Impact of nocturnal railway and aircraft noise on awakening probability in the field

Kurzfassung

Introduction: Surveys suggest that - at the same noise level - railway noise is less annoying than aircraft or road traffic noise. Thus, railway noise is less strongly regulated in some European countries. However, in a laboratory study performed at the DLR-Institute of Aerospace Medicine railway noise lead to higher degrees of sleep fragmentation than aircraft noise. Our objective was to compare reactions to aircraft and railway noise in the field. Methods: In a field study on railway noise, 33 healthy participants (mean age 36.2 years ± 10.3 (SD); 22 females) were examined during nine consecutive nights. Polysomnography and noise events were recorded during every night. In total, 8866 railway noise events were used for analysis of noise-induced awakenings. In a field study on aircraft noise, data from 64 subjects and 10658 noise events were recorded. The datasets from rail and aircraft noise were pooled to facilitate a direct comparison. Results: In agreement with former studies, macrostructure of sleep was only slightly altered by noise. Awakening probability (sleep stage changes to wake/S1) due to railway noise increased significantly from 6.5% at 35 dB(A) to 20.5% at 80 dB(A) maximum sound pressure level (p<0.0001). In the comparison of traffic noise sources, awakening probability decreased in the order freight train noise, aircraft noise, and passenger train noise. Different reaction probabilities were explained amongst others by the sound pressure rise time of the noise event. Conclusions: In contrast to the results of annoyance surveys, nocturnal freight train noise lead to significantly increased awakening probabilities that exceeded those observed for aircraft noise at the same maximum sound pressure level. In line with our laboratory findings these awakening probabilities were higher than for aircraft noise. Freight wagons that are technically outdated or more developed may result in different physiological reaction probabilities.