Although pre-low raising (PLR) has been extensively studied as a type of contextual tonal variation, its underlying mechanism is barely understood. This paper explored the effects of phonetic vs phonological duration on PLR in Cantonese and Thai and examined how speech rate and vowel quantity interact with its realization in these languages, respectively. The results for Cantonese revealed that PLR always occurred before a large falling excursion (i.e., high-low); in other tonal contexts, it was observed more often in faster speech. In the Thai corpus, PLR also occurred before large falling excursions, and there was more PLR in short vowels. These results are discussed in terms of possible accounts of the underlying mechanism of PLR.

中文翻译：

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粤语和泰语的低位预习：语速和元音数量的影响

尽管作为一种语境语调变化，已经对低低起伏（PLR）进行了广泛的研究，但对其潜在机制却鲜为人知。本文探讨了粤语和泰语中语音对语音持续时间对PLR的影响，并考察了语速和元音数量如何与这些语言中的语音交互。粤语的结果显示，PLR总是在大的下降偏移（即高-低）之前发生。在其他音调环境中，通常会以更快的语音观察到它。在泰国语料库中，PLR也在大型下降游览之前发生，短元音中的PLR较多。将根据可能的PLR潜在机制来讨论这些结果。