Acoustic signal processing device, acoustic signal processing method, and acoustic signal processing program

An acoustic signal processing method for converting an input acoustic signal into output acoustic signals for a plurality of speakers in a speaker array formed by arranging the speakers for creating a virtual sound source, comprising:

• obtaining a plurality of sets of initial focal point coordinates, coordinates of the virtual sound source, and a direction of directivity thereof;
• for a pair of sets of initial focal point coordinates with different polarities among the plurality of sets of initial focal point coordinates among the plurality of sets of initial focal point coordinates, multiplying the sets of initial focal point coordinates by a rotation matrix based on the coordinates of the virtual sound source to thereby determine sets of focal point coordinates, the rotation matrix being specified from the direction of the directivity;
• calculating weights to be applied to multipoles including the sets of focal point coordinates from a circular harmonic coefficient;
• for each of the speakers in the speaker array, computing a weighted driving function to be applied to the speaker from the sets of focal point coordinates, polarities of the sets of focal point coordinates, and the weights to be applied to the multipoles;
• and
• for each of the speakers in the speaker array, convolving the weighted driving function for the speaker into the input acoustic signal to output the output acoustic signal for the speaker.

A non-transitory computer readable medium having stored thereon an acoustic signal processing program that causes a computer to perform operations comprising:

• obtaining a plurality of sets of initial focal point coordinates, coordinates of the virtual sound source, and a direction of directivity thereof, and for a pair of sets of initial focal point coordinates with different polarities among the plurality of sets of initial focal point coordinates, multiplies the sets of initial focal point coordinates by a rotation matrix based on the coordinates of the virtual sound source to thereby determine sets of focal point coordinates, the rotation matrix being specified from the direction of the directivity;
• calculating weights to be applied to multipoles including the sets of focal point coordinates from a circular harmonic coefficient;
• for each of speakers in a speaker array, computing a weighted driving function to be applied to the speaker from the sets of focal point coordinates, polarities of the sets of focal point coordinates, and the weights to be applied to the multipoles;
• and
• for each of the speakers in the speaker array, convolving the weighted driving function for the speaker into the input acoustic signal to output the output acoustic signal for the speaker.