Discrimination of low-frequency tones employs temporal fine structure

TL;DR

This study demonstrates that humans use temporal fine structure cues for frequency discrimination at low frequencies, with phase changes impairing discrimination performance, highlighting the importance of temporal information in auditory processing.

Contribution

It provides direct psychoacoustic evidence that temporal fine structure is utilized in human frequency discrimination, especially at low frequencies, which was previously unclear.

Findings

Phase changes impair frequency discrimination at low frequencies.

Temporal fine structure is employed in human auditory processing.

No effect of phase changes at high frequencies where temporal cues are unavailable.

Abstract

An auditory neuron can preserve the temporal fine structure of a low-frequency tone by phase-locking its response to the stimulus. Apart from sound localization, however, little is known about the role of this temporal information for signal processing in the brain. Through psychoacoustic studies we provide direct evidence that humans employ temporal fine structure to discriminate between frequencies. To this end we construct tones that are based on a single frequency but in which, through the concatenation of wavelets, the phase changes randomly every few cycles. We then test the frequency discrimination of these phase-changing tones, of control tones without phase changes, and of short tones that consist of a single wavelets. For carrier frequencies below a few kilohertz we find that phase changes systematically worsen frequency discrimination. No such effect appears for higher carrier frequencies at which temporal information is not available in the central auditory system.