Summary of Current Knowledge

The section below gives a broad summary of the current clinical and acoustical knowledge of how acoustic energy can affect health and how it is measured.

For a detailed recent summary of current knowledge with respect to wind turbines, you can also go to the Waubra Foundation CEO’s Cherry Tree statement. You can hear the residents speak out about their experiences in the Resident Impact Videos.

Residents can get started with a more simple summary

If you’re new to the topic or looking for a less technical summary of the Current Knowledge, please get started with the Information for Residents section.

Recent discovery of old knowledge from US research in 1980s

Rick James, American Acoustician, has recently unearthed some research specifically examining the impacts of wind turbine emissions in the infrasound and low frequency ranges from a single downwind turbine in North Carolina, which was clearly well known to many within the wind industry, academia, NASA, and the US government. Some of the research was presented at a wind industry conference in 1987.

There are two documents of special interest.

1985 Field Research

The first document was a major research initiative funded by the US Government Department of Energy, and was published in 1985. It comprised extensive field research investigating the cause of the complaints from the residents living approximately 3km from the single downwind bladed wind turbine. That research identified a number of important factors, but most importantly, stated that the “annoyance was real, and not imagined” (p2). They went on to make the following points:

1. The cause of the problems experienced by the residents was the acoustic resonance and excitation of the building structures, caused by the infrasound and low frequency noise emissions from the single wind turbine. Page 5 of the report stated the following:

“The source of the annoyance was aerodynamic and involved the passage of the turbine blades through the lee wakes of the large, O.s-m cylindrical tower legs.

  • The coherent characteristics of the radiated acoustic impulses (produced by the leg wake-blade interaction) were responsible for the annoyance of the complaining residents.
  • The responsible acoustic impulses were being propagated through the air and, in some instances, being focused on the complainants’ homes as a consequence of ground reflection and refraction by the atmosphere.”

Thus the direct causal relationship between wind turbine emissions in the infrasound and low frequency noise ranges and the residents symptoms of what was called “annoyance” was established by this research published in 1985 and was confirmed the subsequent laboratory research in 1987. This has clearly been known to the wind industry, and some of those involved in acoustic research, in government departments of energy, and possibly some in government departments of noise regulation.

2. The phenomena of “sensitisation” or what the researchers called “conditioning” was clearly known in the 1980’s, i.e. it was known in 1985 that people became sensitised to the noise and did not “get used to” the sound energy. This has importance for planning and noise pollution regulations, because of the obvious need for greater margins of safety to avoid harm to human health. On page 199, the researchers noted:

“It is clear from our discussion in the previous sections that the only acceptable method of curtailing complaints from residents in the vicinity of an operating MOD-1 turbine is to eliminate, or at least reduce, the impulsive character of the disturbing acoustic radiation to below perceptible levels. The task was made more difficult by the level of conditioning and resulting sensitivity of a few of the families involved, particularly the residents of #2, #7, #8 (and their immediate neighbours).”

3. The sound was often worse at night, and the important role of temperature inversions and a quiet background ambient noise environment at night was identified.

4. The researchers came up with what they considered to be protective limits above which the residents would not be annoyed, and as a consequence, human health would be adequately protected. On page 225, the researchers said:

“the joint radiation levels (expressed in terms of acoustic intensity and measured external to a structure) in the 8, 16, 31.5 and 63 Hz standard (ISO) octaves should not exceed band intensity threshold limits of 60, 50, 40 and 40 dB (re 1 pWm -2) more than 20% of the time. These figures compare favourably with a summary of low-frequency annoyance situations by Hubbard [32].

In other words, the research teams findings were consistent with pre-existing acoustic knowledge in the field relating to resonance within homes and consequent annoyance symptoms resulting from other sound energy sources.

5. The researchers also noted the particular impact in small rooms – often reported by residents to be worst in rooms like the bathroom or toilet (noted on page 6):

“Possibly very important, however, are the strongly oscillatory (harmonic), low-frequency pressure fields created within the smaller rooms and their relation to annoyance of the residents.”

The types of symptoms and perceptions noted by the residents included the following on page 5:

  • “The annoyance was described as an intermittent “thumping” sound accompanied by vibrations.
  • A “feeling” or “presence” was described, felt rather than heard, accompanied by sensations of uneasiness and personal disturbance.
  • The “sounds” were louder and more annoying inside the affected homes.
  • Some rattling of loose objects occurred.
  • In one or two instances structural vibrations were great enough to cause loose dust to fall from high ceilings and create an additional nuisance.”

These are identical to some of the perceptions of residents beside modern upwind bladed wind turbines, except the reports from those residents living near larger wind turbines give a picture of sound energy which is even more intrusive.

