A phonetic inquiry into Dagbani vowel neutralisations

Previous researchers differ on what the feature specifications of Dagbani vowels are, what the vowel inventory is, which vowels are contrastive and how phonological processes affect the surface realisation of Dagbani vowels. This study provides experimental results on Dagbani vowel features from acoustic and perceptual psycholinguistic inquiries with the goal of better defining the vowel features and inventory. Basic formant frequencies of the vowels in different phonological contexts support the view that (1) vowels of all height specifications (including /a/) have [ATR] variants; (2) /i/ and // neutralise in harmonic contexts; and (3) mid vowels surface as low in non-final positions. Results of a perceptual psycholinguistic investigation of the neutralisation between mid and low vowels also show that in certain contexts, speakers are unable to perceive any distinction between different words with these vowels. The paper discusses the implications of these results on the Dagbani vowel inventory, evaluating the merits of different possible approaches in the process.