production of english lexical stress by persian efl learners

this study examines the phonetic properties of lexical stress in english produced by persian speakers learning english as a foreign language. the four most reliable phonetic correlates of english lexical stress, namely fundamental frequency, duration, intensity, and vowel quality were measured across persian speakers’ production of the stressed and unstressed syllables of five english disyllabic stress pairs which differed only in the location of stress, such as contract (noun)/ contract (verb). results showed that persian speakers’ use of the prosodic cues to lexical stress, that is fundamental frequency, duration, and intensity was comparable to the use of the same cues by american english speakers for both the stressed and unstressed syllables. there were, however, significant differences in formant frequency patterns (as the phonetic correlates of vowel quality) across the two language groups, such that persian speakers did not manage to approximate the target native-like productions of the majority of the vowels in the experimental data both in the stressed or unstressed conditions. this observation supports the proposal made by flege and bohn  (1989), namely that l2 learners acquire l1 patterns of vowel reduction only after they have acquired english-like patterns of prosodic cues to stress (f0, duration and intensity), and that their inability to reduce vowels in unstressed syllables does not influence their ability to employ prosodic cues to lexical stress contrast. as will be discussed at the end, the results shall have implications for material developers and efl teachers.