Perception of lexical stress cued by low-frequency pitch and insights into speech perception in noise for cochlear implant users and normal hearing adults.

Abstract

Cochlear implant (CI) users show great difficulty for understanding speech in noise and this fact may partly stem from their poor low-frequency (LF) pitch perception and temporal fine structure (TFS) processing. Clinical assessment of pitch perception is usually based on non-speech tasks. However, linguistically relevant contexts such as lexical stress may better reflect the role of pitch in speech perception, especially for everyday speech where background noise is inevitable. Hence, the study aimed to assess perception of lexical stress cued by LF pitch and TFS cues for CI and normal hearing (NH) listeners, and to investigate relationships with speech perception in noise. The low-pass-filtered Word Stress Pattern (WSP-LPF) test was used to evaluate perception of lexical stress cued by LF pitch. Speech perception was assessed with the sentence test with adaptive randomized roving level (STARR) test which presented everyday sentences at low, medium, and high levels in a fluctuating noise to estimate a Speech Reception Threshold. This new test intended to give a realistic estimate for real-world listening. Median WSP-LPF scores in NH (N = 18) and CI listeners (N = 18) were 12.0Hz and 67.0Hz, respectively. The corresponding STARR scores were - 9.1dB and 17.3dB. Group differences were statistically significant (p < 0.001). Analysis showed significant positive correlations for NH (rs = 0.50) and CI listeners (rs = 0.60). Present findings reveal stronger correlations than previous studies using non-speech materials, supporting that CI listeners' poor speech perception in noise might be strongly associated with their inability for LF pitch perception and TFS processing.