Patent ID: 7890321

Claim:
A noise reduction device comprising: a microphone for converting surrounding sounds to a first observed signal in a frequency domain into a form of an electric signal, wherein the sounds comprise stationary and non-stationary noise components; a discrete transform unit for receiving as a first reference signal an output signal transmitted from an input source to an output source and converting said first reference signal to a second reference signal in a form of a power spectrum in each of a plurality of predetermined time frames; a central processor unit configured to: calculate a predetermined constant by use of an adaptive coefficient for the predetermined constant, calculating calculate a predetermined second reference signal in the frequency domain by use of an adaptive coefficient for the reference signal, and thereby obtaining estimated values respectively of stationary noise components included in a predetermined observed signal in the frequency domain and non-stationary noise components corresponding to the reference signal; the central processor unit configured to perform a noise reduction process on the first observed signal on the basis of each of the estimated values, and updating each of the adaptive coefficients on the basis of a result of the noise reduction process; and a central processor unit configured to repeat the obtaining of the estimated values and the updating of the adaptive coefficients, and thereby learning each of the adaptive coefficients; the central processor unit configured to convert the first observed signal to a second observed signal in a form of a power spectrum in each of a plurality of predetermined time frames; wherein the adaptive coefficient to be used for calculating estimated values respectively of the stationary noise components and the non-stationary noise components is designed to be learned on a basis of the second observed signal and the second reference signal in the frequency domain at a same time.