Ambient noise levels or single noise events at night in urban neighbourhoods: What causes sleep disturbance?

Abstract: Traffic noise exposure is a constant problem even though some measures against it are taken. It causes disturbances both during the day but also during the night when people are sleeping. A literature review, that was part of this thesis, showed that adverse response to noise from railways is more severe that from the main roads on sleep nighttime. Furthermore, exposure of noise from freight trains has a higher negative effect than that from passenger trains. The main adverse effects that have been found in these studies are on the sleep parameters and the cardiovascular system. A study made by Pedersen (2012) showed that there are some areas in the city Halmstad in Sweden where people are especially disturbed by traffic noise during their sleep nighttime. The aim of the study presented in this thesis was to find out if there is a connection between peoples’ reports of noise disturbance during sleep nighttime and the actual noise exposure. Two modes of measurements have been taken in three of the residential areas from the study by Pedersen (2012) which was Area H close to the harbour, Area MW close to the motorway E6/E20 and Area R close to the railway. The two modes of measurements were A-weighted equivalent sound pressure levels, representing ambient noise levels, and A-weighted maximum sound pressure levels, representing single noise events. These modes were used to identify the possible cause of sleep disturbance by the type of noise exposure. For ambient noise levels, 10 measurements at two occasions, each one minute long, were carried out during the same night at 23:00-24:00 and 03:00-04:00. These specific times have been chosen to obtain the traffic noise exposure when people go to sleep and when their sleep is very deep. Single noise events were measured when the harbour, motorway and railway were used nighttime. The Swedish Transport Administration and Halmstad Harbour were contacted for information on possible exposure times. The results show a relationship between peoples’ reported sleep disturbance nighttime and the exposure to single noise events. The highest maximum noise levels were measured in the area close to the railway which exceeded the recommended guidelines 55dB(A) outside the facades nighttime that have been set up by the World Health Organization. There was no connection found for the ambient noise levels and peoples’ reported sleep disturbance. The highest equivalent sound pressure levels were found in the area close to the motorway. The study in this thesis confirms the results from previous studies that show that railway noise have a higher effect on sleep than road traffic noise. It has been shown in other studies but also in this study that the highest noise exposure comes from freight trains. There has not been found any previous studies that investigate the possible relationship between sleep disturbance and noise coming from the harbour and no single noise events could be measured in the area close to the harbour in the current study. The conclusions are that the single noise events have higher negative effects especially at higher noise exposures. More studies should be made in this area to find the connection between noise exposure, sleep disturbance and long-term health effects. The focus should be on long-term studies and more studies should also be made on the noise exposure from harbours.