title: An acoustic-perceptual study of vocal tremor.
abstract: BACKGROUND
  Essential tremor of the voice (ETV) is an involuntary intention tremor of the vocal folds that causes fluctuations in fundamental frequency (f(0)) and/or intensity leading to an unsteady voice. There is limited data on how different acoustic variables affect perception of severity of tremor.
  
  
  OBJECTIVE
  The purpose of the study was to determine if systematic changes in f(0), rate or modulation frequency (f(f0m)), extent or depth of modulation (d(f0m)), and signal-to-noise ratio (SNR) affect perception of severity of tremor.
  
  
  METHODS
  Vowel phonations of four speakers (two male and two female) with a clinical diagnosis of ETV were selected from the Kay Elemetrics Disordered Voice Database (Lincoln Park, NJ). A high fidelity speech vocoder (STRAIGHT; Kawahara, 1997) was used to synthesize the f(0) contour for each of these voices, which were varied in mean f(0), f(f0m), and d(f0m). The f(0) contour was modified 30 Hz above and below the mean f(0) for each speaker. f(f0m) ranged from 3 to 12 Hz in steps of 3 Hz. d(f0m) ranged from 2 to 32 Hz in steps of 6 Hz. Six (three experts and three naïve) listeners rated the "severity" of tremor on a seven-point rating scale.
  
  
  RESULTS
  Significant main effects and interactions were found between the study variables. Perceived severity of tremor increased with f(f0m) and d(f0m). There was no systematic effect of SNR on perceived tremor severity.
  
  
  CONCLUSIONS
  The perception of severity for steady-state tremor results from a complex interaction of multiple acoustic cues with d(f0m) acting as the primary acoustic cue.
authors.affiliation: Department of Speech, Language, and Hearing Sciences, University of Florida, Gainesville, Florida 32611, USA. supraja.anand@ufl.edu
authors.forename: Supraja
authors.initials: S
authors.lastname: Anand
authors.forename: Rahul
authors.initials: R
authors.lastname: Shrivastav
authors.forename: Judith M
authors.initials: JM
authors.lastname: Wingate
authors.forename: Neil N
authors.initials: NN
authors.lastname: Chheda
mesh_terms: D000162:Acoustics; D000368:Aged; D000704:Analysis of Variance; D003463:Cues; D020329:Essential Tremor / Q000175:diagnosis* / Q000503:physiopathology / Q000523:psychology; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D017711:Nonlinear Dynamics; D015588:Observer Variation; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D013061:Speech Acoustics; D013067:Speech Perception; D013068:Speech Production Measurement; D014827:Vocal Cords / Q000503:physiopathology*; D014832:Voice Disorders / Q000175:diagnosis* / Q000503:physiopathology / Q000523:psychology; D014833:Voice Quality