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Possible Duplicate:
How to get Frequency from FFT result

I have one problem. I need to know at which frequencies the signal passes normally. To solve this problem, I am applying to the microphone sound of a particular frequency(for example 1000Hz), and buffer from microphone, and above buffer spend DFT(AForge.Math.FourierTransform.DFT). Sampling frequency = 20480Hz. On exit I have complex(AForge.Math.Complex) array with 2048 elements. What I need to do to find the volume level at a given frequency? If I have the wrong approach, tell me the right one.

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Alexander Mashin
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    Can you post some of the code you have used? – Msonic Oct 30 '12 at 19:55
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    Not a dup: This question asks for volume level, not peak frequency. Some intermediate calculations may be the same, but not the desired end result. The answer here may involve proper magnitude scaling factors. – hotpaw2 Oct 30 '12 at 22:11
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    In what kind of units do you need the volume level? Is the mic calibrated in some way? – hotpaw2 Oct 30 '12 at 22:14
  • I need to know borders of signal, which passes. In my opinion to doing this, I need to verify volume level of passing signal. Since this is the more noise, the lower the volume of the necessary signal. – Alexander Mashin Oct 31 '12 at 08:22

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