Effects of Voice Quality Improvement Program for Professional Voice Users with Functional Voice Disorders

Background/Objectives: One of the most emphasized aspects in voice therapy is voice quality. We investigated the effect of our intervention program on improving voice quality and reducing vocal fatigue.Method/Statistical Analysis: 10 musical actors/actresses with functional voice disorders were given eight training sessions once a week, and both subjective and objective evaluations of their voices were conducted before and after the training. K-SVHI and VFI were used to measure voice handicap index and voice fatigue index. Praat was used to measure the objective acoustic indices. To examine the statistical significance, a paired sample t-test was performed.Findings: The result of subjective voice quality evaluation showed that both scores of voice handicap index and voice fatigue index were decreased. The objective voice evaluation results showed that the jitter (%) and shimmer(%) scores decreased while the harmonics to noise ratio (HNR) and the speaking fundamental frequency (SF0) scores increased. The lower the jitter and shimmer, the better the quality of voice, while the higher the HNR, the better the quality of voice.The difference between pretest and posttest scores was statistically significant except for the SF0. The reason for small changes in the SF0 seems to be that all participants of musical actor/actresses who skillfully use the voice were able to control their voice to maintain the frequency at a certain level.Improvements/Applications: Our findings indicate that patients with functional voice disorders have problems ways to use their voice and showed that their voice quality and vocal fatigue can be improved by modifying and training four stages of voice production.