Differences in self-rated, perceived, and acoustic voice qualities between high- and low-fatigue groups

The present study was performed to examine which factors among self-rated scales, perceptual evaluations, and acoustic parameters, calculated from sustained vowels, are reliable indicators of physical and mental fatigues.

A total of 73 volunteers (male:female, 52:21), aged 19-24 years, were enrolled in this study. We defined the high- and low-fatigue groups using the Chalder Fatigue Scale score. For assessment of self-rated symptoms, each subject was asked to complete Voice Handicap Index (VHI) and Voice Rating Scale (VRS). For perceptual evaluations, three clinicians assessed each subject's vocal quality on the Grade, Roughness, Breathiness, Asthenia, Strain Scale. For acoustic analysis, each subject was asked to produce sustained vowels /a/, /e/, /i/, /o/, and /u/ for 3 seconds. Then, the habitual fundamental frequency (F(0)), jitter, shimmer, F(0) tremor, mean F(0), standard deviation of F(0), maximum F(0), minimum F(0), normalized noise energy, harmonic-to-noise ratio (HNR), signal-to-noise ratio (SNR), amplitude tremor, and ratio within 2-4kHz were calculated using Dr. Speech software.

In men, VHI, VRS, F(0) tremor, shimmer, HNR, SNR, and amplitude tremor were related to mental fatigue. In women, only VHI was related to physical fatigue, and none of the acoustic parameters was related to the fatigue score. Perceptual evaluations were not related to fatigue in men or women.

These findings suggest that self-rated symptoms and acoustic parameters related to voice quality are indicative of mental fatigue, and these features are prominent in men.