Patent Publication Number: US-11653132-B2

Title: Audio signal processing method and audio signal processing apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Nonprovisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 2019-160071 filed in Japan on Sep. 3, 2019 the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     A preferred embodiment of the present invention relates to an audio signal processing method and an audio signal processing apparatus. 
     2. Description of the Related Art 
     Japanese Unexamined Patent Application Publication No. 2015-080068 discloses a configuration in which a difference of the acoustic characteristics of two pairs of headphones of a different type is adjusted by an equalizer. 
     A performer who sings or plays music may listen to monitor sound, using in-ear headphones. An operating person (hereinafter referred to as an engineer) of a mixer also listens to monitor sound, using in-ear headphones or a speaker. 
     However, in a case in which the headphones that the performer uses, and the headphones that the engineer uses are not the same type of devices, the monitor sound to which the performer listens and the monitor sound to which the engineer listens have a different sound quality. Therefore, the engineer has prepared the headphones of the same type as the headphones that the performer uses, and has adjusted the sound quality of the monitor sound closer to the sound quality of the monitor sound to which the performer listens. 
     However, in a case in which a plurality of performers are present, the engineer, even when having adjusted the sound quality closer to the monitor sound to which one of the plurality of performers listens, eventually listens to sound of which the sound quality is different from the sound quality of the monitor sound to which a rest of the plurality of performers listens, when switching the monitor sound of the rest of the plurality of performers. Therefore, the engineer has needed to prepare headphones that each of the plurality of performers uses, and to change the headphones to use every time the monitor sound is switched. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, a preferred embodiment of the present invention is directed to provide an audio signal processing method and an audio signal processing apparatus that are able to listen to sound of which the sound quality is close to the sound quality of monitor sound to which each performer listens, without changing headphones even when switching the monitor sound. 
     An audio signal processing method performs signal processing on a first audio signal to be outputted to a first device that a performer uses, the first audio signal on which the signal processing has been performed being a second audio signal to send to a monitor bus which is for to output the second audio signal, and performing signal processing on the second audio signal, which is received via the monitor bus and is to be outputted to a second device different from the first device, such that a sound quality of a sound to be outputted by the second device is closer to sound quality of a sound to be outputted by the first device than in a case where the signal processing is not performed on the second audio signal. 
     According to a preferred embodiment of the present invention, sound of which the sound quality is close to the sound quality of monitor sound to which each performer listens is able to listen to without changing headphones even when switching the monitor sound. 
     The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a block diagram showing a configuration of an audio signal processing system  1 . 
         FIG.  2    is a block diagram showing a configuration of a mixer  10 . 
         FIG.  3    is an equivalent block diagram of signal processing to be performed by a DSP  14 , an audio I/O  13 , and a CPU  19 . 
         FIG.  4    is a diagram showing a functional configuration of an input channel  302 , a bus  303 , and an output channel  304 . 
         FIG.  5    is a diagram showing a configuration of an operation panel of the mixer  10 . 
         FIG.  6    is a flow chart showing an operation of the mixer  10 . 
         FIG.  7    is a flow chart showing an operation of the mixer  10 . 
         FIG.  8    is a flow chart showing an operation of the mixer  10 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG.  1    is a block diagram showing a configuration of an audio signal processing system  1  according to a preferred embodiment of the present invention. The audio signal processing system  1  includes a mixer  10 , headphones  20 , headphones  71 , a microphone  30 , a microphone  70 , and headphones  40 . The headphones  20  are in-ear headphones that a certain performer P 1  uses. The microphone  30  obtains the singing sound or performance sound of the performer P 1 . The headphones  71  are in-ear headphones that a performer P 2  uses. The microphones  70  obtains the singing sound or performance sound of the performer P 2 . The headphones  20  and the headphone  71  are examples of a first device. The headphones  40  are in-ear headphones that an engineer uses, and are examples of a second device. 
       FIG.  2    is a block diagram showing a configuration of a mixer  10 . The mixer  10  includes a display  11 , an operator  12 , an audio I/O (Input/Output)  13 , a DSP (Digital Signal Processor)  14 , a PC I/O  15 , a MIDI I/O  16 , a diverse (Other) I/O  17 , a network I/F  18 , a CPU  19 , a flash memory  21 , and a RAM  22 . 
