Soprano singing, with and without resonances

Abstract

Oscillating vocal folds are acoustically loaded by resonant ducts upstream (trachea) and downstream (vocal tract). The soprano frequency range covers the first resonance in each duct; indeed, sopranos often tune their vocal tract resonance (R1) near the singing frequency. What happens when R1 is removed? In this study, sopranos sang into an acoustically infinite pipe, which effectively removes R1. The singers performed pitch glides from F3-C6, which covers their subglottal resonance and the normal range of R1. In general, few instabilities were observed. This ability to sing into a non-resonant downstream acoustic load, and on either side of the resonant upstream load, demonstrates that a particular phase is not essential for stable vocal fold oscillation. What happens when the acoustic load suddenly changes? The same singers sang into the same non-resonant load while keeping their eyes closed. A plug was rapidly removed from the pipe, which reintroduced R1. This abrupt change in acoustic load triggered brief instabilities in vocal fold oscillation. A return to steady oscillation after the change was possible regardless of the phase of the acoustic load, which together with the experiment described above, suggests that stable vocal fold oscillation is possible into a range of acoustic loads.