MATLAB: How to divide a signal into groups of peaks

dividegroupsMATLABpeakssavitzky-golay filtersgolayfiltsignalSignal Processing Toolbox

Hi, i have an audio sample , which im trying to divide into groups of signals , for energy and time analysis . here is the signal :
what i'm trying to do is, to get the start and the end indexes of this 4 chunks. right now i dont have a clue how to get this done . Thank you

Best Answer

This is likely the most difficult signal you’ve presented. Probably the best way to produce a derived signal that would allow you to isolate the parts of your signal of interest is to use a bandpass filter and then a Savitzky-Golay filter.
The code:
cs = load('cob signal.mat');
S1  = cs.coarse_d(:,1);
S2  = cs.coarse_d(:,2);
Fs = cs.fs_d;
Fn = Fs/2;
Ts = 1/Fs;
T  = [0:length(S1)-1]*Ts;
Wp = [950 1000]/Fn;
Ws = [0.5 1/0.5].*Wp;
Rp =  1;
Rs = 30;
[n,Wn] = buttord(Wp, Ws, Rp, Rs);
[b, a] = butter(n, Wn);
[sos, g] = tf2sos(b, a);
S1F = filtfilt(sos, g, S1);
SGS1 = sgolayfilt(abs(S1F), 1, 901);
figure(1)
plot(T, S1)
hold on
% plot(T, S1F)
plot(T, SGS1, 'LineWidth',1.3)
hold off
grid
% axis([0.5  1.5    ylim])
The first ‘burst’ of the original signal (with the Savitzky-Golay filter of the bandpass filtered signal superimposed) is:
You could simply threshold the sgolayfilt output, or use findpeaks to determine the locations of each ‘burst’. I didn’t comment-document the code, because it’s similar to my previous filter designs (documented), the only novelty being the addition of sgolayfilt.
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