Comparing two audio signals (guitar chords recognizer)

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Phantom.i7
Phantom.i7 2014-3-4
回答： KIRAN SL 2017-6-16
I want to compare two audio signals and check their similarities however it seems i cannot compare them.. this is supposedly my process.
  • > input audio signal (1 strum on guitar)
  • > read the data and convert to frequency domain
  • > get the raw audio file > read > convert to frequency domain
  • > check their similarities
function guitartrial
recObj = audiorecorder;
disp('Start speaking.')
recordblocking(recObj, 4);
disp('End of Recording.');
myRecording = getaudiodata(recObj);
wavwrite(myRecording,'chordread.wav');
[x, Fs] = wavread('chordread.wav');
[x1, Fs1] = wavread('chordA.wav');
Y = fft(abs(x));
Z = fft(abs(x1));
subplot(3,1,1), plot (Y);
subplot(3,1,2), plot (Z);
[C1, lag1] = xcorr(Y,Z);
subplot(3,1,3), plot(lag1/Fs,C1);
ylabel('Amplitude'); grid on
title('Cross-correlation between Template 1 and Signal')
end
whenever i run the program i get this..
It seems wrong to me.. Im new in matlab programming so If someone can help me I would be very grateful. Is my process wrong? how can I get the percentage of similarity? is there another method that is best suited for my application? thank you very much

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回答（2 个）

Suneesh
Suneesh 2014-3-4
If your confusion is regarding the first and second plots then that is because yo uare plotting the complex values returned by FFT. Try:
subplot(3,1,1), plot(abs(Y));
subplot(3,1,2), plot(abs(Z));
Also, in
Y = fft(abs(x));
The abs(x) is not required since audio signals are real signals.
  2 个评论
Phantom.i7
Phantom.i7 2014-3-5
[C1, lag1] = xcorr(Y,Z);
is that correct or should i make it
[C1, lag1] = xcorr(abs(Y),abs(Z));
Suneesh
Suneesh 2014-3-11
If you need to look for similarities in the magnitude of the two FFT results then
[C1, lag1] = xcorr(abs(Y),abs(Z));
is correct. This does not consider the phases which is lost by the ABS operation. Also, if the samples are of different lengths then make sure both are normalized.

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KIRAN SL
KIRAN SL 2017-6-16
what is the correlation plot means?

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