Patent ID: 7302065
Filing Date: 2007-11-27
Classification: G10L

Abstract:
1. A noise suppressing apparatus, comprising: a time-to-frequency converting unit for performing a frequency analysis for an input signal and converting the input signal to both an amplitude spectrum and a phase spectrum; a noise-likeness analyzing unit for judging the input signal to obtain noise-likeness from the input signal, outputting a noise-likeness signal indicating the noise-likeness, and outputting a noise spectrum updating rate coefficient corresponding to the noise-likeness signal; a noise spectrum estimating unit for updating a noise spectrum according to the noise spectrum updating rate coefficient output from the noise-likeness analyzing unit, the amplitude spectrum output from the time-to-frequency converting unit and an average noise spectrum of a past time, and outputting the noise spectrum; a frequency band signal-to-noise ratio calculating unit for calculating a frequency band signal-to-noise ratio denoting a ratio of a signal to a noise from the amplitude spectrum output from the time-to-frequency converting unit and the noise spectrum output from the noise spectrum estimating unit for each frequency band; an amplitude suppression quantity calculating unit for calculating an amplitude suppression quantity denoting a noise suppression level of a current frame from the noise-likeness signal output from the noise-likeness analyzing unit and the noise spectrum output from the noise spectrum estimating unit; a perceptual weight pattern adjusting unit for determining a perceptual weight distributing pattern denoting a frequency characteristic distributing pattern of both a spectral subtraction quantity denoting a first perceptual weight and a spectral amplitude suppression quantity denoting a second perceptual weight from the amplitude suppression quantity calculated by the amplitude suppression quantity calculating unit and the noise-likeness signal output from the noise-likeness analyzing unit; a perceptual weight correcting unit for correcting the spectral subtraction quantity denoting the first perceptual weight and the spectral amplitude suppression quantity denoting the second perceptual weight output from the perceptual weight pattern adjusting unit according to the frequency band signal-to-noise ratio calculated by the frequency band signal-to-noise ratio calculating unit and outputting a corrected spectral subtraction quantity and a corrected spectral amplitude suppression quantity, wherein the corrected spectral subtraction quantity decreases with increasing frequency and the corrected spectral amplitude suppression quantity increases with said increasing frequency; a spectrum subtracting unit for subtracting a spectrum, which is obtained by multiplying the corrected spectral subtraction quantity output from the perceptual weight correcting unit by the noise spectrum output from the noise spectrum estimating unit, from the amplitude spectrum obtained by the time-to-frequency converting unit to obtain a noise subtracted spectrum; a spectrum suppressing unit for multiplying the noise subtracted spectrum obtained by the spectrum subtracting unit by the corrected spectral amplitude suppression quantity output from the perceptual weight correcting unit to obtain a noise suppressed spectrum; and a frequency-to-time converting unit for converting the noise suppressed spectrum obtained by the spectrum suppressing unit to a time signal according to the phase spectrum obtained by the time-to-frequency converting unit and outputting a noise suppressed signal.