1987 Laboratory Research

2 years later, results of follow up laboratory research by Kelley et al was presented at a Windpower conference. The laboratory research reproduced the symptoms of annoyance in volunteers, not previously sensitised or “conditioned” to wind turbine noise, by exposing them to sound recordings consistent with wind turbine noise emissions.

This was additional confirmation that there was a direct causal relationship between the sound energy and the annoyance symptoms, this time in non residents, who were not previously sensitised. Sound recordings replicating sound energy exposures from other sources were also tested, and the impulsive nature of wind turbine sound was specifically found to be particularly problematic.

Can excessive noise harm health?

It has long been known that excessive noise can harm health in a variety of ways. For example:

  • audible noise can cause damage to hearing, if the noise is excessively loud
  • night time noise which disturbs sleep has well known adverse health consequences.

It is for these reasons that bodies such as the World Health Organisation (WHO) has issued documents such as their “Guidelines for Community Noise” in 1999, “Night noise guidelines for Europe” in 2009 and “Burden of disease from Environmental Noise” in 2011.

This latest 2011 WHO report on environmental noise, which specifically reviewed the scientific evidence of exposure – response relationships and assessed and quantified the burden of disease concluded that:

“There is sufficient evidence from large scale epidemiological studies linking the population’s exposure to environmental noise with adverse health effects. Therefore, environmental noise should be considered not only as a cause for nuisance but also a concern for public health and environmental health.”

In Australia, in 2004, a comprehensive EnHealth report detailing the known non hearing adverse health consequences of environmental noise exposure was issued by the Federal Department of Health, in conjunction with the Environmental Health committee, or En Health. Nearly 10 years later, the recommendations from that report are yet to be implemented and for unexplained reasons the issues appear to have been quietly shelved by the Federal Health Department.

How is environmental noise measured?

The acoustic environment is a composite of inaudible and audible sound and vibration energy. Audible frequencies cover a range of sounds from a deep bass (lower frequencies) to a high trill (higher frequencies), like the range of notes on a piano.

General environmental noise covers components you can hear (audible noise) and those which are inaudible but might still be perceptible to some people (e.g. perceptions of vibration or pulsing). The degree of audibility of a certain noise depends on how quiet the background environment is, other concurrent noises, and the individual’s own range of hearing, which can vary considerably.

A general measurement parameter for environmental noise is A weighting, using the A weighted filter, known as dBA. It is typically applied to domestic air conditioners, factories and motor vehicles.

Where noise has distinct characteristics that make it more discernible or intrusive, such as low frequencies, intermittent noise, tones, or impulsive characteristics; adjustments are made to the A weighted level to take this into account.

For large industrial complexes that consume or generate large amounts of energy, there are typically large machines or equipment that tend to generate low frequency or very low frequency noise (LFN), which travels long distances. These frequencies are not accurately addressed by using only the dBA measurement parameter and the noise must be treated differently for accurate acoustic measurement and assessment. In those instances, the following descriptors apply:

  • <20 Hz refers to infrasound
  • 20 – 200 Hz refers to low frequency noise

Accurate measurement of the low frequency component is via the C weighting or dBC filter.

There is not yet universal acceptance amongst all acousticians about the best method for accurate measurement of infrasound. However acousticians from the USA and Australia who are leading the investigation and accurate measurement of wind turbine noise inside affected resident’s homes agree that using dbG filters or G weighting does not accurately measure frequencies below 10 Hz and that it is preferable to use dB Linear. Special microphones and acoustic loggers which have appropriate noise floors are also required.

One example of environmental audible LFN pollution many city residents may be familiar with is the ‘doof doof’ noise from music from pubs and clubs sited in residential areas. The residents affected by this LFN the sensation of ‘pounding in their heads’ which penetrates their homes and which stops them from sleeping.

As previously stated, levels of infrasound which are inaudible to most people, may still be perceptible to some people in other ways and may induce a physiological response at levels below the accepted audible perception threshold for pure tones.

Recent work by neurophysiologist Professor Alec Salt and his colleagues using animal models has started to explain the science behind why the mammalian inner ear and the brain might be perceiving this inaudible sound energy at low sound power levels (SPL), when it is not necessarily ‘heard’ audibly, particularly in an environment with very quiet background noise.

Which sound frequencies are currently measured by regulatory authorities?

In Australia currently it is usually only audible noise (i.e. above 20 Hz) which is measured, in dBA. Measuring in A weighting does not address low frequency tones, or infrasound.

Typically, the acoustic monitoring conducted by the consultant acousticians or the noise regualatory authorities is not continuous all the time and the data is generally not fully provided to the residents or their acousticians. It is only for short periods of time, and the noise polluter is well aware when the monitoring is occurring, and may adjust the operation of the noise polluting equipment accordingly.

