In Standard Persian the difference between individual vowels in [i,e], [u,o], and [a,ɑ] pairs is of a qualitative nature. Traditionally, [e,o,a] and [i,u,a] are classified as short and long respectively, since they are remnants of short [i,u,ɑ] and long [ī,ū,ā] vowels of Middle Persian. These two classes of vowels still behave differently in the phonological system of Modern Persian. Acoustic analyses of long and short vowels have shown that the two groups are different in duration, but the difference is mainly limited to unstressed open syllables. The duration of the two classes of vowels was measured following Lehiste and Peterson (1961) in hVd stressed syllables in the speech of 14 female and male speakers of Standard Persian. Results show that long and short vowels are not only different in total duration, but they demonstrate different patterns in terms of target and formant transition.
