ls

.                     EnvelopeDetector.m    diary                 
..                    FMFeedback.asv        makeLowPass.m         
AM.m                  FMFeedback.m          playSig.m             
AnalogMod.asv         PlotFT.m              rexkwondo.wav         
AnalogMod.m           VCO.asv               
EnvelopeDetector.asv  VCO.m                 

[s,fs,nbits] = wavread('rexkwondo.wav');
fs

fs =

       11025

su=interp(s,4);
fs=4*fs

fs =

       44100

p = audioplayer(su, fs);
play(p)
bLP=makeLowPass(100, 2000, 200, fs);
freqz(bLP)
sul = filter(bLP,[1],su);
help filter
 FILTER One-dimensional digital filter.
    Y = FILTER(B,A,X) filters the data in vector X with the
    filter described by vectors A and B to create the filtered
    data Y.  The filter is a "Direct Form II Transposed"
    implementation of the standard difference equation:
 
    a(1)*y(n) = b(1)*x(n) + b(2)*x(n-1) + ... + b(nb+1)*x(n-nb)
                          - a(2)*y(n-1) - ... - a(na+1)*y(n-na)
 
    If a(1) is not equal to 1, FILTER normalizes the filter
    coefficients by a(1). 
 
    FILTER always operates along the first non-singleton dimension,
    namely dimension 1 for column vectors and non-trivial matrices,
    and dimension 2 for row vectors.
 
    [Y,Zf] = FILTER(B,A,X,Zi) gives access to initial and final
    conditions, Zi and Zf, of the delays.  Zi is a vector of length
    MAX(LENGTH(A),LENGTH(B))-1, or an array with the leading dimension 
    of size MAX(LENGTH(A),LENGTH(B))-1 and with remaining dimensions 
    matching those of X.
 
    FILTER(B,A,X,[],DIM) or FILTER(B,A,X,Zi,DIM) operates along the
    dimension DIM.
 
    See also <a href="matlab:help filter2">filter2</a> <a href="matlab:help and">and</a>, in the <a href="matlab:help Signal">Signal</a> Processing Toolbox, <a href="matlab:help filtfilt">filtfilt</a>.

    Overloaded functions or methods (ones with the same name in other directories)
       <a href="matlab:help timeseries/filter.m">help timeseries/filter.m</a>
       <a href="matlab:help gf/filter.m">help gf/filter.m</a>
       <a href="matlab:help channel/filter.m">help channel/filter.m</a>
       <a href="matlab:help mfilt/filter.m">help mfilt/filter.m</a>
       <a href="matlab:help adaptfilt/filter.m">help adaptfilt/filter.m</a>
       <a href="matlab:help qfilt/filter.m">help qfilt/filter.m</a>
       <a href="matlab:help fints/filter.m">help fints/filter.m</a>
       <a href="matlab:help dfilt/filter.m">help dfilt/filter.m</a>

    Reference page in Help browser
       <a href="matlab:doc filter">doc filter</a>



p = audioplayer(sul, fs);
play(p)
PlotFT(sul,fs)
max(abs(sul))

ans =

    0.8560

tt=(1:length(sul))/fs;
tt=tt';
AMSig = (1+sul).*cos(2*pi*2500*tt);
p = audioplayer(AMSig, fs);
play(p)
PlotFT(AMSig,fs)
plot(tt,sul)
plot(tt,AMSig)
plot(tt,sul.*cos(2*pi*2500*tt))
plot(tt,AMSig)
absAMSig = abs(AMSig);
PlotFT(absAMSig,fs)
rsul = filter(bLP,[1],absAMSig);
p = audioplayer(rsul, fs);
play(p)
rsul = filter(bLP,[1],rsul);
PlotFT(rsul,fs)
rsul=rsul-mean(rsul);
PlotFT(rsul,fs)
p = audioplayer(rsul, fs);
play(p)
bLP=makeLowPass(101, 2000, 200, fs);
freqz(bLP)
AMSig2 = (1+sul).*cos(2*pi*6500*tt);
TwoAMSigs = AMSig+AMSig2;
PlotFT(TwoAMSigs,fs)
tone = VCO(1000,1,100,zeros(fs,1),fs);
p = audioplayer(tone, fs);
play(p)
m=sin(2*pi*10*(1:fs)/fs);
tone = VCO(1000,1,100,m,fs);
p = audioplayer(tone, fs);
play(p)
spectrogram(tone,128,64,128,fs)
tone = VCO(2000,1,1000,m,fs);
spectrogram(tone,128,64,128,fs)
p = audioplayer(tone, fs);
play(p)
FMSig = VCO(2000,1,1000,sul,fs);
spectrogram(FMSig,128,64,128,fs)
p = audioplayer(FMSig, fs);
play(p)
dFMSig = diff(FMSig);
plot(dFMSig)
rFM = EnvelopeDetector(dFMSig,bLP);
plotFT(rFM,fs)
p = audioplayer(rFM, fs);
play(p)
diary