Duration of vowels before homorganic nasal-obstruent sequences in Tumbuka

The Bantu language Tumbuka, spoken in Malawi and Zambia, has the vowel phonemes /i, e, a, o, u/ but no phonemic contrast in vowel length. In the present study we measured the duration of vowels before homorganic nasal-obstruent sequences (NC) and compared them to the duration of vowels before single obstruents for four speakers of Tumbuka. With this data, we tested whether there is acoustic support for the existence of a phonological process of pre-NC lengthening, as reported for many other Bantu languages. Our results provide no support for such an interpretation in Tumbuka: pre-NC vowels were only 10 ms longer than pre-obstruent vowels, and though this difference was statistically significant, it is below the just noticeable difference for duration of 25 ms and therefore most likely not perceivable. We conclude that the observed pre-NC lengthening in Tumbuka is a purely co-articulatory, phonetic process.