Resource Library Category: Noise (277 items)
Also see NWW press release on noise
Documents presented here are not the product of nor are they necessarily endorsed by National Wind Watch. This resource library is provided to assist anyone wishing to research the issue of industrial wind power and the impacts of its development. The information should be evaluated by each reader to come to their own conclusions about the many areas of debate.
Why is sharp-limited low-frequency noise extremely annoying?
Source: Krahé, Detlef
[Introduction] Low-frequency noise (LFN) is sound focused in the frequency range below ~100 Hz. For example, in Germany sound is defined as low frequency if the C- and A-weighted sound pressure level (SPL) differs by more than 20 dB. For a growing number of people LFN is an urgent problem, and many questions remain unanswered: Why does LFN seem to be a greater problem today than in the past? Are people more sensitive? Is LFN increasing?
It can be assumed that LFN was less common in the past, which doesn’t mean that it was quieter. It is difficult to prove, but not improbable, that A-weighting is in part responsible for increasing LFN, because A-weighting attenuates LFN strongly. Therefore, in the endeavor to meet the limits in regulations, which are mostly defined in dB(A), it is easier (meaning in most cases less expensive) to shift resonances of machines to the low-frequency range than to attenuate the vibration or the sound by technical means. In addition, A-weighting is to blame for an underestimation of the annoyance of LFN.
Another reason for increasing LFN may be found in the growing application of all kinds of noise protection, e.g., noise barriers, special windows, etc. All of these measures have a common property: low-frequency waves can pass through, over, or across them more easily than waves in the middle- or even high-frequency range. Therefore, it isn’t impossible that noise protection bears some responsibility for the problem of LFN. As reported by Persson Waye et al. (2003), after measures had been installed against noise coming from outside, people were suddenly hearing LFN from inside the house and were so annoyed that some of them preferred to sleep with open windows despite the resulting high noise level. Di et al. (2005) reported a similar problem.
In searching for an answer to the question of why some people prefer to endure a louder noise with a broader spectrum than LFN at a lower level, few clues are found in the literature. One clue can be found in the detailed LFN report by Leventhall (2003). According to Bryan (1976) referenced there, the annoyance of LFN is determined by edge steepness limiting the spectrum of LFN to higher frequencies in the way, that a steeper edge causes an unacceptable annoyance while a moderately steep edge is acceptable. The core question is: What is the basic cause for all of these reactions?
In Hansen (2007), many contributions dealing with the effects of LFN on people came to the assumption that the special effects of LFN are caused less by the peripheral processing in the outer, middle, and inner ear but more by the subsequent processing in the nervous system. This might explain the direct influence of LFN on mental health [Persson Waye et al. (2001)], which can be found also in physiologic investigations [Persson Waye et al. (2002)].
Presented at Acoustics ’08, Paris, June 29–July 4, 2008
Detlef Krahé
Univ. of Wuppertal, Wuppertal, Germany
krahe/uni-wuppertal.de
Download original document: “Why is sharp-limited low-frequency noise extremely annoying?”
McPherson Study: The Infrasound Smoking Gun
Source: Gulden, Wayne
Abstract
McPherson is the first (and so far only) study to specifically look for the presence of excessive infrasound due to nearby wind turbines in a home that was identified by the owners as having a problem.* Two professional acousticians, Robert Rand and Steven Ambrose, lived in the home for 3 days during which they took detailed measurements of the infrasound and noted its effects upon themselves. They discovered that the infrasound often crossed the threshold of detection by the ear’s low-frequency detection mechanisms, and did so in a manner that could be very disturbing to individuals, causing potentially significant health problems. This study calls into question all the existing but unsupported claims by the wind energy industry and its supportive governments that infrasound is not a health issue.
[*NWW note: In 2009, Wade Bray and Richard James made such measurements at a house in Ubly, Michigan, as presented at Noise-Con 2011.]
Background
Modern wind turbines are large industrial machines that produce a variety of noises. As these turbines are placed closer to residences the number of complaints, from around the world, have been rapidly increasing. The complaints generally fall into two categories, audible and infrasound.
Audible noise may not seem so loud when casually passing by a turbine on a nice day. But a constant 24-hour exposure to this noise can cause annoyance – and by annoyance I mean something severe enough to lead to, among other stressors, increased blood pressure and all the resultant health issues that flow from that. In addition, the noise is more audible at night when it can lead to sleep disturbance, and all the health problems that follow that.
