Patent Publication Number: US-11647353-B2

Title: Non-transitory computer-readable medium having computer-readable instructions and system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation application of and claims priority benefit of a U.S. application Ser. No. 17/136,002, filed on Dec. 29, 2020, which is a continuation application of and claims priority benefit of a U.S. application Ser. No. 17/109,156, filed on Dec. 2, 2020, which claims the priority of Japan patent application serial no. 2019-219985, filed on Dec. 4, 2019. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification. 
    
    
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a headphone. 
     Description of Related Art 
     In recent years, there have been headphones that receive a signal for reproduced sound from a smartphone and a signal for the performance sound of a guitar through wireless communication and makes it possible to listen to mixed sounds (for example, Patent Document 1). In addition, it is known that a head transfer function of a path based on a user&#39;s posture may be determined from a sound producing position of a musical instrument, and musical sound output from headphones may be localized using the head transfer function (for example, Patent Document 2). In addition, there are headphones that update signal processing details in a signal processing device in accordance with a rotation angle of a listener&#39;s head to localize a sound image outside the head (for example, Patent Document 2). In addition, there is Patent Document 4 as related art pertaining to the invention of the present application. 
     Patent Documents 
     [Patent Document 1] Japanese Patent Laid-Open No. 2017-175256 
     [Patent Document 2] Japanese Patent Laid-Open No. 2018-160714 
     [Patent Document 3] Japanese Patent Laid-Open No. H8-009489 
     [Patent Document 4] Japanese Patent Laid-Open No. H1-121000 
     SUMMARY 
     According to an embodiment, there is provided a headphone including right and left ear pieces and a connecting portion which connects the right and left earpieces to each other, the headphone including a control part which changes a position at which a sound image is localized in accordance with an orientation of a user&#39;s head, with respect to at least one of a first musical sound and a second musical sound different from the first musical sound, the first musical sound and the second musical sound being input to the headphone, and a speaker which is included in each of the right and left earpieces and to which a signal of a mixed sound of the first musical sound and the second musical sound is connected in a case where the position at which at least one sound image is localized is changed by the control part. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram showing an appearance configuration of a headphone according to an embodiment. 
         FIG.  2    shows an example of circuit configurations of a headphone and a terminal. 
         FIG.  3    is a diagram showing operations of a headphone. 
         FIGS.  4 A and  4 B  show an example of a user interface of a terminal. 
         FIG.  5    shows a configuration example in a case where an effect is applied to a performance sound of a guitar, and this processed performance sound is output from a guitar amplifier. 
         FIG.  6    is a diagram showing features of resonance of a guitar amplifier. 
         FIG.  7    shows processing performed by an effect processing part shown in  FIG.  3   . 
         FIGS.  8 A to  8 C  are diagrams showing sound field processing. 
         FIG.  9    is a diagram showing sound field processing. 
         FIG.  10    is a circuit diagram showing sound field processing in a stage mode. 
         FIG.  11    is a circuit diagram showing sound field processing in a static mode. 
         FIG.  12    is a circuit diagram showing sound field processing in a surround mode. 
         FIG.  13 A  is a table showing initial values of X and Y in respective modes, and  FIG.  13 B  is a table showing initial values of Z. 
         FIG.  14    is a table showing transfer functions to be adopted in accordance with respective positions. 
         FIG.  15    shows a specific example of transfer functions to be adopted. 
         FIG.  16    is a table showing transfer functions to be adopted in accordance with installation positions of respective amplifiers. 
         FIG.  17    is a table showing a setting instruction given through a terminal (application) and values transmitted to a headphone. 
         FIG.  18    is a flowchart showing an example of sound field processing. 
         FIG.  19    is a flowchart showing an example of sound field processing. 
         FIG.  20    is a flowchart showing an example of interruption processing. 
         FIGS.  21 A and  21 B  are diagrams showing a relationship between a cabinet and a listener. 
         FIGS.  22 A and  22 B  are tables showing states shown in  FIGS.  21 A and  21 B . 
         FIG.  23    is a diagram showing operations according to an embodiment. 
         FIG.  24    is a diagram showing operations according to an embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     The disclosure provides a headphone capable of controlling a position at which a sound image of each of musical sounds to be mixed is localized. 
     A headphone according to an embodiment is a headphone including right and left ear pieces and a connecting portion connecting the right and left ear pieces to each other, and include the following components.
         (1) A control part that changes a position at which a sound image is localized in accordance with the orientation of a user&#39;s head, with respect to at least one of a first musical sound and a second musical sound different from the first musical sound, which are input to the headphone.   (2) A speaker which is included in each of right and left ear pieces and to which a signal of a mixed sound is connected, the mixed sound being a mixed sound of the first musical sound and the second musical sound in a case where the control part changes a position at which at least one sound image is localized.       

