Effects of noise during sleep with reference to noise sensitivity and habituation

The effect of road traffic noise was investigated among noise-sensitive and noise non-sensitive subjects in a two-week laboratory study. Physiological effects on heart rate and body movements in connection with noise events were found, neither of which decreased toward the end of the noise period. A significant effect on sleep quality was found only among the sensitive subjects. The negative influence of noise on sleep quality, mood and performance was just as pronounced after the last as after the first noisy nights. Preliminary results from a laboratory study on the importance of the number of noise events showed that there is a threshold for effects on sleep quality around 10 events/night for 60 dBA. For 50 dBA, a significant decrease in sleep quality was seen at 64 events/night. Results from a field study in areas characterized by heavy noise suggest that noise during night hours causes different psycho-social and medical symptoms and that decreased sleep quality is more frequent among noise-sensitive individuals.