Real-time implementation of a polyphonic pitch perception model

Abstract

This algorithm is a real-time implementation of a polyphonic pitch perception model previously described in Braasch et al. [POMA 19, 015027 (2013)]. The model simulates the rate code for pitch detection by taking advantage of phase locking techniques. Complex input tones are processed through a filter bank, and the output of each filter is run through its own separate autocorrelation following the Licklider model. After conversion to polar form, analysis is done on the phase output of the autocorrelation, where the algorithm computes the time delay between localized peaks. This gives the fundamental period of the tone within a given filter; these values are then normalized by the magnitude output of the autocorrelation and combined with output data from the other filters to give full spectral information. The algorithm uses an adjustable running frame window to trade off between frequency resolution and rapid changes in pitch. The model can accurately extract missing or implied fundamental frequencies.