Objective: Lip trill production is commonly used in vocal warm up for speakers and singers. Lip trill can be produced with or without phonation. The oscillation of the two lips simultaneously requires adequate trans-labial pressures. This study examines pressures for the onset and the offset of lip oscillations.

Methods: The lip oscillation threshold pressure (LOTP) for onset and offset was obtained for one performer (and will be acquired from three others). The oral air pressure transducer from an early Glottal Enterprise aerodynamic system, EGG, and microphone system were used. The pressure transducer was attached to a small tube that was placed in the corner of the mouth and extended into the oral cavity unobstructed by the tongue. Five trials for onset and offset for unvoiced and voiced lip trill were obtained.

Results: Like PTP for phonation, the onset oral air pressure was significantly higher for onset than for offset. The average onset pressure for unvoiced lip trills was 7.3 cm H2O (SD = 0.33) and 2.55 cm H2O (SD = 0.29) for offset. The average onset pressure for voiced lip trills was 16.82 cm H2O (SD = 1.00) and 13.59 cm H2O (SD = 0.08) for offset. The subglottal pressure for the voiced lip trills was not measured but because the subglottal pressure must be equal to the sum of the transglottal pressure plus trans-labial pressure, most likely the subglottal pressure was greater for voiced lip trill onset and offset than for the unvoiced condition.

Conclusions: Lip trill onset pressures were higher than lip trill offset pressures, with a surprising difference between voiceless lip trill (lower) and voiced lip trill (higher) pressure values. Application to vocal warm up will be discussed.