Pitch detection algorithm

A pitch detection algorithm (PDA) is an algorithm designed to estimate the pitch or fundamental frequency of a quasiperiodic or virtually periodic signal, usually digital recording of speech or a musical note or tone. This can be done in the time domain or the frequency domain.

Related Topics:
Algorithm - Pitch - Fundamental frequency - Quasiperiodic - Periodic - Digital recording - Speech - Time domain - Frequency domain

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

In the time domain, a PDA first estimates the period of the quasiperiodic signal and computes the fundamental frequency to be the reciprocal of the period. A simple approach would be to measure the distance between zero crossing points of the signal. However, this does not work well with complex waveforms which are composed of multiple sine waves with differing periods. A better way is to compare parts of the signal with other parts of it to find a match. AMDF (Average Magnitude Difference Function), ASDF (Average Squared Difference Function), or the similar autocorrelation work this way. These algorithms can give quite accurate results for highly periodic signals, however they have false detection problems (often "octave errors") and are less tolerant of noisy signals. Also, they don't work with polyphonic sounds (which involve more than one pitch).

Related Topics:
Zero crossing - Waveforms - Average Magnitude Difference Function - Autocorrelation - Polyphonic

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

In the frequency domain, polyphonic detection is possible, usually utilizing the Fast Fourier Transformation (FFT) to convert sound to frequency spectrum, however this requires more processing power as the desired accuracy increases.

Related Topics:
Fast Fourier Transformation - Frequency spectrum

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Popular frequency domain algorithms include HPS (Harmonic Product Spectrum algorithm), Cepstrum analysis (used often to deconvolute speech or vibration waveforms) and Maximum Likelihood which attempts to match the frequency domain characteristics to pre defined frequency maps (useful for detecting pitch of fixed tuning instruments).

Related Topics:
Harmonic Product Spectrum algorithm - Cepstrum

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Time domain algorithms also include the YIN algorithm amongst others.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~