Patent Publication Number: US-10321234-B2

Title: Signal processing device and signal processing method

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Phase of International Patent Application No. PCT/JP2015/081268 filed on Nov. 6, 2015, which claims priority benefit of Japanese Patent Application No. JP 2014-233311 filed in the Japan Patent Office on Nov. 18, 2014. Each of the above-referenced applications is hereby incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to signal processing devices, signal processing methods, and programs and particularly to a signal processing device, a signal processing method, and a program that allows for generating an input signal suitable for a multi-way speaker. 
     BACKGROUND ART 
     Wave front synthesis technique is known as a sound field reproduction method to acquire a wave front of sound in a sound field by a plurality of microphones and to reproduce the sound field on the basis of the acquired sound signal. As one type of the wave front synthesis technique, there is a boundary surface control method (for example, see Patent Document 1). 
     The boundary surface control method is a method to arrange microphones in a reproduction space where the sound field is reproduced in the same manner as that in the original space where a sound source has been acquired and to provide input signals to a plurality of speakers installed in the periphery of the reproduction space such that signals observed by the microphones are the same as microphone signals acquired in the original space. 
     In this boundary surface control method, a speaker that outputs a spherical wave in every frequency band is ideal as the plurality of speakers installed in the periphery of the reproduction space; however, no such speaker exists in reality. 
     Therefore, generally used is a multi-way speaker where a plurality of units is included in one enclosure to support by dividing into a plurality of bands such as a high frequency band side and a low frequency band side. 
     CITATION LIST 
     Patent Document 
     
         
         Patent Document 1: Japanese Patent Application Laid-Open No. 2012-10011 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In a multi-way speaker, a deemed acoustic axis determined by weighing a unit of the high frequency band or by other means is set. However, this is different from actual acoustic axes of the respective units and thus an effect of wave front synthesis may not be fully exercised. Therefore there is a need to consider input appropriate for a multi-way speaker. 
     The present disclosure has been devised in consideration to the above circumstances to allow for generation of an input signal suitable for a multi-way speaker. 
     Solutions to Problems 
     A signal processing device of one aspect of the present disclosure includes: a band dividing unit that divides an audio signal into signals in a plurality of bands corresponding to respective bands of a plurality of speaker units of a multi-way speaker; and a wave front synthesis filter processing unit that performs wave front synthesis filter processing on each of the audio signals in the respective bands having been divided into. The audio signal in each of the bands after the wave front synthesis filter processing is output to the speaker unit of the corresponding band in the multi-way speaker. 
     A signal processing method of one aspect of the present disclosure includes the steps of: dividing, by a signal processing device, an audio signal into signals in a plurality of bands corresponding to respective bands of a plurality of speaker units of a multi-way speaker; and performing, by the signal processing device, wave front synthesis filter processing on each of the audio signals in the respective bands having been divided into. The audio signal in each of the bands after the wave front synthesis filter processing is output to the speaker unit of the corresponding band in the multi-way speaker. 
     A program of one aspect of the present disclosure causes a computer to function as: a band dividing unit that divides an audio signal into signals in a plurality of bands corresponding to respective bands of a plurality of speaker units of a multi-way speaker; and a wave front synthesis filter processing unit that performs wave front synthesis filter processing on each of the audio signals in the respective bands having been divided into. The audio signal in each of the bands after the wave front synthesis filter processing is output to the speaker unit of the corresponding band in the multi-way speaker. 
     In one aspect of the present disclosure, an audio signal is divided into signals in the plurality of bands corresponding to the respective bands of the plurality of speaker units of the multi-way speaker and the wave front synthesis filter processing is performed on each of the audio signals in the respective bands having been divided into. 
     Note that the program can be provided by transmission via a transmission medium or being stored in a recording medium. 
     The signal processing device may be an independent device or an internal block included in a device. 
     Effects of the Invention 
     An aspect of the present disclosure allows for generation of an input signal suitable for a multi-way speaker. 
     Note that effects described herein are not necessarily limiting. Any one of the effects described in the present disclosure may be included. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram explaining a boundary surface control method. 
         FIG. 2  is a block diagram illustrating an exemplary configuration of an embodiment of a contents presentation device according to the present disclosure. 
         FIGS. 3A and 3B  are diagrams explaining an acoustic axis of a multi-way speaker. 
