Abstract:
A sound reproducing apparatus is structured to use a first dividing circuit and a determining circuit to analyze a frequency characteristic of an inputted signal and to output a signal adjusted by a first adjusting circuit to have a prescribed frequency characteristic by a switching by a switch circuit. Thus, when signals having different frequency characteristics are inputted, frequency characteristics of the input signals can be automatically adjusted without using an external signal and channels having different frequency characteristics can be reproduced by a single system to provide good speaker-reproduced sound.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a sound reproducing apparatus that can reproduce channels in which sounds having different frequency characteristics are recorded (e.g., woofer channels for CD and DVD) under a single acoustic field environment and with a good sound quality. 
       BACKGROUND ART 
       [0002]    Japanese Patent Unexamined Publication No. 2001-112098 discloses a technique for a conventional sound reproducing apparatus. When this technique is used to reproduce a two channel source such as CD and a multi channel source including a woofer channel such as DVD in which only a low frequency is recorded under a single acoustic field reproducing environment, a switch is used to provide a switching between a two channel signal line and a multi channel signal line. 
         [0003]    However, a sound reproducing apparatus having the conventional structure as described above has required an external signal for making distinction between a two channel and a multi channel when a switching between signals is performed. 
       SUMMARY OF THE INVENTION 
       [0004]    A sound reproducing apparatus includes: a music signal source; a dividing circuit formed of at least one filter for dividing the music signal source into prescribed bands; a determining circuit for determining, based on an output from the dividing circuit, a frequency included in the music signal source; an adjusting circuit formed of at least one filter for adjusting the music signal source to have a prescribed frequency characteristic; and a switch circuit for switching an output of the adjusting circuit. An output from the determining circuit is used to control the switch circuit to output a signal adjusted to have a prescribed frequency characteristic. 
         [0005]    The structure as described above allows, when channels having different frequency characteristics (e.g., a two channel source (e.g., CD) and a multi channel source (e.g., DVD)) are reproduced, the frequency characteristics of the music signal source themselves can be used to switch signal lines to adjust the multi channel source to have a prescribed frequency characteristic. As a result, when channels having different frequency characteristics (e.g., a woofer channel of DVD and CD) are reproduced by a single system, good speaker-reproduced sound can be realized. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0006]      FIG. 1  is a block diagram illustrating a sound reproducing apparatus in Embodiment 1 of the present invention. 
           [0007]      FIG. 2  is a frequency characteristic diagram illustrating an input signal of a music signal source in Embodiment 1 of the present invention. 
           [0008]      FIG. 3  is a frequency characteristic diagram illustrating an output signal of the first adjusting circuit in Embodiment 1 of the present invention. 
           [0009]      FIG. 4  is a frequency characteristic diagram illustrating another input signal of the music signal source in Embodiment 1 of the present invention. 
           [0010]      FIG. 5  is a block diagram illustrating a sound reproducing apparatus in Embodiment 2 of the present invention. 
           [0011]      FIG. 6  is a block diagram illustrating a sound reproducing apparatus in Embodiment 3 of the present invention. 
       
    
    
     REFERENCE MARKS IN THE DRAWINGS 
       [0012]      11  Music signal source 
         [0013]      12  First dividing circuit 
         [0014]      13  Second dividing circuit 
         [0015]      14  First adjusting circuit 
         [0016]      15  Second adjusting circuit 
         [0017]      16  Determining circuit 
         [0018]      17  Switch circuit 
         [0019]      20  Output signal 
       DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0020]    Hereinafter, an embodiment of the present invention will be described with reference to  FIG. 1  to  FIG. 6 . 
       Embodiment 1 
       [0021]      FIG. 1  is a block diagram illustrating a sound reproducing apparatus in Embodiment 1 of the present invention. First, with reference to  FIG. 1 , the structure of the sound reproducing apparatus in Embodiment 1 will be described. 
         [0022]    As shown in  FIG. 1 , a sound reproducing apparatus in Embodiment 1 includes music signal source  11 , first dividing circuit  12 , and first adjusting circuit  14 . Music signal source  11  is an input signal. First dividing circuit  12  is formed of a low-pass filter, a high-pass filter, a band-pass filter or the like and is formed of at least one filter for dividing music signal source  11  into prescribed bands. First adjusting circuit  14  is formed of at least one filter for adjusting music signal source  11  to have a prescribed frequency characteristic (e.g., low-pass filter, high-pass filter, band-pass filter). The sound reproducing apparatus in Embodiment 1 also includes determining circuit  16  and switch circuit  17  Determining circuit  16  uses an absolute value circuit and a comparator or a wind comparator or the like to determine whether an input signal includes a prescribed band signal of a certain level or higher with regards to an output signal of first dividing circuit  12  to output a signal and determines, based on an output from first dividing circuit  12 , a frequency included in the music signal source. Switch circuit  17  uses the output signal of determining circuit  16  to switch whether first adjusting circuit  14  is used as output signal  20  or output signal  20  is directly used as music signal source  11 . 
