Acoustic correlates of English clear speech produced by native Korean speakers

Abstract

Monolingual clear speech is acoustically distinct from casual speech and can aid speech perception (Picheny et al., 1986; Smiljanic and Bradlow, 2005) but little is known about the acoustic properties of clear speech produced by non-native speakers. The current study aims to determine whether Korean non-native speakers of English modify their speech the same way native English speakers do when asked to speak clearly. A group of native Korean speakers residing in the United States (14 recorded to date) and a group of native speakers of English (9 recorded to date) were instructed to read a list of common English words (e.g., beat) using casual and clear speaking styles. The findings showed the effect of speaking style for every acoustic measurement: vowel duration, mean pitch, pitch range, positive and negative VOT, onset f0, and vowel space. With the exception of mean pitch, there were no significant interactions between group and speaking mode, indicating that Korean speakers implemented these acoustic parameters in L2 clear speech similarly to native speakers. Only for mean pitch, the degree of change associated with clear speech was greater for English speakers than for Korean speakers.