Abstract:
A volume controller for controlling volume balance between a front speaker and a rear speaker located within a vehicle, includes a fade volume computing unit for computing an amplifying factor k1 of an input signal for providing an increased volume at the rear or front speaker by the volume at a prescribed position within the vehicle which is equal to an decreased volume in the front or rear speaker when a signal supplied to the front or rear speaker is attenuated by an attenuating factor K1; and a control unit for multiplying the signal supplied to the rear or front speaker by k1 when a signal supplied to the front or rear speaker is attenuated by K1. In this configuration, a volume controller can form an acoustic field with a sense of realism when volume adjustment is performed in a to-and-fro direction.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to a volume controller for balancing the sound volume between a front speaker which is located at the front of a vehicle and a rear speaker which is located at the rear of the vehicle.  
           [0003]    2. Description of the Related Art  
           [0004]    Traditionally, an audio device has been widely used which is provided with four speakers on the left and right sides at the front and the rear within a vehicle, respectively in order to cause a driver/passenger to hear the signal reproduced from a broadcast, CD, DVD, etc.  
           [0005]    Such an in-vehicle audio device can regulate the volume balance in a to-and-fro direction. In this case, as shown in FIG. 3, where a balancing point is moved from the center to the front side by an fade input from a fader inputting unit the volume from the front speaker does not vary whereas the volume from the rear speaker decreases with the fade input. If the balancing point is moved from the center toward the rear side, the volume from the rear speaker does not vary whereas the volume from the front speaker decreases with the fader input.  
           [0006]    The volume balancing regulation having such a characteristic has the following disadvantage. Where a passenger who sits on the rear seat of a one-box car enjoys, a movie using a DVD player, which is now prevailing, using a rear speaker as a main speaker, he or she balances the volume from a center position to the rear side. However, actually, the volume decreases only at the front. It lacks the spreading toward the front at the listening point, and the volume within an entire room varies (decreases). This makes it difficult to form a sound field with a sense of realism.  
         SUMMARY OF THE INVENTION  
         [0007]    An object of this invention is to provide a volume controller capable of regulating the balance in a volume level between a front side and a rear side without decreasing the volume of an entire passenger room.  
           [0008]    In order to attain the above object, in accordance with this invention, there is provided a volume controller for controlling volume balance between a front speaker and a rear speaker located within a vehicle, comprising:  
           [0009]    a fade volume computing unit for computing an amplifying factor k1 of an input signal for providing an increased volume at the rear or front speaker by the volume at a prescribed position within the vehicle which is equal to an decreased volume in the front or rear speaker when a signal supplied to the front or rear speaker is attenuated by an attenuating factor K1; and  
           [0010]    a control unit for multiplying the signal supplied to the rear or front speaker by k1 when a signal supplied to the front or rear speaker is attenuated by K1.  
           [0011]    In the volume controller, preferably, the prescribed position is located at a center of a front seat, at a center of a rear seat, or a center between the front seat and the rear seat.  
           [0012]    In the volume controller, preferably, attenuations when acoustic waves from the front speaker and rear speaker are propagated to the prescribed position are previously recorded, and on the basis of the attenuations, the increased and decreased volumes at the front or rear speaker are computed.  
           [0013]    In the volume controller, preferably, the attenuations are computed on the basis of an input indicative of a relationship between the prescribed position and positions where the front and rear speaker are located.  
           [0014]    In the volume controller, preferably, the increased volumes of the front or rear speaker and of the rear or front speaker are computed on an adjustment value in a level adjusting means to be connected to the front speaker and the rear speaker.  
           [0015]    In accordance with this invention, where the volume balance between the front and the rear speakers is adjusted, when the volume at the front or rear speaker decreases, the volume at the rear or front speaker is increased so that the volume at a prescribed position in a passenger room is equal to that before the balance is adjusted. For this reason, after the volume balance between the front and rear speaker has been carried out, the sound field with a sense of realism can be formed.  
           [0016]    The above and other objects and features of the invention will be more apparent from the following description taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is an arrangement view of the volume controller according to an embodiment of this invention;  
         [0018]    [0018]FIG. 2 is a view for explaining the operation of the embodiment; and  
