1
$\begingroup$

I am using FFT to detect certain frequencies (DTMF). I can clearly see the frequencies in the spectrum. Is there a preferred / optimal way to decide if a certain frequency is present or not by looking at the spectrum?

I can think at least of:

  1. Bin absolute value (ie. bin amplitude)
  2. Difference between maximum bin and second highest
  3. Ratio between maximum bin and second highest
  4. Ratio between maximum bin and sum of all others
$\endgroup$
1
$\begingroup$

Number 4 : Comparing narrow-band energy to the energy of the total spectrum is a commonly described method of DTMF detection. This may involve using more than one FFT result bin and/or interpolation between bins.

The other methods depend on whether one has an accurate estimate of the signal level, noise floor, and how well the tone frequency is centered in a single FFT bin (related to frequency, sample rate, FFT length and window).

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.