     According to the headphone, a user can change a localization position of at least one of the first and second musical sounds in accordance with the displacement of the head and can listen to a mixed sound of the first and second musical sounds respectively localized at desired positions. The control part is, for example, a processor, and the processor may be constituted by an integrated circuit such as a CPU, a DSP, an ASIC, or an FPGA, or a combination thereof. The orientation of the head can be detected using, for example, a gyro sensor. 
     In the headphone, the control part may be configured to apply an effect of simulating a case where the first musical sound is output from a cabinet speaker with the front facing the user to the first musical sound, independently of a position at which a sound image of the first musical sound is localized. In this manner, with respect to the first musical sound, it is possible to listen to a simulation sound in a case where the first musical sound is output from the cabinet speaker with the front facing the user, independently of localization. That is, it is possible to listen to the high-quality first musical sound independently of the displacement of the head. In this case, the orientation of the user may not face the cabinet speaker. 
     In the headphone, the orientation of the head includes a rotation angle of the head in a horizontal direction, and the headphone may be configured such that the position of a sound source outside the head is changed using a head transfer function from the sound source to the user&#39;s right and left ears in accordance with the rotation angle. In this manner, localization can be changed in accordance with the orientation of the user&#39;s head. *The displacement of the head may include not only a rotation angle in the horizontal direction but also a height and an inclination in a vertical direction (elevation: tilt angle). 
     In the headphone, a configuration in which the first musical sound is a musical sound generated in real time by the user may be adopted. Sound generated in real time may be a performance sound of an electronic musical instrument or a smartphone application or may be sound from a user (singing voice) collected by a microphone or an analog musical instrument sound. The second musical sound may be sound reproduced from a smartphone or a smartphone application performance sound. 
     In the headphone, a configuration may be adopted in which the first musical sound is input to the headphone through first wireless communication, and the second musical sound is input to the headphone through second wireless communication. As the first and second musical sounds are inputted in a wireless manner, there is no complexity in handling physical signal lines. Further, in a case where the first and second musical sounds are generated in real time through a performance or the like, it is possible to avoid the physical signal lines inhibiting smooth generation of the musical sounds. Wireless communication standards to be applied to the first wireless communication and the second wireless communication may be the same as or different from each other. Crosstalk, interference, erroneous recognition, or the like can be avoided due to a difference. 
     In the headphone, a configuration may be adopted in which sound when sound is generated from a position of predetermined reference localization is used to generate mixed sound with respect to the first musical sound and second musical sound for which the change of a position at which a sound image is localized, being performed by the control part, is set to be in an off state. The turn-on and turn-off of a reference localization position, a guitar effect, and sound field processing can be set using an application of a terminal, and setting information can be stored in a storage device (flash memory or the like). 
     Hereinafter, a musical sound generation method and a musical sound generation device according to the embodiment will be described with reference to the drawings. A configuration according to the embodiment is an example, and the disclosure is not limited to the configuration. 
     Appearance Configuration of Headphone 
       FIG.  1    is a diagram showing an appearance configuration of a headphone according to the embodiment. In  FIG.  1   , a headphone  10  has a configuration in which a right ear piece  12 R and a left ear piece  12 L are connected to each other through a U-shaped connecting portion  11 . Each of the ear pieces  12 R and  12 L is also referred to as an ear pad, and the connecting portion  11  is referred to as a headband or a headrest. 
     The headphone  10  is worn on a user&#39;s head by covering the user&#39;s right ear with the ear piece  12 R, covering the left ear with the ear piece  12 L, and supporting the connecting portion  11  with the vertex of the head. A speaker is provided in each of the ear pieces  12 R and  12 L. 
     Wireless communication equipment, called a transmitter  20 , which performs wireless communication with the headphone  10  is connected to a guitar  2 . The ear piece  12 R of the headphone  10  includes a receiver  23 , and wireless communication is performed between the transmitter  20  and the receiver  23 . The guitar  2  is an example of an electronic musical instrument, and may be an electronic musical instrument other than an electronic guitar. The electronic musical instrument also includes an electric guitar. In addition, musical sound is not limited to musical instrument sound, and also includes sound such as a person&#39;s singing sound. 
     The transmitter  20  includes, for example, a jack pin, and the transmitter is mounted on the guitar  2  by inserting the jack pin into a jack hole formed in the guitar  2 . Signal of performance sound of the guitar  2  generated by the user himself or herself and other persons is input to the headphone  10  through wireless communication using the transmitter  20 . The signals of the performance sound are connected to the right and left speakers and emitted. Thereby, the user can listen to the performance sound of the guitar  2 . The performance sound of the guitar  2  is an example of a “first musical sound”. 
     The ear piece  12 R of the headphone  10  further include a Bluetooth (BT, registered trademark)) communication device  21 . The BT communication device  21  performs BT communication with a terminal  3  and can receive a signal of musical sound reproduced by the terminal  3  (for example, one or two or more musical instrument sounds such as a drum sound, a bass guitar sound, and a backing band sound). Thereby, the user can listen to a musical sound from the terminal  3 . The reproduced sound of the terminal  3  is an example of a “second musical sound”. However, the second musical sound includes not only a reproduced sound but also a sound based on musical sound data in a data stream relayed by the terminal  3 , a musical sound collected by the terminal  3  using a microphone, and a musical sound generated by operating a performance application executed by the terminal  3 . 
     In this manner, the headphone  10  is provided with a plurality of input systems (two systems in the present embodiment) supplying a signal of a musical sound through wireless communication. A system that inputs a performance sound of the guitar  2  is called a first system, and a system that inputs a musical sound generated by the terminal  3  is called a second system. Communication using the transmitter  20  is an independent wireless communication standard different from BT communication. Wireless communication standards to be applied to the respective systems may be the same, but different wireless communication standards are more preferable in avoiding crosstalk, interference, erroneous recognition, or the like. 
     Further, in a case where a performance sound and a reproduced sound are received in parallel, it is also possible to listen to a mixed sound of the performance sound and the reproduced sound by connecting the synthesized sound or the mixed sound thereof to the speakers by a circuit built into the headphone  10 . 
     The terminal  3  may be a terminal or equipment that transmits a musical sound signal to the headphone  10  through wireless communication. For example, the terminal may be a smartphone, but may be a terminal other than a smartphone. The terminal  3  may be a portable terminal or a fixed terminal. The terminal  3  is used as an operation terminal for performing various settings on the headphone  10 . 
     Hardware Configuration 
       FIG.  2    illustrates an example of circuit configurations of the headphone  10  and the terminal  3 . In  FIG.  2   , the terminal  3  includes a central processing unit (CPU)  31 , a storage device  32 , a communication interface (communication IF)  33 , an input device  34 , an output device  35 , a BT communication device  36 , and a sound source  37  which are connected to each other through a bus B. A digital analog converter (DAC)  38  is connected to the sound source  37 , the DAC  38  is connected to an amplifier  39 , and the amplifier  39  is connected to a speaker  40 . 
     The storage device  32  includes a main storage device and an auxiliary storage device. The main storage device is used as a storage region for programs and data, a work area of the CPU  31 , and the like. The main storage device is formed by, for example, a random access memory (RAM) or a combination of a RAM and a read only memory (ROM). The auxiliary storage device is used as a storage region for programs and data, a waveform memory that stores waveform data, or the like. The auxiliary storage device is, for example, a flash memory, a hard disk, a solid state drive (SSD), an electrically erasable programmable read-only memory (EEPROM), or the like. 
     The communication IF  33  is connection equipment for connection to a network such as a wired LAN or a wireless LAN, and is, for example, a LAN card. The input device  34  includes keys, buttons, a touch panel, and the like. The input device  34  is used to input various information and data to the terminal  3 . The information and the data include data for performing various settings on the headphone  10 . 
     The output device  35  is, for example, a display. The CPU  31  performs various processes by executing programs (applications) stored in the storage device  32 . For example, the CPU  31  can execute an application program (application) for the headphone  10  to input the reproduction/stopping of a musical sound to be supplied to the headphone  10 , the setting of an effect for a performance sound of the guitar  2 , and the setting of a sound field for each input system of a musical sound and supply the sounds to the headphone  10 . 
     When a reproduction instruction for a musical sound is input using the input device  34 , the CPU  31  reads data of the musical sound based on the reproduction instruction from the storage device  32  and supplies the read data to the sound source  37 , and the sound source generates a signal of a musical sound (reproduced sound) based on the data of the musical sound. The signal of the reproduced sound is transmitted to the BT communication device  36 , converted into a wireless signal, and emitted. The emitted wireless signal is received by the BT communication device  21  of the headphone  10 . Meanwhile, the signal of the musical sound generated by the sound source  37  may be supplied to the DAC  38  to be converted into an analog signal, amplified by the amplifier  39 , and emitted from the speaker  40 . However, in a case where the signal of the reproduced sound is supplied to the headphone, muting is performed on the signal of the musical sound transmitted to the DAC  38 . 
     In the present embodiment, the ear piece  12 L of the headphone  10  includes a battery  25  that supplies power to each of the parts of the headphone  10 , and a left speaker  24 L. Power supplied from the battery  25  is supplied to each of the parts of the ear piece  12 R through wiring provided along the connecting portion  11 . The battery  25  may be provided in the ear piece  12 R. 
     The ear piece  12 R includes a BT communication device  21  wirelessly communicating with the BT communication device  36 , a receiver  23 , and a speaker  24 R. In addition, the ear piece  12 R includes a processor  201 , a storage device  202 , a gyro sensor  203 , an input device  204 , and headphone (HP) amplifier  206 . 
     The receiver  23  receives a signal (including a signal related to a performance sound of the guitar  2 ) transmitted from the transmitter  20  and performs wireless processing (down-conversion or the like). The receiver  23  inputs a signal having been subjected to the wireless processing to the processor  201 . 
