Effects of Instructed Laryngeal Manipulation on Vocal Rise Time.

Objectives: Previous research has shown that instructed manipulation of the false vocal fold activity (FVFA), true vocal fold mass (TVFM), and larynx height (LH) impacted on voice quality. It is not known whether these manipulations have any effect on voice onset. Vocal Rise Time (VRT) is an objective acoustic measure of voice onset, which has potential as an assessment tool in clinical settings. The present study aimed to investigate the effects of instructed manipulation of FVFA, TVFM, and LH on VRT.

Study design: Retrospective, observational study.

Methods: Nine vocally trained participants (five females, four males) aged between 19 and 36years were instructed to perform differential manipulation of FVFA, TVFM, and LH while phonating the prolonged /ɑ/ vowel. Recorded voice samples were edited and analyzed using a novel Python-based application, the Voice Onset Analysis Tool (VOAT) to obtain VRT results. The VRT data were compared across conditions using repeated-measures analysis of variance, and were correlated against perceptual ratings of tone onset.

Results: Reliability analysis showed excellent intra- and inter-rater agreement in VRT measurements using VOAT. All laryngeal parameters (FVFA, TVFM, and LH) showed statistically significant main effects on VRT. There was a consistent trend for thin TVFM, constricted FVFA, and lower LH to increase VRT values. However, post hoc analysis showed some statistically insignificant results possibly due to the small sample size. There was a weak positive correlation between VRT and perceptual tone onset ratings.

Conclusion: VRT measurements using VOAT are highly reliable. All three laryngeal parameters were contributors to determining voice onset. Given the limited sample size, careful definition and standardization of VRT measurement protocol is needed for it to become a useful and reliable measure of voice onset in research and clinical settings.