Pure-tone masking patterns in nonsimultaneous masking conditions

Abstract

Forward and backward masking patterns were obtained using a 70-dB SPL sinusoidal masker whose frequency was varied and a 3 000-Hz sinusoidal probe signal through an adaptive two-interval forced choice (2IFC) procedure. The temporal course of the residual excitation pattern produced in the auditory system by the masker could be represented by a set of forward masking patterns at different temporal locations after the end of the masker. The shape of the forward masking patterns was dependent upon the probe delay time and the phenomenon of the maximum masking frequency (MMF) shift was observed at relatively long delay time. Although results of forward masking are free from undesirable interaction effects between a masker and a probe, several other distorting effects are inevitable. As potential causes of these effects, the nonlinear growth of the excitation, the quality-difference cue for detection of a probe, and the off-frequency listening strategy are discussed. As for backward masking, an amount of masking was relatively small for the whole frequency range examined, and so any distinct patterns were not observed.