Changes in the Simultaneous Masked Threshold of Brief Tones

Abstract

Simultaneous monotic masking of a 5- or 10-msec, 1000-cps signal by bursts of wide-band noise of 30-1000 msec. duration (70 dB SPL) changes and is dependent upon delay of the tone ([DELTA]t) relative to masker onset. The elevated masking of the tone at short [DELTA]t''s (overshoot) is independent of masker duration, while minimum masking occurs at delay times of 200 or 300 msec. A 500-msec-long, 400-cps noise band centered at 2550 cps produced little overshoot for 10-msec. tonal signals with frequencies located within the band but considerable overshoot for frequencies just outside it. This occurs also for a 200-cps band centered at 1270 cps, but not for a 100-cps band at 250 cps. These effects were observed for dichotic masking also. For 500-msec. bursts of wide-band masking noise, greater overshoot occurs at higher signal frequencies than at lower.