古止攝元音[i]演變為舌尖前高元音[]是中古以來漢語語音一項重大演變，學界一般稱之為「舌尖化」現象。迄今為止，對其演變過程，尤其是對[i]音變後音值的考察尚少見到。 / 本文據實地調查觀察發現：惠陽淡水客家話止攝開口三等[i]元音正處於演變的過程中：老派基本不變，中派開始發生變化，新派完成部分音變；[i]音變的條件為與音、零聲母相拼；音變的過程先從音開始，再擴至零聲母。通過實驗語音學的分析，本文發現惠陽淡水客家話[i]音變後的音值不是一般漢語方言記錄中的[]，而是[]；[i]不是「前化」、「高化」或「舌尖化」，而是「央化」；[i]與零聲母相拼發生音變，更會衍生濁擦音[z]。這種音變以「詞匯擴散」的方式傳播，並與年齡、性別這兩項社會因素有密切關係。 / 在上述淡水客家話[i]音變後之音值性質分析基礎上，再根據《普通話水平測試實施綱要》内之音檔，考察普通話中「」的音值。經過實驗分析後，本文認爲普通話的「」其實就是[]。漢語看似無[]，但[]只是被「」這層假象覆蓋住。 / 希望本文上述的觀察研究能為漢語方言中古止攝元音[i]的歷史演變研究提供一種全新的思考和假設。 / The sound change of vowel [i] to [] of Zhi-Group 止攝 has been an important issue in Chinese phonetics since medieval times, which is commonly called "apicalization" by the academia. Up to now, there are very few studies on the process of the sound change of [i], especially the exact phonetic value of [i] after sound change, can be found. / According to the results of our field work, [i] of Division III 三等, Open Mouth of Zhi-Group 止攝開口 is undergoing sound change in the Hakka Dialect in Danshui, Huiyang. The phonetic value of [i] basically does not change among the members of the old generation, but changing among the members of the middle generation and has changed among the members of the new generation. The phonetic valueof [i] changes when it combines with sibilants and silent initial. The process of sound change starts from sibilants and followed by silent initial. With the analysis of Experimental Phonetics, we find that the exact phonetic value of [i] after sound changeis not []. Even [] is found in many Chinese dialect records, the exact phonetic value should be []. The nature of the sound change of [i] is not "fronting", "raising" nor "apicalized", it should be "centralized". Under the influence of sound change, when [i] is syllabic, voiced alveolar fricative [z] will be produced. The sound change of [i] is spreading by the process of "lexical diffusion" and is closely related to the social factors of age and gender. / We will also examine the exact phonetic value of "" in Putonghua according to Putonghua Shuiping Ceshi Shishi Gangyao 《普通話水平測試綱要》. After experimental analysis, we find that "" should be [] instead. Actually [] exists in Chinese, but it is "covered" by "". / Hope our findings can provide the stuides on the historial change of [i] of Zhi-Group in Chinese dialects with a different thinking angle and a whole new htpothesis. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / 黃韻瑜. / Thesis (M.Phil.) Chinese University of Hong Kong, 2014. / Includes bibliographical references (leaves 95-100). / Abstracts in Chinese and English. / Huang Yunyu.