Calculate Frequency from sound input using FFT

Question

My app. is displaying the peak frequency of input sound in RPM .. i have array of doubles contains the samples in time domain.

audioRecord.read(buffer, 0, 1024);         


        

Answer 1

The frequency corresponding to a given FFT bin index is given by:

f = i * Fs / N;

where:

Fs = sample rate (Hz)
N = FFT size
i = bin index

So for your peak index maxIndex and FFT size blockSize the frequency of the peak will be:

f = maxIndex * Fs / blockSize;

See this answer for more details.