         FIG. 4  is a block diagram illustrating a detailed exemplary configuration of a wave front synthesis digital filter. 
         FIG. 5  is a diagram illustrating a detailed exemplary configuration of a multi-way speaker. 
         FIG. 6  is a flowchart explaining sound field reproduction processing by a reproduction system. 
         FIG. 7  is a diagram explaining calculation of a transmission function by simulation calculation. 
         FIG. 8  is a diagram explaining calculation of the transmission function by simulation calculation. 
         FIG. 9  is a block diagram illustrating an exemplary configuration of an embodiment of a computer according to the present disclosure. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     &lt;Explanation on Boundary Surface Control Method&gt; 
     First, the boundary surface control method will be described with reference to  FIG. 1 . 
     The boundary surface control method is a method to arrange microphones in a reproduction space where the sound field is reproduced in the same manner as that in the original space where a sound source has been acquired and to provide input signals to a plurality of speakers installed in the periphery of the reproduction space such that signals observed by the microphones are the same as microphone signals acquired in the original space. 
     Specifically, a site A illustrated in  FIG. 1  is assumed as the original space. Sound output from a number of speakers  11  arranged in the periphery of the site A is acquired by a number of microphones  12  arrayed in the site. 
     Moreover, in a site B as a reproduction space, a number of microphones  13  are installed in arrangement similar to that in the original space as illustrated in  FIG. 1 . A reproduction device measures a transmission function (transmission characteristic) G from the multiple speakers  14  arranged in the periphery to the respective microphones  13 . The reproduction device then calculates an inverse function filter H=G −1  which is inverse characteristic of the transmission function G and outputs, from the speaker  14 , the audio signal acquired in the original space through the inverse function filter H, thereby reproducing the sound field of the original space in the reproduction space. A position of the microphone  12  or  13  is also referred to as a control point in the boundary surface control method. 
     Note that actually it is often difficult to measure a transmission function G from the multiple speakers  14  to the respective microphones  13  by installing the multiple microphones  13  in the reproduction space. Therefore there are cases where the transmission function G is derived from simulation calculation using a theoretical value. 
     &lt;Exemplary Configuration of Reproduction System&gt; 
       FIG. 2  is a diagram illustrating an exemplary configuration of an embodiment of a reproduction system according to the present disclosure. 
     A reproduction system  20  in  FIG. 2  is a system used for reproduction of a sound field by the boundary surface control method and includes a signal processing device  31  and multiple (N) multi-way speakers  32 . 
     The signal processing device  31  corresponds to the reproduction device that generates and outputs the audio signal to be provided to the speaker  14  in the reproduction space having described in  FIG. 1 . The multi-way speaker  32  corresponds to the speaker  14 . 
     In the present embodiment, the multi-way speaker  32  includes, in one enclosure, two units including a unit that supports a low frequency band (woofer) and a unit that supports a high frequency band (tweeter). 
     Generally, a specification of a multi-way speaker describes about an acoustic axis. An acoustic axis of a multi-way speaker described in a specification is a deemed acoustic axis where a unit of the high frequency band side is weighted to determine a single acoustic axis as illustrated in  FIG. 3A . 
     However, an acoustic axis of a multi-way speaker is actually different between a unit of the high frequency band side and a unit of the low frequency band side as illustrated in  FIG. 3B . 
     The signal processing device  31  performs signal processing corresponding to each of an acoustic axis in the high frequency band and an acoustic axis in the low frequency band of the multi-way speaker  32 . Here a crossover frequency between the high frequency band and the low frequency band of the multi-way speaker  32  is assumed as 300 Hz. 
     In  FIG. 2 , the signal processing device  31  includes a data storage unit  51 , a controller  52 , wave front synthesis digital filters  53   1  to  53   N , D/A converters  54   1  to  54   N , and amplifiers (AMPS)  55   1  to  55   N . 
     Note that the wave front synthesis digital filters  53   1  to  53   N , the D/A converters  54   1  to  54   N , and the amplifiers (AMPS)  55   1  to  55   N  are N systems of the wave front synthesis digital filter  53 , the D/A converter  54 , and the amplifier  55  provided corresponding to N multi-way speakers  32   1  to  32   N . 
     The data storage unit  51  stores an audio signal acquired in an original space. 
