Patent Publication Number: US-8126169-B2

Title: Super magnetostriction speaker

Description:
TECHNICAL FIELD 
     This invention relates to a supermagnetostriction speaker which vibrates, as a vibration plate, an external body by utilizing a supermagnetostriction phenomenon that occurs in the supermagnetostriction element. Supermagnetostriction has the same meaning as giant-magnetostrictive. 
     BACKGROUND ART 
     A magnetostriction phenomenon has been known in which a material changes its form in a magnetic field given from an external unit. The material that develops the supermagnetostriction phenomenon is called supermagnetostriction material. A new supermagnetostriction material has been developed in recent years producing a dimensional change of 1000 ppm or more in a state where a magnetic field is applied to the supermagnetostriction material from the external unit. 
     It has further been known that the supermagnetostriction materials generate a large stress, and some of them attain 400 kgf/mm 2  or more. Further, the supermagnetostriction material quickly responds when it comes to a change in the shape of the material for a magnetic field from the external unit, and some of them change the size in less than one microsecond after the magnetic field is applied. 
     It has been attempted to form a supermagnetostriction material of this type as a rod-like supermagnetostriction element and to use the dimensional change produced by the supermagnetostriction element as an actuator. It has further been attempted to use the actuator based on the magnetostriction element as a drive source for a speaker. 
     The following patent document discloses an art of using, as a speaker, a rod-like supermagnetostriction element obtained by using the supermagnetostriction material.
     Patent document 1: JP-A-10-145892 (page 1, FIG. 1)   

     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
     The supermagnetostriction speaker disclosed in the above patent document 1 is the one that vibrates a windowpane, a wall surface, or a picture or a photograph hanging on the wall as a vibration plate so as to operate as a speaker. Here, the windowpane, wall surface and picture or photograph hanging on the wall surface are materials that can be vibrated relatively easily, and can be easily used as vibration plates. 
     However, if it is presumed that the supermagnetostriction speaker is placed on a floor surface to use the floor surface as a vibration plate or that the supermagnetostriction speaker is placed on a relatively rigid table to use the table surface as a vibration plate, a problem arouses in that the floor surface or the table surface is so tough and rigid yet having a large area that the displacement of the supermagnetostriction element is used for vibrating the supermagnetostriction speaker itself and the speaker fails to produce a sufficiently large volume of sound. 
     In this connection, further, if it is attempted to vibrate the tough and rigid floor surface of a large area or the table surface by using the supermagnetostriction speaker, a problem newly occurs in that the supermagnetostriction speaker cannot produce voice maintaining high sound quality and high fidelity. 
     This invention was accomplished in order to solve the above problems and has an object of providing a supermagnetostriction speaker which, when used being placed on a horizontal surface, is capable of realizing operation as a speaker maintaining good acoustic characteristics. 
     Means for Solving the Problems 
     In order to solve the above problems, a supermagnetostriction speaker of the invention comprises a yoke of a cylindrical shape having a bottom and a lid and constituting a magnetic path; a supermagnetostriction element which is fixed at its one end to the lid of the yoke, has the other end which is a free end, and is arranged in the direction of cylinder of the yoke to generate displacement depending upon a variation in the magnetic field; a coil arranged to surround the supermagnetostriction element in the yoke and generates a magnetic field in response to signals fed from an external unit; a vibration rod having a flange at an intermediate portion thereof and is so arranged that the one end thereof comes in contact with the free end of the supermagnetostriction element and that the other end thereof penetrating through the center hole in the bottom of the yoke transmits the displacement of the supermagnetostriction element to an external body; a rubbery elastic body arranged being held between the flange of the vibration rod and the bottom of the yoke; and a body portion having a predetermined mass, and exerting a load on the supermagnetostriction element via the yoke in a state where the other end of the vibration rod is placed on the external body in a manner that the supermagnetostriction speaker stands by itself, so that the displacement of the supermagnetostriction element is effectively transmitted to the external body due to the mass. 
     In the supermagnetostriction speaker, it is desired that the vibration rod has, at the other end thereof, a vibration contact plate having an area larger than the sectional area of the vibration rod, and transmits the displacement of the supermagnetostriction element to the external body via the vibration contact plate. 
     In the supermagnetostriction speaker, further, it is desired that the vibration contact plate is made of a material and has an area that differ depending upon the frequency component and amplitude of vibration that is to be transmitted, and is detachably attached to the other end of the vibration rod. 
