title: Vertical Phase Difference and Glottal Efficiency in Musical Theater and Opera Singers.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Voice, College-Conservatory of Music, University of Cincinnati, Cincinnati, Ohio; Department of Otolaryngology, Head and Neck Surgery, University of Cincinnati, Cincinnati, Ohio.
authors.forename: Elliana
authors.initials: E
authors.lastname: Kirsh
authors.affiliation: Center for Pediatric Voice Disorders, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio; Division of Speech and Language Pathology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio. Electronic address: stephanie.zacharias@cchmc.org.
authors.forename: Stephanie R C
authors.initials: SRC
authors.lastname: Zacharias
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, University of Cincinnati, Cincinnati, Ohio; Center for Pediatric Voice Disorders, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.
authors.forename: Alessandro
authors.initials: A
authors.lastname: de Alarcon
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, University of Cincinnati, Cincinnati, Ohio; Center for Pediatric Voice Disorders, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.
authors.forename: Dimitar
authors.initials: D
authors.lastname: Deliyski
authors.affiliation: Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.
authors.forename: Meredith
authors.initials: M
authors.lastname: Tabangin
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, University of Cincinnati, Cincinnati, Ohio.
authors.forename: Sid
authors.initials: S
authors.lastname: Khosla
mesh_terms: D000162:Acoustics; D000328:Adult; D001696:Biomechanical Phenomena; D005931:Glottis / Q000502:physiology*; D006801:Humans; D007600:Judgment; D007828:Laryngoscopy; D008144:Loudness Perception; D008297:Male; D009790:Occupations; D010699:Phonation; D010898:Pitch Perception; D011312:Pressure; D011446:Prospective Studies; D063346:Singing; D049489:Stroboscopy; D014732:Vibration; D014741:Video Recording; D014796:Visual Perception; D014833:Voice Quality; D055815:Young Adult
keywords: Glottal efficiency; Laryngeal mechanics; Singers; Vertical Phase Difference; Voice