Summary: The noise of traffic and wind farms has an impact on sleep, researchers report. The study revealed the effects of the noise were brief, and most study participants’ brain waves returned to baseline sleep activity within thirty seconds of the noises being introduced.
Source: Flinders University
Sleeping people respond to both wind farm noise and road traffic noise, but not usually enough to wake them up, according to new Flinders University research.
Published in the Journal of Sleep Research, researchers used an electroencephalogram (EEG) to analyze the brainwaves of 23 young healthy people while they experienced 3-minute samples of wind farm noise and road traffic noise played at different noise levels (33, 38 and 43 dBA).
“These noise levels span the approximate range of recommended maximum average indoor and outdoor noise levels at night,” says lead author Claire Dunbar from Flinders Health and Medical Research Institute: Sleep Health.
“By noting changes in their brain waves, we found the participants responded similarly to both wind farm and road noise, especially when the sound was louder. Then, during light sleep, we found low-level wind farm noise caused a greater brain activation response, compared to road traffic noise played at the same noise level.”
However, the authors say the effects of the sounds were brief, with most participants’ brain waves returning to baseline sleep activity levels 30 seconds after the start of each noise, with very few people actually waking up, either briefly or for a prolonged period.
“This tells us the overall impacts of the noise on the participants’ sleep was relatively small,” says Ms Dunbar.
The research is an important step towards applying more sensitive brain signal analysis techniques, compared to traditional manual sleep scoring methods, the authors say. With the new approach, researchers can better understand the impacts of noise on sleep, particularly at low noise levels and with different noise characteristics, where sensitive methods are most needed.
“While this study shows there is a response to wind farm and road traffic noise while an individual is sleeping, more research using a similar technique with a larger group of people and longer exposure times is still needed to help better understand noise impacts on sleep and potential longer-term effects,” says Ms Dunbar.
The research is part of an ongoing series of studies being undertaken at Flinders University to investigate the effects of wind farm noise compared to traffic noise on different aspects of sleep.
EEG power spectral responses to wind farm compared with road traffic noise during sleep: A laboratory study
Wind turbine noise is dominated by low frequencies for which effects on sleep relative to more common environmental noise sources such as road traffic noise remain unknown. This study examined the effect of wind turbine noise compared with road traffic noise on sleep using quantitative electroencephalogram power spectral analysis.
Twenty-three participants were exposed to 3-min samples of wind turbine noise and road traffic noise at three sound pressure levels (33, 38 and 43 dBA) in randomised order during established sleep. Acute (0–30 s) and more sustained (30–180 s) effects of noise presentations during N2 and N3 sleep were examined using spectral analysis of changes in electroencephalogram power frequency ranges across time in 5-s intervals.
Both noise types produced time- and sound pressure level-dependent increases in electroencephalogram power, but with significant noise type by sound pressure level interactions in beta, alpha, theta and delta frequency bands (all p < 0.05). Wind turbine noise showed significantly lower delta, theta and beta activity immediately following noise onset compared with road traffic noise (all p < 0.05).
However, alpha activity was higher for wind turbine noise played at lower sound pressure levels (33 dBA [p = 0.001] and 38 dBA [p = 0.003]) compared with traffic noise during N2 sleep. These findings support that spectral analyses show subtle effects of noise on sleep and that electroencephalogram changes following wind turbine noise and road traffic noise onset differ depending on sound pressure levels; however, these effects were mostly transient and had little impact on conventionally scored sleep.
Further studies are needed to establish if electroencephalogram changes associated with modest environmental noise exposures have significant impacts on sleep quality and next-day functioning.