Variability in sound prolongation in typically developing children

Maximum performance tasks (MPTs) such as sound prolongation can be valuable for diagnosing motor speech disorders in children. However, to utilize MPTs for differential diagnosis, a better understanding of normative values for children's performance are needed. This study aimed to investigate variation in performance, and its relationship to age, in a sound prolongation task in 5-6, 7-8, and 9-10 year old children.
Data was collected from 76 children aged 5 to 10 (mean = 7 years; 9 months; SD= 1.69) in Scotland through an iPad app as part of a larger project focusing on variability in children’s speech. The sound prolongation task involved repetitions of /a/, /s/, and /z/. Acoustic measures related to respiration (duration, and s/z ratio) and phonation (jitter, shimmer, Harmonics-to-Noise Ratio, and Cepstral Peak Prominence) were extracted from the recordings and analysed statistically to determine how children’s performance varied between age groups. Results confirmed findings from previous literature that older children (9–10-year-olds) exhibited longer /s/ sound durations compared to younger children (5-6-, and 7–8-year-olds), indicating a potential increase in respiratory support over time. However, the results for /a/ and /z/ were less clear cut, suggesting considerable variation between children’s performances. Regarding phonatory measures, no significant differences were observed, suggesting that children’s voice parameters show comparable values between the ages of 5 and 10.