function?wiener_as（filenameoutfile）

%
%??Implements?the?Wiener?filtering?algorithm?based?on?a?priori?SNR?estimation?[1].
%?
%??Usage:??wiener_as（noisyFile?outputFile）
%???????????
%?????????infile?-?noisy?speech?file?in?.wav?format
%?????????outputFile?-?enhanced?output?file?in?.wav?format

%?????????
%??Example?call:??wiener_as（‘sp04_babble_sn10.wav‘‘out_wien_as.wav‘）;
%
%??References:
%???[1]?Scalart?P.?and?Filho?J.?（1996）.?Speech?enhancement?based?on?a?priori?
%???????signal?to?noise?estimation.?Proc.?IEEE?Int.?Conf.?Acoust.??Speech?Signal?
%???????Processing?629-632.
%???
%?Authors:?Yi?Hu?and?Philipos?C.?Loizou
%
%?Copyright?（c）?2006?by?Philipos?C.?Loizou
%?$Revision:?0.0?$??$Date:?10/09/2006?$
%-------------------------------------------------------------------------

if?nargin<2
???fprintf（‘Usage:?wiener_as（noisyfile.wavoutFile.wav）?\n\n‘）;
???return;
end



[noisy_speech?fs?nbits]=?wavread（?filename）;
noisy_speech=?noisy_speech;?
%?column?vector?noisy_speech

%?set?parameter?values
mu=?0.98;?%?smoothing?factor?in?noise?spectrum?update
a_dd=?0.98;?%?smoothing?factor?in?priori?update
eta=?0.15;?%?VAD?threshold
frame_dur=?20;?%?frame?duration?
L=?frame_dur*?fs/?1000;?%?L?is?frame?length?（160?for?8k?sampling?rate）
hamming_win=?hamming（?L）;?%?hamming?window
U=?（?hamming_win‘*?hamming_win）/?L;?%?normalization?factor

%?first?120?ms?is?noise?only
len_120ms=?fs/?1000*?120;??????????????????????????????????????????????????%%%120ms時間長度內的樣點值
%?first_120ms=?noisy_speech（?1:?len_120ms）.*?...
%?????（hann（?len_120ms?‘periodic‘））‘;
first_120ms=?noisy_speech（?1:?len_120ms）;

%?=============now?use?Welch‘s?method?to?estimate?power?spectrum?with
%?Hamming?window?and?50%?overlap
nsubframes=?floor（?len_120ms/?（L/?2））-?1;??%?50%?overlap
noise_ps=?zeros（?L?1）;
n_start=?1;?
for?j=?1:?nsubframes
????noise=?first_120ms（?n_start:?n_start+?L-?1）;
????noise=?noise.*?hamming_