Acoustic change complex in background noise: phoneme level and timing effects. Issue 20 (19th October 2017)

• Record Type: Journal Article
• Authors: Billings, Curtis J.; Grush, Leslie D.; Maamor, Nashrah
• Is Part Of: Physiological reports. Volume 5:Issue 20(2017)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2017-10-19
• Subjects: Acoustic change complex -- cortical auditory evoked potentials -- neural refractory period -- signal‐to‐noise ratio -- speech stimuli; Physiology -- Periodicals; 571
• DOI: 10.14814/phy2.13464
• Languages: English
• ISSNs: 2051-817X

Abstract

Abstract: The effects of background noise on speech‐evoked cortical auditory evoked potentials (CAEPs) can provide insight into the physiology of the auditory system. The purpose of this study was to determine background noise effects on neural coding of different phonemes within a syllable. CAEPs were recorded from 15 young normal‐hearing adults in response to speech signals /s/, /ɑ/, and /sɑ/. Signals were presented at varying signal‐to‐noise ratios (SNRs). The effects of SNR and context (in isolation or within syllable) were analyzed for both phonemes. For all three stimuli, latencies generally decreased and amplitudes generally increased as SNR improved, and context effects were not present; however, the amplitude of the /ɑ/ response was the exception, showing no SNR effect and a significant context effect. Differential coding of /s/ and /ɑ/ likely result from level and timing differences. Neural refractoriness may result in the lack of a robust SNR effect on amplitude in the syllable context. The stable amplitude across SNRs in response to the vowel in /sɑ/ suggests the combined effects of (1) acoustic characteristics of the syllable and noise at poor SNRs and (2) refractory effects resulting from phoneme timing at good SNRs. Results provide insights into the coding of multiple‐onset speech syllables in varying levels of background noise and, together with behavioral measures, may help to improve our understanding of speech‐perception‐in‐noise difficulties. Abstract : In background noise, the neural response to /s/ in /sɑ/ disappears but the response to /ɑ/ remains stable across SNRs if presented in syllable context. The interaction between context and SNR effects may be attributed to neural refractoriness.