     The controller  52  acquires, from the data storage unit  51 , an audio signal of a sound source instructed by a user at an operation unit (not illustrated) and supplies the audio signal to the wave front synthesis digital filters  53   1  to  53   N . 
     The wave front synthesis digital filters  53   i  (i=1 to N), the D/A converters  54   i , and the amplifiers  55   i  form a processing system that processes the audio signal to be output to the multi-way speakers  32   i . The wave front synthesis digital filter  53 , the D/A converter  54 , and the amplifier  55  execute similar signal processing in each of the systems and thus description is given on one wave front synthesis digital filter  53 , one D/A converter  54 , and one amplifier  55 . 
     The wave front synthesis digital filter  53  executes filter processing of the inverse function filter H=G −1  of the transmission function G in a reproduction space on the audio signal supplied from the controller  52  and supplies the audio signal after the filter processing to the D/A converter  54 . 
     The D/A converter  54  converts the digital audio signal supplied from the wave front synthesis digital filter  53  into an analog signal and supplies the analog signal to the amplifier  55 . 
     The amplifier  55  amplifies the analog audio signal supplied from the D/A converter  54  and outputs to the multi-way speaker  32  connected therewith. 
     &lt;Detailed Configuration of Wave Front Synthesis Digital Filter&gt; 
       FIG. 4  is a block diagram illustrating a detailed exemplary configuration of the wave front synthesis digital filter  53 . 
     The wave front synthesis digital filter  53  includes a band dividing unit  70 , a high frequency band wave front synthesis filter  72 H, a low frequency band wave front synthesis filter  72 L, and a synthesis unit  73 . 
     The band dividing unit  70  includes a high pass filter (HPF)  71 H and a low pass filter (LPF)  71 L and divides the audio signal supplied from the controller  52  into signals in the plurality of bands corresponding to the respective units in the multi-way speaker  32 . 
     Specifically, the HPF  71 H performs filter processing to pass only a signal in the high frequency band side higher than or equal to the crossover frequency of 300 Hz of the multi-way speaker  32  from among the audio signals supplied from the controller  52 . The HPF  71 H supplies the audio signal after filter processing to the high frequency band wave front synthesis filter  72 H. 
     The LPF  71 L performs filter processing to pass only a signal in the low frequency band side lower than the crossover frequency of 300 Hz of the multi-way speaker  32  from among the audio signals supplied from the controller  52 . The LPF  71 L supplies the audio signal after filter processing to the low frequency band wave front synthesis filter  72 L. 
     The high frequency band wave front synthesis filter  72 H executes, on the audio signal in the high frequency band supplied from the HPF  71 H, filter processing of the inverse function filter H_high designed for the high frequency band higher than or equal to the crossover frequency and supplies the audio signal after the filter processing to the synthesis unit  73 . 
     The low frequency band wave front synthesis filter  72 L executes, on the audio signal in the low frequency band supplied from the LPF  71 L, filter processing of the inverse function filter H_low designed for a low frequency band lower than the crossover frequency and supplies the audio signal after the filter processing to the synthesis unit  73 . 
     The synthesis unit  73  synthesizes (adds) the audio signal after the filter processing by the high frequency band wave front synthesis filter  72 H and the audio signal after the filter processing by the low frequency band wave front synthesis filter  72 L and outputs to the D/A converter  54  ( FIG. 2 ). 
     &lt;Detailed Exemplary Configuration of Multi-way Speaker&gt; 
       FIG. 5  is a diagram illustrating a detailed exemplary configuration of the multi-way speaker  32 . 
     The multi-way speaker  32  includes a HPF  81 H, a LPF  81 L, a speaker unit  82 H, and a speaker unit  82 L. 
     The HPF  81 H executes filter processing to pass only a signal in the high frequency band side higher than or equal to the crossover frequency of 300 Hz from among the audio signals supplied from the amplifier  55  in the signal processing device  31  and supplies the audio signal after the filter processing to the speaker unit  82 H. 
     The LPF  81 L executes filter processing to pass only a signal in the low frequency band side lower than the crossover frequency of 300 Hz from among the audio signals supplied from the amplifier  55  in the signal processing device  31  and supplies the audio signal after the filter processing to the speaker unit  82 L. 
