log_mmse.m

这个MATLAB程序是用于对音频信号进行降噪处理

function H = log_mmse(gamma,xihat)
% LOG_MMSE - MMSE log-spectral amplitude estimation (Ephraim & Malah, 1985) 
%    H = LOG_MMSE(GAMMA,XIHAT) returns the MMSE log-spectral amplitude
%    estimation filter H given a posteriori signal-to-noise ratio (SNR)
%    GAMMA and an estimate XIHAT of a priori SNR.  GAMMA and XIHAT may be
%    arrays but must be of equal dimension.
%
% References:
% 
% Y. Ephraim and D. Malah.  Speech enhancement using a minimum mean-square
% error log-spectral amplitude estimator.  IEEE Transactions on Acoustics,
% Speech and Signal Processing, ASSP-33(2):443-445, April 1985.

% Author: Patrick J. Wolfe
%         Signal Processing Group
%         Cambridge University Engineering Department
%         [e-mail]
%
% Copyright (c) 2000 by Patrick J. Wolfe
% $Revision: 1.2 $  $Date: 2001/01/24 13:08:05 $

% MMSE log-spectral amplitude estimation filter calculation
%
frac = xihat./(1+xihat);
upsilon = gamma.*frac;
H = frac.*exp(0.5.*expint(upsilon));