Abstract:
In previous work, it was found that combinations of a long duration, broadband noise simultaneous masker and a 1000-Hz sinusoidal forward masker can produce as much as 14 dB more masking of a 1000-Hz signal than would be predicted on the basis of a linear power summation of the individual effects of the two maskers. In this study, the effects of masker and signal bandwidth and of simultaneous masker duration on this excess masking were explored. Using a 20-ms sinusoidal signal and a combination of 400-ms broadband-noise simultaneous masker and a 300-ms sinusoidal forward masker, the original effect in a new group of four subjects was replicated. When independent broadband noises served as both maskers and as the signal, and when the simultaneous masker was the same duration as the 20-ms signal, excess masking was completely eliminated. Longer duration simultaneous maskers, a sinusoidal signal, or a sinusoidal forward masker all produced excess masking to varying degrees. No existing model of the additivity of masking provides a good account of these effects. [Work supported by NIH.]