     The gyro sensor  203  is, for example, a 9-axis gyro sensor, and can detect movements in an up-down direction, a front-back direction, and a right-left direction, an inclination, and rotation of the user&#39;s head. An output signal of the gyro sensor  203  is input to the processor  201 . Among output signals of the gyro sensor  20 , at least a signal indicating a rotation angle of the head in a horizontal direction (the orientation of the head of the user wearing the headphone  10 ) is used for sound field processing. However, the other signals may be used for sound field processing. 
     The input device  204  is used to input instructions, such as the turn-on or turn-off of effect processing for a performance sound (first musical sound) of the guitar  2 , the turn-on or turn-off of sound field processing related to a performance sound and a reproduced sound (first and second musical sounds) transmitted from the terminal  3 , and the reset of a sound field. 
     The processor  201  is, for example, a system-on-a-chip (SoC), and includes a DSP that performs processing on signals of the first and second musical sounds, a CPU that performs the setting of various parameters used for signal processing and control related to management, and the like. Programs and data used by the processor  201  are stored in the storage device  202 . The processor  201  is an example of a control part. 
     The processor  201  performs processing on a signal of a first musical sound which is input from the receiver  23  (for example, effect processing) and processing on a signal of a second musical sound which is input from the BT communication device  21  (for example, sound field processing), and connects the processed signals (a right signal and a left signal) to the HP amplifier  206 . The HP amplifier  206 , which is an amplifier built into a DAC, performs DA conversion and amplification on the right signal and the left signal and connects the processed signals to the speakers  24 R and  24 L (examples of a speaker). 
     Description of Mode 
     In the headphone  10  of the present embodiment, in a case where a user listens to a mixed sound of first and second musical sounds, the user can listen to the mixed sound of the first and second musical sounds in a mode selected from among a “surround mode”, a “static mode”, and a “stage mode”. 
     The user can set an initial position at which a sound image is localized outside the user&#39;s head with respect to the first musical sound and the second musical sound by using the input device  34  and the output device  35  (touch panel  34 A:  FIG.  3   ) of the terminal  3 . 
     When description is given using, for example,  FIG.  3   , the CPU  31  of the terminal  3  executes an application for the headphone  10 , so that the input device  34  and the output device  35  of the terminal  3  operate as user interfaces. The CPU  31  operates as a sound reproduction part  37 A, an effect processing instructing part  31 A, and a sound field processing instructing part  31 B. The BT communication device  36  operates as a BT transmission and reception part  36 A. 
     As a user interface, an operator capable of setting and inputting at least an instruction for reproducing or stopping a second musical sound, an instruction regarding whether or not to apply an effect to the first musical sound, and relative positions of sound sources of the first and second musical sounds with respect to the user is provided to the user. 
       FIGS.  4 A and  4 B  show an example of a user interface.  FIG.  4 A  shows an operation screen  41  showing the direction of a cabinet, and the like, and  FIG.  4 B  shows an operation screen  42  showing the positions of a performance sound (GUITAR: first musical sound) of the guitar  2  which is output from a guitar amplifier and an audio (AUDIO: a second musical sound of a backing band or the like), and the like. 
     The operation screen  41  is provided with a circular operator indicating the direction of the guitar amplifier with respect to a user, and the angle of the cabinet with respect to the user can be set by tracing an arc. The guitar amplifier is an example of a cabinet speaker, and the cabinet speaker will be hereinafter referred to simply as a “cabinet”. A direction in which the front of the cabinet faces the user is 0 degrees. In addition, a type (TYPE), a gain, and a level of the guitar amplifier can be set using the operation screen  41 . 
     The operation screen  42  is provided with an operator for selecting a mode (any one of a surround mode, a static mode, a stage mode, and OFF). In addition, the operation screen  42  is provided with a circular operator for setting an angle between each of the guitar amplifier (GUITAR) and the audio (AUDIO) and the user wearing the headphone  10 , and an angle can be set by tracing an arc with the user&#39;s finger. In addition, the operation screen  42  includes an operator for selecting a type (stage, studio) indicating a space where the user is present, and an operator for setting a level. 
     The CPU  31  operating as the sound reproduction part  37 A turns on or turns off a reproduction operation of a second musical sound in response to an instruction for reproduction or stopping. The CPU  31  operating as the effect processing instructing part  31 A generates the necessity of applying an effect and parameters (parameters indicating amplifier frequency characteristics, speaker frequency characteristics, cabinet resonance characteristics, and the like) in a case where an effect is applied, and includes the necessity and the parameters in targets to be transmitted by the BT transmission and reception part  36 A. 
     The CPU  31  operating as the sound field processing instructing part  31 B receives information indicating positions (initial positions) at which sound fields of the first and second musical sounds are localized centering on the position of the user, as relative positions of the sound sources of the first and second musical sounds with respect to the user. For example, it is assumed that the first musical sound (the performance sound of the guitar  2 ) is output (emitted) from the guitar amplifier disposed in front of the user. Then, a position at which the guitar amplifier (sound source) is present centering on the user (a relative angle with respect to the user) in a horizontal direction is set. 
     For example, an angle at which the sound source (guitar amplifier) is located is set by setting 0 degrees in a case where the user is facing in a certain direction. This is the same as for audio of which the sound source is the second musical sound. The position of the sound source of the first musical sound and the position of the sound source of the second musical sound may be different from or the same as each other. 
     In the surround mode, even when the user wearing the headphone  10  changes the orientation (rotation angle) of the head in the horizontal direction, the sound fields of the first and second musical sounds are kept fixed at the initial positions. In the static mode, a position at which a sound image of the first musical sound (guitar amplifier) is localized is changed in association with the change in the orientation of the user&#39;s head, while the sound field of the second musical sound (audio) is kept fixed at the initial position. In other words, in the static mode, when the user with a guitar changes the orientation of the head, the position of the sound source (guitar amplifier) of the first musical sound is changed, but the sound field of the second musical sound (audio) is not changed. In the stage mode, the positions of the sound sources of both the first and second musical sounds (the guitar amplifier and the audio) are changed in association with the change in the orientation of the head. 
     The sound field processing instructing part  31 B includes information for specifying the current mode, information indicating the initial positions of the sound sources of the first and second musical sounds, and the like in targets to be transmitted by the BT transmission and reception part  36 A. The BT transmission and reception part  36 A transmits data of a second musical sound in a case where an instruction to perform reproduction is given, information supplied from the effect processing instructing part  31 A, and information supplied from the sound field processing instructing part  31 B through wireless communication using BT. The BT communication device  21  of the ear piece  12 R receives the data and the information transmitted from the BT transmission and reception part  36 A. 
     Effect Processing 
     The receiver  23  receives a signal of a first musical sound, which is a performance sound of the guitar  2 , received through the transmitter  20 . With respect to the first musical sound received by the receiver  23 , the processor  201  operates as an effect processing instructing part  201 A and an effect processing part  201 B. 
     The effect processing instructing part  201 A gives an instruction based on the necessity of applying an effect (effect processing) and parameters in a case where an effect is applied to the effect processing part  201 B, the instruction being acquired by being received from the BT transmission and reception part  21 A, input from the input device  204 , or read from the storage device  202 . 
     In a case where effect processing is not necessary, the effect processing part  201 B does not perform (passes) effect application on the signal of the first musical sound. On the other hand, in a case where effect processing is necessary, the effect processing part  201 B performs a process of applying an effect based on parameters received from the effect processing instructing part  201 A to the first musical sound. 
     Here, effect processing performed on a first musical sound which is executed in the headphone  10  will be described.  FIG.  5    shows a configuration example in a case where an effect is applied to a performance sound of the guitar  2 , and this processed performance sound is output from the guitar amplifier  53 . An effect  51  and an amplifier  52  are inserted into a signal line connecting the guitar  2  and the guitar amplifier  53  to each other. The guitar amplifier  53  includes a cabinet  54  and a speaker  55  accommodated in the cabinet  54 . 
     Regarding characteristics of the effect  51 , various characteristics based on the type of effect selected by a user are applied. For example, in a case where an equalizer is selected for the effect  51 , frequency characteristics in which an amplification level is different for each bandwidth are obtained. The type of effect may be anything other than an equalizer. Frequency characteristics of the amplifier  52  and frequency characteristics of the speaker  55  are frequency characteristics obtained by measuring an output waveform in a case where a sweeping sound is input to the guitar amplifier  53  to be modeled. Meanwhile, a method of obtaining the above-described frequency characteristics may be applied to a guitar amplifier of a type in which the amplifier  52  is built into a cabinet. 
     It is known that the cabinet resonance characteristics are reverberation characteristics of a space in the cabinet  54  and obtained by measuring an impulse response, or the like. As shown in  FIG.  6   , a resonance feature of the guitar amplifier  53  is mainly determined by the speaker  55  and the cabinet  54 . An output sound of the guitar amplifier  53  is characterized not only by a direct sound heard from the speaker  55  but also by a reverberant sound in the cabinet  54 . The reverberant sound reaches the user&#39;s ears as a sound emitted from a bass reflex port provided on the front surface of the guitar amplifier  53  or as a vibration sound of the speaker  55  and the entire cabinet  54 . 
     A signal processing technique for simulating resonance in a space in the cabinet  54  on the basis of an impulse response is known. In the present embodiment, an FIR filter with reduced order in a state where reverberation characteristics of a space obtained on the basis of a measured impulse response are approximated is adopted. 
     The following procedure can be adopted as a method of measuring an impulse response.
         (1) The guitar amplifier  53  and the microphone  56  are installed in an anechoic room with a distance B therebetween. In this case, the guitar amplifier  53  and the microphone  56  are installed such that their front surfaces face each other at an angle of 0 degrees.   (2) An impulse waveform is input to the guitar amplifier  53 , and the guitar amplifier  53  generates a sound.   (3) Filter characteristics of an FIR filter are determined on the basis of an impulse response waveform recorded by collecting the generated sound by the microphone  56 .       

