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Abstract :
[en] BACKGROUND: In Belgium, music theory teachers teach theoretical aspects of rhythm, singing and other music-related skills (such as pitch accuracy or singing in harmony) outside the regular school setting. To date, their voice use and how it may be affected by background noise have hardly been studied. OBJECTIVES: 1) to determine the relationship between music theory teachers’ vocal loading and background noise and 2) to examine if the daily number of vocal fold vibration cycles (vocal loading index, VLI) is reflected in the teachers’ auto-evaluation of their voice. METHODS: A VoxLog voice dosimeter (Sonvox) was used to monitor 13 music theory teachers for one 6-day workweek from the early morning until late evening. Parameters analysed were fundamental frequency (F0, Hz), voice sound pressure level (SPL, dB), time dose (%), noise SPL (dB), and VLI. At the end of each monitoring day, subjects evaluated their voice quality, vocal fatigue, and amount of speaking and singing voice used by means of a visual analogue scale. RESULTS: Statistical analysis revealed positive correlations between noise SPL and F0, voice SPL and time dose. Correlations were also found between VLI and auto-evaluation data: a rise in VLI accompanied a decrease in self-perceived voice quality, an increase in vocal fatigue and an increase in the perceived amount of singing and speaking voice used. CONCLUSION: Three conclusions were drawn from the results. Firstly, vocal loading measured in music theory teachers is connected to the background noise level. Secondly, a great number of vibration cycles is associated with a self-reported increase in vocal fatigue and a lower general voice quality at the end of the day. Finally, correlations between the number of vibration cycles and the self-reported amount of voice use suggest that visual analogue scales are a reliable method to evaluate daily voice use.