No evidence to show that infrasound from wind turbines is harmful to human health

Even as the world’s wind turbine arsenal grows at its fastest pace ever, new wind energy projects often face fierce opposition. A common concern amongst people living near wind farms is that the machines will emit bothersome noise. Opponents of wind power often play up this concern. They frequently claim that wind turbine noise can harm human health and blame any symptoms on infrasound – sound that’s too low-pitched for humans to ordinarily hear.

A recent source of this claim is a 19 November editorial in the HighWire, but such claims are hardly new: anti-wind-energy groups like Stop These Things and Wind Watch, for example, have claimed for years that infrasound can inflict stress, disturb sleep, exacerbate heart conditions, trigger diseases like cancer, and more. Some or all of these symptoms are sometimes looped together as “wind turbine syndrome”, implying a medical condition.

But what does science actually say about wind turbine infrasound? As we’ll show below – and as we’ve previously shown in a French article – there’s insufficient evidence that infrasound from wind turbines is a danger to human health.

Insufficient evidence linking infrasound exposure to symptoms

Wind turbines are large machines, and like any large machine, their moving parts create sound. If you’re near a wind turbine, you might hear its motor, or you might hear its blades slicing through the air.

How loud are those sounds? The answer depends on geography and weather patterns, not to mention distance: logically, a more distant turbine is a quieter turbine. That said, the U.S. Department of Energy estimates that a wind turbine at a distance of 300 meters (1,000 feet) is about 40 decibels (dB), comparable to the loudness of a quiet conversation or a nearby refrigerator (Figure 1). However, 300 meters is relatively close to a turbine; in many countries, the legal minimum setback distance between a wind turbine and the nearest home is 500 meters, 1,000 meters, or further. 

Physics tells us that what we perceive as sounds are actually vibrations, passing as waves through the matter around us. We can measure the frequencies of those vibrations in hertz (Hz): the higher the frequency, the higher-pitched the sound. Most human ears are naturally sensitive to sounds between 20 and 20,000 Hz. Frequencies above that range are known as ultrasound – you may be familiar with this term from ultrasound scans, which use these sound waves to ‘see’ inside the human body.

Inversely, frequencies lower than 20 Hz are therefore known as infrasound (Figure 2). This isn’t a hard threshold; instead, as a sound’s frequency decreases, the ‘louder’ that sound must be in order for the human ear to discern it. Therefore, all but the very loudest sounds below 20 Hz are usually too low-pitched for humans to hear.

Wind turbines emit infrasound, but there’s a lack of evidence actually connecting this noise to health problems. People living near wind turbines do sometimes self-report sleep disturbances, annoyance, and occasionally other symptoms that they attribute to infrasound¹.There’s some experimental evidence linking infrasound exposure with altered brain activity². According to some research, infrasound that is ‘loud’ enough for humans to detect (100 dB or more) can worsen listeners’ moods; but these are not firm pieces of evidence, as we will explain below.

Namely, humans will almost never experience such ‘loud’ infrasound around a wind turbine (or, for that matter, in any environment)^3,4. When researchers have tested more realistic infrasound levels in a controlled setting, they’ve failed to find evidence that infrasound has any effect on health or behavior.

In one study from 2021, Finnish researchers recruited people who lived near wind turbines and placed them in a loudspeaker-walled chamber. Inside, the participants were exposed to infrasound noise simulating what one might experience standing 200 meters (650 feet) or 1,500 meters (4,900 feet) away from a wind turbine. Participants could not discern whether or not infrasound was playing, and the researchers couldn’t find any evidence that infrasound elicited responses in participants’ heart rates or nervous systems³.

Another study that year asked participants to keep a speaker in their bedroom for 28 nights, during which researchers would play infrasound to half the participants. The researchers didn’t observe any significant changes in that infrasound-exposed group’s behavior, including their self-reported health, their sleep, and their cognitive abilities⁵. The authors did find that exposure to infrasound reduced gray matter in areas of the brain related to motor function and speech, but they could not link these to any changes in behavior. “IS [infrasound] does not affect healthy individuals on a global scale”, the authors concluded. 

In 2023, Australian researchers placed participants in a room with speakers for a 72-hour-long period, sometimes activating the speakers to play wind turbine-like infrasound. The researchers found no significant difference in the participants’ sleep quality when exposed to infrasound⁶. The authors write: “This study suggests that the infrasound component of WTN [wind turbine noise] is unlikely to be a cause of ill-health or sleep disruption, although this observation should be independently replicated.”

So, while there is room for further research – for example, the three studies mentioned above were all relatively small, each with fewer than 40 participants – there is no clear link between infrasound and any symptom associated with the so-called “wind turbine syndrome”. Certainly, these studies have not linked infrasound to “vascular regulation” (blood flow to the body’s organs), as the High Wire article claims.

Wind turbine noise is not more disruptive than road traffic

A wind turbine is just one source out of many infrasound sources: both artificial (such as loud music, pumps, generators, and air conditioners) and natural (like storms, lightning bolts, and earthquakes). Any process that moves a large amount of air can create infrasound noise. 

Another source of infrasound – and of noise in general – is road traffic. It’s far more widespread than wind turbine noise. Logically, you’re only likely to hear wind turbine noise near a turbine, while you’ll hear road traffic noise anywhere that combustion-engine-powered vehicles are driven.

So, it should come as little surprise that the number of people exposed to road traffic noise dwarfs the number exposed to wind turbines. As of 2017, in metropolitan France – where wind power accounted for around 4 to 5% of electrical generation that year – only around 0.1% of the population experienced nighttime wind turbine noise louder than 40 dB (about as loud as ambient rainfall or a wind turbine at around 300 meters). Meanwhile, more than 15% of the population experienced nighttime noise from road traffic that was at least as loud, and more than 7% experienced similar sounds from railways⁷.