     It is desired that the supermagnetostriction speaker further includes a first bias magnet arranged between one end of the supermagnetostriction element and the lid of the yoke, and a second bias magnet arranged between the other end of the supermagnetostriction element and the vibration rod, and that the first bias magnet and the second bias magnet generate magnetic fields in the same direction as the axial direction of the supermagnetostriction element. 
     In the supermagnetostriction speaker, further, it is desired that the supermagnetostriction element is divided into a first supermagnetostriction element close to the lid of the yoke and a second supermagnetostriction element close to the bottom of the yoke, and that a third bias magnet is arranged between the first supermagnetostriction element and the second supermagnetostriction element to generate a magnetic field in the same direction as those of the first bias magnet and the second bias magnet. 
     In the supermagnetostriction speaker, further, it is desired that the body portion is so constituted as to possess the center of gravity on the side lower than the center of the yoke. 
     Effect of the Invention 
     According to the supermagnetostriction speaker of the invention, the vibration rod is so arranged as to transmit the displacement of the supermagnetostriction element to the external body via the vibration rod having the flange at the intermediate portion thereof, and the other end of the vibration rod is placed on the external body in a manner that the supermagnetostriction speaker stands by itself enabling the body portion to exert a load on the supermagnetostriction element via the yoke, so that the displacement of the supermagnetostriction element is effectively transmitted to the external body due to the mass of the body portion. 
     Therefore, the external body vibrates due to the displacement of the supermagnetostriction element in response to the signals fed to the coil. Here, the rubbery elastic body is arranged being held between the flange of the vibration rod and the bottom of the yoke, and the vibration due to the displacement of the supermagnetostriction element is quickly converged due to the attenuating force without being imparted with extra vibration. 
     When the supermagnetostriction speaker is used being placed on a horizontal surface such as the floor surface or the table surface, therefore, operation is realized featuring good acoustic characteristics. In the invention of the supermagnetostriction speaker, the displacement of the supermagnetostriction element is transmitted to the external body via the vibration contact plate of an area larger than the sectional area of the vibration rod. 
     When the supermagnetostriction speaker is used being placed on the horizontal surface, therefore, the displacement of the supermagnetostriction element can be reliably and faithfully transmitted to the external body to thereby realize the operation featuring good acoustic characteristics. 
     In the invention of the supermagnetostriction speaker, further, the vibration contact plate is made of a material and has an area that differ depending upon the frequency component and amplitude of vibration that is to be transmitted, and is detachably attached to the other end of the vibration rod. When the supermagnetostriction speaker is used being placed on the horizontal surface, therefore, the displacement of the supermagnetostriction element can be reliably and faithfully transmitted to the external body depending upon the use and the purpose to thereby realize the operation featuring good acoustic characteristics. 
     In the invention of the supermagnetostriction speaker, further, the supermagnetostriction element is held by a plurality of bias magnets; i.e., a uniform bias magnetic field is applied to the supermagnetostriction element to thereby realize the operation featuring good acoustic characteristics. 
     In the invention of the supermagnetostriction speaker, further, the body portion is so constituted as to possess the center of gravity on the side lower than the center of the yoke. When the supermagnetostriction speaker is used being placed on the horizontal surface, therefore, the displacement of the supermagnetostriction element can be reliably and faithfully transmitted to the external body to thereby realize the operation featuring good acoustic characteristics. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view illustrating the constitution of a supermagnetostriction speaker according to a first embodiment of the invention. 
         FIG. 2  is a diagram of characteristics of a supermagnetostriction element in the supermagnetostriction speaker according to the first embodiment of the invention. 
         FIG. 3  is a diagram of characteristics of when the damper material of the supermagnetostriction speaker according to the first embodiment of the invention is changed. 
         FIG. 4  is a view illustrating the constitution of the supermagnetostriction speaker according to a second embodiment of the invention. 
     
    
    
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
           100  supermagnetostriction speaker 
           101  control portion 
           110  supermagnetostriction element 
           111  first supermagnetostriction element 
           112  second supermagnetostriction element 
           120  bias magnet 
           121  first bias magnet 
           122  second bias magnet 
           123  third bias magnet 
           130  coil 
           140  yoke 
           141  upper yoke 
           142  bottom yoke 
           151  vibration rod 
           152  contact 
           160  damper 
           170  O-ring 
           180  body portion 
           181  upper body 
           182  bottom body 
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Described hereinbelow in detail with reference to the drawings is the best mode (hereinafter, embodiment) for carrying out the invention.  FIG. 1  is a sectional view illustrating the sectional constitution of a supermagnetostriction speaker according to a first embodiment of the invention. 
