Abstract:
A speaker system enabling efficient dispersion of intelligible sound far in all directions from a specific point along a certain planar direction, provided with a single speaker, a first reflective (directing) surface arranged facing a sound output direction of the speaker and reflecting the sound to directions different from the output direction, and a second reflective (directing) surface arranged facing the first reflective surface, wherein the distance between the first reflective surface and the second reflective surface increases continuously in proportion to the distance from the center of the speaker and wherein the first reflective surface and the second reflective surface diffuse sound radially from the speaker to directions different to the sound output direction of the speaker.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a speaker system.  
         [0003]     2. Description of the Related Art  
         [0004]     For example, in order to disperse sound from a certain position in all directions along a substantially horizontal direction, it is required to position a plurality of speakers to face different directions. If positioning a plurality of speakers to face different directions, however, interference will occur among the sounds output from the different speakers. As a result, there will be places where the sound is heard strongly and places where it is heard weakly. Therefore, when using a plurality of speakers, effective dispersion of sound is difficult.  
         [0005]     Japanese Unexamined Patent Publication (Kokai) No. 2003-87887 discloses the technique of capturing speech of a participant in a conference by a microphone and dispersing it over a wide area by using a single speaker and a reflective plate. In this technique for dispersing speech captured by a microphone over wide area using a single speaker and a reflective plate, since a single speaker is used, the speech has to be dispersed efficiently.  
         [0006]     To efficiently disperse sound far, a horn-shaped speaker box, for example, can be applied. However, resonance easily occurs in the range of transmission frequency of speech. If resonance occurs in the range of transmission frequency of speech from a single speaker, the sound will be very unintelligible and will not be able to be dispersed far.  
       SUMMARY OF THE INVENTION  
       [0007]     An object of the present invention is to provide a speaker system enabling efficient dispersion of intelligible sound far in all directions from a specific point along a certain planar direction.  
         [0008]     According to the present invention, there is provided a speaker system comprising a single speaker and a dispersing means for dispersing sound radially and evenly from the speaker to directions different from the direction of output of sound of the speaker.  
         [0009]     Preferably, the dispersing means has a first sound directing surface including a concave contour portion perpendicular to the center of the speaker and a flat peripheral portion extending to the end of the concave contour portion, facing the direction of output of sound from the speaker and a second sound directing surface arranged facing the first sound directing surface to thereby direct sound to a direction perpendicular to that of the center of the sound output direction of the speaker by cooperating with the first sound directing means.  
         [0010]     More preferably, the distance between the first sound directing surface and the second sound directing surface increases continuously along the position from the center of said speaker to the end of the surfaces.  
         [0011]     According to the present invention, the dispersing means disperses the sound of the speaker radially and evenly from the speaker in directions different from the direction of output of sound from the speaker. At this time, the sound output from the single speaker is repeatedly reflected between the first sound directing surface and the second sound directing surface of the dispersing means. The sound repeatedly reflected between the first sound directing surface and the second sound directing surface is resistant to resonance since the distance between the first sound directing surface and the second sound directing surface continuously along the position from the center of said speaker to the end of the surfaces.  
         [0012]     Therefore, according to the present invention, it becomes possible to efficiently disperse intelligible sound far in all directions from a specific point along a specific planar direction. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The above and other objects and features of the present invention will be described in more detail with reference to the accompanying drawings, in which:  
         [0014]      FIG. 1  is a perspective view of an exterior appearance of a speaker system according to an embodiment of the present invention;  
         [0015]      FIG. 2  is a plan view of the structure of a printed circuit board held by a holding member;  
         [0016]      FIG. 3  is a cross-sectional view of the internal structure of a speaker system according to an embodiment of the present invention;  
         [0017]      FIG. 4  is a view for describing the positional relation between a reflective surface of a holding member side and a reflective surface of a speaker box side;  
         [0018]      FIGS. 5A and 5B  are views of an example of vibration of a speaker box;  
         [0019]      FIGS. 6A and 6B  are views of an example of vibration of a speaker box in case of no connection bolts; and  
         [0020]      FIG. 7  is a cross-sectional view showing an operation of a filter member. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]     Hereinafter, an embodiment of the present invention will be described with reference to the drawings.  
