Monday, November 14, 2011

Find Local Peak of Signal in GNU Octave

The finding or searching the local peak is needed for some application such as fundamental frequency estimation, finding time delay or timelag or others. The following is a simple program to find the local peak of signal. The example of .wav sound signal

octave:1> [signal, fs] =wavread('signal.wav');    % read signal

octave:2> threshold=0.1;                          % limit the min. peak amplitude

octave for sig_ind = 1:4000
> if signal(sig_ind) > threshold
> x=sig_ind;
> break;
> endif
> endfor
octave:3> x
x = 3822

To give the display and find the rough peak of signal you can see from the figures of signal. The picture below comparing whole signal and the local signal from 1 to 4000 samples. To find the coordinate of local peak, just simply type

[a b]=max(signal(1:4000)

Full length signal and signal from 1 to 4000 samples

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