The wind energy industry admits there is audible noise and it can be disturbing to some neighbors. Since it isn’t disturbing to all the neighbors, the fault must therefore lie with the complaining neighbors themselves. Perhaps they are jealous, or there’s a nocebo effect, or they just didn’t like the turbines to begin with, or they are unusually sensitive. The fact is that wind turbine noise is very much more disturbing than just about any other noise we encounter in our modern world, as shown by this widely-distributed chart from Pedersen:
The McPherson Study and this critique have nothing to add to the discussion about audible noise.
Infrasound is noise whose frequency is too low to be easily audible, generally below 20hz. Modern wind turbines produce a large amount of it, and as they continue to grow larger they produce more of it, even relative to the total amount of noise they produce. Low frequency noise has the potential to cause a number of health issues. Tyrrell Burt’s list is from 1996, which referred to infrasound in buildings: “symptoms resulting from exposure to infrasound can include fatigue, headache, nausea, concentration difficulties, disorientation, seasickness, digestive disorders, cough, vision problems and dizziness, that is, symptoms typical of the sick building syndrome.” The quite similar list from Nina Pierpont’s 2009 Wind Turbine Syndrome is: “sleep disturbance, headache, tinnitus, ear pressure, dizziness, vertigo, nausea, visual blurring, tachycardia, irritability, problems with concentration and memory, and episodes associated with sensations of internal pulsation or quivering”.
The wind energy industry steadfastly denies that their product can produce enough infrasound to cause any health problems. They typically cite acousticians – the names Leventhall, Howe and Jakobsen appear frequently – saying things like Leventhall’s: “Infrasound from wind turbines is below the audible threshold and of no consequence.” Although these assertions sound reassuringly absolute there are two major problems with all of them. First is the idea that what you can’t hear can’t harm you. This is of course rubbish, akin to saying xrays can’t harm you because you can’t see them. Second is that none of these acousticians have ever gone into a home that is reported to be having problems and actually measured the infrasound levels.
The McPherson Study was the first time anyone went into a problematical home and actually measured the infrasound. What they found there puts an end to all the irresponsible speculation by these convenient professionals, some of whom are profiting thereby.
Part One – the Ear
Before we discuss the McPherson Study itself, it is important to set the stage by very briefly discussing the ear and its capabilities. For the purposes of this discussion it is important to know that there are two types of hair cells in the ear that translate physical vibrations (i.e. noise) to the electrical signals that are sent to the brain.
Inner hair cells (IHC) and their nerve impulses have been well studied and are generally accepted to provide for the sounds that we are conscious of – in other words, audible. Outer hair cells (OHC) are more mysterious. They have a different set of nerve connections to the brain and until recently it wasn’t clear that they sent any signals at all, and it is still not clear exactly what all their functions are. In real science, there’s always more to learn.
Alec Salt has been studying the ear for some 30 years at Washington University in St. Louis and he became interested in the topic of wind turbine infrasound when he came across Wind Turbine Syndrome. Given the symptoms he realized infrasound as detected by the ear could be the culprit. From his research he knew that the OHC were sensitive to lower frequencies than the IHC, and did send signals to the brain. And while his research wasn’t aimed at determining what the brain did with these signals, he knew it was irresponsible to blindly assert that inaudibility equaled no effects.
The essence of his argument is that wind turbines are documented to produce enough infrasound in neighbors’ homes to go above the OHC thresholds, and thus send signals to the brain that could lead to the documented symptoms associated with infrasound. The chart below presents this pictorially (from Salt’s SWV Picton presentation, slide #14).
I’m sure the wind energy industry would love to characterize Dr. Salt as some sort of non-mainstream non-scientist, sliming him like they did Dr. Pierpont, but so far they haven’t. Probably a good idea. Salt is well-published, an expert in his field, which currently concentrates on the effects of drugs on the ear. I first came across him in mid-2010, when Responses of the ear to low frequency sounds, infrasound and wind turbines was published in PubMed, peer reviewed and even sponsored by the NIH. I thought Salt’s work was of great value and posted about it at my windfarmrealities.org web site.