         [0022]      FIG. 1  is a perspective view of an exterior appearance of a speaker system according to an embodiment of the present invention. The speaker system  1  according to the embodiment is, for example, a system combining microphones and a speaker as used in remote conferencing such as teleconferencing. As shown in  FIG. 1 , the speaker system  1  according to the present embodiment has a cover member  2 , a holding member  3 , a speaker  15 , and a speaker box  20 .  
         [0023]     The holding member  3  and the speaker box  20  are, for example, formed by acrylonitrile butadiene styrene (ABS) or another plastic. The cover member  2  is provided on the holding member  3  and covers the upper surface of the holding member  3 . The cover member  2  is formed by resin fiber or another material which transmits sound and protects the later-described printed circuit board held on the holding member  3  and the microphones. The holding member  3  is supported on the speaker box  20  through a plurality of support members  10  provided on the speaker box  20 .  
         [0024]      FIG. 2  is a plan view of the holding member  3  in the state with the cover member  2  usually provided on the holding member  3  detached.  FIG. 3  is a cross-sectional view of the internal structure of the speaker system according to the present embodiment. As shown in  FIG. 2 , the holding member  3  has a circular shape and holds the printed circuit board  30  inside the circle.  
         [0025]     The printed circuit board  30  is disk shaped. The printed circuit board  30  is provided with a plurality of directional microphones  40 . The printed circuit board  30  also carries various types of electronic components (not shown) in addition to the directional microphones  40 . The electronic components carried on the printed circuit board  30  form for example an echo canceller circuit, circuits for driving the directional microphones  40  and the later-described speaker, and other circuits required for electrical operations in the speaker system  1 .  
         [0026]     The plurality of the directional microphones  40  are cylindrical in shape and are arranged radially from the center of the printed circuit board  30 , that is, from the center outward in the radial direction, at equal intervals along the circumference. The directional microphones  40  have directivities from the center of the printed circuit board out in the radial direction. The two ends of the directional microphones  40  are supported on the printed circuit board  30  by filter members  60 . Note that the filter members  60  are embodiments of a second filter member of the present invention. The filter members  60  are obtained, for example, by molding rubber or a plastic to predetermined shapes. The filter members  60  attenuate vibration propagated from the printed circuit board  30  side.  
         [0027]     The back ends of the directional microphones  40  are connected to wires which are in turn connected to the printed circuit board  30  through connectors CN. Due to this, audio signals obtained from the directional microphones  40  are input to the electrical circuits formed on the printed circuit board  30 .  
         [0028]     As shown in  FIG. 3 , the printed circuit board  30  is held on the upper surface of the holding member  3 . Specifically, as shown in  FIG. 7 , shaft parts  3   t  are integrally formed sticking out from the upper surface of the holding member  3 . Ring-shaped filter members  51  are inserted at the shaft parts  3   t . The printed circuit board  30  is formed with through holes  30   h  through which the shaft parts  3   t  are inserted. The printed circuit board  30  is placed over the filter members  51 . Further, ring-shaped filter members  50  are provided around the shaft parts  3   t  over the printed circuit board  30 .  
         [0029]     The shaft parts  3   t  are formed with screw holes at their centers. Screws  56  are inserted into the screw holes via ring-shaped presser plates  57 . Therefore, the presser plates  57  press the upper surfaces of the filter members  50 . The printed circuit board  30  is clamped between the filter members  50  and the filter members  51 . That is, the printed circuit board  30  is supported by the filter members  50  and the filter members  51 . Note that the filter members  50  and  51  are embodiments of the first filter member of the present invention. The filter members  50  and  51  are formed by rubber, a plastic, or other material and have similar shapes. Further, the filter members  50  and  51  have different natural frequencies from the filter members  60 .  
         [0030]     Referring to  FIG. 3 , the speaker box  20  is comprised of an upper wall plate  21  and a lower wall plate  22 . The upper wall plate  21  and the lower wall plate  22  have circular shapes. A single speaker  15  is fixed to the center of the upper wall plate  21 . The speaker  15  used is for example a cone speaker. The speaker  15  outputs in a sound output direction A 1  shown by an arrow by vibration of a not shown vibration plate along the voice output direction A 1 .  
         [0031]     The speaker box  20  encloses the back of the speaker  15 . A seal member  80  is provided between the upper wall plate  21  and the lower wall plate  22 . Therefore, the space in the speaker box  20  is an enclosed space.  
