韻律重音對臺灣華語自然語料中雙元音縮減之影響： 以 /aɪ/ 為例

Abstract

元音縮減在自然語料中乃常見現象。先前的研究顯示韻律重音、資訊可預測性和社會語言學等因素會影響元音縮減。其中，韻律重音是影響重音計時語言中元音縮減的關鍵因素。臺灣華語作為音節計時的聲調語言，韻律重音的有無以聲調完整性呈現。在這個研究中，我們探討聲調縮減是否和元音縮減有關。透過具有兩個元音標的的雙元音 /aɪ/，我們研究韻律重音、資訊可預測性和社會語言學因素如何與臺灣華語自然語料中的雙元音縮減相互作用。結果顯示，/aɪ/ 的縮減主要以兩個元音目標合併的單元音化形式進行。此外，重音程度較低的雙元音保留率較低，縮減成中央母音的比例較高，時長較短，且兩個元音標的的舌位向口腔中央縮減。另外，韻律重音在元音縮減上比資訊可預測性具有更大的影響。在社會意涵上，我們並未發現性別或地域上的差異，顯示 /aɪ/ 的縮減可能並不負面。不過，雖然在縮減方面沒有發現地域差異，但南部人在臺灣華語中對 /aɪ/ 的發聲舌位較北部人更靠近口腔邊緣，這可能緣於閩語的負遷移。

Vowel reduction is frequently observed in spontaneous speech. Previous studies have shown that prosodic prominence, information predictability, and sociolinguistic factors influence acoustic vowel reduction. Among them, prosodic prominence was considered a key factor affecting vowel reduction in stress-timed languages. Taiwan Mandarin as a syllable-timed tonal language realizes prosodic prominence via tonal completeness. In this study, we explored whether vowel reduction could be found in tonal reduction. By studying the diphthong /aɪ/, which has two vowel targets, we examined how the effects of prosodic prominence, information predictability, and sociolinguistic factors interact with vowel reduction in Mandarin spontaneous speech. Results showed that /aɪ/ reduction is mostly in the form of monophthongization with two vowel targets merged. Moreover, diphthongs with a lower level of stress had a lower retention rate, a higher centralization rate, shorter duration, and formant undershoot on both vowel targets. Furthermore, prosodic prominence revealed a much larger effect on vowel reduction than information predictability. Also, the reduction of /aɪ/ likely lacks a negative connotation since no gender or regional difference was found. Finally, although regional variation was not found in reduction, southerners had more expanded realization of /aɪ/ in Taiwan Mandarin than northerners, which is likely attributed to negative Min transfer.