چکیده:
This paper reports the results of an experimental study on non-native production of English vowels. Two groups of Persian EFL learners varying in language proficiency were tested on their ability to produce the nine plain vowels of American English. Vowel production accuracy was assessed by means of acoustic measurements. Ladefoged and Maddison’s (1996) F1 F2 measurements for American English vowel space were used as reference values to be compared with the measurements obtained from the production of Persian EFL learners. The acoustic measurements revealed that learners were not able to control acoustic parameters of vowel quality, even for the more similar vowels in the two languages, in a native-like manner due to interference from their native vowel system. Spectral accuracy measures also did not progress toward more native-like values in the productions of the more proficient learners. Interestingly, the positions achieved for the more dissimilar vowels were neither close to their closest L1 counterparts nor close to their native categories. Interpreting this latter result within the Perceptual Assimilation Model proposed by Best (1994), it could be stated that learners established new phonetic categories for the vowel contrasts that were not used in their native phonological system.
خلاصه ماشینی:
Ladefoged and Maddison’s (1996) F1 F2 measurements for American English vowel space were used as reference values to be compared with the measurements obtained from the production of Persian EFL learners.
A number of studies have suggested that non- native speakers’ experience with a particular phonetic or phonological category might contribute to their difficulty in producing and/or perceiving sound units in a second language.
More specifically, results of such studies typically suggest that L2 learners have relatively greater difficulty producing and perceiving non-native contrasts that involve phonetic features dissimilar to those used in their native languages (Best, 1994; Flege, 1995; Flege, Schirru and Mackay, 2003).
In addition, previous research investigating acquisition of L2 speech sounds has clearly suggested a strong influence of the native phonological system on the production and perception of non-native sounds (Flege, Bohn, & Jang, 1997; Flege et al, 1999).
4. 1 Learners’ production of American English vowels Table 4 shows the first and second formant frequencies of English vowels as produced by high-proficient and mid-proficient Persian EFL Learners.
Fisher Post hoc tests further showed that the first and the second formants of vowels produced by both the mid-proficient and high-proficient groups were significantly higher than the F1 and F2 values of tokens produced by the American English speakers, suggesting that language proficiency did not positively influence production of the high front tense vowel [i].