     The display  11 , the operator  12 , the audio I/O  13 , the DSP  14 , the PC I/O  15 , the MIDI I/O  16 , the Other I/O  17 , the CPU  19 , the flash memory  21 , and the RAM  22  are connected to each other through a bus  25 . In addition, the audio I/O  13  and the DSP  14  are also connected to a waveform bus  27  for transmitting an audio signal. It is to be noted that, as will be described below, an audio signal may be sent and received through the network I/F  18 . In such a case, the DSP  14  and the network I/F  18  are connected through a not-shown dedicated bus. 
     The audio I/O  13  is an interface for receiving an input of an audio signal to be processed in the DSP  14 . The audio I/O  13  includes an analog input port, a digital input port, or the like that receives the input of an audio signal. The audio I/O  13 , for example, connects the microphone  30  and the microphone  70 , and receives an input of an audio signal from the microphone  30  and the microphone  70 . 
     In addition, the audio I/O  13  is an interface for outputting an audio signal that has been processed in the DSP  14 . The audio I/O  13  includes an analog output port, a digital output port, or the like that outputs the audio signal. The audio I/O  13 , for example, connects the headphones  20 , the headphones  71 , and the headphones  40 , and outputs an audio signal to the headphones  20 , the headphones  71 , and the headphones  40 . 
     Each of the PC I/O  15 , the MIDI I/O  16 , and the Other I/O  17  is an interface that is connected to various types of external devices and performs an input and output operation. The PC I/O  15  is connected to an information processor such as a personal computer, for example. The MIDI I/O  16  is connected to a MIDI compatible device such as a physical controller or an electronic musical instrument, for example. The Other I/O  17  is connected to a display, for example. Alternatively, the Other I/O  17  is connected to a UI (User Interface) device such as a mouse or a keyboard. Any standards such as Ethernet (registered trademark) or a USB (Universal Serial Bus) are able to be employed for communication with the external devices. The mode of connection may be wired or wireless. 
     The network I/F  18  communicates with a different apparatus through a network. In addition, the network I/F  18  receives an audio signal from the different apparatus through the network and inputs a received audio signal to the DSP  14 . Further, the network I/F  18  receives the audio signal on which the signal processing has been performed in the DSP  14 , and sends to the different apparatus through the network. The different apparatus includes the microphone  30 , the microphone  70 , the headphones  20 , the headphones  71 , and the headphones  40 , each of which has a network I/F. 
     The CPU  19  is a controller that controls the operation of the mixer  10 . The CPU  19  reads out a predetermined program stored in the flash memory  21  being a storage medium to the RAM  22  and performs various types of operations. It is to be noted that the program does not need to be stored in the flash memory  21  in the own apparatus. For example, the program may be downloaded each time from another apparatus such as a server and may be read out to the RAM  22 . 
     The display  11  displays various types of information according to the control of the CPU  19 . The display  11  includes an LCD or a light emitting diode (LED), for example. 
     The operator  12  receives an operation with respect to the mixer  10  from an engineer. The operator  12  includes various types of keys, buttons, rotary encoders, sliders, and the like. In addition, the operator  12  may include a touch panel laminated on the LCD being the display  11 . 
     The DSP  14  performs various types of signal processing such as mixing or equalizing. The DSP  14  performs signal processing such as mixing or equalizing on an audio signal to be supplied from the audio I/O  13  through the waveform bus  27 . The DSP  14  outputs a digital audio signal on which the signal processing has been performed, to the audio I/O  13  again through the waveform bus  27 . 
       FIG.  3    is an equivalent block diagram showing a function of signal processing to be performed in the DSP  14 , the audio I/O  13 , and the CPU  19 . As shown in  FIG.  3   , the signal processing is functionally performed through an input patch  301 , an input channel  302 , a bus  303 , an output channel  304 , and an output patch  305 . 
     The input patch  301  receives an input of an audio signal from a plurality of input ports (an analog input port or a digital input port, for example) in the audio I/O  13  and assigns any one of a plurality of ports to at least one of a plurality of channels (32 channels, for example). As a result, the audio signal is supplied to each channel in the input channel  302 . 
