Background & Objective: Singing and acting teachers have used semi-occluded vocal tract exercises (SOVTs) for many years to help elicit easier and more efficient vocal production. However, there is limited research on whether there is any difference in efficacy across various SOVT exercises. Straw phonation and lip trills are two of the more common SOVTs utilized. This study aimed to evaluate the impact of two semi-occluded vocal tract (SOVT) exercises—straw phonation and lip trill—on vocal function in professional singers. The study is designed to assess whether lip trill produces as much change as that induced by straw phonation. The primary goal was to assess and compare the changes in voice-related quality of life and the physical functioning of the voice.

Methods: Fourteen professional singers were randomized into two groups: straw phonation and lip trill. Participants performed SOVT exercises for 21 days, completing four five-minute sessions spread throughout the day daily. They had one meeting a week for a total of three meetings with study personnel who reviewed their completion of the exercises. The study measured outcomes using the Singing Voice Handicap Index (SVHI) and the Evaluation of the Ability to Sing Easily (EASE). Data were collected pre- and post-exercise, and statistical analyses were conducted to determine significant changes over time and between groups.

Results: Although the SVHI scores showed no significant changes pre- and post-exercise, indicating no significant differences in voice-related quality of life, a significant improvement in physical vocal function was observed post-exercise, as indicated by the EASE scores. A 2 x 2 (Time: Pre- vs. Post-exercise; Group: straw phonation vs. lip trill) analysis of variance revealed a statistically significant main effect of Time but not Group for ratings of the physical functioning of the voice (EASE). The direction of the change on the EASE indicated a perceived improvement in physical functioning of the voice after completing SOVT exercises. The results suggested that EASE scores improved after three weeks of an SOVT, but there was no difference between the two SOVT groups.

Conclusion: Both straw phonation and lip trill exercises resulted in perceived improvements in vocal ease and physical functioning, with no significant difference between the two groups. These results support the fact that all SOVT exercises are equally beneficial to vocal functioning, making them effective vocal exercises for singers. Additional study is required to determine optimal dosing and to further explore the acoustic and physiological changes that coincide with the self-rated changes in physical functioning of the voice.