INFORMATIONAL MASKING FOR MULTICOMPONENT MASKERS WITH SPECTRAL GAPS

Simultaneous maskers comprised of a few random-frequency sinusoids can produce considerable informational (uncertainty-based) masking if the component frequencies are drawn from a wide range and changed with ea ch stimulus presentation. The present experiments examined the effect on informational masking of removing masker energy from large frequenc y regions around the signal. Threshold for a 1000-Hz signal was measur ed in the presence of maskers comprised of 2, 4, 6, 10, 50, or 100 ran dom-frequency sinusoids, notched-noise, or two fixed-frequency sinusoi ds. The multicomponent maskers had a maximum frequency range of 300-30 00 Hz, typically excluding a 160-Hz band around the signal. In compari son conditions, masker frequencies were limited to the high or low sid e of the signal, or the gap around the signal was progressively widene d. Four listeners showed substantial informational masking which was n ot eliminated even by extreme spectral gaps in the maskers. Four other listeners showed much smaller effects of masker uncertainty across al l conditions. Notched-noise measures of auditory-filter width did not distinguish the two subject groups, but indices of processing efficien cy were typically poorer for the high-threshold listeners, as were mea sures of both the width and processing efficiency of presumed ''attent ional filters'' under conditions of masker-frequency uncertainty.