Apparatus and a method for controlling a sound field

1. An apparatus for controlling a sound field, comprising:

a control filter configured to convolute a first filter coefficient and a second filter coefficient with a first acoustic signal to generate a second acoustic signal and a third acoustic signal;

a first speaker to radiate a sound toward a first area having a first control point and a second area having a second control point, based on the second acoustic signal;

a second speaker to radiate a sound toward the first area and the second area, based on the third acoustic signal; and

a calculation unit configured to calculate the first filter coefficient and the second filter coefficient by using spatial transfer characteristics from the first speaker and the second speaker to the first control point and the second control point, and a first sound increase ratio na at the first control point and a second sound increase ratio nb at the second control point, so that a first composite sound pressure from the first speaker and the second speaker to the first control point is na times a first sound pressure from the first speaker to the first control point when the first filter coefficient is a through characteristic, and so that a second composite sound pressure from the first speaker and the second speaker to the second control point is nb times a second sound pressure from the first speaker to the second control point when the first filter coefficient is the through characteristic.

2. The apparatus according to claim 1 , wherein

the calculation unit calculates the first filter coefficient and the second filter coefficient so as to minimize a first acoustic energy of the first area by subtracting na times the first sound pressure from the first composite sound pressure, and so as to minimize a second acoustic energy of the second area by subtracting nb times the second sound pressure from the second composite sound pressure.

3. The apparatus according to claim 1 , further comprising:

a volume adjustment unit configured to amplify the second acoustic signal and the third acoustic signal.

4. The apparatus according to claim 1 , wherein

the first speaker and the second speaker have an allowance amplitude respectively,

further comprising:

a detection unit configured to detect whether an amplitude of any of the second acoustic signal and the third acoustic signal is smaller than or equal to the allowance amplitude; and

an adjustment unit configured to adjust the amplitude to be smaller than or equal to the allowance amplitude when the amplitude is larger than the allowance amplitude.

5. An apparatus for controlling a sound field, comprising:

a control filter configured to convolute a first filter coefficient and a second filter coefficient with a first acoustic signal to generate a second acoustic signal and a third acoustic signal;

a first speaker to radiate a sound toward a first area having a first control point and a second area having a second control point, based on the second acoustic signal;

a second speaker to radiate a sound toward the first area and the second area, based on the third acoustic signal; and

a storage unit configured to store the first filter coefficient and the second filter coefficient calculated by using spatial transfer characteristics from the first speaker and the second speaker to the first control point and the second control point, and a first sound increase ratio na at the first control point and a second sound increase ratio nb at the second control point, so that a first composite sound pressure from the first speaker and the second speaker to the first control point is na times a first sound pressure from the first speaker to the first control point when the first filter coefficient is a through characteristic, and so that a second composite sound pressure from the first speaker and the second speaker to the second control point is nb times a second sound pressure from the first speaker to the second control point when the first filter coefficient is the through characteristic.

6. A method for controlling a sound field in a system including a first speaker and a second speaker, comprising:

convoluting a first filter coefficient and a second filter coefficient with a first acoustic signal to generate a second acoustic signal and a third acoustic signal;

radiating by the first speaker, a sound toward a first area having a first control point and a second area having a second control point, based on the second acoustic signal;

radiating by the second speaker, a sound toward the first area and the second area, based on the third acoustic signal; and

calculating the first filter coefficient and the second filter coefficient by using spatial transfer characteristics from the first speaker and the second speaker to the first control point and the second control point, and a first sound increase ratio na at the first control point and a second sound increase ratio nb at the second control point, so that a first composite sound pressure from the first speaker and the second speaker to the first control point is na times a first sound pressure from the first speaker to the first control point when the first filter coefficient is a through characteristic, and so that a second composite sound pressure from the first speaker and the second speaker to the second control point is nb times a second sound pressure from the first speaker to the second control point when the first filter coefficient is the through characteristic.