Estimating the phase characteristic of the auditory system from masking by harmonic complexes

Abstract

As shown by several recent studies of positive and negative ‘‘Schroeder-phase’’ stimuli, masking by harmonic complexes is strongly affected by the temporal waveform of the masker [e.g., V. Summers and M. Leek, Hearing Res. 118, 139–150 (1998)]. Differences in masking by the Schroeder waves provide a starting point for estimating the phase response of the auditory system. In this study, the gradient of phase change across masker bandwidth was varied by altering the Schroeder-phase algorithm. Depending on signal frequency (ranging from 500 to 4000 Hz), differences in masking could be 5–10 dB for phase gradients changing by only 10%. The phase gradient that resulted in a minimum amount of masking varied systematically with signal frequency, with low frequencies masked least effectively by waveforms with rapidly changing component phases, and high frequencies by waveforms with more shallow phase gradients. This relationship between phase gradient and signal frequency is taken to reflect the phase response of the auditory filter at that frequency. The phase gradients associated with minimal masking at each frequency can be used to construct a piecewise-estimate of the phase characteristic of the auditory system for individual listeners. [Work supported by NIH DC00626.]