     In the supermagnetostriction speaker  100  shown in  FIG. 1 , a supermagnetostriction element  110  is a supermagnetostriction element formed like a rod by using a supermagnetostriction material that exhibits a supermagnetostriction phenomenon in which the material changes its shape when a magnetic field is applied thereto. The supermagnetostriction element  110  is constituted by a first supermagnetostriction element  111  close to the lid of the yoke and a second supermagnetostriction element  112  close to the bottom of the yoke. 
     A bias magnet  120  is constituted by a first bias magnet  121 , a second bias magnet  122  and a third bias magnet  123 , and applies a bias magnetic field in the axial direction of the supermagnetostriction element  110 . 
     Here, the first bias magnet  121  is arranged between one end of the supermagnetostriction element  111  and the lid of the yoke, and applies a bias magnetic field in the axial direction of the supermagnetostriction element  111 . The second bias magnet  122  is arranged between one end of the supermagnetostriction element  112  and the vibration rod, and applies a bias magnetic field in the axial direction of the supermagnetostriction element  112 . The third bias magnet  123  is arranged between the supermagnetostriction element  111  and the supermagnetostriction element  112 , and applies a bias magnetic field in the axial direction of the supermagnetostriction element  111  and the supermagnetostriction element  112 . 
     The first bias magnet  121 , second bias magnet  122  and third bias magnet  123  generate magnetic fields for the supermagnetostriction element  111  and the supermagnetostriction element  112  in the same direction which is in the axial direction of the supermagnetostriction element. 
     A solenoid coil  130  is arranged being wound on a coil bobbin  132  surrounding the supermagnetostriction element  110 , and generates a magnetic field around the supermagnetostriction element  110  in response to signals fed from an external unit through a wire  132 . 
     A yoke  140  is of a cylindrical shape having a bottom and a lid, forms a magnetic path, and is constituted by an upper yoke  141  which includes an upper side of the cylinder and the lid, and a bottom yoke  142  which includes a lower side of the cylinder and the bottom. 
     A center hole is formed near the center of the bottom of the bottom yoke  142 , and a vibration rod that will be described later is penetrating therethrough. The upper yoke  141  and the bottom yoke  142  are threaded at portions that come in contact with each other so as to fit together. The rod-like supermagnetostriction element  110  is arranged near the center axis of the cylindrical yoke  140 , and the coil  130  is wound to surround it. A magnetically closed circuit is constituted by the yoke  140 , the supermagnetostriction element  110  and a vibration rod  151  that will be described later. 
     One end of the vibration rod  15  is in contact with the free end of the supermagnetostriction element  110  (supermagnetostriction element  111  in  FIG. 1 ). The other end of the vibration rod  151  penetrates through the center hole in the bottom of the bottom yoke  142  and transmits the displacement occurring in the supermagnetostriction element  110  to the external body. 
     In this embodiment, the displacement of the supermagnetostriction element stands for a displacement based on a change in the shape caused by a change in the magnetic field applied to the supermagnetostriction element. The vibration rod  151  is so constituted as to possess a flange  151   a  at the intermediate portion thereof. The vibration rod  151 , further, has, on the other end side thereof (on the external body side), a contact  152  which is a vibration contact plate having an area larger than the sectional area of the vibration rod  151 . The vibration rod  151  transmits the displacement of the supermagnetostriction element  110  to the external body via the contact  152 . 
     A damper  160  is an elastic body for absorbing vibration and is, desirably, a rubbery elastic body which is arranged being held between the flange  151   a  of the vibration rod  151  and the bottom of the bottom yoke  142 . In a state where the upper yoke  141  and the bottom yoke  142  are screwed together, the damper  160  is placed in a state where it receives a force toward the contracting side. 
     An O-ring  170  is provided as slipping means for reducing the frictional resistance relative to the center hole in the bottom yoke  142  as the vibration rod penetrating through the center hole in the bottom of the bottom yoke  142  vibrates in response to the displacement of the supermagnetostriction element  110 . 
