Real-time ultrasonographic assessment of true vocal fold length in professional singers

To assess changing true vocal fold (TVF) length with ultrasonography.

Thirty-five professional singers (12 tenors and 23 sopranos) were included in this study. Each subject had a documented TVF length with laryngeal ultrasonography (SonoAce X6 scanner; Samsung Medison, Seoul, Korea) during respiration, phonation, and singing.

The average TVF lengths could be measured in each situation with real-time laryngeal ultrasonography. The mean (standard deviation [SD]) of TVF length was 1.71 cm (0.29) at inspiration, 1.56 cm (0.26) at expiration, 1.70 cm (0.21) at comfort phonation, 2.00 cm (0.22) at the highest tone, and 1.47 cm (0.19) at the lowest tone in tenors. In sopranos, the mean (SD) was 1.35 cm (0.12) at inspiration, 1.17 cm (0.12) at expiration, 1.42 cm (0.12) at comfort phonation, 1.65 cm (0.12) at the highest tone, and 1.14 cm (0.15) at the lowest tone. All variables had significant differences between both sexes (P<0.01). The lengths showed statistically significant differences in each phase (P<0.01). The differences in length between each phase were evaluated as well. When analyzed in each sex, all variables were statistically different except few of them. In both sexes, the highest tone and comfort phonation showed no difference (P=0.081 in tenors and P=0.289 in sopranos). The inspiratory phase and comfort phonation had significant difference only in sopranos (P<0.01) in contrast to tenors (P=0.905).

Ultrasonographic measurement of TVF could be used to assess physiological variation of TVF. To reach a high-pitched voice, the professional singers used similar range of TVF length at comfort phonation. TVF length was affected more by inspiration in tenors. In sopranos, TVF at comfort phonation was significantly lengthened than in tenors.