ASA 124th Meeting New Orleans 1992 October

3aPP13. Masker duration effects frequency resolution in simultaneous and nonsimultaneous masking.

Beverly A. Wright

Psychoacoust. Lab., Psychol. Dept., Univ. of Florida, Gainesville, FL 32611

Frequency resolution was estimated as a function of masker duration in four masking conditions for three subjects. The signal was a 4-ms, 1000-Hz tone. The wideband masker (33-dB spectrum level) had a spectral notch of variable width centered on the signal. Masker duration was 6 (only in simultaneous masking), 62, or 412 ms. Rise/decay time was 2 ms for all stimuli. In two simultaneous-masking conditions, signal offset came 1 ms before masker offset (forward-fringe) or signal onset came 1 ms after masker onset (backward-fringe). In two nonsimultaneous-masking conditions, signal onset came immediately after masker offset (forward masking) or signal offset came immediately before masker onset (backward masking). In all conditions, threshold decreased as the width of the masker notch increased. However, the rate of the threshold decrease tended to increase with masker duration. Further, the threshold decrease was more marked in the two ``forward'' than in the two ``backward'' conditions. These data indicate that measured frequency resolution may dynamically change due to prior, or even subsequent, stimulation. [Work supported by the NIDCD.]