CODEWITHSUNDEEP
c#.netfftnaudio
Alexander Mashin
Alexander Mashin

Reputation: 711

FFT frequency of sound

On microphone at some time, starts flowing sound defined frequency(500hz). How do I know when the signal began to come to the microphone? To solve this problem, I know that I need to use FFT(Fast Fourier transform). But I dont understand, how should I take after FFT frequency? I'm use NAudio on C#. And my buffer from microphone is byte array.

Upvotes: 1

Views: 1418

Answers (3)

hotpaw2
hotpaw2

Reputation: 70743

A narrow IIR bandpass filter followed by an envelope detector might be one possible method to try. Another thing to try might be cross-correlation against a matched filter, if you know the rise time of your tone burst. You will have to calibrate out the latency of your audio input signal path as well.

Upvotes: 1

Paul R
Paul R

Reputation: 213220

Using an FFT for this is overkill and not particularly appropriate. A much simpler solution for this kind of problem (tone detection/onset detection) is the Goertzel filter.

Upvotes: 2

Fredrik
Fredrik

Reputation: 2317

Determining WHEN a signal is sampled into a buffer is a programatical problem.

That has nothing to do with determining WHAT the frequency content of the sampled signal is (using the FFT). See my reply for your other question...

Upvotes: 1

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