Find the frequency in Hz using FMOD [duplicate]

Question

I am trying to find the frequency in hertz for every bin in the fft spectrum. Below is my code just adding the fft spectrum values inside a float list.

for (int len = 0; len < nyquistLength; ++len)
    {
        for (int channel = 0; channel < numChannels; ++channel)
        {
            channs += dspFFT.spectrum[channel][len];
            if (channel == numChannels - 1)
            {
                spectrum.Add(Math.Abs(Mathf.Log10(channs)));
                Debug.Log(spectrum[len]);
                channs = 0;
            }
        }
    }

How can I use this information to obtain the Hz of each entry in the spectrum? Thanks.

You need to know the sample rate in Hz as well as the FFT length in order to know the center frequency of each FFT filter bin in Hz. — hotpaw2
– hotpaw2, Commented Aug 12, 2018 at 20:30
@hotpaw2 So my sample rate is 44100 and my window length is 2048. I have tried to find the bin Hz before by doing something like this: (channs/_windowLength) * (44100/2) but the results I got where barely above zero. — Leonidas Antoniou
– Leonidas Antoniou, Commented Aug 12, 2018 at 20:59

Paul R · Accepted Answer · 2018-08-13 07:57:12Z

1

A N-point FFT of a signal with a sample rate of 44100 produces frequency bins with center frequencies spaced 44100/N apart from 0 Hz to 44100 Hz. From 0 to the Nyquist frequency of 22050 Hz, there are N/2+1 points inclusive. So if you want the center frequencies then compute i*44100/N where i=0,1,...,N/2.

edited Aug 13, 2018 at 7:57

Paul R

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answered Aug 13, 2018 at 5:20

sdbol

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2 Comments

Leonidas Antoniou Over a year ago

So the frequency calculated will correspond to the bin given out by the spectrum. Should I do this calculation for each window (hann)? etc. my window is of type hann and the length is 2048

sdbol Over a year ago

It’s irrespective of the type of window (e.g. hanning, hamming)

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