Residents near coal mines, coal seam gas (CSG) plants, gas fired power stations and wind turbines all report that the noise is uncharacteristically quieter and less intrusive when these periods of noise monitoring are occurring, only to reliably increase when the noise monitors are subsequently removed.

Importantly the measurements are generally not ‘attended’, ie the acoustic consultants are not there in person for any length of time in addition to setting up or removing their equipment. This particularly applies to the noise being experienced by residents at night.

Complete transparency, full provision of all noise and associated operational data and continuous full spectrum noise monitoring freely available in real time, would enable independent external audits of the noise pollution by the residents’ own acousticians. This would help restore the residents’ trust and confidence in the professional ethics of acousticians working for the noise polluters.

Currently this transparency and open provision of acoustic information does not occur, with the exception of aircraft noise data which is available online in real time via the Webtrak system.

In the case of wind turbines particularly, the frequencies below 200 Hz make up the bulk of the sound energy emissions, especially as wind turbines increase in size and power generation capacity.

How far can the sound frequencies travel?

NASA measured wind turbine generated infrasound 10km away from the noise source in 1985.

Australian acoustician Steven Cooper has measured the characteristic wind turbine acoustic signature 8km from the nearest 3MW VESTAS V90 wind turbines at Waterloo in South Australia, at a time when the resident could perceive the wind turbines were operating despite being unable to see them, and could hear the low rumbling from the LFN component of the noise.

As Emeritus Professor Colin Hansen’s recent letter points out, these lower sound frequencies attenuate less rapidly and therefore travel further than the higher frequencies. In quiet rural environments, under the right weather and wind conditions, they are reported by residents to disturb sleep at significant distances from the noise source.

This cumulative sleep disturbance and the characteristic symptoms correlating with infrasound and LFN exposure are being reported by residents living near coal mines, CSG field compressors (out to 15km) and gas fired power stations as well as industrial wind turbines.

Sound energy penetration and resonance

Low frequency noise (20 – 200 Hz) and infrasound (0 – 20 Hz) are both far more penetrating into buildings such as homes and workplaces than audible sound frequencies above 200Hz. The lower frequencies penetrate through walls, roofs and windows, even with insulation.

Once inside building structures, this sound energy can vibrate or resonate and this is precisely what some residents describe perceiving – likening it to living within an “acoustic drum“.

Residents regularly report that installing insulation makes the LFN problems worse. Acousticians explain this is because better insulation changes the proportions of low and high frequency sounds inside the building, as the higher frequencies are blocked but the lower frequencies penetrate through.

What is vibration and can it cause health problems?

Vibration is energy traveling through solid matter, such as the ground, or through structures such as buildings or machinery (e.g. aeroplanes and helicopters).

The health consequences of acute and prolonged high exposure doses of vibration are known to some acousticians and occupational physicians to be serious. International standards specifying safe limits for human exposure have been developed, as a result of existing research, which forms the basis for these current occupational exposure limits.

Less well known, and not well studied, are the consequences to human health of chronically perceiving vibrations at much lower exposure levels overnight when residents are sleeping or lying horizontally, thus potentially increasing their whole body exposure to vibration.

These vibrations are being reported by some rural residents living near CSG field compressors, coal mines and large industrial wind turbines. They report perceptions of vibration coinciding with waking up at night suddenly, in an anxious, frightened, panicked state.

How far can vibrations from wind turbines travel?

There are a number of studies which have documented wind turbine vibrations measured at significant distances from the wind turbines themselves, from Germany, Italy, Scotland and New Zealand.

There is no data yet from investigating the effects on humans of these vibrations, and there is no knowledge in the public domain about the lowest dose required to elicit a physiological response, or whether individual vibration perception thresholds shift to be more sensitive over time. From some of the resident’s descriptions, particularly those living near wind turbines and coal mines, it appears that some people are affected adversely by these vibrations and that this effect worsens over time with ongoing exposure.

What is known about chronic lower dose exposure to environmental noise – especially overnight?

The impacts of chronic exposure to low dose or sound power levels (SPL) of environmental noise, particularly in quiet background noise environments are less well understood because of a lack of research. In particular there is a lack of knowledge about the precise acoustic frequencies and exposures of these residents.

This is the situation whether the source of the environmental noise is coal mining, CSG field compressors, large and small compressors in urban and rural environments, gas fired power stations, or large industrial wind turbines.

Residents from all these circumstances have sought information and assistance from the Waubra Foundation and have described similar patterns of symptoms and their progression, correlating with ongoing exposures. All have improved when they reduced their exposures by either the noise source ceasing emissions (rare) or by leaving their homes, sometimes permanently.

