Neuronal Periodicity Coding and Pitch Effects

Abstract

In harmonic signals the envelope periodicity corresponds to the fundamental frequency of periodic vibrations of sound sources. Signals with the same envelope frequency (or modulation) may produce the same pitch in spite of different waveforms or frequency compositions of their sounds. Harmonic signals are characterized by a well defined periodicity and therefore have the same pitch as long as the period of their envelopes is the same (‘periodicity pitch’, Schouten, 1940, 1970). It is claimed here that periodicity pitch is analyzed in the temporal domain. It is essential that each frequency component of a harmonic sound is an integer multiple of the fundamental frequency and, consequently, each superposition of two or more adjacent frequency components has an envelope with the same frequency as the fundamental. Broadband signals are characterized by a superposition of harmonics in various frequency channels of the auditory periphery and will therefore elicit neural responses synchronized to the fundamental in these frequency channels.