         [0023]    Next, an operation of the sound reproducing apparatus in Embodiment 1 having the structure as described above will be described with reference to  FIG. 2 ,  FIG. 3 , and  FIG. 4 .  FIG. 2  is a frequency characteristic diagram of an input signal of the music signal source in Embodiment 1.  FIG. 3  is a frequency characteristic diagram of an output signal of the first adjusting circuit in Embodiment 1.  FIG. 4  is a frequency characteristic diagram of another input signal of the music signal source in Embodiment 1. 
         [0024]    When the sound reproducing apparatus in Embodiment 1 receives a signal as music signal source  11  including a high frequency component of a certain level or more as shown in  FIG. 2  for example, first dividing circuit  12  formed of a high-pass filter or the like extracts only a high frequency component from music signal source  11 . Then, an absolute value circuit and a comparator or a wind comparator or the like are used to detect the level of the signal of the broadband component to subsequently allow determining circuit  16  to determine whether the level is equal to or higher than a certain level or not. In this manner, it is determined that a mixed signal of a two channel source for CD for example is used as a woofer signal. Then, first adjusting circuit  14  adjusts the frequency characteristic of music signal source  11  and an output of first adjusting circuit  14  as shown in  FIG. 3  is used as an output signal. When a signal not including a high frequency component as shown in  FIG. 4  is inputted as music signal source  11 , it is determined in a similar manner that a woofer signal of a multi channel source for DVD for example is used. Then, music signal source  11  is directly outputted. As described above, by performing the adjustment as shown in  FIG. 3  and  FIG. 4  to provide substantially equal frequency characteristics, the sound reproducing apparatus in Embodiment 1 can favorably reproduce even a source in which different frequency characteristics are recorded such as a two channel source and a multi channel source. 
         [0025]    Although Embodiment 1 has used a high-pass filter as first dividing circuit  12 , a similar control also can be performed by another structure such as a combination of a band-pass filter and another filter so that music signal source  11  can be divided into prescribed bands. 
       Embodiment 2 
       [0026]    A sound reproducing apparatus in Embodiment 2 is characterized in that Embodiment 1 of the present invention is added with a second dividing circuit and a plurality of dividing circuits are used to improve an accuracy at which a frequency characteristic is determined by the determining circuit. 
         [0027]      FIG. 5  is a block diagram illustrating a sound reproducing apparatus in Embodiment 2 of the present invention. First, with reference to  FIG. 5 , the structure of the sound reproducing apparatus in Embodiment 2 will be described. 
         [0028]    As shown in  FIG. 5 , the sound reproducing apparatus in Embodiment 2 includes: music signal source  11 , first dividing circuit  12 , second dividing circuit  13 , and first adjusting circuit  14 . Music signal source  11  is an input signal. First dividing circuit  12  is formed of at least one filter (e.g., low-pass filter, high-pass filter, band-pass filter) and divides an input signal into prescribed bands. Second dividing circuit  13  is formed of at least one filter (e.g., band-pass filter) and divides an input signal into prescribed bands. First adjusting circuit  14  is formed of a low-pass filter, a high-pass filter, and a band-pass filter for example and adjusts music signal source  11  to have a prescribed frequency characteristic. The sound reproducing apparatus in Embodiment 2 also includes determining circuit  16  and switch circuit  17 . Determining circuit  16  determines, with regards to output signals from first dividing circuit  12  and second dividing circuit  13 , whether the input signals include a signal having a prescribed band or not by using an absolute value circuit and a comparator or a wind comparator or the like to output a signal. Switch circuit  17  uses the output signal from determining circuit  16  to switch whether first adjusting circuit  14  is used as output signal  20  or music signal source  11  is directly used as output signal  20 . 
         [0029]    Next, the operation of the sound reproducing apparatus in Embodiment 2 having the structure as described above will be described. 
