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I am new to signal processing, so I did a fourier transform on a frame of 200 samples with NFFT = 512 and then I took the absolute value :

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I am trying to understand these values on the output, are these frequencies ? I tried to plot them, here is the result :

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Does it mean that my frame contains 60khz frequencies, I am a little confused about this output.

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The frequencies at FFT output are relative to the input sampling rate fs and the FFT size N. The $k^{th}$ index corresponds to a frequency $k*fs/ N$. Pay attention that values above $N/2$ correspond to negative frequencies

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