Nonlinear Dynamics of the Perceived Pitch of Complex Sounds

The pitch of a sound is where we perceive it to lie on a musical scale. Like all sensations, pitch is a subjective quantity related to physical attributes of the stimulus, in this case mainly its component frequencies. For a pure tone with a single frequency component, the relation is monotonic and enables us to adopt an operational definition of pitch in terms of frequency: the pitch of an arbitrary sound is given by the frequency of a pure tone of the same pitch. The scientific investigation of pitch has a long history dating back to Pythagoras, but the origin of the pitch of complex tones with several frequency components is still not well understood. The first perceptual theories considered pitch to arise at a peripheral level in the auditory system [1–5]; more recently it has been thought that central nervous system processing is necessary [6–8]. However, the experimental evidence is that this processing is carried out before the primary auditory cortex [9]. The latest models integrate neural and peripheral processing [10,11]. Here we develop a nonlinear theory of pitch perception for complex tones that describes experimental results on the pitch perception of complex sounds at least as well as do current models, and that removes the need for extensive processing at higher levels of the auditory system.