Masking period patterns of harmonic complex tones

Abstract

Masking period patterns, i.e., the SPL [sound pressure level] of just audible triggered sequences of short high frequency test tone bursts as a function of their temporal spacing throughout the period of a masker, were measured [in human subjects] using the following maskers: low-frequency 2-tone and 3-tone complexes, Gaussian-shaped impulses and differentiated Gaussian impulses with both condensation and rarefaction peaks. The similarity between masking period patterns and neurophysiologically measured period histograms was confirmed with respect to the temporal structure. Distinct differences appeared in the amplitude structure of both patterns, indicating a strong nonlinearity involved in the transformation of the masker''s time function into the masking period pattern. Starting a few decibels above thresholds in quiet, the peaks of the patterns were elevated by 10 dB for each 5-dB increment of masker level. This suggests a square law for high frequency test signals and low-frequency maskers. The steepness of slope of the masking period pattern seemed to reach a maximal value of 10 dB/ms. Relations between neurophysiological period histograms and corresponding masking period patterns and differences between the patterns produced by condensation and rarefaction peak maskers, respectively, were discussed.