MATLAB: Hi, i would like make script how use two threshold Lower & upper to filtre the peaks of a periodic signal in frequency domain. Thx

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Use the findpeaks function once each with a different threshold in each funciton call (the 'MinPeakValue' name-value pair argument), and then use the setdiff function on the second output, locs, to find the peaks between the lower and upper thresholds.

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MATLAB: How to filtre an audio signal with low-pass filtre

I cannot access your dropbox file. It would be much easier for us for you to use the ‘paperclip’ icon and upload it here instead.

Even in the absence of your file, it is easy to design your filter. Human voice frequencies are in the range of about 100 Hz to 6000 Hz, so a Chebyshev Type II filter to pass voice frequencies would be:

Fs = 44100;                                             % Sampling Frequency (Change If Different)
Fn = Fs/2;                                              % Nyquist Frequency
Wp = [150  5800]/Fn;                                    % Normalised Passband
Ws = [ 50  6100]/Fn;                                    % Normalised Stopband
Rp =  1;                                                % Passband Ripple (dB)
Rs = 30;                                                % Stopband Ripple (dB)
[n,Ws] = cheb2ord(Wp,Ws,Rp,Rs);                         % Chebyshev Type II Order
[b,a] = cheby2(n,Rs,Ws);                                % IIR Filter Coefficients
[SOS,G] = tf2sos(b,a);                                  % Convert To Second-Order-Section For Stability
figure(1)
freqz(SOS, 4096, Fs)                                    % Check Filter Performance
filt_sig = filtfilt(SOS,G, Your_Signal);

Change the appropriate passband and stopband frequencies depending on the frequency content of your signal.

MATLAB: Exclude zero from domain.

x=-1:0.1:1;
y=-1:0.1:1;
x=nonzeros(x);
y=nonzeros(y)
%y = y(y~=0);
dx=0.1;
[X,Y]=meshgrid(x,y);
u = 1./(X.^2);
v = 1./(Y.^2);
quiver(X,Y,u,v);
axis equal

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MATLAB: How to filtre an audio signal with low-pass filtre

MATLAB: Exclude zero from domain.

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