Model of the "secondary" residue effect in the perception of complex tones

The phenomenon of tonal residue in stimulation of the hearing system by sinusoidally amplitude-modulated tones is examined for its correlation with the temporal fine structure displacements of the basilar membrane. It is suggested that the deviations of the residue pitch from magnitudes anticipated on account of the stimulus pattern at the input to the ear (in anharmonic complexes) represent a secondary effect only. Probably, these deviations arise from the phase modulation of the major carrier peaks of the resultant basilar-membrane displacements, evoked during passage of the stimulating signal to the cochlea. The phase modulation is due to asymmetry introduced the sideband energy of the stimulus as a result of the mechanical filtering by the inner ear. Representing a phenomenon in the time domain, the secondary residue effect is examined as a function of various compositions of the stimulating tone, at various locations along the basilar membrane. It is argued that the magnitude of the effect decreases with the harmonic-number relation between the carrier and modulation frequencies of the stimulus. Possibly, the region on the basilar membrane pertinent to characteristic frequencies lower than (but close to) the central component of the stimulating signal contributes most to determining the magnitude of the secondary effect.