         [0030]    The sound reproducing apparatus in Embodiment 2 uses the structure having a plurality of dividing circuits so that first dividing circuit  12  uses a low-pass filter for extracting only a low frequency and second dividing circuit  13  uses a high-pass filter for extracting only a high frequency for example. Then, signal levels of frequency components as output results extracted by first dividing circuit  12  and second dividing circuit  13  are determined by determining circuit  16  using an absolute value circuit and a comparator or a wind comparator with regards to whether the signal levels are equal to or higher than a certain level. In this manner, only when music signal source  11  as shown in  FIG. 2  includes both of a low frequency and a high frequency, the music signal as shown in  FIG. 3  is outputted that is subjected to a signal processing by first adjusting circuit  14  to provide a prescribed frequency characteristic. When music signal source  11  as shown in  FIG. 2  includes only a low frequency as shown in  FIG. 4 , the signal processing is skipped and music signal source  11  is directly outputted. Therefore, an adjustment as shown in  FIG. 3  and  FIG. 4  to provide substantially equal frequency characteristics can be performed to favorably reproduce even a source in which different frequency characteristics (e.g., a two channel source and a multi channel source) are recorded for example. In this manner, a sound reproducing apparatus can be provided that can allow determining circuit  16  to determine a frequency characteristic with a higher accuracy to realize a favorable sound reproduction. 
       Embodiment 3  
       [0031]    A sound reproducing apparatus in Embodiment 3 is characterized in that Embodiment 2 of the present invention is added with a second adjusting circuit to use a plurality of adjusting circuits. 
         [0032]      FIG. 6  is a block diagram illustrating a sound reproducing apparatus in Embodiment 3 of the present invention. First, the structure of the sound reproducing apparatus in Embodiment 3 will be described with reference to  FIG. 6 . 
         [0033]    As shown in  FIG. 6 , the sound reproducing apparatus Embodiment 3 includes music signal source  11 , first dividing circuit  12 , second dividing circuit  13 , first adjusting circuit  14 , and second adjusting circuit  15 . Music signal source  11  is an input signal. First dividing circuit  12  is formed of a low-pass filter, a high-pass filter, or a band-pass filter or the like and divides an input signal into prescribed bands. Second dividing circuit  13  is formed of a low-pass filter, a high-pass filter, or a band-pass filter or the like and divides an input signal into prescribed bands. First adjusting circuit  14  is formed of a low-pass filter or a band-pass filter or the like and adjusts music signal source  11  to have a prescribed frequency characteristic. Second adjusting circuit  15  is formed of a low-pass filter or a band-pass filter or the like and adjusts music signal source  11  to have a prescribed frequency characteristic. The sound reproducing apparatus Embodiment 3 also includes determining circuit  16  and switch circuit  17 . Determining circuit  16  determines whether uses an absolute value circuit and a comparator or a wind comparator or the like to determine whether an input signal includes a prescribed band signal of a certain level or higher with regards to output signals from first dividing circuit  12  and second dividing circuit  13  to output a signal. Switch circuit  17  uses an output signal of determining circuit  16  to switch whether first adjusting circuit  14  is used as output signal  20  or second adjusting circuit  15  is used as output signal  20 . 
         [0034]    Next, the operation of the sound reproducing apparatus in Embodiment  3  having the structure as described above will be described. 
         [0035]    The sound reproducing apparatus in Embodiment 3 can perform a control by using the similar determination results as in Embodiments 1 and 2. The sound reproducing apparatus in Embodiment 3 also can subject, when music signal source  11  includes only a low frequency component, the signal to a signal processing in which the signal is provided with an optimal frequency characteristic. The sound reproducing apparatus in Embodiment 3 also can subject, when music signal source  11  includes both of a low frequency component and a high frequency component, the signal to a signal processing for specific optimization in which the signal is provided with an optimal frequency characteristic. 
         [0036]    For example, when music signal source  11  includes only a low frequency component for example, the signal processing in Embodiment 3 uses first adjusting circuit  14  to reduce the bandwidth of the signal so that only a signal having a further lower frequency component can be used. When music signal source  11  includes both of a low frequency component and a high frequency component, second adjusting circuit  15  can subject the signal to a signal processing for reducing the bandwidth to a similar bandwidth. In this manner, frequency characteristics of first adjusting circuit  14  and second adjusting circuit  15  can be respectively adjusted so as to have a prescribed frequency characteristic and are appropriately switched, thus realizing a favorable sound reproduction. 
         [0037]    Although Embodiment 3 includes a plurality of dividing circuits, one dividing circuit also may be used. The reason is that the first dividing circuit and the determining circuit can be used to determine a frequency component included in an inputted music signal source as shown in Embodiment 1 and thus a plurality of adjusting circuits can be used to provide the same effect. 
         [0038]    The respective structures of Embodiments 1, 2, and 3 can be provided by hardware or a digital signal processing by software or a combination thereof to perform the same control. 
       INDUSTRIAL APPLICABILITY 
       [0039]    According to the present invention, sources in which different frequency characteristics are recorded in specific channels such as DVD and CD can be reproduced with a good sound quality. Thus, the present invention can be advantageously used for a sound reproducing apparatus that can reproduce multiple channels.