Objective: to investigate how much vocal tract setting affects vocal efficiency and economy.

Methods/Design: Silicone model of vocal folds created from Ecoflex 00-10 and three vocal tract models with circular cross-sections which were 3D printed using an acoustically hard material / experimental study in vitro. Opera setting of the vocal tract (VT) was characterized by prolonged vocal tract corresponding to low larynx position, narrow epilarynx (minimum cross-sectional area 25 mm2), wide pharynx (max. 638 mm2), and a relatively small lip opening (inverted megaphone shape VT). Speech setting had cross-sectional area of epilarynx 32 mm2 and that of pharynx 266 mm2. Belting VT was shortened (corresponding to high larynx position), epilarynx was constricted down to 13 mm2, pharynx was equally narrow as in speech and mouth opening wide. Phonation was studied at airflow rate 0.3 l/s, f0 ca 500 Hz. Oral and subglottic airpressure (Poral, Psub) and acoustic SPL were measured. Glottal width variation was studied from high speed imaging. Vocal efficiency was calculated as SPL /mean airflow * mean Psub. Vocal economy was estimated as SPL/ maximum glottal width declination rate (MWDR).

Results: Opera VT gave the highest SPL and vocal efficiency. Maximum glottal width and MWDR were largest. For Belting VT, maximum glottal width was larger but MWDR the same as for Speech. Belting yielded the lowest efficiency. SPL/MWDR was the same for all three VT settings.

Conclusions: Mere VT setting affects both efficiency and economy of voicing. This may be taken advantage of in voice pedagogy. More realistic comparison between voice types as such, however, requires adjustment of both vocal tract and glottal setting together.