Do we know what dose of acoustic energy people are exposed to?

There is almost no acoustic data publicly available, anywhere in the world, with accurate measurement of the full acoustic spectrum inside these impacted homes, regardless of the source of environmental noise.

Acoustic monitoring is expensive and it is rare that residents themselves can afford to commission it. It is almost never provided by the noise polluters to the impacted residents, nor is there a truly independent noise pollution audit process with transparency of provision of noise measurements. Historically it has rarely been measured inside homes.

Some current government noise regulations in Australia specify the mandatory use of acoustic monitors which do not have the capacity to measure all frequencies below 200 Hz, and do not have the capacity to accurately measure the true background noise level because the noise floor of the specified instruments is too high.

What are the known impacts of exposure to environmental noise?

The well known health impacts from environmental noise in residential settings include:

  • Physiological and psychological stress
  • Sleep disturbance, and
  • A range of other symptoms which have traditionally been called ‘annoyance’ by acoustic engineers, which have also been called ‘wind turbine syndrome’ by some medical practitioners

Sleep disturbance and stress are both individually well known to clinical medicine to cause serious health problems if they are prolonged, regardless of the cause.

The combination of the chronic sleep deprivation and chronic stress occurring together can be catastrophic for individual health and wellbeing, regardless of any other individual ‘annoyance’ or ‘wind turbine syndrome’ symptoms experienced.

What is the evidence of induced physiological stress symptoms from sound energy?

Audible noise, LFN and infrasound are all known to induce a physiological stress response, evidenced by resident’s descriptions of symptoms of a “fight flight” response.

There is research evidence of increased sympathetic nervous system activity (blood pressure and heart rate) in humans in response to infrasound exposure, at sound power levels below the currently accepted audible perception thresholds of infrasound.

There are also animal experiments demonstrating increased adrenaline and cortisol levels with infrasound exposure. Adrenaline and cortisol are two of the body’s main stress hormones. Whilst the experimental doses of infrasound are at higher levels than those measured at wind developments, the exposures are much shorter than the months to years that humans are exposed to operating wind turbines.

Acousticians such as Professor Geoffrey Leventhall have long been aware of research showing elevated cortisol occurring in sleeping children exposed to LFN from trucks overnight for example.

Rare but serious pathology consistent with adrenaline release is being reported by some people exposed to sources of environmental noise including wind turbines and coal mines. The specific conditions are ‘acute hypertensive crises’ and ‘tako tsubo heart attacks’. No other underlying clinical cause for these adrenaline surges was identified, according to the residents.

There are also reports of elevated bedtime salivary cortisol when the resident was exposed to wind turbines for some months, which was subsequently normal in the same resident when rechecked after a period of at least 21 days of non-exposure to environmental noise, when the turbines were off for an extended period of maintenance.

Residents exposed to nighttime environmental noise in very quiet rural environments commonly describe waking up repetitively in an anxious, frightened, panicked state for no obvious reason. They describe being wide awake instantly, having a racing pulse when they wake, and taking a long time to get back to sleep because they are so wide awake. This unusual pattern of waking is also being reported in some of their visitors staying overnight.

This is a typical description of a fight flight response, which results in sympathetic nervous system activity and secretion of adrenaline and indicates an episode of physiological stress is occurring.

What is the research evidence of disturbed sleep from exposure to environmental noise?

Sleep disturbance is the most common problem reported by residents living near sources of environmental noise, if the noise also occurs at night. The WHO’s Night Noise Guidelines referred to above and the EnHealth document previously cited contain multiple references to recent and old research.

Environmental noise from CSG field compressors in Queensland at the Tara gas field has been reported to disturb the sleep of residents up to 15 km away from the source of the noise. Dr Geralyn McCarron’s field survey report stated the following on page 26:

“Sleep disturbance was endemic within the families surveyed. Many people related this directly to the noise associated with CSG activities: trucks moving, reversing, beeping, the noise and vibration from drilling, fracking and seismic testing. Some people were very clear that their sleep was disturbed by noise and vibration from the compressor station, at distances up to 15km away.

With respect to wind turbine noise, there are a number of peer reviewed studies, together with many submissions to Australian Federal Senate Inquiries from affected residents, which report that sleep disturbance is a common problem.

Peer reviewed studies published in journals such as Dr Daniel Shepherd et al’s and Dr Michael Nissenbaum et al’s confirm that sleep disturbance is real in populations exposed to wind turbines in New Zealand and in two locations in the USA.

The argument is commonly advanced by those with a vested or ideological interest in denying the reported symptoms of the residents, that “sleep disturbance is common in the general population and there is no evidence that it is particularly problematic in wind turbine/CSG noise exposed residents”.

