A Comparative View on the Perception of Mistuning: Constraints of the Auditory Periphery

Abstract

Harmonicity serves to group together frequencies from a single source to a perceived auditory object. The peripheral auditory system may exploit either spectral cues resulting in a specific spatial pattern of excitation or temporal cues that are due to the interaction of frequency components in the complex to evaluate whether a component does not belong to a harmonic complex, i.e., is mistuned. Which cues are useful for mistuning detection may depend on the anatomical and physiological constraints in the peripheral auditory system. Here we compare the perception of frequency shifts in harmonic complexes (i.e., mistuning) and in pure tones across species. Mongolian gerbils and birds are superior to humans in detecting small amounts of mistuning in sine phase harmonic complexes. This difference is reduced in the detection of mistuning in random phase harmonic complexes (but not in harmonic complexes with “frozen random phase”). Humans are superior to birds and gerbils in detecting pure-tone frequency shifts. The results suggest that species with a short cochlea and only few hair cells per critical band tend to rely more on temporal fine structure in the analysis of mistuning of components in harmonic complexes whereas excitation patterns may play a larger role in humans with a much longer cochlea. For the analysis of pure-tone frequency shifts, excitation patterns appear to play a more prominent role in all species. Exemplary neurophysiological data obtained in starlings support this view.