北京話連去變調的成因及其與詞重音的關係

北京話去聲連讀存在前去變成升調的社會變體，對於這種變體的成因，學界的看法不盡相同。本文用個案語音和文本分析的方法對北京話連去變調與詞重音之間的關係進行了研究。首先通過聲學測量和兩個聽辨實驗確定了變調樣本的重音格式，發現前去能夠變為升調的兩字組基本上都是聽感上的後重型。然後通過與若干輕音詞表的對比確認發生前去變調的雙音節詞在北京口語中不存在前重式。文章分析了北京話中兩種去聲變調格式——前去變為升調和後去變為低降調——的形成原因以及詞重音對變調格式的作用。作者認為，連去組合中的兩種變調格式實質上都是在重音保留本調原則、重讀音節同化非重讀音節原則和減少曲折原則的基礎上，相鄰音節音高同化作用的結果，同時，去聲連讀中的順向同化和逆向同化作用間接也說明了北京話的雙音節詞存在前重和後重兩種重音模式。

In the social dialect of Beijing Mandarin, Tone 4 (T4), a falling tone, can turn into a rising tone when preceding another T4. Researchers have not been able to reach an agreement on the cause of the tone sandhi rule. This paper investigates the relationship between preceding-T4 sandhi and lexical stress based on the results of a speech case study and text analysis. First of all, two perceptual experiments and an acoustic measurement were conducted to verify stress patterns in disyllabic sample words where the preceding-T4 sandhi can occur. Results showed that in almost all of these samples, listeners confirmed they had final stress. Next, the chosen sample words were cross-checked with lists of neutral-tone words, which further proved they cannot have initial stress in spoken Beijing Mandarin. The causes of two patterns of T4 sandhi, namely, the preceding T4 changing to a rising tone and the following T4 changing to a low falling tone, and the effect of lexical stress on the sandhi patterns were analyzed. We argue that both T4 sandhi patterns are the results of assimilation between adjacent tones under the effects of Principle of Accentual Preservation, Principle of Accentual Attraction, and Principle of Up and Down, and that the effects of progressive and regressive assimilation in T4-sequences imply that two stress patterns—initial and final-stress patterns—exist in Beijing Mandarin.