大部分在台灣的客家人都會說中文,但是其中有些客家人說國語時會留下客語的遺跡。本篇論文已語言上,場合正式性上,地理區域,以及社會因素等方面探討部分客家人把國語的/ɕ/唸成[s]的原因。 本篇論文包含量化分析以及質化分析,在量化分析上透過面對面的交談,念文章,以及唸單字等方法來收集資料。量化分析上總共有32位受試者,且受試者依照性別,教育程度,年齡以及地理區域以二分法的方式。而在質化分析上的受試者和量化分析的受試者為同一批人,但只有29位再次參與調查。 本篇主要的發現為: (1)在語言內部因素中,字頻,鄰近音,以及音節結構對於語音變異皆有影響。(2)語音變異的確有擴散的現象。(3)在語言外部的因素中,年齡以及地理區域的影響比場合正式性及性別來得大,但教育程度的影響則很微弱。整體而言:(1)本篇調查的語音透過語言內部,場合正式性,社會以及地理空間擴散 (2)語言內部以及語言外部皆對與音變異有影響,但語言外部的因素的影響比內部因素來得大。 / Most Hakka speakers in Taiwan, if not all, speak Mandarin Chinese. Among them, many leave some traces of their Hakka background in their Mandarin pronunciation. This thesis aims at analyzing the linguistic, situational, geographical, and social causes of the emergence of [s] as a phonetic variant of /ɕ/ in Mandarin by Hakka speakers. In this study, both quantitative and qualitative analyses were conducted to locate the internal and the external constraints on the target phonetic variation. Those data for quantitative analyses were collected from the linguistic production by 32 native speakers of Hakka in casual conversation, reading passage, and reading characters. Subjects of this study are equally distributed to two genders, two education levels, two age groups, and two geographical areas (namely, in Taoyuan City and Chungli City, two cities in which a large proportion of Hakka speakers reside) . As for data for qualitative analyses collected from 29 of the 32 subjects of the quantitative tests, only those parts of the qualitative design that were implemented correctly were analyzed. The major findings of this study are (1) among the internal factors, word frequency, preceding vowels, and syllable structure were found to be influential to the target phonetic variation; (2) the target phonetic variation does expands through lexical diffusion; and (3) among the external factors, age and geographical area are more influential than situational formality and gender, but the impact of education level is weak. General conclusion of this study include (1) this target phonetic variation is expanding gradually through linguistic, situational, and social/geographical spaces; and (2) both internal and external factors are effective, with external factors being more influential than internal factors. Key words: phonetic variation, lexical diffusion, formality, Hakka dialect, sociolinguistic variation, ethnic identity