     A body portion  180  has an inner space for holding the yoke  140  and a bottom hole through which the vibration rod  151  penetrates and, further, has a predetermined mass. In a state where the contact  152  is placed on the external body so that the supermagnetostriction speaker  100  stands by itself, the body portion  180  exerts the load on the supermagnetostriction element  110  via the yoke  140 . By utilizing its mass, further, the body portion  180  effectively transmits the displacement of the supermagnetostriction element  110  to the external body. 
     The body portion  180  is constituted being divided into an upper body  181  and a bottom body  182 . The upper body  181  and the bottom body  182  are integrated together in a state where the yoke  140  is contained in the inner space thereof. 
       FIG. 2(   a ) illustrates a relationship between a magnetic field H applied to the supermagnetostriction element  110  and a change of shape (magnetostriction) ΔI/I which causes displacement to the supermagnetostriction element  110  due to the magnetic field H. The characteristics exemplified here are such that the magnetostriction due to the magnetic field H increases with an increase in the magnetic field H in either the positive or negative direction. 
     Therefore, while applying a bias magnetic field to the supermagnetostriction element  110 , the magnetic field is varied in response to the signals with the bias magnetic field as a center ( FIG. 2(   b )) to thereby obtain displacement or vibration in response to the signals ( FIG. 2(   c )). 
     Here, by using a region of good linearity in relation to the signals and magnetostriction, it is made possible to generate faithful vibration in response to a change in the magnetic field. It is therefore desired to select in advance the bias magnetic field based on the bias magnets  121  to  123  at the center of the region having good linearity as described above. 
       FIG. 3  is a diagram of characteristics illustrating attenuation modes of the supermagnetostriction speaker  100  due to the displacement of the supermagnetostriction element  110  by using various materials as the damper  160 . The diagram illustrates vibration modes immediately after the interruption of signals following a state where pulse-like signals were fed to the coil  130 . An absolute value of vibration varies depending upon the mass of the supermagnetostriction speaker  100 , amplitude of the signals and shape of the coil  130 . In  FIG. 3 , however, the conditions are set to be the same except the materials of the damper  160 . 
       FIG. 3(   a ) shows vibration attenuation characteristics of when a coil spring having a spring constant of 7.6 [N/mm] is used as the damper  160 , wherein the vibration remains not converged for not shorter than 3 milliseconds. Therefore, the signal waveform fed to the coil  130  is no longer in agreement with the vibration waveform, distortion increases and it becomes difficult to obtain vibration faithful to a change in the magnetic field. 
       FIG. 3(   b ) shows vibration attenuation characteristics of when a lowly elastic rubber having a hardness of 32° is used as the damper  160 , wherein the vibration is nearly converged in about one millisecond. Therefore, the signal waveform fed to the coil  130  is nearly in agreement with the vibration waveform, distortion is small, and vibration that is obtained becomes faithful to a change in the magnetic field. 
       FIG. 3(   c ) shows vibration attenuation characteristics of when a butyl rubber having a hardness of 65° is used as the damper  160 , wherein the vibration is nearly converged in about 1.6 milliseconds. Therefore, the signal waveform fed to the coil  130  is nearly in agreement with the vibration waveform, distortion is small, and vibration that is obtained becomes faithful to a change in the magnetic field. 
       FIG. 3(   d ) shows vibration attenuation characteristics of when a silicone rubber having a hardness of 50° is used as the damper  160 , wherein the vibration is nearly converged in about 2.6 milliseconds. After the passage of 0.6 milliseconds, regular vibration of a small amplitude continues. Therefore, the signal waveform fed to the coil  130  is nearly in agreement with the vibration waveform generating slight sound as a lingering tone, distortion is small, and vibration that is obtained becomes faithful to a change in the magnetic field. 
     As described above, in a state where the other end (contact  152 ) of the vibration rod is placed on an external body such as a floor or a table in a manner that the supermagnetostriction speaker  100  stands by itself, the mass of the body portion  180  is exerted as a load on the supermagnetostriction element  110  via the yoke  140 . Therefore, the displacement of the supermagnetostriction element  110  is effectively transmitted to the external body due to the mass of the body portion  180 . 
     Therefore, not only the supermagnetostriction speaker  100  itself but also the external body undergo the vibration due to the displacement of the supermagnetostriction element  110  in response to the signals fed to the coil  130 . Here, the damper  160  of a rubbery elastic body is held between the flange  151   a  of the vibration rod  151  and the bottom of the yoke  140 , and the vibration due to the displacement of the supermagnetostriction element  110  is quickly converged due to the attenuating force without being imparted with extra vibration. 
