An original paradigm to investigate pure informational masking using complex tones

Abstract

Most usual speech masking situations induce both energetic and informational masking. Energetic masking (E.M.) arises because both signal and maskers contain energy in the same critical bands. Informational masking (I.M.) prevents the listeners from disentangling acoustical streams even when they are well separated in frequency, and is thought to reflect central mechanisms. In order to quantify I.M. without E.M. contamination in complex auditory situations, target and maskers can by presented dichotically. However, this manipulation provides the listeners with important lateralization cues, which dramatically reduces I.M. Therefore, the current study aimed at restoring a fair amount of I.M. using complex tones in a new dichotic paradigm. Regularly repeating signals and random-frequency multitone maskers were presented dichotically, but switched from one ear to the other within a 10s sequence. Switches could either appear at a slow or rapid rate. We compared listeners’ detection performance in these switching situations to that elicited in traditional diotic and dichotic situations. Results showed that the amount of I.M. induced when signal and maskers were rapidly switching throughout a sequence was significantly higher than in classical dichotic situations, and appeared to be comparable to the diotic listening situation. Therefore, this paradigm provides an original tool to evaluate auditory perception in situations of pure I.M. using complex tones.