcrum member  30  and the anchor member  38 , a rubber layer may be provided on the surface of the fulcrum member  30  and/or the anchor member  38  so that the frictional force between these members and the strings  9  may be increased. 
     The anchor member  38  is supported by a plurality of strings  9  while the single load point member  24  provided centrally in the vibration transmission member  26  is supported by the bridge  13  so that the vibrating device  20  is supported at three points including the fulcrum provided by the fulcrum member  30 . Therefore, the vibrating device  20  can be mounted on the guitar  1  firmly against vibrations without modifying the guitar  1  for mounting the vibrating device  20 . Because the vibrating device  20  engages the strings  9  at the fulcrum member  30  and the anchor member  38  and the bridge  13  at the load point member  24 , the vibrating device  20  is required to engage only the relatively strong parts of the guitar  1 , and the vulnerable parts of the guitar  1  such as the front board  3  of the guitar  1  are spared from loading. 
     When the vibration generator  50  is activated under this condition, the produced vibrating force is transmitted to the front board  3  via the bridge  13 , and the vibration energy produced from the vibration generator  50  can be converted into acoustic energy at a high efficiency via the vibration of the front board  3  and the resulting vibration of the air in the body  5 . 
     The signal that is to be applied to the vibrating device  20  may be derived from various sound sources such as compact disks, radio broadcasts and live music captured by microphones. It is also possible to attach a vibration pickup device on a part of a string instrument itself such as the body and the bridge, and use the output from the pickup device as a sound source. Thereby, the sound produced by the string instrument can be reproduced in a highly favorable manner. If the vibrating device  20  is mounted on a plurality of string instruments of either a same kind or different kinds, a particularly impressive sound quality can be achieved. 
     According to the experiments conducted by the inventors, when the device of the present invention is attached to a guitar, not only guitar musical pieces but also musical pieces of other musical instruments having a similar sound quality and sound range could be favorably reproduced. It was also demonstrated that the device of the present invention attached to a relatively small musical instrument can produce sound of a wider frequency range and a greater volume than a loudspeaker provided with a loudspeaker box of a comparable size. 
       FIG. 9  shows a second embodiment of the present invention. In  FIG. 9 , the parts corresponding to those of the previous embodiment are denoted with like numerals without necessarily repeating the description of such parts. 
     In this embodiment, the vibration transmission member  26  is provided with a pair of projections serving as the load point members  24  that are to be engaged by the bridge  13 . In this case, the two load point members  24  provided on the vibration transmission member  26  are supported by the bridge  13 . In this case, the vibrating device  20  can be supported by the guitar  1  in a stable manner even when the anchor member  38  is supported by only one string  9  in the center. 
       FIGS. 10 and 11  illustrate the third embodiment of the present invention. In  FIGS. 10 and 11 , the parts corresponding to those of the previous embodiments are denoted with like numerals without necessarily repeating the description of such parts. 
     In this embodiment, one of the lengthwise ends of the base member  22  is bifurcated into two bifurcated parts  22 A and  22 B. A vibration generator  50 A,  50 B is attached to each bifurcated part  22 A,  22 B. One of the vibration generators  50 A is for producing sound in a high frequency range, and the other vibration generator  50 B is for producing sound in a low frequency range. Each vibration generator  50 A,  50 B may be constructed similarly as the one shown in  FIGS. 6 and 7 , and the spring member  58  of the vibration generator  50 A for the high frequency range is provided with a higher stiffness than that of the vibration generator  50 B for the low frequency range. 
     The backside of the base member  22  is provided with a vibration transmission member  26  extending laterally at the position corresponding to the vibration generators  50 A and  50 B, and a pair of projections project from parts of the vibration transmission member  26  corresponding to the central positions of the vibration generators  50 A and  50 B, respectively, as the load point members  24  that are to be engaged by the bridge  13 . The central part of the vibration transmission member  26  is made of highly deformable member such as rubber so that the two bifurcated parts  22 A and  22 B are allowed to vibrate with relatively little resistance and independently from each other toward and away from the string instrument. 
     According to this illustrated embodiment the string instrument can be vibrated over a wide sound frequency range so that musical pieces covering a wide sound range such as orchestra music pieces can be reproduced in a favorable manner. 
     In this embodiment, the vibration transmission member  26  extends over the two bifurcated parts  22 A and  22 B of the base member  22 , but two such vibration transmission members  26  each provided with a separate load point member  24  may also be provided individually on the two bifurcated parts  22 A and  22 B, respectively. The locating projection  28  may be provided on each vibration transmission member  26 , or on only one of the two vibration transmission members  26 . Alternatively, the locating projection  28  may be provided on positions other than the vibration transmission member  26  such as the base member  22 . 
