title: Relationship Between the Electroglottographic Signal and Vocal Fold Contact Area.
abstract: OBJECTIVE
  Electroglottography (EGG) is a widely used noninvasive method that purports to measure changes in relative vocal fold contact area (VFCA) during phonation. Despite its broad application, the putative direct relation between the EGG waveform and VFCA has to date only been formally tested in a single study, suggesting an approximately linear relationship. However, in that study, flow-induced vocal fold (VF) vibration was not investigated. A rigorous empirical evaluation of EGG as a measure of VFCA under proper physiological conditions is therefore still needed.
  
  
  METHODS
  Three red deer larynges were phonated in an excised hemilarynx preparation using a conducting glass plate. The time-varying contact between the VF and the glass plate was assessed by high-speed video recordings at 6000 fps, synchronized to the EGG signal.
  
  
  RESULTS
  The average differences between the normalized [0, 1] VFCA and EGG waveforms for the three larynges were 0.180 (±0.156), 0.075 (±0.115), and 0.168 (±0.184) in the contacting phase and 0.159 (±0.112), -0.003 (±0.029), and 0.004 (±0.032) in the decontacting phase.
  
  
  CONCLUSIONS
  Overall, there was a better agreement between VFCA and the EGG waveform in the decontacting phase than in the contacting phase. Disagreements may be caused by nonuniform tissue conductance properties, electrode placement, and electroglottograph hardware circuitry. Pending further research, the EGG waveform may be a reasonable first approximation to change in medial contact area between the VFs during phonation. However, any quantitative and statistical data derived from EGG should be interpreted cautiously, allowing for potential deviations from true VFCA.
authors.affiliation: Voice Research Lab, Department of Biophysics, Faculty of Science, Palacký University, Olomouc, Czech Republic. Electronic address: vit.hampala@gmail.com.
authors.forename: Vít
authors.initials: V
authors.lastname: Hampala
authors.affiliation: Laboratory of Bio-Acoustics, Department of Cognitive Biology, University of Vienna, Vienna, Austria.
authors.forename: Maxime
authors.initials: M
authors.lastname: Garcia
authors.affiliation: Voice Research Lab, Department of Biophysics, Faculty of Science, Palacký University, Olomouc, Czech Republic.
authors.forename: Jan G
authors.initials: JG
authors.lastname: Švec
authors.affiliation: Department of Communication Sciences and Disorders, 200 Health and Human Services, Bowling Green State University, Bowling Green, Ohio.
authors.forename: Ronald C
authors.initials: RC
authors.lastname: Scherer
authors.affiliation: Voice Research Lab, Department of Biophysics, Faculty of Science, Palacký University, Olomouc, Czech Republic.
authors.forename: Christian T
authors.initials: CT
authors.lastname: Herbst
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D003670:Deer; D004568:Electrodiagnosis / Q000379:methods*; D005260:Female; D007828:Laryngoscopy; D010699:Phonation; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D014732:Vibration; D014741:Video Recording; D014827:Vocal Cords / Q000033:anatomy & histology* / Q000502:physiology*
keywords: Electroglottography; Excised hemilarynx; High-speed imaging; Vocal fold contact area