     A size A shown in  FIG.  6    indicates the size of the cabinet of the guitar amplifier  53 , and an angle C indicates an angle between the cabinet  54  and the microphone  56  (0 degrees in a case where the front surface of the cabinet  54  faces the microphone  56 ). Meanwhile, the distance B may be set according to preferences depending on hearing conditions of resonance of the cabinet  54 . In general, a case where the distance B is set to be short is called on microphone setting, and a case where the distance is set to long is called off microphone setting. That is, the distance B is not related to sound field processing to be described later. A sound collected by the microphone  56  is a monaural sound collected by one microphone  56 , but resonance elements of the cabinet  54  are included in the monaural sound. 
       FIG.  7    shows processing performed by the effect processing part  201 B shown in  FIG.  3    and the like. Effects of a type and characteristics instructed by the effect processing instructing part  201 A are applied to a performance sound of the guitar  2  which is input from the receiver  23 . In addition, as guitar amplifier characteristics processing, modification corresponding to amplifier frequency characteristics, speaker frequency characteristics, and cabinet resonance characteristics obtained by measurement is performed on an input signal, so that a predetermined effect (for example, sound volume adjustment using an equalizer) is applied, and a performance sound of the guitar  2  obtained by simulating a case where a sound is emitted from the guitar amplifier  53  (an example of a cabinet speaker) to be simulated is output. 
     Sound Field Processing 
     The processor  201  operates as a sound field processing instructing part  201 D and a sound field processing part  201 E by executing a program. A first musical sound transmitted from the effect processing part  201 B and a second musical sound transmitted from the BT transmission and reception part  21 A are input to the sound field processing part  201 E. 
     The sound field processing instructing part  201 D outputs an instruction to the sound field processing part  201 E on the basis of information regarding sound field processing (the type of mode, a setting value of the orientation of the cabinet, initial positions (setting values) of the guitar amplifier and the audio, and the like) transmitted from the BT transmission and reception part  21 A, the orientation of the head (a rotation angle of the head) in the horizontal direction which is detected by the gyro sensor  203 , and information which is input by an input device of the headphone  10 . 
     Regarding the sound field processing, as shown in  FIG.  8 A , when a sound pressure O is generated from a sound source G, a transfer function to the left ear of a listener M is set to be H L , and a transfer function from the sound source G to the right ear of the listener M is set to be H R , an input sound pressure E 1L  for the left ear and an input sound pressure E 1R  for the right ear are shown as the following expressions. 
     
