Changes in the vocal tract shape of sopranos at high pitch

Abstract

As sopranos increase their fundamental frequency (F0) to sing at higher pitches, they also increase the first resonance frequency (R1) of their vocal tract. This is probably to avoid sudden F0 changes when F0 and R1 cross. It is unclear, however, how sopranos change vocal tract shape to increase R1. Therefore, the vocal tract shapes of two Japanese sopranos during production of the sung vowel /a/ in the modal register (A4 and D5) and in the falsetto register (G5) were measured by MRI. The measured vocal tract shapes were compared with each other and their area functions were extracted to calculate acoustic characteristics. Results showed that changes in the vocal tract shape were small between A4 and D5, while changes were large between D5 and G5. At G5, it was observed in both subjects that the lower jaw opened, the pharyngeal wall and tongue root advanced, and the larynx retracted. In addition, one subject shortened the laryngeal cavity length. All these changes achieved R1 increase, in agreement with the acoustic sensitivity function. Thus, in conclusion, sopranos selectively modified parts of the vocal tract with high sensitivity to R1. This research was partly supported by Kakenhi (Grant Nos. 21500184, 21300071, 22520156).