     Further, the present inventors have conducted experiment to measure the frequency characteristics of the supermagnetostriction speaker  100 , and obtained the following results. That is, when the coil spring is used as the damper  160 , a peak occurs conspicuously at around 2 kHz while the low zone gradually decreases. Therefore, flat frequency characteristics are not obtained, and characteristics desired for the magnetostriction speaker are not obtained. 
     When the lowly elastic rubber having a hardness of 32°, the butyl rubber having a hardness of 65° and the silicone rubber having a hardness of 50° are used as the damper  160 , the peak does not occur like that of when the coil spring is used. Besides, characteristics are improved in the low zone, flat frequency characteristics are obtained, and characteristics desired for the magnetostriction speaker are obtained. Accordingly, the signal waveforms fed to the coil  130  become nearly in agreement with the vibration waveforms over a wide range of frequencies, a difference in the level decreases irrespective of the frequency, and vibration that is obtained becomes faithful to a change in the magnetic field. 
     As a result, when the supermagnetostriction speaker  100  is used being placed on a horizontal surface such as a floor or a table, use of the rubbery elastic material as the damper  160  makes it possible to realize the operation maintaining good acoustic characteristics. 
     In the supermagnetostriction speaker  100 , the displacement of the supermagnetostriction element  110  is transmitted to the external body via the contact  152  which is the vibration contact plate having an area larger than the sectional area of the vibration rod  151 . As a result, when the supermagnetostriction speaker  100  is used being placed on the horizontal surface, the displacement of the supermagnetostriction element  110  can be reliably and faithfully transmitted to the external body, and the operation can be realized maintaining good acoustic characteristics. 
     In the supermagnetostriction speaker  100 , further, it is desired that the contact  152  which is the vibration contact plate is made of a material and has an area that differ depending upon the frequency component (wide/narrow frequency characteristics) of vibration to be transmitted and upon the amplitude thereof (large/small sound volume). It is desired that the contact  152  is attached in a manner of being allowed to be replaced such as being screwed into the other end of the vibration rod  151 . Upon constituting the contact  152  in a manner that it can be replaced, the displacement of the supermagnetostriction element can be reliably and faithfully transmitted to the external body depending upon the use and the purpose with the supermagnetostriction speaker  100  being placed on the horizontal surface, and the operation can be realized maintaining good acoustic characteristics. Further, the material and the area of the contact  152  which is the vibration contact plate may be changed depending upon the material, hardness and vibration absorption of the floor or the table which is the external body. 
     In the supermagnetostriction speaker  100 , further, the supermagnetostriction element  110  is divided into the first supermagnetostriction element  111  and the second supermagnetostriction element  112 , and is held by three bias magnets to thereby apply a uniform magnetic field to the supermagnetostriction element  110  making it possible to realize the operation maintaining good acoustic characteristics. 
     In the supermagnetostriction speaker  100 , further, the body portion  180  is formed in a shape resembling the conical shape or the solid bell shape so as to possess a center of gravity on the side lower than the center of the yoke  140 , i.e., so as to possess a low center of gravity. To lower the center of gravity, the bottom body  182  may be made of a material different from that of the upper body  181  and having a large specific gravity. By lowering the center of gravity of the body portion  180 , the supermagnetostriction speaker  100  stands by itself maintaining stability when it is used being placed on the horizontal surface. Besides, the displacement of the supermagnetostriction element  110  can be reliably and faithfully transmitted to the external body to realize the operation maintaining good acoustic characteristics. 
     Upon bringing impedance characteristics of the coil  130  into agreement with the characteristics (about 4Ω to about 16Ω) of general speakers, the supermagnetostriction speaker  100  can be connected to various audio equipment in the same manner as that of general speakers without requiring any particular equipment or wiring and making it easy to handle. 
       FIG. 4  is a sectional view illustrating the sectional constitution of the supermagnetostriction speaker  100 ′ according to a second embodiment of the invention. The supermagnetostriction speaker  100 ′ according to the second embodiment of  FIG. 4  has basically the sectional constitution similar to that of the supermagnetostriction speaker of the first embodiment shown in  FIG. 1 . Therefore, the same portions are denoted by the same reference numerals but are not described here again. 
