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How do I parse the FFT output (array [512])?

What do the FFT output values ​​mean?

I am using the AudioKit FFT algorithm (a framework written for Swift) and when Ifft AudioNode (microphone sound) it gives me a variable containing fft data. It is a 512-position variable (0 to 511).

When I do this it gives me small results like 0.00004231 or even 2.41233e-7, sometimes 2.41233e-12. What do these values ​​mean?

What I think:

    index 0: 0 - x Hz
          1: x - 2x Hz
          2: 2x- 3x Hz
          ::
          ::
          and so on...

    Each array has the Amplitude value of that position.

I'm right? If not, please explain to me. This will help me a lot.

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1 answer


Fourier transform maps the signal from the time domain to the frequency domain. Thus, each FFT sample measures a given frequency in the original signal.



For example, it fft[2]

indicates how strong the frequency 2 hz is in the original signal. Be aware that there may be some scaling in the array fft

returned by AudioKit , so please check the actual frequency range covered by those 512 samples.

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