However, this is counter to the consistent reports of the residents themselves, who report their sleep quality decreases with new and prolonged exposure to environmental noise. The residents also clearly describe experiencing the consequences of exhaustion, including more accidents, poor concentration, falling asleep during the day and irritability in addition to the well documented health consequences of long term sleep deprivation.

Australian Sleep Physician Dr Wayne Spring, stated the following in his submission to the second Federal Senate Inquiry:

“As a Sleep Physician, working in Ballarat in Western Victoria, I have already been seeing patients from Waubra, Leonard’s Hill, Glenthompson and Cape Bridgewater who have disturbed sleep which has coincided with the commencement of operation of nearby wind farms. I do not believe that we yet know the full extent of the consequences to these people of their exposure to wind farms or even the cause of the untoward effects which may not just be from “noise”. Nonetheless, assessment of noise is a start in the monitoring of what is going on.”

Dr Sandy Reider, a family physician from Vermont, USA, has given an excellent clinical description of the way a resident’s sleep can be affected by wind turbine noise. In testimony to the Vermont State Legislature in the USA, he described the experiences of one of his patients:

“About 3 weeks after the installation he began to experience quite severe insomnia, something he had never dealt with before and he had no clue why… He complained of abrupt waking 30-40 times a night, like a startle reflex, associated with some anxiety. As a result he was almost never able to fall into a deep restful sleep, very distressing for someone used to sleeping 10-11 hours every night.”

The Waubra Foundation has long advocated full spectrum acoustic surveys and concurrent ‘in home’ sleep studies, to investigate why so many people are reporting disturbed sleep, in order to determine if particular sound or vibration frequencies at certain doses (SPL’s) are directly causing these problems, as we suspect they might be.

Is there research evidence of “direct correlation” between symptoms and specific sound frequencies?

Professor Con Doolan’s recent Waterloo case study is a good example of the direct correlation between the resident’s perception of specific symptoms described as ‘annoyance’, and specific low frequencies at specific doses or SPL’s. The resident was “blinded” to the acoustic data when recording their symptoms, meaning the resident had no way of knowing what acoustic frequencies and sound power levels were being recorded by the acoustic monitor at the time they were recording the symptoms they were experiencing.

Unfortunately the wind developer at Waterloo did not cooperate with requests for information by Professor Doolan, which may have determined conclusively that the low frequency noise he measured inside the resident’s home did indeed come from the wind turbines, as the resident was telling him, rather than ‘wind in the trees’ or ‘the refrigerator’ as the wind developers frequently assert.

There is also recently rediscovered field research by Neil Kelley and colleagues commissioned by the US Department of Energy in 1981, reported in 1985, and a subsequent laboratory research project the results of which were reported in 1987 to a Windpower conference.

The research papers are compelling evidence of direct causation of symptoms of “annoyance” from wind turbine infrasound and low frequency noise, which then resonates inside some building structures. This research is consistent with previous research by Harvey Hubbard which investigated the same phenomena of infrasound and low frequency noise from a variety of other sources causing resonance within homes and buildings.

The wind industry’s response predictably has been that the single turbine used was an old “downwind” turbine and it is “therefore of no relevance”. However Neil Kelley has confirmed that the modern upwind bladed turbines studied subsequently produced the same frequencies, and the complaints from neighbours to these modern turbines are identical to those he heard during the field research reported in 1985.

It is clear that whilst the acoustic profile might differ between old downwind and new upwind bladed turbines, both still emit infrasound and low frequency noise, and as the turbines increase in size, there is more sound energy in the low frequencies, as Moller & Pedersen’s 2011 research demonstrates.

The impacts on residents being reported at places like Waterloo in South Australia suggest that the impact of multiple 3MW V90 VESTAS upwind wind turbines is indeed much worse than the single wind turbine studied so intensively in the early 1980’s in the US by Kelley et al.

What does “annoyance” mean?

The term “annoyance” means different things to different people. Because there is not a universally accepted definition, and because it is not a diagnosis, to medically trained health practitioners, researchers and investigators annoyance is a useless and misleading term which has been misused by some to hide the severity of the impact of exposure to environmental noise on those affected.

Annoyance is therefore commonly able to be dismissed by those with a vested interest in denying the existence of these health problems as being of no consequence. However the precise symptoms which have been categorized as annoyance by some acousticians may include nausea, vertigo, dizziness, palpitations, painful ear pressure, sleep disturbance, body vibrations and a range of other symptoms. These symptoms are anything but trivial and can lead to a significantly diminished quality of life for the individual, as well as serious physical and mental illness if there is chronic exposure.

