Pitch perception of complex sounds: Nonlinearity revisited

The ability of the auditory system to perceive the fundamental frequency of a sound even when this frequency is removed from the stimulus is an interesting phenomenon related to the pitch of complex sounds. This capability is known as residue or virtual pitch perception and was rst reported last century in the pioneering work of Seebeck. It is residue perception that allows one to listen to music with small transistor radios, which in general have a very poor and sometimes negligible response to low frequencies. The rst attempt, due to von Helmholtz, to explain the residue as a nonlinear eect in the ear considered it to originate from dierence combination tones. However, later experiments have shown that the residue does not coincide with a combination tone. These results and the fact that the dichotically presented signals also elicited residue perception have led to nonlinear theories being gradually abandoned in favor of central processor models. In this paper we use recent results from the theory of nonlinear dynamical systems to show that physical frequencies produced by generic nonlinear oscillators acted upon by two independent periodic excitations can reproduce with great precision most of the experimental data about the residue without resorting to any kind of central processing mechanism.