       FIG.  4    is a diagram showing a functional configuration of the input channel  302 , the bus  303 , and the output channel  304 . The input channel  302  includes a plurality of signal processing blocks, for example, in order from a signal processing block  3001  of a first input channel, and a signal processing block  3002  of a second input channel, to a signal processing block  3032  of a 32nd input channel. Each signal processing block performs various types of signal processing such as an equalizing or compressing, to the audio signal supplied from the input patch  301 . 
     The bus  303  includes a stereo bus  313 , a MIX bus  315 , and a monitor bus  316 . A signal processing block of each of the input channels inputs the audio signal on which the signal processing has been performed, to the stereo bus  313 , the MIX bus  315 , and the monitor bus  316 . Each signal processing block of the input channels sets an outgoing level with respect to each bus. 
     The stereo bus  313  corresponds to a stereo channel used as a main output in the output channel  304 . The MIX bus  315  corresponds to a monitor speaker or monitor headphones (the headphones  20  and the headphones  71 , for example) for each performer, for example. The monitor bus  316  corresponds to a monitor speaker or monitor headphones (the headphones  40 , for example) for an engineer. Each of the stereo bus  313 , the MIX bus  315 , and the monitor bus  316  mixes inputted audio signals. Each of the stereo bus  313 , the MIX bus  315 , and the monitor bus  316  output the mixed audio signals to the output channel  304 . 
     The output channel  304 , as with the input channel  302 , performs various types of signal processing on the audio signal inputted from the bus  303 . For example, a signal processing block  3051  of a first output channel and a signal processing block  3052  of a second output channel perform signal processing on a first audio signal to be sent out from a first MIX bus and a second MIX bus. A signal processing block  3071  of a monitor channel performs signal processing on a second audio signal to be sent out from the monitor bus  316 . The signal processing block  3051  and the signal processing block  3052  are examples of a first signal processor. The signal processing block  3071  is an example of a second signal processor. 
     The output channel  304  outputs the audio signal on which the signal processing has been performed in each signal processing block, to the output patch  305 . The output patch  305  assigns each output channel to any one of a plurality of ports serving as an analog output port or a digital output port. As a result, the output patch  305  supplies the audio signal on which the signal processing has been performed, to the audio I/O  13 . 
     An engineer sets a parameter of the above-described various types of signal processing, through the operator  12 .  FIG.  5    is a diagram showing a configuration of an operation panel of the mixer  10 . As shown in  FIG.  5   , the mixer  10  includes on the operation panel a touch screen  51  and a channel strip  61 . Such components correspond to the display  11  and the operator  12  shown in  FIG.  2   . It is to be noted that, although  FIG.  5    only shows the touch screen  51  and the channel strip  61 , a large number of knobs, switches, or the like may be provided in practice. 
     The touch screen  51  is the display  11  obtained by stacking the touch panel being one preferred embodiment of the operator  12 , and constitutes a GUI (Graphical User Interface) for receiving an operation from a user. 
     The channel strip  61  is an area in which a plurality of physical controllers that receive an operation with respect to one channel are disposed vertically. Although  FIG.  5    only shows one fader and one knob for each channel as the physical controllers, a large number of knobs, switches, or the like may be provided in practice. In the channel strip  61 , a plurality of faders and knobs disposed on the left side correspond to the input channel. The two faders and two knobs disposed on the right side are physical controllers corresponding to the master output. An engineer operates a fader and a knob, sets a gain of each input channel or sets an outgoing level with respect to the bus  303 . The CPU  19  controls signal processing to be performed by the input patch  301 , the input channel  302 , the bus  303 , the output channel  304 , and the output patch  305 , based on the received setting of the gain and the received setting of the outgoing level. 
     An engineer selects an audio signal to be sent out to the monitor bus  316 . For example, the engineer instructs to send out the first audio signal of the first MIX bus to the monitor bus  316 . 
     Each signal processing block in the output channel  304  sends out the first audio signal on which signal processing has been performed, to the monitor bus  316 . For example, when the engineer instructs to send out the first audio signal of the first MIX bus to the monitor bus  316 , the signal processing block  3051  sends out the first audio signal on which the signal processing has been performed, to the monitor bus  316 . The signal processing block  3071  of the monitor channel receives the first audio signal on which the signal processing has been performed in the signal processing block  3051 , as a second audio signal. At such a time, the CPU  19  may control the audio signals to be sent out to the monitor bus  316  so as to reduce the level of the audio signals other than the first audio signal on which the signal processing has been performed in the signal processing block  3051 . In such a case, the engineer can listen to only the monitor sound to which the performer P 1  listens. 
