Lip Trill: Aerodynamic, Acoustic, and Laryngeal Interactions

The lip trill (an oscillatory semioccluded vocal tract (SOVT) exercise) is commonly used by singers and speakers to improve voice production skills. The specific objective of this study was to investigate the relationships between aerodynamic and acoustic signals during lip trills.

One trained female singer performed lip trill with and without voicing and a lip trill followed immediately by a /bap:/ syllable string. The audio, airflow, electroglottography (EGG), and oral air pressure signals were obtained. EGG was used to compute EGGW25, EGG height (EGGH), and fundamental frequency (f_o).

This participant's EGGW25 reduced from over 0.5 during vowel production to 0.2 during lip trill. Oral air pressure during voiced lip trill never reached atmospheric pressure and was higher during unvoiced than voiced lip trill production. EGGW25, EGGH, and f_o changed regularly within a lip trill cycle: EGGW25 and EGGH decreased with lip opening, and f_o increased by as much as three semitones above the target frequency.

The results indicate that lip trill greatly reduced the glottal EGGW25, an indication of less glottal adduction. During the lip trill, the EGGW25 and EGGH decreased as the lips separated, contrary to what was expected, indicating a complex relationship among transglottal pressures, adduction, and airflow. Conversely, fundamental frequency increased during lip separation as expected, albeit to a greater magnitude than anticipated. Unvoiced lip trill reported higher oral air pressures presumably due to the lack of glottal resistance.