Effects of Attenuation of One of Two Channels on Perception of Opposing Pairs of Nonsense Syllables When Monotically and Dichotically Presented

Abstract

A two-channel listening experiment was carried out in which subjects had to identify each member of pairs of nonsense syllables which coincided in time of onset and offset. The purpose of the experiment was to compare the effect of varying the intensity of the stimuli in one channel when stimuli pairs were presented dichotically (one to each ear) with the effect that occurred when both stimuli were directed monotically to a single ear. We could thus compare the effect of attenuation of one of the two competing speech signals when the competition involved peripheral masking (the monotic condition) with the effect obtained when the locus of masking was exclusively central (the dichotic condition). In the monotic case, the decrement in identification performance was nearly asymptotic with 10 dB of attenuation, whereas in the dichotic case the decrement in performance with attenuation was much less steep, not having reached asymptote at 25 dB of attenuation. These results agree with findings in visual masking studies with respect to the relatively greater importance of intensity difference among stimuli in peripheral masking than in central masking. [This research was supported in part by NSF Grant No. GJ-9.]