Hi guys, I have an audiowave file, I have gotten the time domain and the fft graph. My question what is the next step to find the frequency from the fft graph? Thanks.
MATLAB: How do find the frequency from a FFT graph
audioread noise audio sound
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Qusay - let us assume the following concerning your signal, sampling rate (Fs), and FFT block size (N)
Fs = 4096; % sampling rate in Hertz
t = linspace(0,1-1/Fs,Fs); % one second time vector given Fs
N = 4096; % FFT block size is same as sampling rate (true for your ex)
signal = 2.3*sin(2*pi*t*227); % signal with amplitude of 2.3 and frequency of 227 Hertz
Now for your code
% transforms the signal from the time domain to the frequency domain with fft
% note that y is complex
Y = fft(signal); % shifts the frequency components so that the zero frequency is at the centre
% of spectrum
Y = fftshift(Y); % determines the magnitude of the complex data
Y = abs(Y);The following lines of code just sets the frequencies for each bin and can be reduced to
f = [0:N-1] * Fs/N; % must ensure that zero is the centre frequency due to our fftshift from above
f = f - ceil(N/2); % plot the data
plot(f,Y);The result of the plot is
Note the frequency at 227 Hz, as expected. The symmetry is due to the input signal being real.
I found the solution, I didn't post the frequency of sampling. But apparently fftshift just swaps X axis and then if there were no 0 between samples they get joined. So I had to add zeroes to the fft result in order for the fftshift to work properly, this is by extending the sampled rate of the original function. (Making sampling frequency higher extends repeating time in frequency domain vice versa making sampled range larger adds samples to the frequency domain in between the existing samples.)
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