EFFECTS OF LOW-LEVELS OF ROAD TRAFFIC NOISE DURING THE NIGHT - A LABORATORY STUDY ON NUMBER OF EVENTS, MAXIMUM NOISE-LEVELS AND NOISE SENSITIVITY

The objective of the laboratory study presented here was to elucidate the importance of the number of noise events of a relatively low maxim um noise level for sleep disturbance effects (body movements, subjecti ve sleep quality, mood and performance). Twelve test persons slept eig ht nights under home-like laboratory settings. During four of these ni ghts, each test person was exposed to 16, 32, 64 and 128 noise events respectively from recorded road traffic noise at a maximum noise level of 45 dB(A). All test persons (aged 20-42 years) considered themselve s rather or very sensitive towards noise. The results show a significa nt decrease in subjective sleep quality at 32 noise events per night, At 64 noise events, 50% of the test persons experienced difficulties i n falling asleep and, as compared with quiet nights, the time required to fall asleep was on average 12 minutes longer. The occurrence of bo dy movements was significantly related to the reported number of awake nings, and the number of body movements was three times higher during the noisy periods of the night as compared with the quiet periods, ind icating acute noise effects. The results of a vigilance test indicate that noise during the night might prolong the time needed to solve the test. Finally, and regardless of number of noise events, a significan t increase in tiredness during the day was found after nights with noi se exposure. In the paper comparisons are also made with earlier exper iments using maximum noise levels of 50 and 60 dB(A).