Print Article

—James Delingpole, The Telegraph (UK), 7/25/13

How much more dirt needs to come out before the wind industry gets the thorough investigation it has long deserved?

The reason I ask is that it has now become clear that the industry has known for at least 25 years about the potentially damaging impact on human health of the impulsive infrasound (inaudible intermittent noise) produced by wind turbines. Yet instead of dealing with the problem it has, on the most generous interpretation, swept the issue under the carpet – or worse, been involved in a concerted cover-up operation.

A research paper prepared in November 1987 for the US Department of Energy demonstrated that the “annoyance” caused by wind turbine noise to nearby residents is “real not imaginary.” It further showed that, far from becoming inured to the disturbance people become increasingly sensitive to it over time.

This contradicts claims frequently made by wind industry spokesmen that there is no evidence for so-called Wind Turbine Syndrome (the various health issues ranging from insomnia and anxiety to palpitations and nausea reported by residents living within a mile or more of wind turbines). Until recently, RenewableUK – the British wind industry’s trade body – claimed on its website: “In over 25 years and with more than 68,000 machines installed around the world, no member of the public has ever been harmed by the normal operation of wind farms.”

In a section called Top Myths About Wind Energy’ section it claimed that accusations that wind farms emit ‘infrasound and cause associated health problems’ are ‘unscientific’.

Other pro-wind campaigners, such as Australian public health professor Simon Chapman, have gone still further by insisting that the symptoms reported by Wind Turbine Syndrome victims around the world are imaginary and often politically motivated.

But the 1987 report, based on earlier research by NASA and several universities, tells a different story. A team led by physicist ND Kelley from the Solar Energy Research Institute in Golden, Colorado tested under controlled conditions the impact of low-frequency noise generated by turbine blades.

It found that the disturbance is often worse when indoors than when outside (a sensation which will be familiar to anyone who has heard a helicopter hovering above their house).

In subsequent lab tests involving seven volunteers, it found that “people do indeed react to a low-frequency noise environment”. As a result of its findings, the report recommended that in future wind turbines should be subject to a maximum noise threshold to prevent nearby residents experiencing “low-frequency annoyance situations.”

However these recommendations – widely publicised at the Windpower 87 Conference & Exposition in San Francisco – fell on (wilfully, it seems more than plausible) deaf ears.

Rather than respond to the issues raised, the industry devised a code of practice apparently contrived to ignore those very acoustic levels of most concern. ETSU-R-97 – the UK industry standard, which became the model for wind developers around the world – places modest limits on sound within the normal human hearing range, but specifically excludes the lower frequency “infrasonic” noise known to cause problems.

Last month the Department of Energy and Climate Change (DECC) published a report by the Institute of Acoustics examining whether ETSU-R-97 was still adequate to the task. Remarkably, instead of stiffening regulations, it made them more lax, not only continuing to ignore the Low Frequency Noise and infrasound issue, but actually giving wind farms leeway to make more noise at night and to be built even closer to dwellings.

John Constable, director of the Renewable Energy Foundation, commented: “The report may represent current wind industry practice but it is very poor guidance and fails in its duty of care.”

The industry’s response is that turbine design has grown so much more sophisticated since the late Eighties that the problems identified in the 1987 report – which built on work from another report two years before – no longer apply.

“We’re often hearing these weird and wacky reports on the effects of wind. It seems anyone can stand up and say anything, which we find somewhat worrying because it gives a false impression. We don’t accept the suggestion that there are any health impacts caused by wind turbine noise, though we welcome any new research into the issue,” a spokesman for Renewable UK told me.

However this is contradicted by the author of the original reports Neil Kelley. Kelley has told Graham Lloyd – the environment editor from The Australian who (uncharacteristically for an environment editor puts truth before green ideology) broke the story – that research has shown that it is still possible for modern wind turbines to create “community annoyance.”

Kelley, who served as the principal scientist (atmospheric physics) at the National Renewable Energy Laboratory’s National Wind Technology Centre from 1980 to 2011, told Lloyd:

“Many of the complaints I have heard described are very similar to those from residents who were exposed to the prototype wind turbine we studied.”

He said the original research was performed to understand the “totally unexpected community complaints from a 2MW downwind prototype wind turbine.”

He said: “While follow-on turbine designs moved the rotors upwind of the tower, the US Department of Energy funded an extensive multi-year research effort in order to develop a full understanding of what created this situation.”

“Their goal was to make such knowledge available to the turbine engineers so they could minimise the possibility of future designs repeating the experience. We found the majority of the physics responsible for creating the annoyance associated with this downwind prototype are applicable to large upwind machines.”

The wind industry has resisted demands from campaigners to investigate this problem further. For example, in Australia, Lloyd reports, the wind turbine manufacturer Vestas has argued in a submission to the NSW government that low frequency noise not be measured.

But as Kelley said to Lloyd, if low frequency noise from turbines does not influence annoyance within homes, “then why should [the industry] be concerned?”

Those readers with an appetite for even more technical detail may be interested in the views of acoustics expert Dr Malcolm Swinbanks:

The important aspect to understand is that the old-fashioned downwind rotor-turbines did indeed generate a wider spectrum of infranoise and low-frequency noise, extending from 1Hz to 50Hz or 60Hz. Modern upwind rotor turbines are definitely very much quieter in the 32 and 64 Hz octave bands, but under some circumstances they can be similarly noisy over the frequency range 1Hz – 10Hz.

