The clear speech effect for non-native listeners

TLDR

Clear speech improves intelligibility over conversational speech for hearing‑impaired and normal‑hearing listeners in degraded listening conditions. This study aimed to determine how effective clear speech is as an intelligibility aid for non‑native listeners. Thirty‑two non‑native and 32 native listeners heard English sentences spoken in conversational or clear style at –4 or –8 dB SNR by a male or female talker. Native listeners benefited substantially from clear speech (≈16 rau units), whereas non‑native listeners gained only a modest improvement (≈5 rau units), indicating clear speech is tailored to native listeners.

Abstract

Previous work has established that naturally produced clear speech is more intelligible than conversational speech for adult hearing-impaired listeners and normal-hearing listeners under degraded listening conditions. The major goal of the present study was to investigate the extent to which naturally produced clear speech is an effective intelligibility enhancement strategy for non-native listeners. Thirty-two non-native and 32 native listeners were presented with naturally produced English sentences. Factors that varied were speaking style (conversational versus clear), signal-to-noise ratio (-4 versus -8 dB) and talker (one male versus one female). Results showed that while native listeners derived a substantial benefit from naturally produced clear speech (an improvement of about 16 rau units on a keyword-correct count), non-native listeners exhibited only a small clear speech effect (an improvement of only 5 rau units). This relatively small clear speech effect for non-native listeners is interpreted as a consequence of the fact that clear speech is essentially native-listener oriented, and therefore is only beneficial to listeners with extensive experience with the sound structure of the target language.