Abstract
Background: Sleep inertia, characterized by reduced alertness and cognitive functioning upon waking, has been well-researched in its effects on cognitive and motor abilities. However, its impact on voice quality remains less clear. Objectives: This study aimed to investigate the relationship between sleep inertia following nocturnal sleep and changes in acoustic and perceptual voice parameters in adults. Methods: Ninety healthy participants (45 females, 45 males, ages: 18 - 30 years) took part in a pre-post study using convenience sampling. Their voices were recorded before and after nocturnal sleep across multiple tasks, including vowel /a/ phonation, spontaneous speech, text reading, and maximum phonation time (MPT). Recordings were made in a quiet room using a Zoom H6 recorder at a 44.1 kHz rate. The acoustic analysis included measures of fundamental frequency (F0), standard deviation of F0 (SD F0), vocal intensity, harmonics-to-noise ratio (HNR), cepstral peak prominence smoothed (CPPS), jitter, shimmer, and formant frequencies. Auditory-perceptual evaluation was conducted using the GRBAS Scale. Statistical analysis was performed using SPSS-19. The Shapiro-Wilk test assessed normality, and a paired t-test compared variables, separately for males and females at a 0.05 significance level. Results: Acoustic analysis revealed that both females and males experienced a decrease in mean F0, mean intensity, HNR, and CPPS, and an increase in jitter, shimmer, and SD F0 across most voice samples after sleeping. These changes were particularly significant for females in all voice samples (P < 0.001). Perceptual analysis also showed a significant increase in grade, roughness, breathiness, asthenia, and strain for both genders after sleep (P < 0.001). Conclusions: This study demonstrated that sleep inertia negatively impacts vocal performance, resulting in a decline in voice quality for both genders after sleep compared to before. Notably, this decline in voice quality was more pronounced in women than in men.