For those unfortunates forced to live with incessant turbine generated low-frequency noise and infrasound, the cause of their inability to sleep is no mystery.
Following the same trail being blazed by the Max Planck Institute in Germany which found infrasound exposure as the scientific cause of stress, sleep disruption and much more – Wind Farm Victim’s Smoking Gun: German Research Reveals Infrasound Exposure Causes Stress, Sleep Disruption & More – a Swedish research group is working on proving the obvious connection between wind turbine noise emissions and sleep problems in the lab – problems which are universally experienced by wind farm neighbours around the globe, including farmers paid hundreds of thousands a year to host turbines (see our post here).
STT hears that the Swedish group has recently met with Australian sleep/noise researchers and that the results of further and more detailed work by the Swedes is due to be published soon. Here is last year’s conference paper with their preliminary results.
effects of wind turbine noise on sleep
Michael Smith, Mikael Ögren, Pontus Thorsson, Eja Pedersen and Kerstin Persson Waye
22nd International Congress on Acoustics; Buenos Aires
5-9 September 2016
In accordance with the EU energy policy, wind turbines are becoming increasingly widespread throughout Europe, and this trend is expected to continue globally. More people will consequently live close to wind turbines in the future, and hence may be exposed to wind farm noise. Of particular concern is the potential for nocturnal noise to contribute towards sleep disturbance of nearby residents.
To examine the issue, we are implementing a project titled Wind Turbine Noise Effects on Sleep (WiTNES). In a pilot study described in this paper, we performed an initial investigation into the particular acoustical characteristics of wind turbine noise that might have the potential to disturb sleep. Six young, healthy individuals spent 5 nights in our sound exposure laboratory.
During the final 3 nights of the study, the participants were exposed to wind turbine noise, which was synthesised based on analysis of field measurements. Exposures involved periods of different amplitude modulation strengths, the presence or absence of beats, different blade rotational periods, and outdoor LAEq,8h=45 or 50 dB with indoor levels based on the windows being fully closed or slightly open.
Physiological measurements indicate that nights with low frequency band amplitude modulation and LAEq,8h=45 dB, slightly open window (LAEq,8h=33 dB indoors) impacted sleep the most. The presence of beats and strong amplitude modulation contributed to sleep disturbance, reflected by more electrophysiological awakenings, increased light sleep and wakefulness, and reduced REM and deep sleep. The impact on sleep by these acoustic characteristics is currently the focus of interest in ongoing studies.
According to the European Wind Energy Association, there was almost 13 000 MW of wind power installed across the EU in 2015. This represents a 6.3% increase over the previous year. Annoyance from wind turbine noise has previously been evaluated, primarily in cross-sectional studies. However, long term health consequences, including sleep disturbance, have not been studied and the physiological effects are not known.
Present debate on one side argues that “sound from wind turbines does not pose a risk of… any adverse health effect in humans”. On the other side, there have been claims for symptoms including impairment of mental health. Studies such as have been subject to criticism, both in terms of the conclusions drawn from the data and the experimental design itself. Whilst many claims of adverse effects are anecdotal, sleep disturbance is one of the issues most frequently reported and supported by previous crosssectional studies.
There is ample evidence illustrating that adequate sleep is necessary for maintaining good health. Disturbed sleep can hence be of consequence for immediate and long-term health. Night time noise has the potential to adversely affect sleep, which has been recognised by the World Health Organisation and reflected by their publication of night time noise limits.
The Environmental Noise Directive (2002/49/EC) recognises that community noise is potentially harmful and so requires that all EU member states map the noise exposure of their populations.
Despite this, wind turbines are often erected in quiet rural areas, where sleep disturbance due to wind turbine noise is reported more frequently. However, reported effects of this noise on sleep may be biased by perceived annoyance and so objective measures of sleep structure and other physiological response, for instance cardiovascular effects, are clearly needed.
