本研究透過聲學的分析工具與社會語言學的研究方法，對東勢客家話的舌尖前音聲母[ts, ts^h, s]是否顎化為[tç, tç^h, ç]進行探究。共60名說東勢客家話的客家鄉親參與本項研究，依據他們的性別（男、女）、年齡（老、中、青）分成六組，每組10人。本研究透過自行設計的發音字表與閱讀短文，採集東勢客家話[s]與國語[ç]在不同語言與社會變項（後接元音、性別、年齡、語體）影響下所發出的語音樣本，並利用PRAAT對擦音的兩個重要聲學特徵─「摩擦噪音時長」與「頻譜能量高峰頻率」進行手動測量。研究結果顯示，不論影響變項為何，[s]的摩擦噪音時長明顯短於[ç]，[s]的頻譜能量高峰頻率顯著高於[ç]，亦即[s]並未顎化成[ç]。值得注意的是，高前元音[i]確實會使[s]的摩擦噪音時長增長，頻譜能量高峰頻率降低，但與[ç]相較仍呈現明顯差異。最後，本研究一方面從穩定性的角度出發，探討摩擦噪音時長及頻譜能量高峰頻率作為感知客家話輔音的不同，另一方面也從語音產製、語音環境、語音感知等面向為東勢客家話[ts, ts^h, s]為何不顎化成[tç, tç^h, ç]提供可能的合理解釋。

This study examined whether [ts], [ts^h], and [s] in Dongshi Hakka are palatalized into [tç], [tç^h], [ç] acoustically and sociolinguistically. A total of 60 native Dongshi Hakka speakers participated in this study. They were evenly distributed into six groups according to gender and age (old, middleaged, and young). The participants were asked to read a word list and a reading passage to collect speech tokens of [s] and [ç] in consideration of variables, such as following vowel context, gender, age, and speech style. PRAAT was manually used to measure frication duration and spectral peak frequencies of the fricatives [s] and [ç] in Dongshi Hakka and Mandarin. The results show that, regardless of which variables were considered, [s] was significantly shorter in frication duration and higher in spectral peak frequency than [ç]. Remarkably, the high-front vowel [i] lengthened the frication duration and lowered the spectral peak frequencies of [s]; however, signifi cant difference still existed between [s] and [ç]. Finally, regarding stability, this study revealed the distinct roles of frication duration and spectral peak frequency in the distinction of consonants in Hakka as well as the reason that [ts], [ts^h], and [s] cannot be palatalized into [tç], [tç^h], and [ç] in Dongshi Hakka in terms of the dimensions of speech production, phonetic context, and speech perception.