UC Davis

Becoming a competent language user involves the acquisition of different speaking styles, including the acquisition of a clear speech style wherein speakers hyperarticulate in order to make it easier for a listener to understand. The present dissertation investigates the acoustic properties and perceptual benefits of clear speech in first language (L1), heritage language (HL), and second language (L2) speakers of Mandarin Chinese.The first experiment compares the global clear speech strategies of longer duration, increased intensity, higher f0, and expanded f0 range in both English and Mandarin. 8 L1 Mandarin-L2 English speakers, 11 English-dominant heritage Mandarin speakers, and 10 L1 English-L2 Mandarin speakers produced monosyllabic Mandarin and English words. Longer duration and expanded f0 range were the primary acoustic enhancements of clear speech across speaker groups and languages, although HL Mandarin speakers did not expand f0 range in Mandarin clear speech.The second experiment compares the pitch contour enhancement of the pitch contours of the same monosyllables in Mandarin and English clear and casual speech. The findings show that the contour of the pitch is enhanced in both English and Mandarin, with characteristic aspects of the tone contour being enhanced in both languages. HL and L2 speakers’ enhancements were sometimes smaller than L1 speakers’ enhancements, and HL and L2 speakers sometimes enhanced different aspects of the contour than L1 speakers.The third experiment investigates the perceptual benefits of L1, HL, and L2 Mandarin clear speech. There was a clear speech intelligibility benefit for Mandarin in all speaker groups, though results differed by tone. HL and L2 Mandarin speakers’ Tone 3 productions were often perceived as Tone 2.The results of these experiments suggest 1) that HL and L2 Mandarin speakers make acoustic enhancements in Mandarin clear speech, including enhancing the tone contour; 2) that these enhancements result in intelligibility benefits for L1 Mandarin listeners; and 3) that there is a great deal of inter-talker variation in which clear speech strategies are used by each individual speaker.