Variability of Cepstral Peak Prominence in Children with Vocal Fold Nodules

Objective: Cepstral peak prominence (CPP) is an acoustic measure of vocal periodicity that is used clinically to provide a metric of dysphonia. Individuals with increased dysphonia have decreased CPP values as compared to nondysphonic individuals. The objective of this study was to examine CPP in children with vocal fold nodules (VFN) over multiple repetitions of a phrase.

Methods: The voices of fourteen children with VFN (7 male, 7 female, average (M) = 7.1 years, range = 9.2 – 5.3 years) were analyzed for this study. All children were diagnosed with VFN at Boston Children’s Hospital by a pediatric laryngologist. CPP was analyzed using Praat, with a custom plug-in that allowed voicing detection. The phrase “a baby and bee” was selected for analysis. The fourteen participants included in this study each had 4-6 repetitions of the target phrase. The median CPP value across a participant’s repetitions was calculated as an acoustic measure of overall dysphonia severity. The variability of CPP (defined as the coefficient of variation) was calculated to examine the between-phrase variability of CPP for each participant.

Results: There was a strong negative correlation between the median CPP value and variability of CPP, after controlling for age and number of instances (r = -0.71, p = 0.009). Female children had a significantly lower median CPP (M = 7.59) than male children (M = 10.47, p = 0.009).

Conclusions: Children with VFN with CPP values had increased variability of CPP. This suggests that additional measures of CPP variability may provide useful information about dysphonia severity in children. The finding of a gender difference in median CPP was unexpected based on the current study’s age ranges. One possibility for this difference is some children may have begun experiencing pre-pubertal changes that impacted vocal fold stability. However, visual examination indicated that the youngest male children had the highest CPP, making this explanation unlikely. Another explanation is the child’s gender may impact the perception of dysphonia for caregivers and/or medical providers, resulting in girls being brought into clinic only when their voices are more severely dysphonic. Additional work is needed to explore these potential explanations.