Pitch detection with computeSpectrum() return FFT values

Question

• I\'m developing using Actionscript 3.0 for Flash Player 10.3
• I\'m using computeSpectrum() on a loaded .mp3
• Running *Event.ENTER_FRAM

Answer 1

You can use the Harmonic Product Spectrum method to estimate the distance (frequency difference) between overtone peaks in a frequency spectrum (FFT results), even if some peaks are missing, as long as there are not too many spurious frequency peaks (noise).

To do a Harmonic Product Spectrum, print the FFT out on semi-transparent paper and roll it up into a cylinder (or do the equivalent in software). Wrap the cylinder tighter and tighter until the greatest amount of peaks overlap. The circumference will be a good estimate of the pitch. This works for any musical sounds that have lots of harmonics, even if a fundamental pitch frequency peak is missing or weak.