Targeted Call for Research into Wind Farms and Human Health 2015

Final reports 

Funding for the two research projects has concluded and the research teams have provided final reports summarising their achievement and the impact of their research.  

Establishing the physiological and sleep disruption characteristics of wind farm versus traffic noise disturbances in sleep 

Chief Investigator A – Associate Professor Peter Catcheside, Flinders University of South Australia (grant value: $1,357,652). 

This project investigated wind farm noise effects on sleep using four studies: 1) a computer assisted telephone interview (CATI) survey in 542 individuals, and direct measures of sleep through 2) a 2-night field study in 27 individuals, 3) a 2-night pilot laboratory study in 25 volunteers, and 4) a 7-night laboratory study in 68 participants. 

The survey employed geographic and random sampling and computer assisted telephone interviews to investigate self-reported sleep difficulties (falling or staying asleep, waking too early, or feeling unrefreshed) attributed to road traffic noise, wind farm noise or other factors. Three groups of residents were investigated. These included 372 rural residents living within 10 km of a wind farm (n=38-84 in five 2 km bands), 87 urban residents living within 800 m from a busy road (>50,000 vehicles/day) and 83 residents living in a quiet rural area. In residents living near a wind farm, reports of moderate-to-very severe sleep difficulties from wind farm noise were low (0.8%), similar to road traffic noise (2.2%) and lower than sleep difficulties from other sources (16.1%). Overall sleep difficulties were not different between groups, although trended towards higher rates in urban road traffic noise exposed residents. These findings suggest a similar prevalence of sleep difficulties in residents exposed to wind farm noise, road traffic noise, and quiet rural areas. Survey responses were also used to help recruit participants with and without noise related sleep difficulties into the main laboratory study to more specifically investigate wind farm compared to traffic noise impacts on sleep in a tightly controlled laboratory environment. 

The field study was designed to evaluate noise and sleep conditions in a real-world wind-farm noise exposure setting and was conducted in 27 residents living in 16 different residences within 1-9 km (mean ± standard deviation 2.7±1.8 km) from a South Australian wind farm. Measurements included approximately 3 weeks of outdoor wind speed and direction along with outdoor and indoor acoustic measurements, hearing assessments and 2 consecutive nights with full sleep study recordings time-synchronised to acoustic recordings. Saliva and hair samples were also taken for measurements of short- and longer-term stress-hormone (cortisol) responses. Sleep efficiency, which is the percentage of time spent asleep during the sleep period, was 79±9% across both nights and was slightly but significantly below a normal cut-off of 85%. Sleep efficiency was also reduced on the first compared to second night, which is common with sleep study recordings largely due to initial discomfort from wearing the sleep measurement equipment, which is the main reason for conducting two sleep study nights. A range of analyses are ongoing to test for potential relationships between sleep quality and naturally variable wind farm noise levels within- and between-nights, and to compare sleep quality and other measurements between field study and in-laboratory study groups. 

Given the lack of previous in-laboratory studies using direct sleep recordings and experimental manipulation of wind farm compared to road traffic noise, a pilot study was conducted to help test and refine the acoustic and sleep measurement and analysis methods prior to the larger main laboratory study. Twenty-five young healthy good sleepers underwent audiology assessments and were studied on two separate nights in the Flinders University Psychology sleep laboratory following building works needed to reduce background and air-conditioning noise levels. On both nights, participants underwent detailed sleep study recordings during exposure to a battery of wind farm and road traffic noise stimuli presented at levels in random order interspersed with periods of silence. On one night, noise stimuli were 20-sec in duration to assess brief arousal and physiological activation responses in response to noise exposure. On the other night, noise stimuli lasted 3-min to examine longer exposure effects including full awakenings. These noise stimuli were presented only when participants were already asleep or had returned to sleep in the event of any awakenings. However, to also test the ability of individuals to fall asleep in the presence of ongoing wind farm noise, participants were randomised to receive either silence or ongoing wind farm noise exposure during the sleep onset period and any periods of wake overnight. Published results to date show that sleep remains relatively well preserved in the presence of realistic levels of wind farm and road traffic noise exposure, with no evidence of prolonged time to fall asleep in the presence of wind farm noise during the sleep onset period in healthy good sleepers. However, as is well-known with noise presentations during sleep, brief physiological activation responses to noise were strongly dependent on noise level and the depth of sleep. There were also some more subtle noise level dependent differences in activation responses between wind farm compared to traffic noise. This study substantially helped to test and refine core study methods and analysis techniques ahead of the main laboratory study. 