Dr Eja Pedersen, one of the leading researchers in this area from Scandinavia, described annoyance in the following way in her correspondence on this topic with Dr Michael Nissenbaum, an American medical practitioner:

“Annoyance is a response, rather than an effect. However, to be annoyed means a lowered wellbeing, and annoyance should therefore be avoided. The relationship between annoyance and symptoms of lowered health goes, from what I have found in my studies, two ways.
– People who have lowered physical or mental health are more vulnerable and therefore get annoyed.
– People who get annoyed may not get the physiological and psychological restoration that they need and annoyance could hence increase the risk for impaired health.”

How are the consequences of exposure to environmental noise reported by the residents?

Consequences of short term exposure to this sound and vibration energy are relatively benign for most people, providing the dose or SPL is low, and the exposure time is very short. This is one reason why a brief visit to a wind development in the daytime is so misleading and bears no relationship to the lived experiences of the nearby residents.

More serious and widespread problems are being reported, particularly with prolonged cumulative exposure to some sources of environmental noise, especially at night, in quiet background noise environments.

Frequent sleep disturbance is commonly reported by residents exposed to this environmental noise, whether it is from CSG field compressors, coal mining activities overnight, gas fired power stations, or wind turbine noise. Over time, it is consistently reported by residents and some of their health practitioners, that their symptoms, and their general physical and mental health, worsens.

People affected in this way do not “get used to” the noise, but they consistently improve if they remove themselves from the source of the environmental noise. This is generally achieved by going away, if they can afford to. It is rare that the noise ceases for any length of time.

Some people are so badly impacted they resort ultimately to abandoning their homes. Where family members have different experiences, families can be split, with those unable to live with the noise moving or living away.

Once sensitised, residents may find that other sources of environmental noise in other environments can also trigger some of their symptoms, again predictably resolving if they move away from the source of the noise.

Are some people more susceptible than others?

Some population subgroups seem to be more susceptible to developing symptoms of vestibular dysfunction acutely and early, such as nausea and vertigo, for reasons which are not yet entirely clear, but which appear to be related to disturbances of the vestibular system mediated via abnormal stimulation of the inner ear.

Research by Dr Nina Pierpont, a researcher and paediatrician from the USA, identified the very young, the elderly, and those with a history of motion sickness, migraines, and inner ear pathology as being particularly susceptible to developing symptoms, which she named ‘Wind turbine syndrome‘.

There are other groups in the population who are known to be noise sensitive and these people often consciously seek out quiet rural environments and value them for the peace and quiet. People with autism spectrum disorders, a past history of a head injury, and post-traumatic stress disorders are some of those particularly vulnerable individuals who have reported a rapid adverse response to new environmental noise.

What percentage of the population is affected?

There are very few population surveys which have been done, especially with larger wind turbines, so it is not possible to answer this question accurately; each wind development has different characteristics, topography, distance to houses and housing density within a certain distance. Early Scandinavian surveys were performed on much smaller wind turbines.

Because more people report being affected as time goes on, initial population surveys will underestimate the subsequent proportions of the local population who are likely to be affected after a few years exposure.

Drs Arra and Lynn’s recent literature review listed the early population surveys in Europe, with much smaller less powerful wind turbines. Their literature review noted all the peer reviewed published studies showed evidence of what they called “human distress” after wind developments started operating.

There are three population surveys conducted in Australia, two at Waterloo wind development in South Australia, with 3MW VESTAS wind turbines, and the other at Cullerin wind development in New South Wales, with 2MW Repower wind turbines.

Zhenhua Wang’s survey for his Masters degree at Adelaide University examined the population living within 5km of the Waterloo wind development. Wang found that with a 64% response rate, 50% of households reported being moderately to severely affected by the noise.

Mary Morris, a concerned local resident, repeated the Waterloo survey out to 10km, and found some residents were affected out to 10km, confirming earlier anecdotal reports.

Patina Schneider, a concerned NSW resident, completed a survey of residents near the Cullerin wind development and found that out of the 71% of households out to 7.5km who participated, 70% of them had disturbed sleep reported to be from noise from the wind turbines.

Disturbed sleep is the most common symptom and the above population surveys indicate that the percentage of households affected and the distance of the effect is much greater than the 10% often asserted by the wind industry.

“Sensitisation” – what is it and why is it important?

The phenomena of people reporting becoming sensitised to low frequency sound energy from a range of sources has been reported for over 25 years by researchers investigating the effects of infrasound and low frequency noise. The US research report stated the following in section 8.0 at page 199:

“It is clear from our discussion in the previous sections that the only acceptable method of curtailing complaints from residents in the vicinity of an operating MOD-1 turbine is to eliminate, or at least reduce, the impulsive character of the disturbing acoustic radiation to below perceptible levels. The task was made more difficult by the level of conditioning and resulting sensitivity of a few of the families involved, particularly the residents of #2, #7, #8 (and their immediate neighbours).”

