A scientific review has found that wind farm noise has no systemic effects on the sleep of nearby residents but may have more subtle impacts, prompting a need for further study on whether these crucial renewable energy sources actually disrupt the lives of those around them.

The literature review1, conducted by scientists at Flinders University, looked at five past studies on the the low-frequency, far-travelling noise from wind turbines and its effects on the wellbeing on those living nearby.

“Comparing wind turbine noise to quiet background noise conditions showed no systematic effects on the most widely used objective markers of sleep, including time taken to fall asleep, total sleep time, time spent awake during the night and time spent asleep relative to overall time in bed,” said lead author Tessa Liebich of the Adelaide Institute for Sleep Health.

“However, some more subtle effects on sleep in some objective studies were established including shifts in sleep stages, less time spent in deep sleep and more time spent in light sleep.”

The paper is the first stage of a five-year collaborative project, the next of which is an experimental study of over 70 volunteers examining potential noise disruption from wind farms in a controlled environment and further our knowledge in this area.

Low frequency noises known to impact sleep

Liebich told Lab Down Under that environmental noises such as traffic noise were already known to impact sleep, and that noise from wind turbines might have a similar effect.

“Wind farm noise is lower frequency, so can travel further and through buildings more easily, and can have prominent time-varying features such as amplitude modulation, mostly from blade movement past the towers. These effects could make wind farm noise more noticeable, annoying and problematic for sleep compared to other noise types.”

However, there is very little evidence out there about how wind farm noise impacted sleep, particularly from studies using objective sleep measures that compared wind farm noise to noise from other sources, she said.

Prior reviews on wind farm noise looked at cross-sectional studies that replied on self-reported data rather than looking at more objective sleep measures. This means any causal relationship between wind farm noise and sleep remains unclear.

“Experimental studies investigating the impact of wind turbine noise on sleep using more widely used objective measures of sleep have begun to emerge. This review sought to provide an updated summary of the most relevant literature in this area,” Liebich said.

The five studies2,3,4,5,6 were chosen through a systemic literature review, using predefined keyword searches, she told Lab Down Under.

“Our focus was on studies that used direct measures of sleep or well-established and widely-used self-report measures of sleep in the presence versus absence of wind turbine noise. We did not include studies that used researcher developed self-report assessments that could not be directly compared and combined between studies.”

Existing studies show need for clarity

The main focus of the literature review was to evaluate the strength of the presently available published research to look for objective markers of sleep including time taken to fall asleep, total sleep time, time spent awake during the night and time spent asleep relative to overall time in bed.

“The available studies in this area do not appear to show consistent effects of windfarm noise on these sleep measures, however, this does not rule out important impacts on sleep and in some people more than others,” Liebich said.

The more subtle effects found in one particular study supported a “cautious interpretation” that insomnia severity, sleep quality and daytime sleepiness could be impacted by wind farm noise. However, the researchers say that it is difficult to draw any strong conclusions without further research.

“These more subtle effects were from one research study that investigated the impact of wind turbine noise in a well-controlled laboratory study, which provides a higher level of evidence compared to observational studies. Given only one study in a relatively small number of people has shown these effects, further studies are needed to help clarify these findings,” Liebich said.

Other limitations of the review were the small number of high quality papers available to compare and the mixed methodology used between each study. Furthermore, the biases of the individuals involved in the study may be one more varying factor, the researchers said.

“For example, strong negative or positive attitudes towards wind turbines and awareness of study conditions or interventions appear likely to impact study participation, self-reported and potentially objective sleep parameters through expectation effects on abilities and times taken to fall asleep, remain asleep versus awake overnight, and to wake following sleep.”

An objective look at wind farm noise

In order to build on the findings of past studies, Flinders researchers are now studying sleep patterns in over 70 volunteers through a controlled in-laboratory experimental study to investigate the impacts of wind turbine noise both while asleep and during the day.

“Our ongoing study is using more sensitive markers of sleep disturbance to look more closely at potential sleep disturbance effects using both electro-encephalography and subjective sleep assessment methods in different groups of people,” Liebich said.

The impacts are being tested on different groups of individuals with varying levels of prior exposure to wind farm noise or traffic noise.

“We are also testing different noise levels to help directly compare ‘dose-response’ effects of wind farm compared to traffic noise to specifically test for possible differences between noise types. This approach should help to directly establish noise effects on sleep and next day impacts on mood and daytime functioning, especially in people most impacted by these noise types,” explained Liebich.

The final results of this laboratory study are expected in mid-2021.

Tackling challenges in further research

While the short-term study with 70 volunteers could bring about new insights, Liebich said that further research was needed, which presented its own unique challenges.

“Potential longer-term exposure effects on sleep and other aspects of health would require further and more difficult longer-term studies. Current sleep measurement methods may also not be sufficiently sensitive to detect some noise impacts on sleep.”

The Flinder’s study introduces more sensitive markers of sleep disturbance using advanced signal processing methods for EEG, heart rate and other physiological signals.

“This approach may well be needed and useful for further studies in this area. There are also large individual differences in noise-sensitivity, annoyance, experiences, attitudes and hearing acuity that need to be considered, in our study and in future work in this area.”

The Flinders University Wind Farm Noise Study is funded through the Australian National Health and Medical Research Council. The five-year collaborative study will examine the effect of wind farm noise on people’s health and also compare its impacts to traffic noise.

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1 Liebich T, Lack L, Hansen K, Zajamšek B, Lovato N, Catcheside P and Micic G. A systematic review and meta‐analysis of wind turbine noise effects on sleep using validated objective and subjective sleep assessments. Journal of Sleep Research, November 2020.

2,3 Ageborg Morsing J, Smith MG, Ögren M, Thorsson P, Pedersen E, Forssén J, Persson Waye K (2018). Wind turbine noise and sleep: Pilot studies on the influence of noise characteristics. International Journal of Environmental Research and Public Health, 15, 2573.

4 Jalali L, Bigelow P, Nezhad-Ahmadi MR, Gohari M, Williams D, McColl S (2016). Before–after field study of effects of wind turbine noise on polysomnographic sleep parameters. Noise & Health, 18, 194.

5 Lane JD, Bigelow PL, Majowicz SE, McColl RS (2016). INTERNATIONAL PERSPECTIVES: Impacts of industrial wind turbine noise on sleep quality: Results from a field study of rural residents in Ontario, Canada. Journal of Environmental Health, 79, 8–13.

6 Smith MG, Ögren M, Thorsson P, Hussain-Alkhateeb L, Pedersen E, Forssén J, Ageborg Morsing J, Persson Waye K (2020). A laboratory study on the effects of wind turbine noise on sleep: Results of the polysomnographic WiTNES study. Sleep, 43, 1–14.

Featured image: Wind turbine on farm by Roy Harryman. Used under the Pixabay License.

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