# taking FFT from a part of the signal

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Negar on 21 Sep 2013
Hello all, I have a sound signal in time domain , How can I take the FFT of a excerpt of it, say a 40ms section from 0.026sec to 0.3sec? Ive just been able to plot that segment in time domain, but I can not figure out how to plot its spectrum.. Here is my code, I hope someone can make it done.. Cheers,
clear all
close all
clc
figure
tSampling=1/Fs;
n=length(signal);
t=(0:n-1)*tSampling; %Making the time vector
plot(t,signal); % Plot
sound(signal,Fs); % Listen
%%2)Plot a 40ms section in the middle of the vowel /iy/
figure
plot(t,signal)
axis([0.3 0.34 -0.2 0.2]);
%%Taking FFT
signalF=fft(signal(0.03:0.34),1024);
fAxis=-Fs/2:Fs/1024:Fs/2-Fs/1024; %Making the frequency vector
plot(fAxis,abs(signalF));
title('Spectrum of signal(t)');
xlabel('Frequency (Hz)');
ylabel('|signal(f)|');

Matt J on 21 Sep 2013
Edited: Matt J on 21 Sep 2013
You mean you want to do a Short Time Fourier Transform (STFT)? If so, there are a number of offerings on the File Exchange, e.g.
##### 3 CommentsShow 1 older commentHide 1 older comment
Matt J on 21 Sep 2013
signal(t>=300 & t<=340)
Negar on 22 Sep 2013
Thank you Matt J :)