Signal and masker uncertainty with noise maskers of varying duration, bandwidth, and center frequency.

The detectability of sinusoidal signals added to repeatable noise bursts was measured under conditions of signal-frequency uncertainty and masker-waveform uncertainty. Either source of uncertainty raised thresholds by 2-5 dB over those measured in a fixed-signal, fixed-masker condition, while the combination of both types of uncertainty raised thresholds by 8-12 dB. The magnitude of these elevations are similar to those found in a previous study, which employed maskers composed of random sets of equal-amplitude tones (Spiegel et al., J. Acoust. Soc. AM. 70, 1015-1019 (1981)]. When masker level varied by up to 40 dB between the two intervals of a forced-choice trial, and signal thresholds were elevated by only 2.5 dB. The results support a form of profile analysis in which listeners detect signals by noticing a relative change in the masker spectrum.