       FIGS. 12 and 13  illustrate the fourth embodiment of the present invention. In  FIGS. 12 and 13 , the parts corresponding to those of the previous embodiments are denoted with like numerals without necessarily repeating the description of such parts. 
     As shown in  FIG. 13 , the vibrating device  100  includes a base member  102  made of aluminum and elongated in the lengthwise direction of the strings  9 . A circular opening  104  is passed through a lengthwise end part of the base member  102 . 
     A vibration generator  140  is placed in the opening  104 . The vibration generator  140  includes a solid cylindrical permanent magnet  142 , a hollow cylindrical yoke member  144  with a closed upper end and made of magnetic material which is magnetically connected to the upper end (one of the magnetic poles) of the permanent magnet  142 , a hollow cylindrical bobbin  150  made of non-magnetic material and connected to the yoke member  144  in a vertically moveable manner via a support member  146  and a spring member  148 , a disk shaped vibration transmission member  152  attached to the bobbin  150  and a voice coil (moving coil)  154  wound around the bobbin  150 . 
     The vibration transmission member  152  is centrally provided with a projection  158  projecting downwardly from the vibration transmission member  152  so that the center of the projection  158  serves as a load point member  156 . The spring member  148  may be similar to the spring member  58  of the first embodiment. 
     The base member  102  is provided with a radial flange  106  extending radially inward from a vertically (axially) middle point of the inner circumferential of the opening  104 . A vibration insulation sheet (first vibration insulation member)  108  is attached to the lower surface of the flange  106  by using an adhesive agent. The vibration transmission member  152  is supported by the base member  102  via a support plate  110  having an outer peripheral part attached to the vibration insulation sheet  108  by using an adhesive agent and a central part attached to the flat bottom surface of the vibration transmission member  152  by using an adhesive agent. In other words, the base member  102  supports the vibration transmission member  152  via the support plate  110  and the vibration insulation sheet  108 . 
     The vibration insulation sheet  108  is made of cushioning material such as foamed plastic and ether polyurethane, and minimizes the transmission of mechanical vibrations from the vibration transmission member  152  to the base member  102  by undergoing an elastic deformation. 
     The support plate  110  may be made of metallic or plastic material and is provided with slits  110 A or slots so as to demonstrate a spring property. Therefore, the vibration generator  140  is resiliently supported by the base member  102 . 
     When an electric signal (electric current) is supplied to the voice coil  154  of the vibration generator  140 , owing to the magnetic interaction of the coil  154  with the permanent magnet  142  and the yoke member  144 , the vibration transmission member  152  is vertically displaced or mechanically vibrates with respect to the side of the yoke member  144  against the spring force of the spring member  148 . 
     The support plate  110  and the vibration transmission member  152  are provided with air openings  110 B and  152 A, respectively, for communicating the inner space of the bobbin  150  with the exterior so that a fluid resistance due to the compression of air in the bobbin  150  may be avoided during the vibratory movement of the bobbin  150 . The slits  110 A in the support plate  110  may function as holes for communicating the interior of the opening  104  with the exterior. 
     The upper peripheral part of the opening  104  is provided with a protective ring member  112  for closing the upper end of the opening  104  without interfering with the yoke member  144 . 
     The other lengthwise end part of the base member  102  is centrally provided with a support hole  114  having an open lower end. The support hole  114  receives a support rod  118  therein via a vibration insulation sleeve (second sound vibration insulation member)  116 . The lower end of the support rod  118  projects downward from the base member  102 , and the projecting lower end of the support rod  118  is fitted with a fulcrum member  120  consisting of a rod member extending perpendicularly to the lengthwise direction of the strings  9 . 
     The vibration insulation sleeve  116  is made of cushioning material such as ether polyurethane having a rubber resiliency. A rubber sheet  122  is bonded to the lower surface of the fulcrum member  120  by using an adhesive agent. The rubber sheet  122  prevents the slippage between the fulcrum member  120  and the strings  9  during use, and insulates vibrations between the fulcrum member  120  and the strings  9  at the same time. 
     A lengthwise middle part of the base member  102  is centrally provided with a support hole  124  passed through the thickness of the base member  102 . A support shaft  128  is received in the support hole  124  via a vibration insulation sleeve (third vibration insulation member)  126  in a rotatable and vertically slidable manner. The lower end of the support shaft  128  extends downward from the base member  102 , and the projecting lower end of the support shaft  128  is fitted with an anchor member  130 . The anchor member  130  consists of a rod member extending perpendicularly to the lengthwise direction of the strings  9  between the vibration transmission member  152  (load point member  156 ) and the fulcrum member  120 . 