       
         
           
             
               E 
               
                 1 
                 ⁢ 
                 L 
               
             
             = 
             
               O 
               · 
               
                 H 
                 L 
               
             
           
         
       
       
         
           
             
               E 
               
                 1 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 R 
               
             
             = 
             
               O 
               · 
               
                 H 
                 R 
               
             
           
         
       
     
     Regarding a positional relationship between the listener M and the sound source G, the following state is considered that: a sound image is localized based on a positional relationship between the listener M and the sound source G in a space covered with a reflecting wall W as shown in  FIG.  9    instead of  FIG.  8 A  is simulated. As sound field processing, the following method can be used focusing on a head transfer function. 
     That is, the following transfer function transfer functions are defined with respect to a case where a sound pressure O is generated from the sound source G in the space.
         A transfer function H F-L(1)  until a sound pressure O of a point sound source signal is directly input to the left ear of the listener M   A transfer function H F-L(2)  until a sound pressure O of a point sound source signal is reflected from a left wall and then input to the left ear of the listener M   A transfer function H R-L  until a sound pressure O of a point sound source signal is reflected from a right wall and then input to the left ear of the listener M through the head   A transfer function H F-R(1)  until a sound pressure O of a point sound source signal is transmitted to the head and input to the right ear of the listener M   A transfer function H F-R(2)  until a sound pressure O of a point sound source signal is reflected from the left wall and then input to the right ear of the listener M through the head   A transfer function H R-R  until a sound pressure O of a point sound source signal is reflected from the right wall and then input to the right ear of the listener M       

     As shown in  FIG.  8 B , in headphone, when a transfer function until sound pressures of a left sound signal P L  and a right sound signal P R  are input to right and left ears to which the sound signals are input is set to be H H , an input sound pressure E LH  for the left ear and an input sound pressure E RH  for the right ear are represented as follows. 
     
       
         
           
             
               E 
               
                 L 
                 ⁢ 
                 H 
               
             
             = 
             
               
                 P 
                 L 
               
               · 
               
                 H 
                 H 
               
             
           
         
       
       
         
           
             
               E 
               
                 R 
                 ⁢ 
                 H 
               
             
             = 
             
               
                 P 
                 R 
               
               · 
               
                 H 
                 H 
               
             
           
         
       
     
     A sound image is localized at the position of the sound source G as shown in  FIG.  9    using the headphone under the following conditions. 
     
       
         
           
             
               
                 E 
                 
                   L 
                   ⁢ 
                   H 
                 
               
               = 
               
                 E 
                 
                   2 
                   ⁢ 
                   L 
                 
               
             
             ⁢ 
             
               
 
             
             ⁢ 
             
               
                 E 
                 
                   R 
                   ⁢ 
                   H 
                 
               
               = 
               
                 E 
                 
                   2 
                   ⁢ 
                   R 
                 
               
             
           
         
       
     
     Accordingly, modified expressions for the right and left sound signals P L  and P R  that are input to the headphone are as follows. 
     
       
         
           
             
               P 
               L 
             
             = 
             
               O 
               · 
               
                 
                   H 
                   L 
                 
                 / 
                 
                   H 
                   H 
                 
               
             
           
         
       
       
         
           
             
               P 
               R 
             
             = 
             
               O 
               · 
               
                 
                   H 
                   R 
                 
                 / 
                 
                   H 
                   H 
                 
               
             
           
         
       
     
     An input sound pressure E 2L  for the left ear and an input sound pressure E 2R  for the right ear are shown as the following expressions. 
     
       
         
           
             
               E 
               
                 2 
                 ⁢ 
                 L 
               
             
             = 
             
               
                 
                   O 
                   · 
                   
                     H 
                     
                       F 
                       ⁢ 
                       
                         - 
                       
                       ⁢ 
                       
                         L 
                         ⁡ 
                         
                           ( 
                           1 
                           ) 
                         
                       
                     
                   
                 
                 + 
                 
                   O 
                   · 
                   
                     H 
                     
                       F 
                       ⁢ 
                       
                         - 
                       
                       ⁢ 
                       
                         L 
                         ⁡ 
                         
                           ( 
                           2 
                           ) 
                         
                       
                     
                   
                 
                 + 
                 
                   O 
                   · 
                   
                     H 
                     
                       R 
                       ⁢ 
                       
                         - 
                       
                       ⁢ 
                       L 
                     
                   
                 
               
               = 
               
                 O 
                 · 
                 
                   ( 
                   
                     
                       H 
                       
                         F 
                         ⁢ 
                         
                           - 
                         
                         ⁢ 
                         
                           L 
                           ⁡ 
                           
                             ( 
                             1 
                             ) 
                           
                         
                       
                     
                     + 
                     
                       H 
                       
                         F 
                         ⁢ 
                         
                           - 
                         
                         ⁢ 
                         
                           L 
                           ⁡ 
                           
                             ( 
                             2 
                             ) 
                           
                         
                       
                     
                     + 
                     
                       H 
                       
                         R 
                         ⁢ 
                         
                           - 
                         
                         ⁢ 
                         L 
                       
                     
                   
                   ) 
                 
               
             
           
         
       
       
         
           
             
               E 
               
                 2 
                 ⁢ 
                 R 
               
             
             = 
             
               
                 
                   O 
                   · 
                   
                     H 
                     
                       F 
                       ⁢ 
                       
                         - 
                       
                       ⁢ 
                       
                         R 
                         ⁡ 
                         
                           ( 
                           1 
                           ) 
                         
