Effect of traffic noise on the cyclical nature of sleep

Abstract

It is well known that normal sleep, as measured by the EEG is not a uniform state but varies from shallow to deep sleep in a cyclical manner. The duration of the cycle is roughly 1.5 h. It has been suggested that disruption of these cycles can have unfavorable effects on a subject's performance during the following day [M. Herbert and R. T. Wilkinson, Proc. Mt. Congress on Noise as a Public Health Problem (1973)]. Twelve subjects slept in 60 dB of free‐flowing traffic noise on 12 alternate nights while the level during the other 12 nights was the ambient level of about 32 dB. If every waking or shift to a shallow sleep level is considered to be the beginning of a new cycle, then the average number of cycles per night during the noise night is about 6% greater than during the quiet nights. If only an extended period of shallow sleep is judged to be the beginning of a new cycle, then noise has no effect on the number of cycles per night.