     The aforementioned HPF  71 H and the LPF  71 L of the wave front synthesis digital filter  53  are digital filters while the HPF  81 H and the LPF  81 L of the multi-way speaker  32  are analog filters. 
     The speaker unit  82 H outputs sound corresponding to the audio signal in the high frequency band supplied from the HPF  81 H. 
     The speaker unit  82 L outputs sound corresponding to the audio signal in the low frequency band supplied from the LPF  81 L. 
     Note that, according to the configurations in  FIG. 4  and  FIG. 5 , audio signals divided into the high frequency band and the low frequency band corresponding to the speaker unit  82 H and the speaker unit  82 L, respectively, are once synthesized in the wave front synthesis digital filter  53  and then again divided into the high frequency band and the low frequency band in the multi-way speaker  32 . However, the audio signals divided into the high frequency band and the low frequency band in the wave front synthesis digital filter  53  may be supplied to the HPF  81 H and the LPF  81 L of the multi-way speaker  32  as they are without being synthesized. 
     &lt;Sound Field Reproduction Processing&gt; 
     Next, sound field reproduction processing by the reproduction system  20  will be explained with reference to a flowchart in  FIG. 6 . This processing is initiated upon instruction of reproduction of a predetermined audio signal by a user at the operation unit (not illustrated), for example. 
     First in step S 1 , the controller  52  acquires, from the data storage unit  51 , the predetermined audio signal of instructed by the user at the operation unit (not illustrated) and supplies the audio signal to the wave front synthesis digital filters  53   1  to  53   N . 
     In step S 2 , the band dividing unit  70  in the wave front synthesis digital filter  53  performs band dividing processing to divide the audio signal supplied from the controller  52  into signals in the plurality of bands. 
     That is, the HPF  71 H performs filter processing to pass only a signal in the high frequency band side higher than or equal to the crossover frequency of 300 Hz of the multi-way speaker  32  from among the audio signals supplied from the controller  52  and supplies the audio signal after the filter processing to the high frequency band wave front synthesis filter  72 H. That is, the LPF  71 L performs filter processing to pass only a signal in the low frequency band side lower than the crossover frequency of 300 Hz of the multi-way speaker  32  from among the audio signals supplied from the controller  52  and supplies the audio signal after the filter processing to the low frequency band wave front synthesis filter  72 L. 
     In step S 3 , the high frequency band wave front synthesis filter  72 H and the low frequency band wave front synthesis filter  72 L of the wave front synthesis digital filter  53  perform wave front synthesis filter processing by the inverse function filter H=G −1  of the transmission function G in the reproduction space. 
     Specifically, the high frequency band wave front synthesis filter  72 H performs, on the audio signal in the high frequency band supplied from the HPF  71 H, filter processing of the inverse function filter H_high designed for the high frequency band higher than or equal to the crossover frequency and supplies the audio signal after the filter processing to the synthesis unit  73 . 
     The low frequency band wave front synthesis filter  72 L performs, on the audio signal in the low frequency band supplied from the LPF  71 L, filter processing of the inverse function filter H_low designed for the low frequency band lower than the crossover frequency and supplies the audio signal after the filter processing to the synthesis unit  73 . 
     In step S 4 , the synthesis unit  73  synthesizes the audio signal in the high frequency band after the filter processing by the high frequency band wave front synthesis filter  72 H and the audio signal in the low frequency band after the filter processing by the low frequency band wave front synthesis filter  72 L and outputs to the D/A converter  54 . 
     In step S 5 , the D/A converter  54  converts the digital audio signal supplied from the synthesis unit  73  in the wave front synthesis digital filter  53  into an analog signal and supplies the analog signal to the amplifier  55 . 
     In step S 6 , the amplifier  55  amplifies the analog audio signal supplied from the D/A converter  54  and outputs to the multi-way speaker  32  connected therewith. 
     In step S 7 , the multi-way speaker  32  outputs sound corresponding to the audio signal supplied from the amplifier  55 . 
     Specifically, the HPF  81 H of the multi-way speaker  32  executes filter processing to pass only a signal in the high frequency band side higher than or equal to the crossover frequency of 300 Hz from among the audio signals supplied from the amplifier  55  and outputs the audio signal after the filter processing as sound from the speaker unit  82 H. Furthermore, the LPF  81 L of the multi-way speaker  32  executes filter processing to pass only a signal in the low frequency band side lower than the crossover frequency of 300 Hz from among the audio signals supplied from the amplifier  55  and outputs the audio signal after the filter processing as sound from the speaker unit  82 L. 