In the main laboratory study, 68 participants were recruited via the survey, advertising, and word of mouth to undertake a seven consecutive night study in the new Flinders University Nick Antic sleep laboratory facility. This laboratory has two very low-background noise bedrooms to support acoustic sleep experiments. Participants included four groups: two groups habitually exposed to wind farm noise at night (one group with (n = 14) and one without (n = 18) self-reported wind farm noise related sleep disruption), a group of rural residents without wind farm noise exposure (n = 18), and a group of urban residents who reported road traffic noise related sleep disruption (n = 18). All participants completed a range of questionnaires and underwent hearing tests, detailed sleep study measurements each night, and a range of daytime listening tests to evaluate perceptions around noise annoyance and acceptability for sleep with different types and levels of noise. Sleep signals included brain activity, eye movement, muscle activity, respiratory and other sensor measures needed to discriminate wake from light, deep and rapid-eye-movement sleep and provide markers of sleep disruption such as short micro-arousal events, longer full-awakenings, cardiovascular changes and respiratory disturbance events. After a habituation night (1) to help participants get used to the laboratory environment and measurement procedures, participants were exposed in random order to; a quiet control night (2); a night of 20-second wind farm and road traffic noise exposures interspersed with periods of silence (3); a similar night with 3-minute noise exposures (4); and three full nights of continuous wind farm noise at a realistic levels above background noise (5), continuous wind farm noise played only during sleep (6), or continuous wind farm noise played only during periods of wake (7). The 20-second and 3-minute noise nights were designed to compare shorter and longer sleep disruption effects of wind farm compared to road traffic noise overall and between participant groups. The remaining nights evaluated overall sleep disturbance effects with and without wind farm noise similar to average levels near wind farms. Results to date support that both noise types promote sensory responses that can briefly disrupt sleep depending on noise level, but with relatively minor impacts on overall sleep at noise levels similar to average noise levels in real-world exposure environments. Further analyses to more comprehensively compare between noise types are ongoing and will be released as soon as they become available following peer-review. 

Project outcomes to date have been reported through 14 peer reviewed publications, 5 peer reviewed conference publications and 12 conference abstracts presented at a range of national and international sleep and acoustics conference presentations. A protocol manuscript outlining the main aims, methods and statistical analysis plan along with the main laboratory trial findings are approaching peer-review towards publication. A range of secondary manuscripts are also anticipated to arise from the extensive data collected through this project. In addition to supporting two post-doctoral researchers and direct project costs, this project supported the successful completion of four Honours, two Masters and three PhD students to date, and two further PhD students are due to complete in 2022.  

Significance, likely impact and potential benefits of this research 

A large body of evidence already supports that sleep is critical for normal daytime functioning and health and that chronic poor sleep is enormously costly nationally and internationally through negative impacts on safety, health, productivity and quality of life.  Environmental noise is also well-known to disturb sleep according to noise intensity and this underpins noise abatement strategies and guidelines such as building codes, urban design and airport curfews. More limited evidence suggests that other noise characteristics such as frequency content, amplitude modulation and other spectral features also impact on levels of annoyance and potentially sleep disruption. 

Rapid expansion of wind farms in the Australian context has been associated with community concerns surrounding noise annoyance and potential impacts on sleep, health and well-being. However, National Health and Medical Research Council and Canadian reviews of available literature concluded that there was insufficient evidence to determine if wind farm noise exposure negatively impacts sleep and health, and if noise exposure effects are different compared to other noise types. By specifically investigating the sleep disruption characteristics of wind farm noise compared to road traffic noise, project findings will help to clarify the nature and level of sleep disruption specific to wind farm noise. These findings will also help to evaluate if current noise guidelines and policies, which are based largely on traffic noise with substantially different acoustic characteristics, are appropriate or warrant revision to help protect sleep in communities regularly exposed to wind farm noise. Clarifying wind farm noise impacts on sleep are also important to help address community concerns regarding wind farm noise impacts and will provide a critically important evidence-base needed to meaningfully guide policy and industry responses to improve community acceptance of existing and planned future wind farm developments.  

