Voice Onset Time in Children With and Without Vocal Fold Nodules

Abstract

Purpose: This study examined voice onset time (VOT) in children with and without vocal fold nodules (VFN). The purpose of this study was to provide further evidence regarding the need for individualized research and treatment dedicated to the pediatric population. The pediatric population has a distinctly different laryngeal mechanism than adults, as they are still developing. Although the pediatric system is anatomically different from that of a fully mature adult system, treatment for children with VFN is largely based on adult research. This study examined the VOTs of voiceless consonants, as the transition from the voiceless consonant to the subsequent vowel requires significant vocal and articulatory control and coordination. Measures of VOT change throughout the maturation as VOT follows a significant developmental pattern. Children with and without VFN were enlisted in order to examine the effects VFN have on VOT. Hypotheses: We hypothesize that children with VFN would have differences in 1) average VOT values compared to the control group, with no prediction for direction of difference (shorter and longer), and 2) between-word variability of VOT values compared to the control group, with no prediction for direction of difference (more variable and less variable). Methods: Participant data were retrospectively collected and included children between 6 and 12 years old with VFN and age- and sex-matched controls. Participants were recorded producing the six CAPE-V sentences. Four voiceless consonants were selected for VOT analysis. Praat was utilized to manually mark the vocal onset of the stop consonant by the current researcher. A previous researcher identified the vocal offset, and each placement was confirmed by the current researcher. VOT was calculated as the time between the stop consonant burst and the vocal onset of the vowel. Results: There was no significant difference between the VFN and the control groups in average VOT or VOT variability. Within the VFN group, participants who were more dysphonic (lower cepstral peak prominence (CPP) values) had more variable VOT values. Participants in the VFN group had lower CPP values than the control group, suggesting that CPP measures are a reliable indicator of dysphonia. Additionally, within the VFN group, male children had lower CPP values than female children. Conclusion: Although no group difference was found, the within-group analyses indicated that VFNs impacted productions. Children with VFN who were more dysphonic had increased VOT variability. This may suggest that VFN impact a child’s ability to phonate therefore causing more variability within productions. Future research is needed to study the impact dysphonia treatment for children with VFN may have on VOT values. Additionally, a longitudinal study of the impact of VFNs on VOT values during developmental stages may be warranted.