     The processing of steps S 2  to S 7  is executed in parallel in each of the N processing systems corresponding to the multi-way speakers  32   1  to  32   N . 
     The processing of steps S 1  to S 7  described above is executed continuously until no audio signal is supplied from the data storage unit  51 . When no more audio signal is supplied, the sound field reproduction processing in  FIG. 6  is terminated. 
     According to the reproduction system  20 , the signal processing device  31  performs, on the speaker unit  82 H that supports the high frequency band and the speaker unit  82 L that supports the low frequency band in the multi-way speaker  32 , wave front synthesis filter processing corresponding to each of the bands thereof as described above. This allows for obtaining better sound image localization. That is, an input signal suitable for the multi-way speaker can be generated. 
     &lt;Calculation of Transmission Function G by Simulation Calculation&gt; 
     As described above, it is often difficult to measure the transmission function G and thus there are cases where the transmission function G is derived from a simulation calculation using a theoretical value. 
     When the transmission function G is derived by simulation calculation, usually N×M acoustic simulation formulas that includes the number of speakers  14  (N) and the number of control points (microphones) (M) as illustrated in  FIG. 7  are calculated using a finite element method, a boundary element method, an FDTD method, or other methods and a pseudo inverse matrix thereof is solved. 
     Meanwhile, in the case of deriving transmission functions G that are different between the high frequency band and the low frequency band as in the present embodiment, it is assumed that a spherical wave is output from a unit position of each of the speaker unit  82 H in the high frequency band and the speaker unit  82 L in the low frequency band and thereby acoustic simulation formulas to the control points are generated. 
     In this case, N×M acoustic simulation formulas corresponding to the speaker unit  82 H in the high frequency band and N×M acoustic simulation formulas corresponding to the speaker unit  82 L in the low frequency band are generated and a pseudo inverse matrix thereof is solved. The computation amount is thus doubled. 
     In the low frequency band, however, the wavelength is long and thus the control points are not required to be dense as compared to those in the high frequency band. That is, the number of simulations may be small. An interval among the control points may be approximately half the wavelength. 
     For example when the crossover frequency is 300 Hz, calculation can be performed while the control points are thinned to an interval of approximately 50 cm in the simulation formulas in the low frequency band. As illustrated in  FIG. 8 , therefore, calculation can be performed with M′ control points which is a smaller number than the actual number M in the simulation formula of the low frequency band side and thus the size of the matrix becomes smaller in calculation of a pseudo inverse matrix upon design of the filter. This allows for preferable calculation efficiency and shorter design time of the filter. 
     In the example described above, the case where the multi-way speaker  32  is a two-way speaker where the sound range is divided into two including the high frequency band and the low frequency band has been described; however, the above is similarly applicable even if the multi-way speaker  32  is a speaker where the sound range is divided into three or more frequency bands. 
     The series of processing described above may be executed by hardware or may be executed by software. When the series of processing is executed by software, a program that forms the software is installed in a computer. The computer here includes, for example, a computer incorporated in dedicated hardware, a generic personal computer capable of executing various functions by installing various programs, or other types of computers. 
       FIG. 9  is a block diagram illustrating an exemplary configuration of hardware of a computer that executes the series of processing described above by a program. 
     In the computer, a central processing unit (CPU)  101 , a read only memory (ROM)  102 , and a random access memory (RAM)  103  are connected to each other by bus  104 . 
     The bus  104  is further connected with an input/output interface  105 . The input/output interface  105  connected with an input unit  106 , an output unit  107 , a storage unit  108 , a communication unit  109 , and a drive  110 . 
     The input unit  106  includes a keyboard, a mouse, a microphone, or other devices. The output unit  107  includes a display, a speaker, or other devices. The storage unit  108  includes a hard disk, a nonvolatile memory, or others. The communication unit  109  includes a network interface or others. The drive  110  drives a removable recording medium  111  such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory. 
     In the computer configured in the above manner, the series of processing described above is performed by the CPU  101 , for example, by loading a program stored in the storage unit  108  to the RAM  103  via the input/output interface  105  and the bus  104  and executing the program. 