New methods developed through this project are more sensitive to noise-induced sleep disruption compared to traditional sleep measures. Thus, by combining sleep and acoustic researcher expertise this project also provided a major impetus towards improved methods for assessing acoustic and sleep signal features of noise-induced sleep disruption. These are likely to have major future applications towards improved assessments of sleep quality relevant to investigating both environmental noise and clinical sleep problem impacts. 

Grant: 1113615 Multidimensional assessment of the health impacts of infrasound: two randomised controlled trials 

Chief Investigator A – Professor Guy Marks, University of New South Wales (grant value: $1,943,934)  

Laboratory based study: We conducted a randomized double-blind triple-arm crossover laboratory-based study of 72 hours exposure in our noise-insulated sleep laboratory in the style of studio apartment. The exposures were: Infrasound (~90dB pk), sham infrasound (same speakers not generating infrasound) and traffic noise exposure (active control; at a sound pressure level of 40-50dB LAeq,night and 70dB LAFmax transient maxima, night=22:00-07:00). We randomized 37 noise sensitive but otherwise healthy adults (aged 18-72; 51% female) into the study before the NSW COVID-19 related public health order forced the study to close. We successfully measured human sleep using full in-laboratory polysomnography for a total of 316 nights of recording as well as a host of other repeated psychological and physiological tests. Infrasound did not worsen sleep or any other subjective or objective measures used. This provides reassurance that the infrasound component of wind turbine noise is unlikely to cause ill-health or sleep disruption. 

Home based study: We faced enormous difficulty implementing the component of the project that assessed longer-term in- home exposure to simulated wind turbine infrasound. We were asking healthy people from rural areas whether we could put simulated infrasound speakers in the bedroom for six months and see what happened to them. Despite our best efforts to recruit for this study we only managed to recruit 4 participants willing to participate. We redesigned the study and reduced the exposure period to 1 month, moved recruitment to metropolitan areas, removed some aspects of in-home monitoring and made some clinical tests optional in the hope this would enhance recruitment. We also engaged an advertising company to develop recruitment materials and strategies for the project. The COVID-19 pandemic caused significant delays and further restructure of the project through 2020 and 2021. We did manage to recruit another 12 participants into the one-month study but unfortunately the second Sydney lockdown, June to October 2021, meant that we could not collect reliable health outcome measures from six of these participants. To be able to reliably answer the research question we required a target sample size of 120 participants, so we feel far short of this target. 

Significance, likely impact and potential benefits of this research  

Laboratory based study: Prior to this study being conducted there were some concerns expressed that the specific, but inaudible, low frequency infrasound arising from wind turbines may cause ill health.  This has been called “wind turbine syndrome”. However, the existence of this syndrome had never been demonstrated in scientifically robust studies.  In a double-blind controlled experimental study, we found no evidence that 72 hours exposure to low frequency, powerful but inaudible infrasound makes people feel ill or detrimentally alters any physiological characteristic we measured. This finding provides reassurance that the infrasound component of wind turbine noise is unlikely to cause ill-health or sleep disruption.  The findings have now been published in Environmental Health Perspectives https://doi.org/10.1289/EHP10757. 

Home based study: Despite our repeated, and best, efforts we were not able to answer the research question about what happens to people exposed to simulated wind turbine infrasound in the home over the longer term. To ensure this research has impact we are currently writing a manuscript to share the experience and particularly the difficulties through the peer- reviewed literature. It is worth noting that since we commenced this project in early 2016 there has been significant change in community attitudes to renewable energy and climate change which in part may have contributed to the difficulty recruiting participants. Prior to the COVID-19 pandemic we had annual contact with the Australian Energy Infrastructure Commissioner and with members of the Independent Scientific Committee on Wind Turbines.