Patent ID: 7054808

Claim:
A noise suppression apparatus comprising: a conversion section that converts an input speech signal to a speech spectrum in frame units; a speech/non-speech determining section that determines, on a per frame basis, whether or not the speech spectrum includes a speech component; a noise estimating section that estimates a noise spectrum based on the speech spectrum; an SNR calculating section that calculates a signal-to-noise ratio based on the speech spectrum and the noise spectrum; a suppression coefficient control section that: (i) updates a suppression lower limit coefficient using a first predetermined coefficient, when the speech spectrum includes a speech component and the signal-to-noise ratio is greater than a predetermined value, and (ii) for other cases, updates the suppression lower limit coefficient using a second predetermined coefficient, said second coefficient being greater than the first coefficient; and a suppressed speech spectrum calculating section that: (i) compares: (a) a subtraction spectrum, in which the noise spectrum is subtracted from the speech spectrum, and (b) a subtraction lower limit spectrum, in which the speech spectrum is multiplied by the suppression lower limit coefficient, and (ii) outputs a suppression speech spectrum formed with greater parts selected from the subtraction spectrum and the subtraction lower limit spectrum.