Method for determining unbiased spectral amplitude estimates after cepstral variance modification

摘要

The invention claims a method for determining unbiased signal amplitude estimates S k ^ after cepstral variance modification of a discrete time domain signal (s(t)), whereas the cepstrally-modified spectral amplitudes S k Ü of said discrete time domain signal (s(t)) are Ç-distributed with 2µ degrees of freedom comprising:
- determining a bias reduction factor (r) using the equation r 2 = ¼ ¼ Ü �¢ e È ¼ Ü - È ¼
where 2µ are the degrees of freedom of the Ç-distributed spectral amplitudes of said discrete time domain signal (s(t)) and È x = - 0.5772 - ˆ‘ n = 0 ˆž 1 x + n - 1 1 + n , and
- determining said unbiased signal amplitude estimates S k ^ by multiplying said cepstrally-modified spectral amplitudes S k Ü with said bias reduction factor (r) according to the equation S k ^ = r �¢ S k Ü . A method for speech enhancement and a hearing aid using the method for determining unbiased signal amplitude estimates S k ^ are claimed as well. The invention offers the advantage of spectral modification, e.g. smoothing, of spectral quantities without affecting their signal power.