Prosodic modulations on the formant excursions of diphthongs

Abstract

The excursions of the first two formants of diphthongs in Chinese, English, and Japanese were investigated to see how diphthongs are affected by the hierarchical prosodic structure. The production of /ai, au, ou/ was examined in Chinese and English, and /ai, au, ae/ in Japanese. Three prosodic contexts were examined: word-final, list-final, and IP (intonational phrase)-final positions. The results of GAM analysis of F1 and F2 show that (1) F2 was more affected than F1; (2) diphthong offset was more affected than the onset; (3) only the diphthong onset in Japanese was affected by the prosody. The by-language analysis further shows that the offset of diphthongs at word-final positions in Chinese was less resistant to the coarticulatory effect: F2 raises earlier and higher toward the end of the diphthong due to the influence of the following coronal consonant. Meanwhile, in English and Japanese /ai, ae/ with lower F2 and higher F1 and /au, ou/ with higher F1 and F2 at word-final positions were found, indicating hypoarticulation at lower prosodic boundaries. Some of the diphthong onsets in Japanese were influenced as well. The result suggests hyperarticulation as a prosodic strengthening effect in English and Japanese.