The precise neurophysiological mechanisms for this sensitisation or “conditioning” as it has been called are currently unclear. In the literature review for DEFRA from 2003, Professor Geoffrey Leventhall stated on page 4:

“Low frequency noise causes extreme distress to a number of people who are sensitive to its effects. Such sensitivity may be a result of heightened sensory response within the whole or part of the auditory range or may be acquired. The noise levels are often low, occurring in the region of the hearing threshold, where there are considerable individual differences.”

Two possible explanations include a shift in the perception thresholds, mediated in the inner ear, and neuroplasticity in the brain. The latter explanation was suggested over 10 years ago by acousticians (eg Professor Geoffrey Leventhall p 24) but both may be occurring and there may well be other as yet unidentified physiological pathways. But there is no doubt it is occurring, and that people do not “get used to” these frequencies.

This issue is vitally important to appreciate for planning and noise regulatory purposes, because whilst some residents initially may not have health and sleep problems, that can change over time with cumulative exposure, as they become ‘sensitised’.

This makes it all the more imperative that adequate precautionary distances and noise regulation parameters are in place and enforced to prevent increasing long term damage to the health of vulnerable groups in the population from cumulative exposure to environmental noise in frequencies below 200 Hz.

Longer term tissue pathology – Vibro Acoustic Disease (VAD)

Long term exposure to environmental noise has also been reported to result in a range of tissue pathology including collagen thickening, in animals and humans, and given the name Vibro Acoustic Diease (VAD) by the Portuguese researchers, Professor Mariana Alves-Pereira and Dr Nuno Castelo Branco.

Increasingly some of these findings are being observed and reported by other research teams, for example Taiwanese researchers Chao et al investigating cardiac tissue thickening in aviation workers with variable exposures to infrasound and low frequency noise (together known as ILFN) directly correlating with variable observed collagen thickening via echocardiogram, and veterinary research into pathology described in horses exposed to ILFN in Portugal.

There are emerging private reports of the characteristic cardiac valve thickening in German residents exposed chronically to wind turbine noise. There was also the case report of two Portuguese families, including the case of a Portuguese child exposed to ILFN in a residential setting but with a lower dose of ILFN than the dose measured in the home of another family living near wind turbines who subsequently also developed some of the characteristic symptoms. A follow up report 3 years later makes for disturbing reading.

The Portuguese researchers have expressed their concerns about the the implications of these cases especially in young children, which would appear to be well founded given that the pathology is being identified in various individuals exposed chronically to infrasound and LFN in both occupational and residential settings. At the very least, a prospective study with concurrent acoustic measurements and echocardiography used in the Chao et al study would help to give more information to determine ‘safe’ exposure doses.

What is the evidence for the “nocebo effect” hypothesis?

The “nocebo effect” hypothesis is put forward intermittently by wind developers and some of their advocates in public health academic circles. Essentially the simplistic nocebo hypothesis is that the symptoms being reported by the residents are all caused by the publicity about the symptoms, rather than any external cause such as sound and vibration energy.

The nocebo hypothesis which has been suggested by wind developers, their lobbying organisations and their advocates, ignores the extensive body of evidence contained in the WHO documents such as the “Guidelines for Community Noise” in 1999, “Night noise guidelines for Europe” in 2009 and “Burden of disease from Environmental Noise” in 2011, and the Australian EnHealth 2004 report, relating to the known, well accepted, adverse health consequences of exposure to environmental noise, especially at night.

Interestingly, the nocebo hypothesis is solely proffered by wind energy advocates with respect to wind turbine noise alone, but not other sources of environmental noise, such as coal mining, gas fired power stations and field compressors used in coal seam gas operations, despite identical symptom reports and exposure patterns from residents living near these industrial facilities.

This hypothesis also conveniently ignores the evidence of medical practitioners from nearly 10 years ago, such as Dr Amanda Harry (UK, 2003) and Dr David Iser (Australia, 2004) who confirm that, as with any new disease, the patients with new symptoms and patterns of illness present for clinical care first, and the data collection and increased knowledge and publicity follow.

There are two recent research papers which claim to prove or support the nocebo hypothesis explains the symptoms reported by wind turbine neighbours. These papers have been supported by a plethora of media and online articles, and have been widely and rapidly distributed globally by the well-funded wind developers, who at times assert that the nocebo effect is now proven by this research.

Closer scrutiny reveals that numerous opinion pieces mentioning the nocebo effect, or “communicated disease” theory, particularly those by Professor Simon Chapman, were written some months to years before the research itself was conducted in late 2012.

