Relation Between Tone and Vowel Quality in Twi

This study is part of a programmatic research on Twi undertaken at the laboratory of general and experimental phonetics at the Institut de Phonétique de Strasbourg. Twi is a register tone language spoken in Ghana, West Africa. It has a two tone system (high/low) and the downstep phenomena. The aim of this paper is two-fold. First, some phonological aspects of Twi tones are described. Second, preliminary acoustic measurements are carried out to investigate for differences between vowel quality in the two groups. In this preliminary analysis, two adult male speakers produced a series of isolated words belonging to the two phonological classes. The evidence from our acoustic data is for high tones to have higher fundamental frequency values than low tones. Acoustic results further show that high and low tones show sparse qualitative (F1, F2, F3 and F4) as well as sparse syllabic durational differences. However, the tendency is also for low tones to have lower F1, higher F2, higher F3 and lower F4 values than the high counterparts.