     The vibration insulation sleeve  126  is made of cushioning material such as ether polyurethane having a rubber resiliency. 
     A lever cam  132  is provided on the base member  102 . The lever cam  132  consists of an L-shaped member including an arm  132 A and a cam  132 B extending perpendicularly from each other and having a pivot pin  134  passed through the junction of these two parts. A slot  132 C is formed in the cam  132 B. The slot  132 C receives the upper end of the support shaft  128 , and the pivot pin  134  is passed through the junction of the lever cam  132  and through the upper end of the support shaft  128  across the slot  132 C so that the lever cam  132  is pivotally connected to the support shaft  128  via the pivot pin  134 . 
     In this support structure, when the arm  132 A of the lever cam  132  is placed in the horizontal posture illustrated in  FIG. 12  by solid lines, the cam  132 B is in the upright position so that the anchor member  130  is placed in a raised position. When the arm  132 A of the lever cam  132  is pivoted into the upright posture as shown in  FIG. 12  by imaginary lines, the cam  132 B is laid horizontally on the base member  102  so that the anchor member  130  is placed in a lowered position. 
     The mode of operation of the vibrating device  100  is described in the following. 
     The cam  132 B of the lever cam  132  is laid horizontally by lifting the arm  132 A as shown by the imaginary lines in  FIG. 12  so that the anchor member  130  is placed in the lowered position. By suitably turning the anchor member  130  so as to be perpendicular to the strings  9 , the rod-shaped anchor member  130  is passed through the gap between the adjoining strings  9  in the center and positioned below the strings  9 . The anchor member  130  is then put back to the original position perpendicular to the lengthwise direction of the strings  9 , and the load point member  156  is placed on the strings  9  on the bridge  13  or on the bridge  13  itself while the rubber sheet  122  of the fulcrum member  120  is placed on the strings  9 . 
     The lever cam  132  is then tilted down as shown by the solid lines in  FIG. 12  so that the arm  132 A is placed into the upright posture to raise the support shaft  128 . As a result, the anchor member  130  is placed in the raised position so that the strings  9  are pushed upward by the anchor member  130  at the part of the strings  9  located between the parts of the strings  9  engaging the load point member  156  and the fulcrum member  120 . 
     The lifting of the strings  9  in this manner causes the base member  102  to act as a third class lever which has the fulcrum at the engagement point between the fulcrum member  120  and the strings  9 , the effort point at the engagement point between the anchor member  130  and the strings  9  and the load point at the engagement point between the load point member  156  and the strings  9 . Thus, by pressing the fulcrum member  120  against the upper side of the strings  9 , and the anchor member  130  against the lower side of the strings  9 , with the vibrating device  100  supported by the strings  9 , the free end of the projection  158  of the vibration transmission member  152  or the load point member  156  is pushed against the bridge  13 . As a result, without requiring to modify the guitar  1  for mounting the vibrating device  100  thereon, the vibrating device  100  can be mounted on the guitar  1  in a highly firm manner against vibrations. 
     Thus, the vibrating device  100  engages the strings  9  at the fulcrum member  120  and the anchor member  130 , and engages the bridge  13  at the load point member  156  so that the vulnerable parts of the guitar  1  such as the soundboard are left untouched, and only the parts having a high mechanical strength are engaged by the vibrating device  100 . Furthermore, this vibrating device  100  allows the load point member  156  to be adequately firmly pressed against the bridge  13 . 
     When an electric signal is supplied to the voice coil  154  of the vibration generator  140  to cause the vibration transmission member  152  to undergo a mechanical vibration, this mechanical vibration is transmitted from the vibration transmission member  152  to the bridge  13  via the projection  158  so that the soundboard such as the front board  3  vibrates, and the body  5  functions as a loudspeaker box. Because the vibrating device  100  is mounted on the guitar  1  with a high resistance against vibrations, impairment of sound quality that could be caused by the rattling of the vibrating device  100  on the guitar  1  can be avoided, and the possibility of the detachment of the vibrating device  100  from the guitar  1  during use can be eliminated, 
     Furthermore, because the load point member  156  is so firmly attached to the bridge  13  that the mechanical vibration from the vibration transmission member  152  can be efficiently transmitted to the bridge  13 , and the guitar  1  can be sounded with a large sound volume and a high sound quality. 