The lead researchers of each research paper, Professor Simon Chapman and Psychology PhD candidate Fiona Crichton publicly argue that their data supports the contention that publicity or knowledge about the symptoms described by other residents is itself causing the reported problems experienced by wind turbine neighbours, and have accused people who publicise the plight of the residents of “scaremongering”.

Whilst there is no doubt that the power of suggestability is part of the human condition and has been for centuries, the research data of these two researchers does not provide any evidence that a nocebo effect is causing the symptoms reported by the residents, in some cases years before any publicity about the problems. Neither the Chapman nor the Crichton research directly investigates the residents impacted by wind turbine sound and vibration, nor does it recreate their acoustic environment.

The Crichton experiment in laboratory conditions subjected a group of young fit and healthy volunteers to either “infrasound” or “sham infrasound”. Careful peer review of their paper by researchers working in this area has revealed that the exposures and frequencies used in this laboratory study bore no relationship to either the combination of frequencies or the dose of wind turbine noise currently being measured inside residents’ homes. The infrasound dose of 40 dB at 5 Hz was considered by Emeritus Professor Jerry Punch (audiologist) and Dr Malcolm Swinbanks (acoustician) to be incapable of generating any physiological response, thus all the study participants were in effect exposed to sham infrasound.

Furthermore the exposure of the laboratory study participants to sham infrasound was for only 10 minutes during the day, whereas residents living near wind turbines (and other industrial facilities) reporting health problems are generally not young, fit and healthy, are exposed for up to 25 years, day and night, and report sleep disturbance at night as their most common problem.

The Chapman paper, which relies heavily on the Crichton paper’s findings to support the alleged nocebo effect, also relies on three indirect sources of information to assert that there were only a relatively small number of people affected by wind turbine noise in Australia. Information provided by treating medical practitioners with direct knowledge and experience of the problems has been ignored or dismissed, and so too the crucial peer reviewed published acoustic research showing that larger more powerful wind turbines generate more low frequency noise.

However the sources of information used, such as wind developer company complaints registers, media reports and public submissions to senate inquiries, are notoriously unreliable and incomplete because of under recording of complaints by the wind developers, and an understandable reluctance on the part of rural residents to speak or disclose private health problems publicly.

Relying on these three data sets of indirect evidence will inevitably significantly understate the extent of the problems occurring in some of these rural communities, especially those with larger wind turbines close to homes.

This can be clearly seen when the data from the Chapman research is compared to the few population surveys which have been conducted, at Waterloo in South Australia and at Cullerin.

Direct investigation of the acoustic emissions and correlation with symptom diaries and physiological testing such as sleep monitoring and ambulatory blood pressures, would soon clarify whether the symptoms were related to acoustic emissions from the turbines, as Professor Con Doolan has shown in his Waterloo case study, or suggestability from ‘scaremongering’ as Crichton and Chapman assert.

Direct multidisciplinary acoustic and physiological investigation is precisely what the Australian Federal Senate Inquiry recommended in June 2011, and is what the Waubra Foundation have been advocating since 2010.

Finally, a word of caution; as Dr Michael Nissenbaum commented in his response to the second Federal Senate Inquiry:

“suggesting a diagnosis of ‘nocebo’ without investigating ‘boots on the ground’, for more plausible, better understood, or more logical causes of a medical condition would normally constitute medical malpractice in most Western-based medical systems, including Australia.

What cumulative dose and peak level is safe for the different acoustic frequencies below 200 Hz?

We don’t know. Until recently, old research evidence resulting from major research initiatives in the US in the 1980’s was known to members of the wind industry but was not known to current researchers independent of the wind industry until located by American Acoustician Rick James. Its significance is detailed in the section immediately below.

There appears to be considerable individual human variation in both susceptibility to developing symptoms, severity of effect of the noise, and the rate of deterioration in mental and physical health. That is why this multidisciplinary research is so urgent and why better knowledge about the precise acoustic exposures or doses and sound frequencies inside homes is so important.

The assumption by health, planning and noise regulatory authorities historically appears to have been that exposure to what is considered low dose frequencies emitted by wind turbines and other sources of environmental noise are not damaging, because of the lack of specific research evidence to the contrary. This of course has changed with the knowledge of the US research from the 1980’s, where certain “dose response” relationships were noted. Whilst these are yet to be verified more widely, they are at least a start, and an acknowedgement that these frequencies below 200 Hz can damage health, via resonance of building structures, at significant distances.

Given the mounting research evidence and adverse health event reports from residents, it is clear that research is urgently needed in order to determine safe exposure levels and accurate dose response curves for modern upwind turbines, including the effects of multiple turbines, with sufficient margin for safety given the issues of sensitisation and deterioration in mental and physical health, with ongoing exposure.