REDUCING INFORMATIONAL MASKING BY SOUND SEGREGATION

Informational masking was reduced using three stimulus presentation schemes that were intended to perceptually segregate the signal from the masker. The maskers were sets of sinusoids chosen randomly in frequency and intensity on each stimulus interval or, in some conditions, on every masker burst in a series of bursts within intervals. Masker components were excluded from the frequency region surrounding the 1000-Hz signal to minimize the energetic masking. Masked thresholds as great as 60-70 dB above quiet threshold were observed for some subjects in some conditions. It was shown that this informational masking could be reduced as much as 40 dB by: (1) presenting the masker to both ears and signal to one ear; (2) playing different masker samples sequentially in each interval of every trial; or (3) presenting the signal in alternate bursts of multiple, identical masker samples. For the binaural manipulation, informational masking was reduced because the masker and signal were perceived as originating from different interaural locations. In the latter two manipulations, a difference in the spectral or temporal pattern of the signal and masker provided the detection cue. These effects were interpreted as evidence of the importance of perceptual segregation of sounds in noisy listening environments where signal reception is not limited by energetic masking.