         [0032]     Support parts  21   t  extending toward the lower wall plate  22  are integrally formed on the lower surface of the upper wall plate  21 . Projecting parts  22   a  projecting toward the upper wall plate  21  are formed on the upper surface of the lower wall plate  22 . The lower end faces of the support parts  21   t  abut against the upper end faces of the projecting parts  22   a . Through holes  21   p  are formed through the centers of the support parts  21   t . The upper ends of the through holes  21   p  are formed with female threads. The projecting parts  22   a  are also formed with female threads.  
         [0033]     Connection bolts  11  are inserted from the projecting part  22   a  side into the through holes  21   p  of the support parts  21   t . The connection bolts  11  are screwed into both the female threads  21   h  formed at the upper wall plate  21  and the female threads  22   h  formed at the lower wall plate  22 . The connection bolts  11  is formed by steel or another metal material and have sufficiently higher rigidity compared with the plastic material forming the speaker box  20  and the holding member  3 . Note that the connection bolts  11  are an embodiment of the connection member of the present invention. The connection bolts  11  and the female threads  21   h ,  22   h  constitute the restraint means of the present invention which partly restrain relative displacement between the facing wall plates  21  and  22  of the speaker box  20 .  
         [0034]     The connection bolts  11  pass through the female threads  21   h  and are screwed into female threads  3   h  formed at the holding member  3 . Therefore, relative displacement is restrained among the female threads  21   h  of the upper wall plate  21 , the lower wall plate  22 , and the female threads  3   h  of the holding member  3 . A plurality of support members  10  are provided between the lower surface of the holding member  3  and the upper wall plate  21 . The support members  10  are formed with through holes  10   h . These through holes  10   h  receive the connection bolts  11 .  
         [0035]     Next, the configuration and action of the reflective (directing) surface  3   f  of the holding member  3  and the reflective (directing) surface  21   f  of the speaker box will be described with reference to  FIG. 4 . The reflective surface  3   f  constituting the lower surface of the holding member  3  is an embodiment of the first reflective surface of the present invention, while the reflective surface  21   f  constituting the upper surface of the upper wall plate  21  is an embodiment of the second reflective surface of the present invention.  
         [0036]     The reflective surface  3   f  and the reflective surface  21   f  disperse sound radially from the speaker  15  in directions substantially perpendicular to the sound output direction A 1  of the speaker  15  by reflecting the sound from the speaker  15 .  
         [0037]     As shown in  FIG. 4 , the reflective surface  3   f  is formed by a curved surface projecting smoothly outward toward the speaker  15 . The reflective surface  3   f  is, for example, formed substantially by a rotational curved surface formed by rotating a hyperbolic curve about the center axis Ct of the speaker  15 . Similarly, the reflective surface  21   f  is formed substantially by a rotational curved surface having the center axis Ct of the speaker  15  as its axis of rotation.  
         [0038]     R 1 , R 2 , and R 3  are radii from the center axis Ct of the speaker  15 . L 1 , L 2 , and L 3  are distances between the reflective surface  3   f  and the reflective surface  21   f  at R 1 , R 2 , and R 3  respectively. As will be understood from  FIG. 4 , the distance between the reflective surface  3   f  and the reflective surface  21   f  increases continuously in proportion to the distance from the center axis Ct of the speaker  15 .  
         [0039]     If the distance between the reflective surface  3   f  and the reflective surface  21   f  were constant, resonance would occur at a resonance frequency in accordance with that the constant distance. If resonance occurs, the sound would become very unintelligible and the speech of the participants in the conference would not be able to be faithfully reproduced.  
         [0040]     On the other hand, according to the present embodiment, since the distance between the reflective surface  3   f  and the reflective surface  21   f  increases continuously in proportion to the distance from the center axis Ct of the speaker  15 , the sound output from the speaker  15  will not resonate at a specific frequency. Therefore, it becomes possible to accurately reproduce speech of conference participants. Further, according to the present embodiment, sound output from the speaker  15  is dispersed in directions different from the sound output direction A 1  of the speaker  15  without resonating, that is, in all directions (360 degrees radially) in directions substantially perpendicular to the center axis Ct of the speaker  15 . Particularly, since a single speaker  15  is used, the sound is dispersed evenly without interference around the center axis Ct. Further, since resonance does not occur between the reflective surface  3   f  and the reflective surface  21   f , it becomes possible to efficiently disperse sound far.  
