Changes in speech and voice characteristics following two hours and eight hours of acute sleep deprivation

Abstract

Objectives: Sleep loss is known to affect aircrew performance. The study intended to examine the changes in speech and voice characteristics following 2 and 8 h of sleep deprivation for their potential usage as screening methods for detecting sleep deprivation in aircrew. Material and Methods: In a repeated measure design, the study analyzed the effects of 2 h and 8 h of acute sleep deprivation on speech and voice parameters among 30 healthy male volunteers by analyzing standard paragraph reading for 15 s and sustained vowel/a/for 6 s using the commercially available Dr. Speech Voice assessment tool. Subjective appreciation of sleepiness and fatigue was measured by Stanford Sleepiness Scale (SSS) and Chalder’s Fatigue Scale (CFS), respectively, and objective assessment of performance by psychomotor vigilance task (PVT). Results: The subjective markers (SSS and CFS) and objective parameters (PVT reaction time) indicated evidence of fatigue onset even after 2-h of sleep deprivation. In speech parameters, average fundamental frequency (F0), F0 range, and % silence time decreased significantly; whereas, speech time, percent voiceless time, and mean percent voiced time increased significantly following 8-h of sleep deprivation, while percent silence time decreased significantly after 8-h of sleep deprivation . In voice parameters, shimmer % and NNE increased significantly while harmonic-to-noise ratio and signal-to-noise ratio decreased significantly after 8-h of sleep deprivation. Mean shimmer % showed a significant change even after 2-h of sleep deprivation. Conclusion: The findings of the study bring out significant changes in both the speech and voice spectrum following periods of acute sleep deprivation. The changes were more pronounced during sleep deprivation of 8-h as compared to 2-h. These findings have potential application in aviation environment in objective detection of aircrew fatigue following periods of continuous wakefulness and resultant sleep deprivation.