MATLAB: Should I shift the fft function

audioreadfftshiftfft

Good afternoon,
I'm trying to take the fourier transform of a recorded file. Do i need to apply the function shiftfft to the signal? If so, how do I plot the signal correctly and how do I read the graph?
%Read Voice
[y,fs] = audioread('Testing.m4a');
fourier_shift = abs(fftshift(fft(y)));
plot(fourier_shift)

Best Answer

It depends on the result you want. The shifted version plots the negative and positve frequencies (the Fourier transform is symmetric). The unshifted version (plotting only half of the result) is generally more informative.
The two options: 
%Read Voice
[y,fs] = audioread('Testing.m4a');
L = size(y,1);
fourier_shift = abs(fftshift(fft(y)/L));
Fn = fs/2;
freqvct = linspace(-Fn, Fn, L);
figure
plot(frqvct,  fourier_shift*2)                          % Two-Sided, With Frequency Vector
grid
fourier = abs(fft(y)/L);
Fv = linspace(0, 1, fix(L/2)+1)*Fn;
Iv = 1:numel (Fv);
figure
plot(Fv, fourier(Iv)*2)                                 % One-Sided, With Frequency Vector
grid
Choose the option you want.
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