Three-Dimensional Finite Element Modeling of the Singer’s Formant Cluster Optimization by Epilaryngeal Narrowing With and Without Velopharyngeal Opening

Abstract

This study aimed to find the optimal geometrical configuration of the vocal tract to increase the total acoustic energy output of human voice in the frequency interval 2-3.5 kHz “singer’s formant cluster”, (SFC) for vowels [a:] and [i:] considering epilaryngeal changes and the velopharyngeal opening (VPO). The study applied 3D volume models of the vocal and nasal tract based on computer tomography (CT) images of a female speaker. The epilaryngeal narrowing (EN) increased the total sound pressure level (SPL) and SPL of the SFC by diminishing the frequency difference between acoustic resonances F3 and F4 for [a:] and between F2 and F3 for [i:]. The effect reached its maximum at the low pharynx/epilarynx cross-sectional area ratio 11.4:1 for [a:] and 25:1 for [i:]. The acoustic results obtained with the model optimization are in good agreement with the results of an internationally recognized operatic alto singer. With the EN and the VPO, the vocal tract input reactance was positive over the entire fo singing range (ca. 75-1500 Hz). The VPO increased the strength of the SFC and diminished the SPL of F1 for both vowels, but with EN the SPL decrease was compensated. The effect of EN is not linear and depends on the vowel. Both the EN and the VPO alone and together can support (singing) voice production.