Masking of short tone bursts of frequency sweeps

Abstract

Masked thresholds for a short probe tone are greater for sweep‐frequency tonal maskers than for stationary sinusoidal maskers at equal SPL, and greatest for sweep rates of 20–30 oct/s [G. F. Smoorenburg and F. Coninx, Hearing Res. 3, 301–316 (1980)]. The present study examined possible explanations for this surprising phenomenon and concentrated on the effects of masker level on probe threshold. Masked thresholds were obtained for a 10‐ms, 1‐kHz tone temporally centered in the 100‐ms masker. The maskers were swept in frequency at rates of 0–80 oct/s and passed through 1 kHz at 50 ms. At the lower masker levels, maximum masking occurred at sweep rates of 15–25 oct/s. At higher levels, little influence of sweep rate on masked thresholds was seen. Although there were substantial individual differences in slopes, the growth‐of‐masking functions had slopes less than one with minimum slopes at 20–25 oct/s. The shallow slopes are a distinguishing feature of sweep‐frequency masking and may provide a basis for understanding this important phenomenon. [Supported by NINCDS grant NS12125 and SSHRC‐Canada.]