     In the computer, a program can be installed in the storage unit  108  via the input/output interface  105  by mounting the removable recording medium  111  to the drive  110 . Moreover, a program may be received by the communication unit  109  via a wired or wireless transmission medium such as a local area network, the Internet, and digital satellite broadcasting and installed in the storage unit  108 . Alternatively, a program may be installed in the ROM  102  or the storage unit  108  in advance. 
     Note that the program executed by the computer may perform processing in time series according to the order described herein or may perform processing in parallel or at necessary timing such as upon a call. 
     Note that, in the present description, a system means a collection of a plurality of components (devices, modules (parts), or the like) regardless of whether all the components are in the same housing. Therefore, any one of a plurality of devices in separate housings and connected via a network and one device where a plurality of modules is included in one housing is a system. 
     Embodiments of the present disclosure are not limited to the aforementioned embodiments and may include various modifications within a scope not departing from the principles of the present disclosure. 
     For example, an embodiment where all or a part of the plurality of embodiments described above are combined may be employed. 
     For example, the present disclosure may employ cloud computing where one function is processed by a plurality of devices in a shared and collaborative manner via a network. 
     Moreover, each of the steps described in the above flowchart may be executed by one device or may be executed by a plurality of devices in a collaborative manner. 
     Furthermore, when a plurality of types processing is included in one step, the plurality of types of processing included in that one step may be executed in one device or may be executed by a plurality of devices in a collaborative manner. 
     Note that effects described herein are merely examples and thus are not limited. Effects other than those described herein may also be included. 
     Note that the present disclosure may be as follows. 
     (1) 
     A signal processing device, including: 
     a band dividing unit that divides an audio signal into signals in a plurality of bands corresponding to respective bands of a plurality of speaker units of a multi-way speaker; and 
     a wave front synthesis filter processing unit that performs wave front synthesis filter processing on each of the audio signals in the respective bands having been divided into, 
     wherein the audio signal in each of the bands after the wave front synthesis filter processing is supplied to the speaker unit of the corresponding band in the multi-way speaker. 
     (2) 
     The signal processing device according to item (1), further including: 
     a synthesis unit that synthesizes the audio signals in the respective bands after the wave front synthesis filter processing, 
     wherein the audio signal after synthesis is supplied to the multi-way speaker. 
     (3) 
     The signal processing device according to item (1) or (2), wherein a filter of the wave front synthesis filter processing corresponding to the speaker unit of a low frequency band side from among the plurality of speaker units in the multi-way speaker is generated by simulation where the number of control points is set smaller than an actual number thereof. 
     (4) 
     A signal processing method, including the steps of: 
     dividing, by a signal processing device, an audio signal into signals in a plurality of bands corresponding to respective bands of a plurality of speaker units of a multi-way speaker; and 
     performing, by the signal processing device, wave front synthesis filter processing on each of the audio signals in the respective bands having been divided into, 
     wherein the audio signal in each of the bands after the wave front synthesis filter processing is supplied to the speaker unit of the corresponding band in the multi-way speaker. 
     (5) 
     A program for causing a computer to function as: 
     a band dividing unit that divides an audio signal into signals in a plurality of bands corresponding to respective bands of a plurality of speaker units of a multi-way speaker; and 
     a wave front synthesis filter processing unit that performs wave front synthesis filter processing on each of the audio signals in the respective bands having been divided into, 
     wherein the audio signal in each of the bands after the wave front synthesis filter processing is supplied to the speaker unit of the corresponding band in the multi-way speaker. 
     REFERENCE SIGNS LIST 
     
         
           13  Microphone 
           14  Speaker 
           20  Reproduction system 
           31  Signal processing device 
           32  Multi-Way speaker 
           52  Controller 
           53  Wave front synthesis digital filter 
           54  D/A converter 
           55  Amplifier 
           70  Band dividing unit 
           71 H HPF 
           71 L LPF 
           72 H High frequency band wave front synthesis filter 
           72 L Low frequency band wave front synthesis filter 
           73  Synthesis unit 
           82 H,  82 L Speaker unit 
           101  CPU 
           102  ROM 
           103  RAM 
           106  Input unit 
           107  Output unit 
           108  Storage unit 
           109  Communication unit 
           110  Drive