A study of voice quality and acoustic variability in sound prolongation performance in a large corpus of 5–12-year-old children

Voice disorders, or dysphonia, in children impact communication, social interactions, and quality of life, emphasizing the need for effective assessment tools with accurate reference norms. Acoustic measures taken during sound prolongation are widely used to evaluate voice quality, but variability in children’s performance and limited norms from children from diverse backgrounds pose challenges for clinicians. This study investigated voice quality and variability in sound prolongation tasks among 5–12-year-old school children, contributing to the development of acoustic reference data.
Method: A total of 275 primary school-aged children in Scotland participated, producing sustained phonations of [a], [s], and [z] to evaluate respiratory and phonatory performance. Durations and acoustic measures, including jitter, shimmer, Harmonics-to-Noise Ratio (HNR), Cepstral Peak Prominence (CPP), and s/z ratio, were analyzed to capture variability in performance.
Results: Analysis indicated significant age-related increases in sound prolongation durations, with older children (7–12 years) outperforming younger children (5–6 years), reflecting enhanced respiratory capacity and vocal fold control. While jitter, shimmer, and HNR did not differ significantly across age groups, CPP values were higher in older children, indicating improved vocal stability and harmonic richness. Median s/z ratios also showed significant age-related changes, highlighting developmental changes in phonatory and respiratory coordination. Notably, children exhibited longer average sound prolongation durations than previously reported norms, with considerable variability in performance. No significant sex differences were found, except for the s/z ratio, where females had higher values.
These findings contribute and advance the growing body of reference data for assessing voice quality in children and emphasize the importance of factors such as age and sex in large, diverse samples. The study highlights the need to account for developmental variability and robust, comprehensive methodologies to contextualize voice quality issues in children.