title: Acoustic correlate of vocal effort in spasmodic dysphonia.
abstract: OBJECTIVE
  This study characterized the relationship between relative fundamental frequency (RFF) and listeners' perceptions of vocal effort and overall spasmodic dysphonia severity in the voices of 19 individuals with adductor spasmodic dysphonia.
  
  
  METHODS
  Twenty inexperienced listeners evaluated the vocal effort and overall severity of voices using visual analog scales. The squared correlation coefficients (R2) between average vocal effort and overall severity and RFF measures were calculated as a function of the number of acoustic instances used for the RFF estimate (from 1 to 9, of a total of 9 voiced-voiceless-voiced instances).
  
  
  RESULTS
  Increases in the number of acoustic instances used for the RFF average led to increases in the variance predicted by the RFF at the first cycle of voicing onset (onset RFF) in the perceptual measures; the use of 6 or more instances resulted in a stable estimate. The variance predicted by the onset RFF for vocal effort (R2 range, 0.06 to 0.43) was higher than that for overall severity (R2 range, 0.06 to 0.35). The offset RFF was not related to the perceptual measures, irrespective of the sample size.
  
  
  CONCLUSIONS
  This study indicates that onset RFF measures are related to perceived vocal effort in patients with adductor spasmodic dysphonia. These results have implications for measuring outcomes in this population.
authors.affiliation: Department of Speech and Hearing Sciences, University of Washington, Seattle, Washington, USA.
authors.forename: Tanya L
authors.initials: TL
authors.lastname: Eadie
authors.forename: Cara E
authors.initials: CE
authors.lastname: Stepp
mesh_terms: D000328:Adult; D000368:Aged; D001307:Auditory Perception; D055154:Dysphonia / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index; D013061:Speech Acoustics; D014831:Voice; D014833:Voice Quality; D055815:Young Adult