DETECTABILITY OF SIMULTANEOUSLY MASKED SIGNALS AS A FUNCTION OF MASKER BANDWIDTH AND CONFIGURATION FOR DIFFERENT SIGNAL DELAYS

Signal detectability was measured in three temporal conditions as a fu nction of the bandwidth and configuration of simultaneous maskers that either did or did not spectrally overlap the signal. The 20-ms signal was 250 Hz wide and was centered at 2500 Hz (f(s)). Although there we re marked individual differences, performance was typically poorer whe n signal onset came 1 ms rather than 250 ms after the onset of a 420-m s masker, and poorest when signal onset came 1 ms after the onset of a 23-ms masker. The results support the idea that two separate across-c hannel processes contribute to temporal changes in signal detectabilit y. One process contributes to the improvement observed as signal onset is delayed from masker onset, and its influence is reduced by the pre sence of masking components at f(s) only when the masker extends exclu sively below f(s). The other process is associated with the improvemen t observed as masker offset is delayed from signal offset, and its inf luence is reduced by the presence of masking components at f(s) when t he masker extends exclusively above, or both below and above f(s). Bot h of these processes are primarily activated by frequencies ranging fr om 0.6 to 0.8f(s) and 1.2 to 1.4f(s). The data also demonstrate that t he measured critical bandwidth narrows as signal onset is delayed from masker onset. (C) 1997 Acoustical Society of America.