Vertical Phase Difference and Glottal Efficiency in Musical Theater and Opera Singers

Abstract

The objectives of this study were to (1) determine the relationship between vertical phase difference (VPD) and glottal efficiency (GE) in singers and (2) to compare VPD and GE between musical theater and opera singing styles. Five opera and three musical theater singers (Mean age = 25.3, 100% male) performed a series of vocal tasks at two pitches (low pitch C#3, 133 ± 5 Hz; high pitch C#4, 277 ± 5 Hz) for three levels of loudness (soft, baseline, and loud), while undergoing flexible distal chip videostroboscopy. Aerodynamic and acoustic information for each vocal task was recorded using the Phonatory Aerodynamic System. VPD was qualitatively measured via visual-perceptual judgments of repeated comparison tests, where a blinded rater was asked to select the video in which the subject demonstrated the greatest VPD. Aerodynamic data were analyzed for differences in GE. Qualitative visual-perceptual analysis indicated that increased magnitude of VPD was correlated with tasks involving increased loudness or higher pitch. GE was similarly correlated with increased loudness or higher pitch. GE was minimally correlated with subglottal pressure at high pitch. This prospective study reveals novel human subject evidence that VPD may correlate with GE. Future studies will further explore the implications of VPD with respect to GE, subglottal pressure, and laryngeal mechanics.