Level discrimination in roving-level, notched-noise maskers as a function of masker bandwidth and rove range

Abstract

This experiment examines how level discrimination (also called intensity discrimination) of a three-tone complex depends on the bandwidth and rove range of a notched-noise masker. Previous experiments used fixed-level maskers, which may provide profile-discrimination cues. In the present experiment, a roving masker obviated profile cues. Level discrimination thresholds, ΔL’s (=20 log[(p+Δp)/p], where p is pressure), were measured in four listeners. The equality intense signal components at 0.84, 1, and 1.17 kHz were set to 25, 55, or 85 dB SPL. The two masker bands extended 1 or 7 critical bands below 0.77 kHz and above 1.27 kHz. Results show that ΔL’s increase somewhat as the rove range increases from 0 to 20 dB, but for rove ranges less than 10 dB, the increase is small. Contrary to predictions based on profile discrimination, ΔL’s at 60 and, especially, 90 dB SPL tend to be larger with 7-than with 1-Bark-wide masking bands. At 30 dB SPL there is almost no effect of masker bandwidth. These results indicate that profile cues probably did not affect appreciably previous measurements of level discrimination in notched-noise maskers. [Work supported by NIDCD.]