                       
                     
                   
                 
                 + 
                 
                   O 
                   · 
                   
                     H 
                     
                       F 
                       ⁢ 
                       
                         - 
                       
                       ⁢ 
                       
                         R 
                         ⁡ 
                         
                           ( 
                           2 
                           ) 
                         
                       
                     
                   
                 
                 + 
                 
                   O 
                   · 
                   
                     H 
                     
                       R 
                       ⁢ 
                       
                         - 
                       
                       ⁢ 
                       R 
                     
                   
                 
               
               = 
               
                 O 
                 · 
                 
                   ( 
                   
                     
                       H 
                       
                         F 
                         ⁢ 
                         
                           - 
                         
                         ⁢ 
                         
                           R 
                           ⁡ 
                           
                             ( 
                             1 
                             ) 
                           
                         
                       
                     
                     + 
                     
                       H 
                       
                         F 
                         ⁢ 
                         
                           - 
                         
                         ⁢ 
                         
                           R 
                           ⁡ 
                           
                             ( 
                             2 
                             ) 
                           
                         
                       
                     
                     + 
                     
                       H 
                       
                         R 
                         ⁢ 
                         
                           - 
                         
                         ⁢ 
                         R 
                       
                     
                   
                   ) 
                 
               
             
           
         
       
     
     Accordingly, modified expressions for the right and left sound signals P L  and P R  (see  FIG.  8 B ) that are input to the headphone are as follows. 
     
       
         
           
             
               P 
               L 
             
             = 
             
               O 
               · 
               
                 
                   ( 
                   
                     
                       H 
                       
                         F 
                         ⁢ 
                         
                           - 
                         
                         ⁢ 
                         
                           L 
                           ⁡ 
                           
                             ( 
                             1 
                             ) 
                           
                         
                       
                     
                     + 
                     
                       H 
                       
                         F 
                         ⁢ 
                         
                           - 
                         
                         ⁢ 
                         
                           L 
                           ⁡ 
                           
                             ( 
                             2 
                             ) 
                           
                         
                       
                     
                     + 
                     
                       H 
                       
                         R 
                         ⁢ 
                         
                           - 
                         
                         ⁢ 
                         L 
                       
                     
                   
                   ) 
                 
                 / 
                 
                   H 
                   H 
                 
               
             
           
         
       
       
         
           
             
               P 
               R 
             
             = 
             
               O 
               · 
               
                 
                   ( 
                   
                     
                       H 
                       
                         F 
                         - 
                         
                           R 
                           ⁡ 
                           
                             ( 
                             1 
                             ) 
                           
                         
                       
                     
                     + 
                     
                       H 
                       
                         F 
                         ⁢ 
                         
                           - 
                         
                         ⁢ 
                         
                           R 
                           ⁡ 
                           
                             ( 
                             2 
                             ) 
                           
                         
                       
                     
                     + 
                     
                       H 
                       
                         R 
                         ⁢ 
                         
                           - 
                         
                         ⁢ 
                         R 
                       
                     
                   
                   ) 
                 
                 / 
                 
                   H 
                   H 
                 
               
             
           
         
       
     
     Here, the above-described transfer functions can be set as follows using a distance X from the sound source, an angle Y with respect to the sound source, and a size Z of the space. For example, the distance X from the sound source has three stages of small, medium, and large. Setting values set by the terminal  3  are used for the distance X, the angle Y, and the size Z. 
     
       
         
           
             
               
                 H 
                 L 
               
               ⁡ 
               
                 ( 
                 
                   X 
                   , 
                   Y 
                   , 
                   Z 
                 
                 ) 
               
             
             = 
             
               
                 
                   H 
                   
                     F 
                     ⁢ 
                     
                       - 
                     
                     ⁢ 
                     
                       L 
                       ⁡ 
                       
                         ( 
                         1 
                         ) 
                       
                     
                   
                 
                 ⁡ 
                 
                   ( 
                   
                     X 
                     , 
                     Y 
                     , 
                     Z 
                   
                   ) 
                 
               
               + 
               
                 
                   H 
                   
                     F 
                     ⁢ 
                     
                       - 
                     
                     ⁢ 
                     
                       L 
                       ⁡ 
                       
                         ( 
                         2 
                         ) 
                       
                     
                   
                 
                 ⁡ 
                 
                   ( 
                   
                     X 
                     , 
                     Y 
                     , 
                     Z 
                   
                   ) 
                 
               
               + 
               
                 
                   H 
                   
                     R 
                     ⁢ 
                     
                       - 
                     
                     ⁢ 
                     L 
                   
                 
                 ⁡ 
                 
                   ( 
                   
                     X 
                     , 
                     Y 
                     , 
                     Z 
                   
                   ) 
                 
               
             
           
         
       
       
         
           
             
               
                 H 
                 R 
               
               ⁡ 
               
                 ( 
                 
                   X 
                   , 
                   Y 
                   , 
                   Z 
                 
                 ) 
               
             
             = 
             
               
                 
                   H 
                   
                     F 
                     ⁢ 
                     
                       - 
                     
                     ⁢ 
                     
                       R 
                       ⁡ 
                       
                         ( 
                         1 
                         ) 
                       
                     
                   
                 
                 ⁡ 
                 
                   ( 
                   
                     X 
                     , 
                     Y 
                     , 
                     Z 
                   
                   ) 
                 
               
               + 
               
                 
                   H 
                   
                     F 
                     ⁢ 
                     
                       - 
                     
                     ⁢ 
                     
                       R 
                       ⁡ 
                       
                         ( 
                         2 
                         ) 
                       
                     
                   
                 
                 ⁡ 
                 
                   ( 
                   
                     X 
                     , 
                     Y 
                     , 
                     Z 
                   
                   ) 
                 
               
               + 
               
                 
                   H 
                   
                     R 
                     ⁢ 
                     
                       - 
                     
                     ⁢ 
                     R 
                   
                 
                 ⁡ 
                 
                   ( 
                   
                     X 
                     , 
                     Y 
                     , 
                     Z 
                   
                   ) 
                 
               
             
           
         
       
     