The wind industry denies this aspect, namely that they do not generate impulsive infrasound – I was present at a public meeting, with 400 farmers enthusiastically wanting wind-turbines on their land, when a wind-industry representative argued that I was incorrect to quote NASA research because the NASA research related only to downwind turbines. In fact NASA led the world in developing upwind rotor turbines, with the first, MOD-2 in 1981. They were fully aware of the differences between downwind and upwind configurations as long ago as 1981. Although upwind turbines are indeed quieter in respect of audible sound, NASA was well aware that inflow turbulence or wind-shear could give rise to enhanced infrasound from upwind turbines.

In the context of that particular public meeting, the chairman refused to let me respond at that time to correct the wind-industry presentation, and argued that I could only send a letter to the Planning Committee, which I duly did under strong protest. So I have encountered the wind-industry position directly at first hand.

The problem is that while the acoustics community fully acknowledge that the audible component of low-frequency sound (>20Hz) can cause adverse human reaction, they consistently deny that infrasound (<20Hz) can cause similar effects unless it is “above” the threshold of hearing. Yet there is at least one reported laboratory experiment (Chen et al, 2004) which showed that infrasound 10dB below the hearing threshold caused adverse psychological and physiological effects after 1 hour exposure. This particular test signal was a tone 110dB at 2.14Hz, where the threshold is around 120dB. So infrasonic sound pressure levels “below” the threshold of hearing have indeed been shown to cause adverse effects.

The response of the Australian Senate Inquiry to this information was that wind-turbines don’t generate 110dB. But just as sound pressure levels are always weighted in the audible frequency range, using the dBA scale – one does not quote absolute sound pressure levels, but dBA levels, so the infrasound range is correctly measured using the weighted dBG scale. This is an ISO internationally approved scale, and 110dB at 2.14Hz represents 82 dBG on the dBG scale. Modern wind turbine peak infrasonic impulsive levels have been measured as high as 76-80dBG, which is only marginally below the 82dBG level that was found to cause adverse effects in the Chen laboratory tests.

It is notable that when some acousticians wish to argue that wind turbine infrasound is not a problem, they quote known problematic infrasonic sound levels using the unweighted decibel dB scale, which makes these levels seem well “out-of-reach” of wind turbine infrasound levels. Yet these same acousticians would not dream of using absolute sound pressure levels to evaluate conventional audible sound, but will always quote correctly weighted dBA levels.

Thus, for example, the Chen infrasonic tests were at 110dB at 2.14Hz. This is 82dBG. In contrast, a “child-on-a swing” is also quoted by some acousticians as “not-a-problem”, when it is experiencing 110dB. This 110dB is at around 0.5Hz, so the corresponding dBG level is only 50dBG. Although the absolute sound pressure levels are identical, the perceived infrasound levels in these two cases are very different and cannot be equated to each other.

So I am unimpressed by the casual practice of quoting absolute sound pressure levels for describing infrasound, in order to exaggerate differences, when it is well recognized that the response of the ear is not uniform, and weighted sound pressure levels should be used for describing the likely hearing response.

This feature is responsible for much of the confusion that arises – interchange of unweighted and weighted levels can lead to very different conclusions – a situation which does not help to clarify the overall impact of infrasound.

It is noteworthy that some recent research indicates that at the very lowest frequencies (around ~1Hz) infrasound may be perceived by a different, separate mechanism than the ear’s conventional auditory mechanisms, so that at these frequencies, the G-weighting may no longer be accurate. But this is only a very recent deduction. Wind turbines undoubtedly generate their strongest signals at around 1Hz, so this is a new area of investigation which may also reveal additional adverse effects.

Malcolm Swinbanks, PhD

And here is the expert opinion of another US acoustics expert, Rick James – who thinks it somewhat unlikely that the wind industry is unaware of the problem:

The “Kelly paper” is just one of many studies and reports published in the period from 1980 to 1990 by acousticians and other researchers working under grants from the US Dept. of Energy (DOE), NASA, and other agencies and foundations. All of these papers are still available on web sites open to the public. I have attached one of the later papers (“Wind Turbine Acoustics, Hubbard and Shepherd”) that summarize many of those studies.

The acoustical conferences, at least those here in the US, all had presentations on wind turbine noise and it was one of the “hot” topics in the field. Earlier papers such as the 1982 Hubbard paper on Noise Induced House Vibrations was reporting some of the early research showing wind turbines were heard at lower auditory thresholds and that the infrasound was affecting people inside homes in much the same was jet noise at airports was affecting communities along flight paths.

As a general rule, all of this research noted the need for caution if large upwind wind turbines of the type being installed today were to be located near homes and communities. As you can see in the Kelly paper there was concern over health impacts by the research community.

Concurrent with this type of work the US DOD and NASA were investigating human response to infrasonic sound and vibration to help select candidates for jet pilots and space missions. This led to studies of nauseogenicity like the “1987 report on Motion Sickness Symptoms and Postural Changes……”

Suffice it to say that between the issues of dynamically modulated infra and low frequency sound causing adverse health effects called “Sick Building Syndrome,” similar effects observed from wind turbines leading to the Kelley paper, military interest in motion sickness and other similar issues for large ships with slowly rotating engines to jet aircraft noise few acousticians in that period would have discounted the premise that for some people these types of sounds posed serious issues.

Rick James, Acoustician (USA)

Can anyone imagine a potential scandal of this magnitude in the fossil fuel industry going uninvestigated by the green lobby – and hitting the front pages of all the newspapers?

I can’t.