Efficacy of a Tesla Valve Straw in a Semi-Occluded Vocal Tract Exercise in a Normal-Voiced Population.

Objective: Voice disorders affect a significant portion of the US population, affecting communication and professional performance. Semi-occluded vocal tract (SOVT) straw phonation exercises are widely used in voice therapy to enhance phonation efficacy. The Tesla valve, a structure Nikola Tesla designed, could be applied to SOVT straw phonation therapy and increase its effectiveness by increasing resistance without requiring a longer straw length. This study aimed to evaluate the effectiveness of the Tesla valve straw compared to a standard straw and assess the impact of straw length on phonation efficiency.

Methods: Twenty-nine normal-voiced participants were randomly assigned to complete SOVT tasks using standard and Tesla valve straws of lengths 25.50 and 31.50 cm. Participants' aerodynamic and acoustic measurements, including phonation threshold pressure (PTP), mean flow rate (MFR), and fundamental frequency (F), were recorded before and after completing the SOVT task involving sustained phonation into a mechanical interrupter. Repeated measures ANOVA analyses were used to analyze the effects of straw type, length, and time on the measured parameters.

Results: Significant reductions in PTP were observed across all conditions regardless of straw type or length, supporting the use of SOVT straw phonation exercises to reduce PTP. However, no significant differences were observed between the standard and Tesla valve straw types or between the short and long straw lengths. MFR and F did not display significant changes before and after the SOVT exercises, as statistical analyses showed no significant interactions between straw type, length, and time.

Conclusion: The results suggest that while long and short Tesla valve straws generated a greater average PTP decrease than standard straws, the differences were not statistically significant. Additionally, the length of the straws tested did not significantly affect the therapeutic effects of the exercises in the confines of this study. These results support the presence of straw is the most important consideration in straw phonation therapy. Further Tesla valve straw designs should be tested to understand the efficacy of the Tesla valve straw at a wider range of lengths and configurations.