Interdependent processing of speech and background noise

Abstract

Speech processing can often take place in listening conditions that involve the mixing of speech and background noise. This study used a speeded classification paradigm to investigate whether background noise is perceptually integrated with indexical (Exp. 1) and phonetic (Exp. 2) dimensions of the speech signal. In each experiment, English listeners classified words along one of two dimensions: noise (pure tone vs. white noise) or a speech dimension, either gender (male vs. female in Exp. 1a), talker identity (Sue vs. Carol in Exp. 1b), or phoneme (/p/ vs. /b/ in Exp. 2), while ignoring the other dimension, which could be held constant (control), co-vary (correlated), or vary randomly (orthogonal). The results indicated that background noise was not completely segregated from speech, even when the two auditory streams were spectrally non-overlapping. Perceptual interference was asymmetric, whereby irrelevant indexical and phonetic variation slowed noise classification to a greater extent than the reverse. This suggests that while context-specific information (e.g., noise) and within-signal speech features are coupled together, they are unevenly weighted during this early stage in processing. This asymmetry may stem from the fact that speech features have greater salience and are thus more difficult to selectively ignore than environmental noise.