Representation of Spectral Profiles in the Auditory System. Part 1. Detection of Spectral Peak Shapes and Ripple Phases.

摘要

This paper explores the question of how spectral profiles are represented in the auditory system. Using profile analysis methods, listeners' sensitivities to changes in spectral peak shapes and ripple phases were measured. Peak shapes were uniquely described in terms of two parameters: a symmetry factor (SF) which roughly measures the local evenness or oddness of a peak, and a bandwidth factor (BWF) which reflects the tuning or sharpness of a peak. Thresholds to changes in these parameters (defined as delta-SF and delta- BWF/BWF) were measured together with the effects of several manipulations such as using different peak levels, varying spectral component densities, and randomizing the frequencies of the peaks. The basic result that emerges is that delta-SF and delta-BWF/BWF thresholds are largely constant regardless of the standard's peak shape. The only exception occurs for the narrowest peaks (smallest BWF's) where delta-SF thresholds rise. A fundamental conclusion arising from these data is that peak profiles are represented along two sensitive and largely independent axes: peak bandwidth and symmetry factors. More generally, it is conjectured that for an arbitrary spectral profile these two axes correspond to the magnitude and phase of a Fourier transformation of the profile. In this light, the last set of experiments measured listeners' sensitivity to ripple phase changes in sinusoidal ripple stimuli. The thresholds obtained are similar in value and trends to delta-SF thresholds.