Variability and Duration of Voice Onset Time in Childhood Apraxia of Speech in Korea: Results of the Spectrum Study

Childhood apraxia of speech(CAS) is considered as an impairment of purposeful speech movements and is generally defined as a disorder of motor planning or motor programming. There have been a variety of studies about CAS and the diagnostic criteria were set up in English-speaking countries, but studies about diagnostic criteria of CAS for Korean speakers are needed. The purpose of the study was to examine voice onset time (VOT) and its variability in children with childhood apraxia of speech (CAS) compared to typically developing children. Twelve children with CAS aged 9-12 years old and 20 children who were age-matched participated in the study. This study measured VOT and variabilities of VOT during the production of /p' a/, /t' a/, /k' a/. For variability measures of VOT, each participant was asked to repeat speech tasks three times and the average value of the rates and its standard deviation were obtained The verification of the hypotheses was tested by using T-test of the significance level of 0.05.The results showed that the variability of VOT in CAS group was more significantly higher than control group. But VOT of /p' a/, /t' a/, /k' a/ between the experimental group and the control group was not significantly different. The results suggested that variability of VOT might be more distinctive speech feature to children with CAS than the VOT. This study is meaningful because of two points; one is that it was conducted to fit the characteristics of Korea language while English cases are revitalized in the domestic situation, and the other is that it could be utilized as a resource for subsequent studies.