function H = mmse_pow(gamma,xihat)
% MMSE_POW - MMSE spectral power estimation (Wolfe and Godsill, 2001) 
%    H = MMSE_POW(GAMMA,XIHAT) returns the MMSE spectral power 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:
% 
% P. J. Wolfe and S. J. Godsill. Simple alternatives to the Ephraim and
% Malah suppression rule for speech enhancement. In Proc. IEEE Workshop on 
% Statistical Signal Processing, pages 496-499, August 2001.

% Author: Patrick J. Wolfe
%         Signal Processing Group
%         Cambridge University Engineering Department
%         p.wolfe@ieee.org
%
% Copyright (c) 2001 by Patrick J. Wolfe
% $Revision: 1.2 $  $Date: 2001/01/24 13:09:23 $

% MMSE spectral power estimation filter calculation
%
upsilon = gamma.*xihat./(1+xihat);
H = sqrt((xihat./(1+xihat)).*((1+upsilon)./gamma));