Acoustic control apparatus

An acoustic control apparatus, comprising:

• a first control filter configured to multiply a first acoustic signal by a first control filter coefficient to obtain a second acoustic signal;
• a second control filter configured to multiply a third acoustic signal having an amplitude ratio and a phase difference with respect to the first acoustic signal by a second control filter coefficient to obtain a fourth acoustic signal;
• a first loudspeaker configured to emit the second acoustic signal;
• and
• a second loudspeaker configured to emit the fourth acoustic signal,
• wherein the first control filter coefficient is calculated based on the second control filter coefficient and at least one head-related transfer function set from the first loudspeaker and the second loudspeaker to at least one target binaural position in such a manner that a spatial average of at least one complex sound pressure ratio at the at least one target binaural position when the first loudspeaker and the second loudspeaker emit the second acoustic signal and the fourth acoustic signal is approximated to a complex sound pressure ratio of the first acoustic signal and the third acoustic signal.

An acoustic control apparatus, comprising:

• X−C−1 (X is an integer not smaller than 3, C is an integer less than X and not smaller than 1) first control filters configured to multiply a first acoustic signal by first, . . . , and X−C−1th control filter coefficients to obtain second, . . . , X-Cth acoustic signals;
• C second control filters configured to multiply an X+1th acoustic signal having an amplitude ratio and a phase difference with respect to the first acoustic signal by X−C, . . . , and X−1th control filter coefficients to obtain X−C+1, . . . , and Xth acoustic signals;
• and
• X loudspeakers configured to emit the first, . . . , and Xth acoustic signals,
• wherein the first, . . . , and X−1th control filter coefficients are calculated based on at least X−1 head-related transfer function sets from the X loudspeakers to at least X−1 target binaural positions in such a manner that a spatial average of at least X−1 complex sound pressure ratios at the at least X−1 target binaural positions when the X loudspeakers emit the first, . . . , and Xth acoustic signals is approximated to a complex sound pressure ratio of the first acoustic signal and the X+1th acoustic signal.

An acoustic control apparatus, comprising:

• a control filter configured to multiply a first acoustic signal by a control filter coefficient to obtain a second acoustic signal;
• a first loudspeaker configured to emit the second acoustic signal;
• and
• a second loudspeaker configured to emit the first acoustic signal,
• wherein the control filter coefficient is calculated based on a first head-related transfer function set from the first loudspeaker and the second loudspeaker to a target binaural position and a second head-related transfer function set from a target virtual acoustic source to the target binaural position in such a manner that a complex sound pressure ratio at the target binaural position when the first loudspeaker and the second loudspeaker emit the second acoustic signal and the first acoustic signal is approximated to a complex sound pressure ratio at the target binaural position if the target virtual acoustic source emitted the first acoustic signal, the target virtual acoustic source being different from the first loudspeaker and the second loudspeaker.

An acoustic control apparatus, comprising:

• a first control filter configured to multiply a first acoustic signal by a first control filter coefficient to obtain a second acoustic signal;
• a second control filter configured to multiply the first acoustic signal by a second control filter coefficient to obtain a third acoustic signal;
• a first loudspeaker configured to emit the second acoustic signal;
• and
• a second loudspeaker configured to emit the third acoustic signal,
• wherein the first control filter coefficient is calculated based on the second control filter coefficient, a first head-related transfer function set from the first loudspeaker and the second loudspeaker to a target binaural position, and a second head-related transfer function set from a target virtual acoustic source to the target binaural position in such a manner that a complex sound pressure ratio at the target binaural position when the first loudspeaker and the second loudspeaker emit the second acoustic signal and the third acoustic signal is approximated to a complex sound pressure ratio at the target binaural position if the target virtual acoustic source emitted the first acoustic signal, the target virtual acoustic source being different from the first loudspeaker and the second loudspeaker.