An empirical study of phonetic transfer in English monophthong learning by Tibetan (Lhasa) speakers

English teaching has been carried out in every region of China. However, the teaching of English phonetics in minority regions faces the problems of poor teaching quality and low intelligibility of phonetic production. Under the framework of Speech Learning Model (SLM), the current research adopts the experimental phonetic approach to select 10 Lhasa students (5 male and 5 female) from the Corpus of Chinese, English, Tibetan by Tibetan Speakers (CETTS) and examine the characteristics of the vowel space of their English in continuous speech, with a purpose to explore minority students' phonetic transfer of L1 and L2 on L3 vowel system. Euclidean distances between Tibetan speakers' English and Tibetan, and between Tibetan speakers' English and Chinese, reveal the degree of phonetic transfer of Tibetan (L1) and Chinese (L2) on English (L3). Results show that the nonstandard English vowel production by Lhasa speakers are more influenced by the similar vowels in L1 or L2. Due to equivalence classification, Lhasa students' English vowels /a:/, /i:/ and /i/ are more influenced by Tibetan similar vowels, and their English vowels /α/ and /u:/ are more influenced by Chinese similar vowels. In addition, Tibetan female speakers' /α:/ is more influenced by the similar vowel in Chinese. The study has revealed that when Tibetan speakers learn L3, the interference seems to be partly from their L1 and partly from their L2. Therefore, in minority students' L3 vowel learning, both L1 and L2 have influence on their L3 vowel system.