So how does the wind energy industry discuss his work? Not being able to dismiss it out-of-hand, they try to minimize it by saying things like (from Howe (2011), Low Frequency Noise and Infrasound – Wind Turbine Generators):
Salt acknowledges that “the fact that some inner ear components (such as the [outer hair cells]) may respond to infrasound at the frequencies and levels generated by wind turbines does not necessarily mean that they will be perceived or disturb function in any way”, but hypothesizes that there is a “possibility that wind turbine noise could be influencing function or causing unfamiliar sensations”. Salt also indicates that there are medical conditions where individuals may become hypersensitive to infrasound. Salt calls for more research.
Notice the attempts to minimize the effects and blame the victims? Even when Pedersen’s curves show that a third or more of the neighbors are highly annoyed by the noise? Where I strongly disagree with Howe and others like him is that even with the acknowledged unknowns, they never suggest that maybe, just maybe, they should slow the installation of wind turbines close to homes down a little. Bad for business, you see. At least Howe, in this case, finally started fudging on the infrasound issue. In the paper containing the above quote, he had four recommendations. Three of them involved more research, and one of the three specifically mentioned doing indoor testing. Well, McPherson is exactly what Howe requested, published two days before he did so!
Part Two – the Study
Falmouth, MA is located on the southern extension of Cape Cod, the part that ends at Woods Hole. Several years ago the town fathers decided to install a wind turbine (now grown to three) in an area that was close to a number of homes. Almost immediately the neighbors started complaining. Concerned about the welfare of his neighbors, one Bruce McPherson ponied up enough money to hire two professional acousticians, Rob Rand and Steven Ambrose, to do a throughout acoustical study of several of the homes that were affected.
The actual report is well written, and deserves to be read by everyone. To sum it up, both of Rand and Ambrose started feeling uncharacteristically unwell shortly after arriving at the home as they set up their equipment. Totally separate from Salt, I also posted on this at windfarmrealities.org. They recorded the noises for several days and then spent several months analyzing their results and doing additional research. I will present a brief summary – the full report really does deserve a reading.
We start with with the overall noise measurements taken indoors, as shown in their figure 8b:
The IHC and OHC thresholds are shown same as above with the average (RMS) unweighted dB level. Note that there wasn’t much audible noise (from above the IHC threshold, remember?) from the turbine indoors, and yet the neighbors generally complain that they are more disturbed indoors than out. The tone that is of the most interest was at 22.9Hz, which was confirmed as characteristic of the nearby turbine. It was on average just above the OHC threshold. It doesn’t seem possible that this slightly-sensed tone, averaging 50 dB with a threshold of 45 dB could cause very significant problems.
Rand and Ambrose then studied the 22.9Hz tone in more detail, filtering out the other noises. Here’s what they found, per their figure 9:
Note the time scale – that entire picture covers just 3 seconds! As Rand says:
Figure 9 reveals a remarkable range of modulation in the 22.9 Hz tone, which peaks in this example time record as high as 60 dB SPL, 10 dB higher than the 50 dB SPL mean established by the FFT averaging. Nulls between peaks drop down several tens of decibels below the OHC threshold. The figure suggests that the inner ear OHC circuitry
is receiving individual low-frequency pressure events 43 milliseconds apart at the 22.9 Hz driving frequency.
Imagine your brain getting continually pounded by the coming and going of the signals the OHC would be generating. The end result was that the acousticians themselves became nauseated etc and recovered as the measured levels of noise went up and down with the change of wind speeds during the several days they were in the home. As Rand states with a great deal of New England reserve:
The research is more than just suggestive. Our experiencing of the adverse health effects reported by others confirms that industrial wind turbines can produce real discomfort and adverse health impacts.
Discussion
The “smoking gun” portion of this report’s title is some indication of how important I think this study is, especially when combined with Salt’s pre-existing work. Salt established the physiology that explains fairly precisely how infrasound could cause the reported symptoms. It is difficult to dismiss his work. Rand and Ambrose then examine a situation where those symptoms have been reported by a large number of people in circumstances that lend credibility to the reports. They then find that the conditions that Salt hypothesized do in fact exist. It is difficult to dismiss their work. At this point anyone with any sense of precaution would have warning flags popping up all over. To add icing to the cake, the researchers themselves suffer the same symptoms in concert with their measurements crossing the threshold that was previously established by Salt. In the real world it isn’t often that the evidence is this clear-cut.