     The signal processing block  3071  performs sound quality adjustment with respect to the second audio signal so that the sound quality of sound to be outputted from the headphones  40  is similar to the acoustic characteristics of the headphones  20 . For example, the signal processing block  3071 , with respect to the second audio signal, adjusts frequency characteristics so as to cancel the acoustic characteristics of the headphones  40  and so as to add the acoustic characteristics of the headphones  20 . As a result, the engineer can listen to sound outputted from the first MIX bus with a sound quality reflecting the acoustic characteristics of the headphones  20  that the performer P 1  uses. 
     Herein, for example, when the engineer instructs to send out the first audio signal of the second MIX bus to the monitor bus  316 , the signal processing block  3052  sends out the first audio signal on which the signal processing has been performed, to the monitor bus  316 . The signal processing block  3071  of the monitor channel receives the first audio signal on which the signal processing has been performed in the signal processing block  3052 , as a second audio signal. The signal processing block  3071  performs sound quality adjustment with respect to the second audio signal so that the sound quality of sound to be outputted from the headphones  40  is similar to the acoustic characteristics of the headphones  71 . For example, the signal processing block  3071 , with respect to the second audio signal, adjusts frequency characteristics so as to cancel the acoustic characteristics of the headphones  40  and so as to add the acoustic characteristics of the headphones  71 . As a result, the engineer can listen to sound outputted from the second MIX bus with a sound quality reflecting the acoustic characteristics of the headphones  71  that the performer P 2  uses. 
     In such a manner, according to the mixer  10  of the present preferred embodiment, an engineer can listen to monitor sound with a sound quality close to the acoustic characteristics of the headphones that each performer uses, without having to perform a complicated operation, only by performing an operation to switch a channel to be monitored. 
     The mixer  10  performs the following operations, for example, in order to perform sound quality adjustment so as to be closer to the acoustic characteristics of target headphones (the first device). 
       FIG.  6   ,  FIG.  7   , and  FIG.  8    are flow charts showing an operation of the mixer  10 . The operation shown in  FIG.  6    and  FIG.  7    is performed when an engineer operates the mixer  10  before a rehearsal. The operation shown in  FIG.  8    is performed when an engineer operates mixer  10  during a rehearsal or during an actual performance. 
     As shown in  FIG.  6   , first, the CPU  19  receives a selection of a channel through an operator  12  (S 11 ). Subsequently, the CPU  19  receives a model name of the headphones used by a performer of the selected channel (S 12 ). The model name is an example of information associated with a second device. The CPU  19  associates the selected channel with the information on the model name (S 13 ), and stores the associated channel and information in the flash memory  21  or the RAM  22 . 
     In addition, as shown in  FIG.  7   , the CPU  19  receives the model name of the headphones connected to a monitor channel through the operator  12  (S 15 ). In other words, the CPU  19  receives the model name of the headphones that the engineer uses. The model name is an example of information associated with the first device. The CPU  19  stores information on the received model name in the flash memory  21  or the RAM  22  (S 16 ). 
     As shown in  FIG.  8   , the CPU  19  receives from an engineer a selection of a channel to be sent out to the monitor bus  316  (S 21 ). Subsequently, the CPU  19  refers to the information stored in the flash memory  21  or the RAM  22  and reads out the model name of the headphones associated with the selected channel (S 22 ). 
     The CPU  19  reads out the acoustic characteristics corresponding to the read model name, and the acoustic characteristics of the second device (the headphones  40 ) at an output destination (S 23 ). The information on the acoustic characteristics with respect to a model name is stored in the flash memory  21  or the RAM  22 , for example. The CPU  19  reads out corresponding acoustic characteristics from the flash memory  21  or the RAM  22 . Alternatively, the CPU  19  may obtain acoustic information corresponding to a model name from another apparatus such as a server. The acoustic characteristics of the headphones  40  are also stored in the flash memory  21  or the RAM  22 , for example. The CPU  19  reads out the acoustic characteristics corresponding to the model name of the headphones  40  stored in S 16 , from the flash memory  21  or the RAM  22 . Alternatively, the CPU  19  may obtain the acoustic characteristics of the headphones  40  from another apparatus such as a server. 