     The supermagnetostriction speaker  100 ′ of the second embodiment has a signal amplifier  190  incorporated in the supermagnetostriction speaker  100 ′. The signal amplifier  190  is supplied with electric power from an external unit through a wire  192   a  and is supplied with signals from an external unit through a wire  192   b . The signals amplified by the signal amplifier  190  are fed to the coil  130  through a signal line that is not shown. 
     According to the constitution which incorporates the signal amplifier  190  as described above, the mass of the body portion  180  is exerted as a load on the supermagnetostriction element  110  via the yoke  140  in a state where the other end (contact  152 ) of the vibration rod is placed on the external body such as the floor or the table in a manner that the supermagnetostriction speaker  100 ′ stands by itself. Therefore, the displacement of the supermagnetostriction element  110  is effectively transmitted to the external body due to the mass of the body portion  180 . 
     According to the supermagnetostriction speaker  100 ′, the external body vibrates due to the displacement of the supermagnetostriction element  110  in response to the signals amplified through the amplifier  190  and fed to the coil  130 . Here, the damper  160  made of a rubbery elastic material is held between the flange  151   a  of the vibration rod  151  and the bottom of the yoke  140 , and the vibration due to the displacement of the supermagnetostriction element  110  is quickly converged due to the attenuating force without being imparted with extra vibration. 
     As a result, the operation is realized maintaining good acoustic characteristics when the supermagnetostriction speaker  100 ′ is used being placed on a horizontal surface such as the floor or the table. The contact  152  can be constituted or modified in the same manner as in the first embodiment to realize the operation maintaining good acoustic characteristics. Further, the supermagnetostriction element  110 ′ and the bias magnet  120  may be arranged in the same manner as in the first embodiment to realize the operation maintaining good acoustic characteristics. 
     In the supermagnetostriction speaker  100 ′, further, the body portion  180  is formed in a shape resembling the conical shape or the solid bell shape so as to possess a center of gravity on the side lower than the center of the yoke  140 , i.e., so as to possess a low center of gravity. To lower the center of gravity, the bottom body  182  may be made of a material different from that of the upper body  181  and having a large specific gravity. By lowering the center of gravity of the body portion  180 , the supermagnetostriction speaker  100 ′ stands by itself maintaining stability when it is used being placed on the horizontal surface. Besides, the displacement of the supermagnetostriction element  110  can be reliably and faithfully transmitted to the external body to realize the operation maintaining good acoustic characteristics. 
     In the body portion  180 , a space is provided in a lower portion, and the signal amplifier  190  is arranged in the space to effectively utilize the body portion  180 . In this case, a bottom cover  183  holds the signal amplifier  190 . 
     Further, the body portion  180  that is constituted by using a metal also works as means for radiating the heat of the signal amplifier  190  to obtain favorable performance. Upon bringing the input level of the signal amplifier  190  into agreement with the input characteristics of general powered speakers, the connection to various portable audio equipment can be handled in the same manner as that of the general powered speakers to improve the handling without requiring any particular attention. 
     In the above description, the body portion  180  is formed in a conical shape or a solid bell shape so as to possess the center of gravity on the side lower than the center of the yoke  140 . The body portion  180 , however, may assume any other shape such as a pyramidal shape with the bottom surface. Or, the body portion  180  may be of a cylindrical shape with its upper portion being light and its lower portion being heavy to realize a low center of gravity. 
     INDUSTRIAL APPLICABILITY 
     By placing on the floor or on the table, the supermagnetostriction speaker of the invention can be extensively used to vibrate the floor or the table by utilizing the supermagnetostriction phenomenon that occurs in the supermagnetostriction element. Upon vibrating a table for many people in, for example, a conference room or the like room, therefore, supermagnetostriction speaker can be used for transmitting sound in the whole conference room without the need of executing the work for installing the speakers. 
     Upon arranging the supermagnetostriction speaker of the invention on each table, further, it is allowed to produce sound that differs for each of the tables or to execute the calling for each of the tables. The supermagnetostriction speaker can be further placed on the floor in a store or on a site of amusement to transmit the sound to the required areas without executing the work for installing the speakers. Further, when placed on the floor of the store or on the site of amusement, supermagnetostriction speaker  100  can be quickly moved as required. 
     In the general household, too, the supermagnetostriction speaker of the invention can be quickly installed and used depending upon the required place and the required timing.