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In the previous diagrams there was a stage where we effectively did detection of the envelope of the signal. |
Envelope detection can work on either the peak amplitude of the waveform or on the RMS (Root Mean Square). We're going to be looking at the peak. |
octave:1 > piano = sndfile_load ('~/IADSPL/AudioFiles/pianoe2.wav') ;
octave:2 > piano = abs (piano) ;
octave:3 > clg ; plot (piano) ; hold on
octave:4 > piano = piano (1:1000) ;
octave:5 >
octave:6 > smoothed_peak = 0 ; env = zeros (1, length (piano)) ;
octave:7 > for k = 1:length (piano),
> if (piano(k) > smoothed_peak),
> smoothed_peak = piano (k) ;
> else
> smoothed_peak = 0.999 * smoothed_peak ;
> endif
> env (k) = smoothed_peak ;
> endfor
octave:6 > hold on
octave:7 > plot (env)
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