Impact of Loud Noise on Sympathetic Nervous System Function, Training Efficacy, and Workplace Accuracy.

Objectives: Noise is a pervasive environmental factor in manufacturing settings and is a well-known cause of noise-induced hearing loss. However, its effects on autonomic nervous system function and cognitive work performance have not been thoroughly investigated. This study aimed to elucidate the impact of high-intensity noise exposure on autonomic activity and cognitive performance using objective physiological and behavioral indicators.

Methods: Task performance was assessed using two 15-minute sessions of the Uchida-Kraepelin test. Autonomic nervous system activity was evaluated through continuous monitoring of heart rate variability (HRV) and measuring salivary amylase activity at three time points: immediately before the first test, between the two test sessions, and immediately after the second test. All measurements were conducted on two separate days under the absence of noise or the presence of 90 dB[A] pink noise.

Results: Exposure to noise significantly increased low-frequency (LF) and the LF / (LF + high-frequency [HF]) ratio. HF and the coefficient of variation of R-R intervals (CVRR) showed no significant change. Salivary amylase activity was also significantly elevated during noise exposure, particularly after task completion. Performance on the Uchida-Kraepelin test revealed a significant decrease in the response volume ratio under noise exposure. The number and rate of incorrect responses remained unchanged.

Conclusion: High-intensity noise exposure activates the sympathetic nervous system and impairs work performance by reducing processing speed while maintaining accuracy. These findings underscore the importance of considering noise not only as an auditory hazard but also as a factor affecting cognitive ergonomics and occupational performance.