Science Feedback was unable to find similar figures for the U.S., but we can make a very rough comparison. An estimated 29% of the U.S. population is exposed to traffic noise louder than 45 dB. Meanwhile, as of 2015, 1.4 million U.S. homes (less than 2% of the U.S. total) were within 5 miles (8 kilometers) of a utility-scale wind farm, and a Lawrence Berkeley National Laboratory survey indicated that only 16% of U.S. respondents living within that distance of a wind project had heard any noise. The result is that, at most, significantly less than 1% of the U.S. population has been exposed to significant levels of wind turbine noise.

In fact, another study compared the two types of noise in a controlled environment. Sleeping participants were exposed to samples of either wind turbine noise or road traffic noise. The researchers found that road traffic noise was actually marginally more likely to disturb participants’ sleep. Separately, the researchers exposed sleeping participants to either a full spectrum of wind farm noise or just isolated infrasound, ‘loud’ enough to be at “near worst-case levels”. Full noise triggered brain activity and increased the likelihood of awakening, but the researchers found no such changes in participants only exposed to infrasound.

There is other evidence that humans can be affected by the audible part of wind turbine noise. A 2023 meta-analysis of 15 studies found that, on average, 34% of respondents living near wind turbines reported sleep disorders, rising to 79% of respondents living less than 500 meters (1,600 feet) from a turbine⁸. But remember that wind turbines are frequently significantly further than 500 meters away from their nearest house; moreover, the first number is actually well within the estimated range for adults in the general population, which varies from 23 to 56% depending on the country⁸. And, again, the number of people exposed to wind turbine noise is significantly less than the number exposed to road traffic noise, which is possibly more disruptive.

The ‘nocebo effect’ may explain wind turbine syndrome

Given the findings above, why do people continue to blame infrasound for health concerns?

Some researchers attribute these responses to a so-called ‘nocebo’ effect – when people expect negative symptoms, they’re more likely to experience negative symptoms. The nocebo effect is well known in pharmaceutical studies; it’s the inverse of the better-known placebo effect, as its name suggests. When it comes to wind turbine infrasound, we have some evidence that the nocebo effect may be responsible.

In a 2015 study, researchers told participants about the supposed dangers of wind turbine infrasound, then played them a combination of infrasound and audible wind turbine noise. Participants generally reported increased annoyance. Researchers then gave one group of participants more information about symptoms, while informing the others about the nocebo effect. When the researchers exposed both groups to more infrasound, the nocebo group’s mood returned to normal⁹. Other studies have shown similar findings^6,10.

The Finnish study cited earlier, which placed people who lived near turbines in a loudspeaker-walled chamber, compared the responses of participants who had previously reported symptoms from wind turbine exposure to the responses of those who had not. Those who had previously reported symptoms were no more able to detect infrasound than those who had not reported symptoms, nor did they initially react any differently. Only after the researchers told participants they would be exposed to infrasound, those participants who had previously reported symptoms then self-reported higher stress levels. “[S]ome of the symptoms subjectively attributed to wind turbine infrasound may be related to experiencing wind turbines as disruptive and considering them a health risk,” the authors explain³.

It’s also worth noting that “wind turbine syndrome” messaging has been pushed by groups linked to the fossil fuel industry, which may have an economic motive to oppose the growth of wind energy. When you see a warning about the health effects of wind energy, it’s best to confirm its origin and check that it comes from a reputable, peer-reviewed scientific source. If not, then it may be disinformation.

Conclusion

Although some people living near wind turbines might report sleep difficulties, worsened mood, or other health issues, there’s no evidence linking these symptoms to infrasound noise from wind turbines. Studies that have exposed participants in a controlled setting to infrasound, simulating that emitted from wind turbines, have not found a link between the noise and any symptoms. On the contrary, some studies have suggested that a ‘nocebo” effect may cause symptoms in people who believe that wind turbine noise will harm them. Furthermore, the number of people who are exposed to wind turbine noise is very low compared to the number exposed to other noise sources, such as road traffic.

References:

1. Turunen et al. (2021) Symptoms intuitively associated with wind turbine infrasound. Environmental Research.
2. Weichenberger et al. (2017) Altered cortical and subcortical connectivity due to infrasound administered near the hearing threshold – Evidence from fMRI. PLoS One.
3. Maijala et al. (2021) Annoyance, perception, and physiological effects of wind turbine infrasound. The Journal of the Acoustical Society of America.
4. Nguyen et al. (2023) Audibility of wind farm infrasound and amplitude modulated tonal noise at long-range locations. Applied Acoustics.
5. Ascone et al. (2021) A longitudinal, randomized experimental pilot study to investigate the effects of airborne infrasound on human mental health, cognition, and brain structure. Scientific Reports.
6. Marshall et al. (2023) The Health Effects of 72 Hours of Simulated Wind Turbine Infrasound: A Double-Blind Randomized Crossover Study in Noise-Sensitive, Healthy Adults. Environmental Health Perspectives.
7. Ecotière et al. (2022) Quantification of Sound Exposure from Wind Turbines in France. International Journal of Environmental Research and Public Health.
8. Godono et al. (2023) Association between exposure to wind turbines and sleep disorders: A systematic review and meta-analysis. International Journal of Hygiene and Environmental Health.
9. Crichton and Petrie. (2015) Health complaints and wind turbines: The efficacy of explaining the nocebo response to reduce symptom reporting. Environmental Research.
10. Crichton et al. (2014) Can Expectations Produce Symptoms From Infrasound Associated With Wind Turbines? Health Psychology..