Acquisition of the word-initial stop voicing contrast: a longitudinal single case study

Abstract

In order to fully understand disordered speech and be able to treat it we must be able to compare this to typical speech development characteristics. Voicing contrast is a speech characteristic that has received a lot of attention in the literature. This is the difference between a voiced and voiceless phoneme at the same place of articulation (e.g. the difference between a /p/ and a /b/). Acoustically, we can analyse this by recording the voice onset time (VOT) in each phoneme. The length of time between the release of the stop consonant and the onset of the vibration of the glottis, describes VOT. In this study, we looked at the acquisition of voice onset time through a single case study of an English-speaking child. This child's VOT was recorded bimonthly from 70 weeks to 144 weeks old. The labial and alveolar targets were extracted from the data and the VOT was recorded. This data was then analysed using both means and token-by-token data analysis methods. We found similarly to Hitchcock and Koeing (2013, 2015), that VOT acquisition is not a discreet acquisition event and instead it is variable and may take months if not years to reach adult like VOT values consistently.