         [0019]    [0019]FIG. 3 is a view for explaining a conventional volume controller. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]    Now referring to FIG. 1, an explanation will be given of an embodiment of a volume controller according to this invention.  
         [0021]    [0021]FIG. 1 is an arrangement view of an embodiment of a volume controller according to this invention.  
         [0022]    As seen from FIG. 1, a front seat  2  and a rear seat  3  are located at the front and at the rear thereof within a vehicle  1 , respectively.  
         [0023]    On the front left side and front right side of the vehicle  1 , a front left side speaker (SFL)  4  and a front right side speaker (SFR)  5  are arranged, and on the rear left side and the rear right side of the vehicle  1 , a rear left speaker (SRL)  6  and a rear right speaker (SRR)  7  are arranged.  
         [0024]    Attenuators  8 TFL,  8 TFR,  8 TRL and  8 TRR are provided so as to correspond to the (SFL)  4 , (SFR)  5 , (SRL)  6  and (SRR)  7 , respectively. An R signal to be reproduced is supplied to the attenuators  8 TFR and  8 TRR, and an L signal to be reproduced is supplied to the attenuators  8 TRL and  8 TRR.  
         [0025]    The R and L signals, which have been level-regulated by the attenuators  8 TFR, are amplified by amplifiers  9 AFR,  9 ARR, and  9 AFL and  9 ARL by a predetermined amount. The R and L signals are reproduced by the speakers (SFR)  5 , (SRR)  7 , and (SFL)  4 , (SRL)  6 .  
         [0026]    In FIG. 1, reference numeral  10  denotes a preset attenuation value recording unit for recording a preset attenuation value described later,  11  a loss recording unit; and  12  a fade volume computing unit for computing a signal amplifying factor (described later) on the basis of the preset value recorded on the preset attenuation value recording unit  10 , an attenuated amount recorded on the loss recording unit  11  and a movement (“fade”) of a balancing point from the center to the front or rear side inputted form the fade input unit. Reference numeral  13  denotes an entire volume input unit for controlling the volume of the signals reproduced by the front left speaker (SFL)  4 , front right speaker (SFR)  5 , rear left speaker (SRL)  6  and rear right speaker (SRR)  7 . Reference numeral  14  denotes an individual volume input unit for individually controlling the volume of the signal reproduced by each of the front left speaker (SFL)  4 , front right speaker (SFR)  5 , rear left speaker (SRL)  6  and rear right speaker (SRR)  7 . Reference numeral  15  denotes the fade input unit for setting the above “fade” in the conventional volume controller as shown in FIG. 3. Reference numeral  16  denotes a control unit. Reference numeral  17  denotes an interface (I/O) for supplying various values to the attenuators  8 TFL,  8 TFR,  8 TRL and  8 TRR under the control by a processor (CPU)  18 . Reference numeral  18  denotes the processor for executing the control processing for the preset value recording unit  10 , loss recording unit  11 , fade volume computing unit  12 , entire volume input unit  13 , individual volume input unit  14 , fade input unit  15  and control unit  16 .  
         [0027]    As shown in FIG. 2, with a central point P between the the front seat  2  and the rear seat  3 , the loss recording unit  11  previously records an attenuated amount L 1  of an acoustic wave produced from the front left speaker (SFL)  4  or the front right speaker (SFR)  5  while it reaches the central point P, and an attenuated amount L 2  of an acoustic wave produced from the rear left speaker (SRL)  6  or the rear right speaker (SRR)  7  while it reaches the central point P.  
         [0028]    In recording, with attenuated amounts for distances which have been acquired experimentally being recorded, the loss recording unit  11  may compute the attenuated amounts L 1  and L 2  by inputting the distances to the central point P.  
         [0029]    The distances to the central point P may be computed from the distance D 1  between the left and right speakers, the distance D 2  between the front and rear speakers, distance D 3  between the front speakers and the front seat P 1 , and distance D 4  between the front seat P 1  and rear seat P 2 .  
         [0030]    An explanation will be given of the operation of the volume controller according to this invention.  
         [0031]    Now it is assumed that the volume produced from the speaker is proportional to the level of the signal supplied thereto.  
         [0032]    Assuming that the R signal and L signal supplied to the volume controller according to this invention have equal signal levels and the amplifiers  9 AFR,  9 AFL,  9 ARL and  9 ARR connected to the speakers provide equal gains, the volume of the sound produced from the front left speaker (SFL)  4 , front right speaker (SFR)  5 , rear left speaker (SRL)  6  and rear right speaker (SRR)  7  is proportional to the attenuating amount in the attenuators  8 TFL,  8 TFR,  8 TRL and  8 TRR.  
         [0033]    Assuming that the attenuations in the attenuators  8 TFL,  8 TFR,  8 TRL and  8 TRR are TFL, TFR, TRL and TRR, respectively, if an increment or decrement of a constant K is input from the entire volume unit  13 ,  
         TFL=K  
         TFR=K  
         TRL=K  
         TRR=K  (1)  
         [0034]    Therefore, the respective attenuators provide the increment or decrement of the same value K.  7   
         [0035]    Where the individual volume input unit  14  performs the volume adjustment for each speaker input unit  14  to supply the attenuating amounts kFL, kFR, kRL and kRR to the attenuators  8 TFL,  8 TFR,  8 TRL and  8 TRR,  
         
