Speech signal separation apparatus and method

1. A speech signal separation apparatus for separating an observation signal in a time domain of a plurality of channels wherein a plurality of signals including a speech signal are mixed using independent component analysis to produce a plurality of separation signals of the different channels, comprising:

a first conversion section configured to convert the observation signal in the time domain into an observation signal in a time-frequency domain;

a non-correlating section configured to non-correlate the observation signal in the time-frequency domain between the channels;

a separation section configured to produce separation signals in the time-frequency domain from the observation signal in the time-frequency domain; and

a second conversion section configured to convert the separation signals in the time-frequency domain into separation signals in the time domain;

said separation section being operable to produce the separation signals in the time-frequency domain from the observation signal in the time-frequency domain and a separation matrix in which initial values are substituted, calculate modification values for the separation matrix using the separation signals in the time-frequency domain, a score function which uses a multi-dimensional probability density function, and the separation matrix, modify the separation matrix until the separation matrix substantially converges using the modification values and produce separation signals in the time-frequency domain using the substantially converged separation matrix;

each of the separation matrix which includes the initial values and the separation matrix after the modification which includes the modification values being a normal orthogonal matrix.

2. The speech signal separation apparatus according to claim 1 , wherein the score function returns a dimensionless amount as a return value thereof which has a phase which relies upon only one argument.

3. A speech signal separation method for separating an observation signal in a time domain of a plurality of channels wherein a plurality of signals including a speech signal are mixed using independent component analysis to produce a plurality of separation signals of the different channels, comprising the steps of:

converting the observation signal in the time domain into an observation signal in a time-frequency domain;

non-correlating the observation signal in the time-frequency domain between the channels;

producing separation signals in the time-frequency domain from the observation signal in the time-frequency domain and a separation matrix in which initial values are substituted;

calculating modification values for the separation matrix using the separation signals in the time-frequency domain, a score function which uses a multi-dimensional probability density function, and the separation matrix;

modifying the separation matrix using the modification values until the separation matrix substantially converges; and

converting the separation signals in the time-frequency domain produced using the substantially converged separation matrix into separation signals in the time domain;

each of the separation matrix which includes the initial values and the separation matrix after the modification which includes the modification values being a normal orthogonal matrix.

4. The speech signal separation method according to claim 3 , wherein the score function returns a dimensionless amount as a return value thereof which has a phase which relies upon only one argument.