cutOffFreq=1000;	% Cutoff frequency
filterOrder=5;		% Order of filter
au=myAudioRead('wubai_solicitude.wav');
[b, a]=butter(filterOrder, cutOffFreq/(au.fs/2), 'low');
au.signal=au.signal(60*au.fs:90*au.fs);	% 30-second signal
y=filter(b, a, au.signal);
% ====== Plot the result
time=(1:length(au.signal))/au.fs;
subplot(2,1,1);
plot(time, au.signal);
subplot(2,1,2);
plot(time, y);
% ====== Save output files
myAudioWrite(au, 'wubai_solicitude_orig.wav');
au.signal=y;
myAudioWrite(au, sprintf('wubai_solicitude_%d.wav', cutOffFreq));