Resonance Tube or Lax Vox

Summary Objective This study compares the flow resistance of Resonance tube (RT) and Lax Vox tube (LVT) when submerged 2 cm and 10 cm in water, as well as phonation into the tubes in these conditions. Methods In the in vitro experiment, the air pressure for flow rates of 60–600 mL/s was measured at the tube inlet, when the outer end of the tube was submerged 2 cm and 10 cm below water surface in 30°, 45°, and 90° angle. In the in vivo experiment, 14 subjects phonated in habitual loudness and loudly into both tubes, with the outer end 2 cm and 10 cm in water. RT was immersed in a 45° angle and LVT in a 90° angle in water. Oral pressure, contact quotient from electroglottographic signal, and sound pressure level were studied. Sensations during phonation were reported in an interview. Results Flow resistance was slightly lower with LVT than with RT, and slightly lower for smaller immersion angles. In habitual loudness, transglottic pressure and frequency of oral pressure variation were lower for LVT phonation and amplitude of oral pressure variation was higher for LVT 2 cm in water. Some subjects preferred RT, whereas others preferred LVT or reported no differences between them. Conclusions The tubes differed slightly in flow resistance. Higher oral pressure oscillation with LVT 2 cm in water may offer stronger massage effect on vocal folds.