Quantification of Loudness Instability in Tone Production in Embouchure Dystonia

Embouchure dystonia (ED) is a task-specific disorder of voluntary fine motor control that severely affects musicians' ability to perform tasks. One critical skill for professional musicians is the ability to produce sustained notes with consistent loudness; however, this ability has not been well defined in musicians with ED. The present study, therefore, compared the time-varying dynamics of loudness in musicians with ED with those in healthy musicians, as well as their relationship with the variability of the fundamental frequency (F0), by performing a sound analysis of sustained notes. The findings revealed significantly greater variability with respect to both loudness and F0 among ED patients. Furthermore, loudness and F0 variability were strongly correlated, suggesting a shared pathological basis. We conclude that F0 variability and loudness instability are reliable measures for objectively characterizing ED and assisting accurate diagnosis. The incorporation of quantitative acoustic tools into future diagnostic and therapeutic frameworks has the potential to increase the objectivity and reproducibility of ED assessment.