Although objective measures have been made on the human effects of numerous environmental sources, particularly traffic noise, the majority of studies on the effects of wind farm noise have used only subjective means, and only using calculated equivalent sound levels in dBA at the façade based on simplified sound radiation and propagation models.
A notable recent study has however examined wind turbine noise using wrist actigraphy. Compared to traffic noise where much research has been performed, little is known regarding how noise from wind turbines objectively influences sleep. The aim of the current project is therefore to determine whether noise from wind turbines can impact on human sleep, and how any such impacts are manifested.
In this study, the effects of wind turbine noise on sleep were investigated using physiological measures. There is some evidence that compared to control nights with no noise, sleep during nights with WTN had a reduced amount of SWS, more time spent awake, increased sleep latency and a reduction in sustained SWS and N2 sleep.
The amount of REM sleep, SWS and WASO were affected by sound characters with strong amplitude modulation. N1 (“light”) sleep was more prevalent during noise with beats. SWS in particular has been identified as important for declarative memory in humans. Furthermore, SWS is considered to be important for physical restoration and is accordingly prioritised after sleep deprivation. REM sleep is believed to be important for cognition. Despite the observed physiological disruptions, it is unclear at present whether the size of these effects of WTN on SWS and REM would interfere with any associated biological processes.
During sleep, the body reacts more strongly to an abrupt change in acoustic environment than a gradual change. For instance, awakening probability is linked with noise rise time. As such it was hypothesised if WTN had negative effects on sleep, such effects would manifest during high rotational speeds, strong amplitude modulation and the presence of beats.
The indication, albeit non-significant, that the frequency of SSCs was lower during periods of high RPM, lower during periods of strong amplitude modulation and lower during periods with beats could therefore appear surprising. However, during periods of strong amplitude modulation and periods with beats there seems to be a higher frequency of awakenings, which do not include changes to a wake stage. In other words, rather than the participants simply changing sleep stage, full awakenings seemed to occur instead during these periods.
Although the frequency of awakenings and sleep stage changes were influenced by the strength of AM, the total number of awakenings and sleep stage changes did not differ between across any of the experimental nights, including the control. This means that in order for these reactions to occur at a higher rate during certain times, they are not occurring during other times when they may have spontaneously appeared as part of the natural rhythm of sleep. These awakenings and SSCs are being redistributed throughout the night, which may have implications for certain neuronal processes performed during sleep, such as the clearance of waste products that accumulate during wakefulness that has been demonstrated in animal studies.
This small-scale experiment served as a pilot study, and was therefore limited by a number of factors. The participants cannot be considered as representative of the population who are exposed to WTN at home. Together with the small sample size, the conclusions drawn should not be taken outside of the context of the work; to provide input for future work with a more appropriate study sample, size, and exposure design.
The chosen noise levels were higher than those recommended in Sweden, but were not unrealistically high for other countries, in order to increase the likelihood of inducing a physiological response. The rationale for this decision was to increase the expected effect size so as to better detect what elements of the sound character contributed to response in this small pilot study. An ongoing study has the aim of examining sleep under the influence of noise from wind turbines at more commonly occurring levels.
Physiological measurements indicate that nights with low frequency band amplitude modulation and LAEq,8h=45 dB, slightly open window (LAEq,8h=33 dB indoors) impacted sleep the most. In particular, amplitude modulation and the presence of beating were important constituents of the wind turbine noise contributing to sleep disruption.
Download the full paper here: Physiological effects of wind turbine noise on sleep ICA2016-0440
Smith, Ögren, Thorsson, Pedersen and Waye
While recreating wind turbine noise in a laboratory setting has its limitations, what is clearly evident is that it’s the pulsing element of low-frequency noise (ie amplitude modulation) that is causing a whole lot of totally unnecessary suffering.
Liability for those causing that suffering is inevitable and, with each new piece in the scientific jigsaw puzzle, the noose is tightening. For many, stringing up their tormentors can’t come soon enough, but it will.