title: Comparing Vocal Fold Contact Criteria Derived From Audio and Electroglottographic Signals.
abstract: OBJECTIVE
  Collision threshold pressure (CTP), that is, the lowest subglottal pressure facilitating vocal fold contact during phonation, is likely to reflect relevant vocal fold properties. The amplitude of an electroglottographic (EGG) signal or the amplitude of its first derivative (dEGG) has been used as criterion of such contact. Manual measurement of CTP is time consuming, making the development of a simpler, alternative method desirable.
  
  
  METHODS
  In this investigation, we compare CTP values measured manually to values automatically derived from dEGG and to values derived from a set of alternative parameters, some obtained from audio and some from EGG signals. One of the parameters was the novel EGG wavegram, which visualizes sequences of EGG or dEGG cycles, normalized with respect to period and amplitude. Raters with and without previous acquaintance with EGG analysis marked the disappearance of vocal fold contact in dEGG and in wavegram displays of /pa:/-sequences produced with continuously decreasing vocal loudness by seven singer subjects.
  
  
  RESULTS
  Vocal fold contact was mostly identified accurately in displays of both dEGG amplitude and wavegram. Automatically derived CTP values showed high correlation with those measured manually and with those derived from the ratings of the visual displays. Seven other parameters were tested as criteria of such contact. Mainly, because of noise in the EGG signal, most of them yielded CTP values differing considerably from those derived from the manual and the automatic methods, although the EGG spectrum slope showed a high correlation.
  
  
  CONCLUSIONS
  The possibility of measuring CTP automatically seems promising for future investigations.
authors.affiliation: Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden; Department of Speech, Music and Hearing, Royal Institute of Technology (KTH), Stockholm, Sweden; Department of Speech, Language and Hearing Sciences, Boston University, Boston, Massachusetts. Electronic address: lenflo@kth.se.
authors.forename: Laura
authors.initials: L
authors.lastname: Enflo
authors.affiliation: Voice Research Laboratory, Department of Biophysics, Faculty of Science, Palacký University Olomouc, Olomouc, Czech Republic; Laboratory of Bio-Acoustics, Department of Cognitive Biology, University of Vienna, Vienna, Austria.
authors.forename: Christian T
authors.initials: CT
authors.lastname: Herbst
authors.affiliation: Department of Speech, Music and Hearing, Royal Institute of Technology (KTH), Stockholm, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Sundberg
authors.affiliation: Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden; Department of CLINTEC, Karolinska Institute, Stockholm, Sweden.
authors.forename: Anita
authors.initials: A
authors.lastname: McAllister
mesh_terms: D000162:Acoustics / Q000295:instrumentation; D001696:Biomechanical Phenomena; D004568:Electrodiagnosis; D005260:Female; D006801:Humans; D008297:Male; D015588:Observer Variation; D010699:Phonation; D011312:Pressure; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D063346:Singing; D013018:Sound Spectrography; D014160:Transducers, Pressure; D014827:Vocal Cords / Q000033:anatomy & histology / Q000502:physiology*; D014831:Voice
keywords: Collision threshold pressure; EGG derivative; EGG spectrum slope; Relative dEGG amplitude; Vocal fold contact; Wavegram