Consonant identification in noise: Effects of temporal asynchrony, noise fluctuations, and temporal envelope expansion

Abstract

The effects of two temporal envelope expansion schemes on consonant identification performance were investigated with normal-hearing listeners. These effects were examined in the presence or absence of short-term energy fluctuations in the masker. The effects of adding a 500-ms forward fringe to the background noise was also investigated. Speech stimuli were 16 consonant–/a/ syllables. The expanded stimuli were obtained by raising their original envelope to the power k. In the first scheme, k was fixed at 2. In the second scheme, k varied from 4 to 0.3 as a function of the envelope power; the low-level parts of the envelope were therefore expanded whereas the high-level parts were compressed. As reported in many studies, identification was substantially improved by the presence of energy fluctuations in the masker. Adding the forward fringe generally degraded identification in fluctuating noise, but could improve identification in the stationary noise. Overall, expansion led to (i) poorer consonant identification when k was a constant and (ii) better consonant identification when k was varied. These effects were larger in stationary noise. This study suggests that consonant identification can be improved by a dual expansion/compression scheme. Some results obtained with hearing-impaired listeners will be presented.