     As described above, the above-described transfer functions can be obtained by an FIR filter or the like formed on the basis of an impulse response waveform obtained by observing an impulse waveform emitted from a sound source installed at an arbitrary position in the space, using a sound absorbing device such as a microphone installed at the position of the listener. As a specific example, transfer functions for respective displacements of X, Y, and Z based on resolutions required for the specifications of the device may be calculated in advance and stored, and the transfer functions may be read in accordance with a special position of a user and used for sound processing. 
       FIG.  8 C  shows a circuit example which is applied to the sound field processing part  201 E, that is, a circuit example in which the left sound signal P L  and the right sound signal P R  are output from input sound signals. A circuit  301  includes a circuit  201 Ea for obtaining H L /H H  and a circuit  201 Eb for obtaining H R /H H , and the circuit  201 Ea multiplies an input sound signal by H R /H H  and outputs a signal equivalent to the left ear signal P L . The circuit  201 Eb multiplies an input sound signal by H R /H H  and outputs a signal equivalent to the right ear signal P R . 
       FIG.  10    shows a circuit configuration of the sound field processing part  201 E in a stage mode. The sound field processing part  201 E includes a circuit  301  ( 301 A) using a first musical sound as an input signal (O) and a circuit  301  ( 301 B) using a second musical sound as an input signal (O). Configurations of the circuits  301 A and  301 B are as shown in  FIG.  8 C , and a transfer function to which a value (X,Y,Z) G  of X,Y,Z regarding a guitar amplifier is applied is used as the transfer functions H L (X,Y,Z) and H R (X,Y,Z) of the circuit  301 A. A transfer function to which a value (X,Y,Z) A  of X,Y,Z regarding an audio is applied is used as the transfer functions H L (X,Y,Z) and H R (X,Y,Z) of the circuit  301 B. Signals P L  and P R  are output from the circuits  301 A and  301 B, respectively. An adder  302  performs addition of the signals P L  and addition of the signals P R  and outputs addition results. The outputs are connected to the amplifier  206 . 
       FIG.  11    shows a circuit configuration of the sound field processing part  201 E in a static mode. The sound field processing part  201 E includes the circuit  301 A and the circuit  301 B described above. Configurations of the circuits  301 A and  301 B are as shown in  FIG.  8 C . A transfer function to which a value (X,Y,Z) G  of X,Y,Z regarding the guitar amplifier is applied is used as the transfer functions H L (X,Y,Z) and H R (X,Y,Z) of the circuit  301 A. A transfer function to which a setting value P(Y) of Y regarding the audio is applied is used as the transfer functions H L (X,Y,Z) and H R (X,Y,Z) of the circuit  301 B. The signals P L  and P R  are output from the circuits  301 A and  301 B, respectively. The adder  302  performs addition of the signals P L  and addition of the signals P R  and outputs addition results. The outputs are connected to the amplifier  206 . 
       FIG.  12    shows a circuit configuration of the sound field processing part  201 E in a surround mode. The sound field processing part  201 E includes the circuit  301 A and the circuit  301 B described above. Configurations of the circuits  301 A and  301 B are as shown in  FIG.  8 C . A transfer function to which a setting value P(Y) of Y regarding the guitar amplifier is applied is used as the transfer functions H L (X,Y,Z) and H R (X,Y,Z) of the circuit  301 A. In addition, a transfer function to which a setting value P(Y) of Y regarding the audio is applied is used as the transfer functions H L (X,Y,Z) and H R (X,Y,Z) of the circuit  301 B. Signals P L  and P R  are output from the circuits  301 A and  301 B, respectively. The adder  302  performs addition of the signals P L  and addition of the signals P R  and outputs addition results. The outputs are connected to the amplifier  206 . 
     Specific Example 
     Hereinafter, a specific example of the headphone  10  will be described.  FIG.  13 A  shows an example of initial values of X and Y, and  FIG.  13 B  shows an example of a value of Z. As shown in  FIG.  13 A , with respect to stage, static, and surround modes, initial values of X and Y regarding the guitar amplifier and the audio are set. In a case where the stage mode is selected, the values of X and Y of the guitar amplifier and the audio can be updated using a user interface of the terminal  3  and transmitted to the headphone  10  as setting values. The value of Z indicating the size of the space is treated as a fixed value in two stages. A selected value of Z is also transmitted to the headphone  10  as a setting value. 
       FIG.  14    is a table showing a correspondence relationship between the values of X, Y, and Z and transfer functions H L  and H R . A predetermined number of records of the transfer functions H L  and H R  corresponding to a transfer function H G (X,Y,Z) and a transfer function H A (X,Y,Z) as shown in  FIG.  15    can be stored in the storage device  202  in advance using such a table. In the example of  FIG.  15   , the predetermined number of records is five, but may be more than or less than five. Meanwhile, the transfer functions H L  and H R  may be able to be acquired from anything other than storage device  202 . 
       FIG.  16    shows installation positions (A, B, and C) of the guitar amplifier (cabinet).  FIG.  17    shows values of setting instructions transmitted to the headphone  10  through an application of the terminal  3 . A, B, and C are as follows.
         A indicates the size of the cabinet of the guitar amplifier. In a specific example, two types of sizes, that is, large (ID: 2) and small (ID: 1) are adopted.   B indicates a distance between the guitar amplifier and the microphone acquiring an impulse response. In a specific example, two types of distances of the microphone, that is, long (off microphone (ID: 2)) and short (on microphone (ID: 1)) are adopted.   C indicates an angle between the guitar amplifier and the microphone acquiring an impulse response. In a specific example, 0, 3, 6, . . . , and 357 (initial value 0) are adopted.       