     Because the vibration transmission member  152  is attached to the base member  102  via the vibration insulation sheet  105  that insulates vibrations, the mechanical vibration of the vibration transmission member  152  is prevented from being transmitted to the base member  102 . Therefore, the mechanical vibration of the vibration transmission member  152  that could be otherwise transmitted to the fulcrum member  120  or the anchor member  130  via the base member  102  is prevented from vibrating the strings  9  via the base member  102 . 
     Thereby, the sounding of the body  5  or the acoustic emission from the body  5  due to the vibration of the strings  9  can be avoided, and is caused solely by the vibration of the body  5  which is in turn caused by the vibration of the bridge  13  by the vibrating device  100 . Therefore, the sound is emitted from the body  5  so that the produced sound is high in quality, and is free from noises in high frequency ranges. 
     Even if the mechanical vibration of the vibration transmission member  152  were transmitted to the base member  102 , because the vibration insulation sleeves  116  and  126  are interposed between the fulcrum member  120  and the base member  102  and between the anchor member  130  and the base member  102 , respectively, the mechanical vibration of the base member  102  would not be transmitted to the fulcrum member  120  or the anchor member  130 . For this reason also, the mechanical vibration of the vibration transmission member  152  is prevented from being transmitted to the fulcrum member  120  or the anchor member  130  so that the fulcrum member  120  or the anchor member  130  are prevented from vibrating the strings  9 . Therefore, the vibrating device  100  causes the sound to be emitted exclusively from the body  5  so that a high sound quality can be achieved. 
     According to the embodiments discussed above, sound can be emitted from the guitar having an attractive appearance so that the listener can enjoy a pleasing visual and audio ambiance. 
     The present invention has been described in terms of specific embodiments, but as can be appreciated by a person skilled in the art, the present invention is not limited by such embodiments, and can be modified without departing from the spirit of the present invention. 
     For instance, in the foregoing embodiments, a cam mechanism was used to urge the load point member  24  of the vibration transmission member  26  against the bridge  13  by pushing the anchor member  38  onto the lower side of the strings  9 . However, it is also possible to fixedly secure the anchor member  38  to the base member  22 , and use a cam mechanism to urge the load point member against the bridge by pushing the fulcrum member  30  onto the lower side of the strings  9 . 
     In the illustrated embodiments, the vibration generators  50  and  140  consisted of moving coil vibration generators, but may also consist of moving iron vibration generators and piezo electric vibration generators. The spring members  58  and  148  for the vibration generators  50  and  140  may also consist of bellows. 
     The musical instruments that can be used for the working of the present invention are not limited to guitars and violins, but any other musical instruments having parts corresponding to the strings and the bridges. The present invention can also be used for seasoning and aging string instruments. 
     The various components described in conjunction with the foregoing embodiments are not entirely essential for the present invention, but can be appropriately substituted and omitted without departing from the spirit of the present invention. 
     The contents of the original Japanese patent application (JP2013-121936 filed Jun. 10, 2013) which serves as the basis for the Paris Convention priority claim made for this application are incorporated into this application by reference. 
     INDUSTRIAL APPLICABILITY 
     According to the present invention, sound can be emitted from a string instrument having an attractive appearance so that the listener can enjoy a pleasing visual and audio ambiance. Therefore, the present invention can be worked in both public and private environments, and is beneficial for both individuals and the public in wide. 
     GLOSSARY OF TERMS 
     
         
           1  guitar 
           3  front board 
           5  body 
           7  sound hole 
           9  string 
           11  bridge base member 
           13  bridge 
           15  bridge pin 
           20  vibrating device 
           22  base member 
           24  load point member 
           26  vibration transmission member 
           28  locating projection 
           30  fulcrum member 
           32  projection 
           34  support hole 
           36  support member 
           38  anchor member 
           40  lever cam 
           42  pivot pin 
           44  mushroom pin 
           50  vibration generator 
           52  permanent magnet 
           54  magnetic gap 
           56  yoke member 
           58  spring member 
           60  voice coil 
           62  disk 
           100  vibrating device 
           102  base member 
           108  vibration insulation sheet 
           110  support plate 
           116  vibration insulation sleeve 
           118  support rod 
           120  fulcrum member 
           122  rubber sheet 
           125  vibration transmission member 
           126  vibration insulation sleeve 
           130  anchor member 
           132  lever cam 
           140  vibration generator 
           142  permanent magnet 
           144  yoke member 
           146  support member 
           148  spring member 
           150  bobbin 
           152  vibration transmission member 
           154  voice coil 
           156  load point member 
           158  projection