Patent ID: 8208666
Filing Date: 2012-06-26
Classification: G10L

Abstract:
1. A method for determining unbiased signal amplitude estimates after cepstral variance modification of a discrete time domain signal, wherein cepstrally modified spectral amplitudes of the discrete time domain signal are χ-distributed with 2{tilde over (μ)} degrees of freedom, the method which comprises: determining a cepstral variance of cepstral coefficients of the discrete time domain signal prior to cepstral variance modification; determining a mean cepstral variance after cepstral variance modification of modified cepstral coefficients using the cepstral variance prior to cepstral variance modification; determining the 2{tilde over (μ)} degrees of freedom after the cepstral variance modification using the mean cepstral variance; determining a bias reduction factor with the equation where 2μ are the degrees of freedom of the χ-distributed spectral amplitudes of the discrete time domain signal (s(t)) and determining the unbiased signal amplitude estimates by multiplying the cepstrally-modified spectral amplitudes with the bias reduction factor according to the equation where  are the unbiased signal amplitude estimates,  are the cepstrally-modified spectral amplitudes, and r is the bias reduction factor.