     The table shown in  FIG.  17    is stored in the storage device  32  of the terminal  3 . In the terminal  3 , when the type (TYPE) of AMP is selected using the operation screen  41 , A and B (ID) in the table shown in  FIG.  17    are transmitted to the headphone  10 . For example, when a type “T 1 ” is selected, A=2 and B=1 are transmitted to the headphone  10 . In addition, the value of C which is set in the operation screen  41  is transmitted to the headphone  10 . The table shown in  FIG.  16    is stored in the storage device  202  of the headphone  10 , and transfer functions corresponding to the values of A, B, and C are used. 
       FIGS.  18  and  19    show a processing example of the processor  201  operating as the sound field processing part  201 E. In step S 01 , the processor  201  acquires a first coordinate setting value (A,B,C). In step S 02 , the processor  201  acquires a second coordinate setting value (X,Y,Z). 
     In step S 03 , the processor  201  waits for a detection time of the gyro sensor  203 . In step S 04 , the processor  201  determines whether or not to use the gyro sensor  203 . In a case where it is determined that the gyro sensor  203  is used, the processing proceeds to step S 05 , and otherwise, the processing proceeds to step S 10 . 
     In step S 05 , the processor  201  obtains an angle displacement Δω constituted by the past output of the gyro sensor  203  and an output acquired this time and causes the processing to proceed to step S 06 . In step S 10 , the processor  201  sets the value of the angle displacement Δω to 0 and causes the processing to proceed to step S 06 . 
     In step S 06 , it is determined whether or not a reset button has been pressed. In a case where it is determined that the reset button has been pressed, the processing proceeds to step S 11 , and otherwise, the processing proceeds to step S 07 . Here, in a case where a user desires to reset the position of a sound field, the user presses the reset button. 
     In step S 07 , the processor  201  determines whether or not the second coordinate setting value has been changed. Here, it is determined whether or not the values of X, Y, and Z have been changed in association with the reset. The determination in step S 07  is performed on the basis of whether or not a flag (received from the terminal  3 ) indicating the change of the second coordinate setting value is in an on state. In a case where it is determined that the value has been changed (flag is in an on state), the processing proceeds to step S 11 , and otherwise, the processing proceeds to step S 08 . 
     In step S 11 , the value of ω is set to 0, and the processing proceeds to step S 14 . In step S 08 , the processor  201  sets the value of the angle ω which is a cumulative value of Δω to a value obtained by adding Δω to the current value of ω, and causes the processing to proceed to step S 09 . 
     In step S 09 , the processor  201  determines whether or not the value of ω exceeds  360  degrees. In a case where it is determined that ω exceeds 360 degrees, the processing proceeds to step S 12 , and otherwise, the processing proceeds to step S 13 . In step S 12 , the value of ω is set to a value obtained by subtracting 360 degrees from ω, and the processing returns to step S 09 . 
     In step S 13 , the processor  201  determines whether or not the value of ω is smaller than 0. In a case where ω is smaller than 0, the value of ω is set to a value obtained by adding 360 degrees to the current value of ω (step S 18 ), and the processor causes the processing to return to step S 13 . In a case where it is determined that ω is equal to or larger than 0, the processing proceeds to step S 14 . 
     In step S 14 , the processor  201  sets the value of Y to a value obtained by adding ω to the value of a setting value Y 0 , and causes the processing to proceed to step S 15 . In step S 15 , it is determined whether or not the value of Y is larger than 360 degrees. In a case where it is determined that the value of Y is larger than 360 degrees, the processor sets the value of Y to a value obtained by subtracting 360 degree from the current value of Y (step S 19 ) and causes the processing to return to step S 15 . In a case where it is determined that the value of Y is smaller than 360 degrees, the processing proceeds to step S 16 . 
     In step S 16 , the processor  201  sets a transfer function H C (A,B,C) corresponding to the values of A, B, and C in a cabinet simulator that simulates a cabinet (guitar amplifier) of a type selected by the user. 
     In step S 17 , the processor  201  acquires transfer functions H L  and H R  corresponding to the values of X, Y, and Z to perform sound field processing. When step S 17  is terminated, the processing returns to step S 03 . 
       FIG.  20    is a flowchart showing interruption processing in a case where a second coordinate setting value (an angle or the like) has been changed by the terminal  3 . When a setting value of Y of at least one of a guitar amplifier and an audio is changed through an operation using the operation screen  42 , the CPU  31  sets a changed value Y 0  to be a setting value (step S 001 ). In this case, the CPU  31  sets a flag indicating that the second coordinate setting value has been changed to be in an on state. The on-state flag and the updated second coordinate setting value are transmitted to the headphone  10  and used for the process of step S 07 , or the like. 
       FIGS.  21 A and  21 B  show an example in a case where the position of the guitar amplifier (GUITAR POSITION: Y G ) and an angle C of the cabinet (CABINET DIRECTION) are operated using the operation screens  41  and  42 .  FIG.  21 A  shows a case where the angle C is fixed to 0 at all times regardless of the value of Y G  ( FIG.  22 A ). In this case, a listener (user) always feels as if the guitar amplifier is facing the front. In this manner, the processor  201  applies an effect of simulating a case where a first musical sound is output from a cabinet speaker with the front facing the user, regardless of a position at which a sound image of the first musical sound is localized. 
       FIG.  21 B  shows a case where setting for conforming the angle C to the value of Y G  is performed. In this case, the guitar amplifier faces the back side of the user at all times, and a band member behind the user feels as if the guitar amplifier faces the front at all times. 
     In the setting related to  FIG.  21 B , the CPU  31  may perform processing so that any one of the angle C and the angle Y G  is updated to the same value as that of the other in a case where the angle is updated, and the updated angle C and Y G  are transmitted to the headphone  10 . 
       FIG.  23    is a diagram showing operations according to an embodiment of a stage mode. The left drawing in  FIG.  23    shows initial states of an angle Y G  between a guitar amplifier G and a user and an angle Y A  between an audio A and the user. In this example, Y G  and Y A  are both 180 degrees and are positioned right behind the user. Meanwhile, a triple concentric circle indicates distances (small, medium, large) from the user. 
     As shown in the middle of  FIG.  23   , the user can set the angles Y G  and Y A  using the operation screen  42 . In this example, the angle Y G  is set to 135 degrees, and the angle Y A  is set to 225 degrees. 
     Thereafter, as shown in the right drawing in  FIG.  23   , when the user faces right behind, the angle Y G  is changed to 315 degrees, and the angle Y A  is changed to 45 degrees in the stage mode. That is, the guitar amplifier and the audio do not move, and a listening feeling in a case where only the user faces right behind is obtained. 
     Here, a case where the user performs a reset operation such as the pressing of a reset button of the headphone  10  is assumed. In this case, the processor  201  may return the values of the angles Y G  and Y A  to the values in the initial state to set a state shown on the left side. Values in the initial state may be notified in advance by the terminal  3  or set in the headphone  10  in advance. Alternatively, the processor  201  may erase an angle displacement Δω to return the state to the state in the middle drawing. 
       FIG.  24    is a diagram showing operations according to an embodiment. In a static mode, the processor  201  adjusts panning (right and left volumes) in accordance with a change in the orientation of the user&#39;s head. Further, in the static mode, the angle Y G  of the guitar amplifier changes depending on the orientation of the user&#39;s head. In the example of  FIG.  24   , when the user faces right behind, the angle Y G  changes to 180 degrees, and a listening feeling in which a sound from the guitar amplifier is heard from right behind is obtained. According to the embodiment, it is possible to provide the headphone  10  capable of controlling a position at which a sound image of each of first and second musical sounds to be mixed is localized. The configurations shown in the embodiments can be appropriately combined with each other without departing from the object. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure covers modifications and variations provided that they fall within the scope of the following claims and their equivalents.