         [0041]     Next, the action and the effect of the connection bolts  11  will be described.  FIGS. 6A and 6B  are views for explaining an example of vibration of a speaker box in the case of no connection bolts, in which  FIG. 6A  shows the case in which the sound pressure in the speaker box is low, while  FIG. 6B  shows the case in which the sound pressure is high. As shown in  FIGS. 6A and 6B , if the sound pressure in the speaker box varies, the upper wall plate  21  and the lower wall plate  22  will vibrate in opposite directions. At this time, if the connection positions of the support members  10  to the upper wall plate  21  are Cp, the connection positions Cp will vibrate due to the variation in the sound pressure in the speaker box.  
         [0042]      FIGS. 5A and 5B  are schematic views of an example of vibration of the speaker box  20  according to the present embodiment. As shown in  FIGS. 5A and 5B , the upper wall plate  21  and the lower wall plate  22  are joined by connection bolts  11 . If the sound pressure in the speaker box  20  varies, the upper wall plate  21  and the lower wall plate  22  will vibrate in opposite directions, however, the connection positions Cp will not vibrate since they are restrained by the connection bolts  11 .  
         [0043]     In the present embodiment, since the connection positions Cp are restrained by the connection bolts  11  and do not vibrate much at all, it becomes difficult to transmit vibration to the holding member  3  as it is connected by connection bolts  11  and the support members  10  at those positions. That is, vibration directly propagated from the speaker box  20  to the holding member  3  carrying the microphones  40  is restrained.  
         [0044]     The positions restrained by the connection bolts  11  form new nodal points of vibration. That is, since the new nodal points are formed, the vibration frequency of the speaker box  20  increases. By positively utilizing the change of the vibration frequency, it also becomes possible to change the vibration of the speaker box  20  to a vibration of a frequency substantially not influencing the microphones  40 . Further, by changing the vibration frequency of the speaker box  20  to a frequency which is easy to attenuate by the filter members  50 ,  51 ,  60 , etc., it becomes possible to efficiently restrain vibration by the filter members  50 ,  51 , and  60 .  
         [0045]     Next, the actions and effects of the filter members  50 ,  51 , and  60  will be described with reference to  FIG. 7 . The vibration from the vibration sources constituted by the speaker  15  and the speaker box  20 , as shown in  FIG. 7 , is propagated for example from the reflective surface  3   f  of the holding member  3  to the printed circuit board  30  through the filter members  50  and  51 . The vibration propagated to the printed circuit board  30  is propagated through the filter member  60  and wires etc. connecting the connectors CN and the microphones  40 .  
         [0046]     Here, the filter members  50  and  51  support the relatively heavy weight of the printed circuit board  30  and the plurality of the microphones etc. Therefore, the filter members  50  and  51  have the effect of attenuation of vibration of a relatively low frequency. However, it is difficult to attenuate vibration of a relatively high frequency as well. Therefore, the filter members  60  provided between the microphones  40  and the printed circuit board  30  are used attenuate vibration of a relatively high frequency. Since the weight which the filter members  60  support is relatively small, it is possible to relatively easily attenuate vibration of a relatively high frequency.  
         [0047]     In this way, since resonance is actively prevented from occurring when sound from the speaker  15  is reflected and dispersed by the reflective surfaces  3   f  and  21   f , vibration of a very wide frequency band is propagated from the speaker  15  to the microphones  40 . According to the present embodiment, by combining filter members with different natural frequencies for vibration of this wide frequency band, it becomes possible to attenuate vibration at a wide frequency band.  
         [0048]     The present invention is not limited to the above embodiment. In the above embodiment, the reflective surface  3   f  and the reflective surface  21   f  were both curved surfaces, however, either the reflective surface  3   f  or the reflective surface  21   f  may be a flat surface as well. It is also possible to instead use a fixed surface such as a wall for the reflective surface  21   f  if affixing the speaker system  1  to a wall etc. Further, in the above embodiments, a case in which the speaker system has the microphones  40  was described, however, the system may also have the speaker  15 , the reflective surface  3   f , and the reflective surface  21   f  and not have the microphones  40 . Also, in the above embodiment, the case in which the speaker system was used on a table was described, however, the system may also be installed on a ceiling of a domed baseball stadium etc. In this case, the speaker system does not have to have the microphones  40 .