Changes in the hypnograms of subjects exposed to repeated truck-passing sounds of 45, 50 and 55 dB (A)

Abstract

The effects of traffic noise on sleep were evaluated in an experimental room using recorded truck-passing sounds. Peak sound levels were 45, 50, 55 dB (A) at a frequency of one per hour. The background noise of the exposure night was Leq 32.4 dB (A). The subjects were five male students 22 to 23 years old. The sleep stage of each epoch with a 20-second duration was judged visually based on the criteria of a standardized sleep EEG atlas. Data for 10 noise exposed nights and the same number of control nights were analyzed excluding the first-night data. The sleep parameters used were total sleep time (TST), each sleep stage in minutes, % of sleep stage against TST, sleep efficiency, sleep latency, REM latency, REM cycle, REM duration, waking from sleep, number of stage shifts and subjective sleep as judged by the OSA sleep inventory. The Mann-Whitney test was used for statistical analysis. TST, each sleep stage in minutes,% of sleep stage against TST, sleep efficiency, sleep latency, REM latency, REM cycle, REM duration, waking from sleep and the number of stage shifts of the exposure night did not significantly change compared to those of the control night. However, the sleep latency of the noise-exposed night increased significantly. Subjective sleep measured by five-factor scores and 8 items out of 29 constructing the five-factor scores of the OSA sleep inventory were decreased significantly by noise exposure, indicating deterioration of sleep quality. Exposure to intermittent truck-passing sounds 20 to 30 times per night with peak levels of 45, 50 and 55 dB (A), and a background noise of Leq 32.4 dB (A), caused the sensitivity to sleep disturbance in subjective sleep to be higher than those in objective sleep parameters.