Created
May 17, 2018 01:04
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Loads an audio file and plots its waveform and FFT
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| ## Adapted from https://www.mathworks.com/help/matlab/ref/fft.html | |
| function retval = fftandplot (filename, tStart, tEnd) | |
| Fs = audioinfo(filename).SampleRate; | |
| X = audioread(filename); | |
| # Convert to mono | |
| X = X(:,1); | |
| # Convert times to sample indexes | |
| iStart = round(tStart*Fs); | |
| iEnd = round(tEnd*Fs); | |
| timeDomain = [max(iStart,1):iEnd]; | |
| L = length(timeDomain); | |
| # TODO does the duration have to be even? | |
| # Show original audio | |
| figure; | |
| plot(timeDomain, X(timeDomain)) | |
| title('Original audio signal') | |
| xlabel('t (samples)') | |
| ylabel('X(t)') | |
| # Compute fft | |
| Y = fft(X); | |
| P2 = abs(Y/L); | |
| P1 = P2(1:L/2+1); | |
| P1(2:end-1) = 2*P1(2:end-1); | |
| # Show fft | |
| f = Fs*(0:(L/2))/L; | |
| figure; | |
| plot(f, P1) | |
| title('DFT of audio') | |
| xlabel('f (Hz)') | |
| ylabel('amplitude?') | |
| # Find max freq component | |
| [xMax, iMax] = max(P1); | |
| printf("Freq with highest amplitude is %d Hz\n", f(iMax)) | |
| endfunction |
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