Effect of Noise on the Perceptual Contribution of Cochlea-Scaled Entropy and Speech Level in Mandarin Sentence Understanding

Many studies investigated the impact of various speech segments to speech intelligibility in order to identify important information-bearing regions for the design of new speech processing methods, e.g., speech enhancement. Early findings suggested that cochlea-scaled entropy (CSE) and speech level were important indicators accounting for speech intelligibility in quiet condition. This study further compared the perceptual contributions of CSE and speech level under noisy conditions. Mandarin sentences were masked by steady-state noise and two-talker babble, edited to generate high-entropy-only and high-level-only stimuli, preserving segments with the largest CSEs and the highest levels in clean sentences respectively and replacing the rest with noise, and played to normal-hearing listeners to recognize. Results showed that high-entropy-only stimuli were more intelligible than high-level-only stimuli under noisy conditions. This intelligibility benefit may be attributed to the amount of vowel-consonant transitions, and not to differences in effective signal-to-noise ratios, between the two types of stimuli.