     The CPU  19  performs a setting to send out a first audio signal of the selected channel to the monitor bus  316  (S 24 ). As a result, the signal processing block  3071  receives the first audio signal of the selected channel as a second audio signal. The CPU  19  sets the signal processing block  3071  being a second signal processor so as to perform the sound quality adjustment of the second audio signal based on a difference of the acoustic characteristics between devices (S 25 ). The signal processing block  3071 , for example, as described above, adjusts frequency characteristics so as to cancel the acoustic characteristics of the headphones  40  and so as to add the acoustic characteristics of the first device (the headphones  20  or the headphones  71 , for example). Alternatively, the signal processing block  3071  may perform the sound quality adjustment based on the difference of the acoustic characteristics between the first device and the second device. 
     It is to be noted that the acoustic characteristics are also able to be measured using a microphone. For example, an engineer prepares a small microphone such as a capacitor microphone, and a dummy head. The engineer attaches the microphone and the target headphones to the ears of the dummy head. The engineer operates the mixer  10 , outputs a test sound such as white noise from the headphones, and measures the acoustic characteristics of an audio signal obtained by the microphone. As a result, the mixer  10  measures the acoustic characteristics. In such a case, the mixer  10  does not need to perform the processing of S 12  of  FIG.  6   . In addition, the mixer  10 , in the processing of S 13 , associates the selected channel with the measured acoustic characteristics, and stores the associated channel and acoustic characteristics in the flash memory  21  or the RAM  22 . In addition, the mixer  10 , in the processing of S 16  in  FIG.  7   , stores the measured acoustic characteristics. The mixer  10  does not need to perform the processing of S 22  of  FIG.  8   . The mixer  10 , in the processing of S 23 , reads out the acoustic characteristics corresponding to the selected channel. 
     It is to be noted that the mixer  10 , in the processing of S 11 , may receive an input of information (a name of a performer, for example) associated with a performer. In such a case, the mixer  10 , in the processing of S 12 , receives the model name of the headphones that a received performer uses. Then, the CPU  19 , in the processing of S 13 , associates the information associated with the performer with the model name of the headphones, and stores the associated information and model name in the flash memory  21  or the RAM  22 . 
     In addition, the mixer  10 , in the processing of S 21  of  FIG.  8   , receives an input of the information associated with the performer. In such a case, the mixer  10 , in the processing of S 22 , reads out a model name corresponding to the information associated with the received performer. Therefore, the mixer  10 , in S 23 , reads out acoustic characteristics corresponding to the information associated with the received performer. 
     In such a manner, the mixer  10  is able to obtain information associated with a performer and information associated with a second device, and also perform the sound quality adjustment based on the information associated with a performer and the information associated with a second device. 
     The description of the foregoing preferred embodiments is illustrative in all points and should not be construed to limit the present invention. The scope of the present invention is defined not by the foregoing preferred embodiment but by the following claims. Further, the scope of the present invention is intended to include all modifications within the scopes of the claims and within the meanings and scopes of equivalents. 
     For example, the preferred embodiment provides an example in which both a performer and an engineer use in-ear headphones. However, for example, a performer or an engineer may use a speaker. In such a case as well, the mixer  10  performs the sound quality adjustment of a second audio signal to be outputted to the monitor headphones or a speaker for an engineer, according to the acoustic characteristics of headphones or a speaker to be monitored. 
     In addition, the preferred embodiment provides an example in which the sound quality adjustment of a second audio signal is performed according to the acoustic characteristics of headphones or a speaker to be monitored. However, the mixer  10 , as long as performing the sound quality adjustment so that the sound quality of sound to be outputted from the second device is closer to the sound quality of sound to be outputted from the first device, may perform any type of processing. For example, in a case in which the headphones  20  of the performer P 1  performs effect processing such as compressing on an inputted first signal, the mixer  10  may perform the same effect processing on a second audio signal. 
     In addition, the preferred embodiment provides an example in which an engineer inputs information according to a device, such as a model name. However, an engineer does not need to manually input such information including a model name. For example, the mixer  10 , in a case of being connected to headphones through a network, obtains information (including a manufacturing number) unique to a device. The mixer  10  obtains a model name corresponding to a manufacturing number from a management server or the like that manages the manufacturing number and the model name.