Direct Comparison of Lateralization and the MLD for Monaural Signals in Gated Noise

Abstract

Lateralization models of the masking-level difference (MLD) argue that detection under such conditions is of a lateral shift in the perceived acoustic image. We examined that assertion by presenting monaural 500-Hz signals in diotic noise (N0SM) and asking listeners to indicate the lateral position of the resulting auditory image. On randomly chosen trials, we presented a diotic signal in diotic noise (N0S0). Responses to these were assumed to represent perceived “center” and served as the standards against which the responses to N0SM were compared. Signal levels under N0SM and N0S0 were equally detectable as determined in a separate task. Both signals and noise were gated for a duration of 100 msec. As predicted from the model, the lateral scatter under N0SM was sufficient to account for the detection of those signals in an ordinary detection task. We did not find the loss in detection usually associated with gated noise; we attribute this to the fact that subjects had only to lateralize the signal-plus-noise, not to compare it to a remembered “center” or to judge the extent of the lateral shift.