Voice onset time in Swedish children with phonological impairment

Mastering spatial and temporal co-ordination in speech production is a challenge for children. Voice onset time (VOT) reflects timing in speech. The objective was to study VOT in Swedish children with a diagnosed phonological impairment and compare results with normative data. Thus 38 children, aged 4-11 years, in three age-groups were audio-recorded when producing minimal pairs with the plosives /p b t d k g/. Waveforms and spectrograms were analysed. Results show that children with phonological impairment produced plosives with deviant VOT values and greater variability compared to normative data. No developmental trend was seen with increasing age. Also, no relationship was found between VOT values and degree of impairment measured by percentage phonemes correct. Furthermore no relation was found between number of errors on auditory discrimination of nine minimal pairs with the different plosives and number of deviant VOT. Findings were interpreted as displaying motor co-ordination difficulties.