Patent ID: 7890319
Filing Date: 2011-02-15
Classification: G10L

Abstract:
1. A signal processing apparatus for smoothing power spectral density of a speech signal, comprising: an acquisition section configured to acquire the power spectral density of a plurality of frames of the speech signal; an estimator configured to estimate an estimated value of power spectral density of noise based on the power spectral density of the plurality of frames of the speech signal; a subtraction section configured to subtract the estimated value from the power spectral density of each frame of the speech signal so as to determine a spectral subtraction of the power spectral density of each frame of the speech signal; and a determiner configured to perform a first filtering process and a second filtering process on the spectral subtraction of the power spectral density of each frame of the speech signal, and to linearly combine results of the first and second filtering processes so as to determine a smooth spectral subtraction of the power spectral density of each frame of the speech signal, wherein the first filtering process begins at the lowest frequency of the power spectral density and proceeds towards the highest frequency of the power spectral density, and the second filtering process begins at the highest frequency of the power spectral density and proceeds towards the lowest frequency of the power spectral density, and wherein the first and second filtering processes use a plurality of filtering coefficients, where each of the filtering coefficients respectively depends on the frequency of each frame contained between the lowest frequency and the highest frequency of the power spectral density of the speech signal.