Patent ID: 8355908

Claim:
An audio signal processing device comprising: a frame division unit dividing inputted audio signals into frames as predetermined units; a frequency converter converting the audio signals on a frame-to-frame basis from time-domain signals to frequency signals as frequency-domain signals; a level detector detecting respective levels of spectrums of respective frequencies from the frequency signals with respect to each frame; a level control value setting unit executing a reduction amount setting process of setting a level control value for reducing the levels of the spectrums having levels within a level range between a first threshold value and a second threshold value set lower than the first threshold value, with respect to each frame; and the level control value setting unit executing an amplification amount setting process of setting a level control value for increasing the level of a spectrum in a predetermined frequency band having a level within a range between a third threshold value set more than the first threshold value and a fourth threshold value set more than the first threshold value and less than the third threshold value, with respect to each frame; a level control value smoothing unit executing a smoothing process of temporally smoothing a difference between one level control value set in a present frame as an object to be processed for reducing noise presently and another level control value that has been used in another frame preceding to the present frame by one frame temporally; a storage unit storing the level control value after the smoothing process; a spectral adjustment unit multiplying the level control value after the smoothing process, of the frame as the object to be processed for reducing noise, by the frequency signals of the frame thereby executing a level adjustment; and a reverse frequency converter converting the frequency signals, whose levels have been controlled by the spectral adjustment unit, into a time-domain audio signals.