客語兒向語聲調研究：聲學觀點

Tones in Hakka Infant-Directed Speech: An Acoustic Perspective

本研究比較客語「兒向語」與「成人語」的六個單字調，藉以檢視客語「兒向語」聲調的擴張及曲解情形，並特別關注文獻上未曾探討過的議題，即「兒向語」裡的舒入聲調對比。十六對母子參與本研究，嬰兒年齡介於六至二十六個月之間。本研究採用十八個以 C1V1C2V(C) 為結構的雙音節詞作為研究字表，其中 C1 與 C2 為無聲輔音，V1 為三個頂點元音 [i, a, u] 其中之一，並為目標聲調所在。研究中，「兒向語」與「成人語」的語料皆在受訪者家中錄製，且均來自於母親與其嬰兒及研究者的自然言語互動。每次錄音裡，各個聲調的前兩個清晰樣本被截取出來，並透過 PRAAT 進行基頻分析。研究結果顯示，客語「兒向語」裡的各個單字調均呈現調形誇大、調值提升、調域變寬、聲調升降急遽、調長延長、及聲調差異擴大的情形，但並未造成聲調扭曲的現象。此外，這些擴張的基頻音徵，不僅提升了語言訊號的感知突出性，更有助於嬰兒的聲調辨識與範疇學習。更有趣的發現是，舒（去聲）入（陽入）聲調在「兒向語」與「成人語」中的語音表現不同。在「成人語」中兩個聲調彼此重疊，但在「兒向語」裡卻是相互分離，入聲調高於舒聲調。本文主張，「兒向語」裡這種舒入聲調分離現象導因於入聲音節韻尾 [p, t, k] 在連續語流中快速發音時所產生的喉塞化作用。

This study explores lexical tones in Hakka infant-directed speech (IDS) in comparison with adult-directed speech (ADS), investigating whether lexical tones are hyperarticulated and distorted in Hakka IDS. Special attention is directed at the tonal contrast between unchecked and checked tones, an issue never investigated previously. Sixteen mother–infant dyads participated in this study, with infants’ age ranging from 6 to 26 months. The speech stimuli contained 18 disyllabic phrases in the form of C1V1C2V(C), where C1 and C2 are voiceless consonants and V1 (a corner vowel [i, a, u]) carried the target tone. Mothers interacted with their infants and the researcher naturally at their homes. Interviews were recorded as IDS and ADS. For each recording, the first two clear tokens of each target tone were segmented out for acoustic analysis of fundamental frequency (F0) by PRAAT. Results show that lexical tones in IDS are phonetically enhanced by exaggerated F0 contour, elevated F0 mean, widened F0 range, steepened F0 slope, lengthened F0 duration, and expanded tonal distance. Yet they are not distorted because they can still be distinguished by one or more F0 cues. All hyperarticulated cues contribute to perceptually salient linguistic signals, and help infants with tonal identification and categorical learning. More significantly, checked and unchecked tones have different tonal behaviors in ADS and IDS. Both tone types overlap in ADS, but separate in IDS. This tonal separability results from glottalization of the [p, t, k] codas in the production of checked-tone syllables in spontaneous and continuous speech.