       TFL=K+k 
       FL  
     
         
       TFR=K+k 
       FR  
     
         
       TRL=K+k 
       RL  
     
           TRR=K+k   RR   (2)  
         [0036]    The attenuations TFL, TFR, TRL and TRR are recorded in the preset value recording unit  10 .  
         [0037]    Assuming that the input from the fade input unit  15  is a “center” value (attenuating factor K F =1), the entire volume P at the position P in FIG. 2 is represented by  
           P=SV ( TFL+TFR ) L   1   +SV ( TRL+TRR ) L   2   (3)  
         [0038]    where SV represents a product of an input signal (L signal, R signal) and the gain of the amplifier  9 .  
         [0039]    In the following explanation, the entire volume P in Equation (3) is normalized by SV, and the normalized value is represented by P. Namely,  
           P =( TFL+TFR ) L   1  and ( TRL+TRR ) L   2   (4)  
         [0040]    If a movement of a balancing point from the center to the rear side (the signal for the front speaker is attenuated by the attenuating factor K F  (K F &gt;1.0)) is inputted by the fade input unit  15 , TFL and TFR are represented by  
           TFL=KF ( K +k   FL )  
           TFR=KF ( K+k   FR )  (5)  
         [0041]    The volume P F  from the front speakers at the point P is a sum of TFL and TFR in Equation (5). Namely,  
           P   F   =K   F {( K+k   FL )+( K+k   FR )} L   1   (6)  
         [0042]    In this invention, where the balancing point is moved to the rear side by the fade input unit, when the volume from the front speaker becomes PF expressed by Equation (6), the volume P R  from the rear speaker is increased so that the volume at point P is equal to the volume before the balancing point moves.  
         [0043]    Namely,  
           P   F   +P   R   =P   (7)  
         [0044]    Assuming that the signal amplification factor kR for the rear speaker (k R =1.0-0.0),  
                     P   R     =         k   R          (     TRL   +   TRR     )            L   2                   =       k   R          {       (     K   +     K   RL       )     +     (     K   +     k   RR       )       }          L   2                     (   8   )                               
 
         [0045]    Substituting Equations (4), (6) and (8) into Equation (7),  
           K   F ={( K+k   FL )+( K+k   FR )} L   1   +k   R {( K+k   RL )+( K+k   RR )} L   2 ={( K+k   FL )+( K+k   FR )} L   1 +{( K+k   RL )+( K+k   RR )} L   2   (9)  
         [0046]    Therefore, k R  is acquired from Equation (9),  
           k   R =1+(1− K   F ){( K+k   FL )+( K+k   FR ) L   1 /{( K+k   FL )+( K+k   RR ) L   2   (10)  
         [0047]    In Equation (10), (K+k FL ), (K+k FR ), (K+k FL ) and (K+k RR ), as explained in connection with Equation (2), have been recorded as TFT, TFR, TRL and TRR in the preset value recording unit  10 . L 1  and L 2  have been recorded in the loss recording unit  11 . If the movement of a balancing point from the center to the rear side (the signal for the front speaker is attenuated by the attenuating factor K F  (K F &gt;1.0)) is supplied from the fade input unit  15 , the face volume computing unit  12  read the data from the preset value recording unit  10  and the loss recording unit  11  to execute the operation of Equation ( 10 ), thereby computing k R .  
         [0048]    The control unit  16  multiplies the attenuated amount in  10  the attenuators  8 TRL and  8 TRR by k R .  
         [0049]    Upon completion of the operation of computing the fade volume, the control unit  16  records the K F -times values of the attenuators  8 TFL and  8 TFR and the KR-times values of the attenuators  8 TRL and  8 TRR in the preset value recording unit  10  to deal with a next fade input. The preset values are set at the recorded attenuations in the attenuator  8 TFR,  8 TFL,  8 TRL and  8 TRR.  
         [0050]    On the other hand, if a movement of the balancing point from the center to the front side is supplied from the fade input unit  15  (the signal for the rear speaker is K R  attenuated (K R &gt;1.0)), the attenuations in the attenuators  8 TRL and  8 TRR are multiplied by K R .  
         [0051]    Assuming that the signal amplification factor k F  for the rear speaker (k F =1.0-0.0), the fade volume computing unit  12  computes k F  from the following Equation  
           k   F =1+(1− K   R ){( K+k   RL )+( K+k   RR ) L   2 /{( K+k   FL )+( K+k   FR ) L   1   (11)  
         [0052]    Upon completion of computing the fade volume, the K F -times and K R -times attenuations are recorded in the preset value recording unit  10  to deal with a next fade input. The preset values are set at the recorded attenuations in the attenuator  8 TFR,  8 TFL,  8 TRL and  8 TRR.  
         [0053]    In the embodiment described above, although the center point P was located between the front seat  2  and the rear seat  3 , as seen from FIG. 2, it may be a center point P 1  of the front seat  2  or center point P 2  of the rear seat  3 . The center point may be exchanged among P, P 1  and P 2 .