In spite of the overwhelming nature of this evidence there are still some loose ends. In science, there always are. The 22.9Hz tone may be characteristic of this particular turbine (a Vestas V82), or it may be due to location, the turbine type, the wind, this home etc. It may be common or not, it may be 22.9 or some other value. Establishing the entire truth will take many more studies, studies that cost a fair amount of money. But what is clear that for this home in this situation, the complaints of the owners are real and are beyond any reasonable doubt due to the noise generated by the turbine.
Another loose end is how the incoming signals from the OHC trigger the symptoms. Given the complexity of the brain this may never be wholly understood. But so what? We may not totally understand how, for example, bipolar disorder occurs but nobody doubts that it does, and treats it as best as they can.
The wind energy industry is always scolding the opponents for not being scientific. That is nonsense. The industry is simply accusing opponents of what they themselves are guilty of, an old trick worthy of scoundrels. The industry trots out about half a dozen “studies” that purport to show that there are no infrasound issues, but not one of them went into a troubled home and measured anything. The same pattern holds for the industry’s oft-quoted health studies, where not one of them interviewed any victims, nor their doctors, let alone ran a health study. And what happens when a real study comes
along, like Nissenbaum, Pierpont, Salt or McPherson? They belittle it, usually along with the author. They’ve apparently read Doubt Is Their Product, by David Michaels.
It has been two weeks since McPherson has been released and so far neither CanWEA nor AWEA have responded. Perhaps the Ontario re-release of Howe two days after McPherson was meant to be an answer, but given the speed of governments that seems unlikely (even though nobody can figure out any other motive). So I can only guess how they’ll respond, if they ever do. They’ll have trouble attacking either Salt’s work (peer-reviewed, NIH support) or the measurements of Rand and Ambrose (vetted by the Acoustical Society of America). So that leaves attacking the symptoms reported by them as anecdotal and thus automatically discardable, or attacking their obviously anti-turbine bias, or blaming the victims (or in this case, blaming the victim’s home), or saying it needs yet more proof.
It seems that some homes suffer and some victims suffer, but it isn’t yet clear what (if any) combination has to exist. The industry has already taken to blaming the victim for any health problems they might be having (i.e. attitude, nocebo, sensitive, jealous etc.) so maybe in this case they’ll try to blame the homes – too big, too small, not constructed properly, whatever. The homes in the neighborhood where the measurements were taken were built in the 1980’s and are rather small, less than 1,000 sq ft, and were presumably built to modern standards. There is nothing noteworthy about these particular homes. I’ve long thought that there might well be some characteristics to a particular home that would make it prone to having noise problems. To date it is impossible to determine what those characteristics might be. Should the neighboring homeowners be forced to take the entire risk that this new industrial development will render their home unlivable? Aside from an industry-government oligarchy, in what sort of political system is this acceptable? In what sort of ethical, moral or even religious system is this acceptable?
As for saying you need more proof, one has to wonder exactly what it is going to take to convince the governments there’s a problem. Thousands of reports, too consistent and widespread to be part of a conspiracy; too tied to wind turbines to be the result of something else? Check. A plausible physiological mechanism? Check. Measurements that show the mechanism is satisfied? Check. First-hand disinterested professional observation that agrees with the measurements? Check. Or perhaps this is a case of one’s salary depending on not understanding something.
References
Robert Rand et al.
(1) Rand has his own web site: http://randacoustics.com/
It contains a variety of wind-turbine-related materials, including the McPherson Study.
(2) The McPherson Study, available at Rand’s web site at: http://randacoustics.com/wind-turbine-sound/wind-turbines-published-articles/the-bruce-mcpherson-ilfn-study/
(3) The McPherson Study, a backup copy, from my web site at: http://windfarmrealities.org/wfr-docs/rand-mcpherson-study.pdf
(4) My posting about Rand and his illness in what eventually became the McPherson Study: http://windfarmrealities.org/?p=962
(5) Rand’s writings led me to post about community noise levels set way back in the
1970’s: http://windfarmrealities.org/?p=927
Articles on McPherson.
(1) The article that seems to have gotten replicated many places was originally at Cape Cod Online, at: http://www.capecodonline.com/apps/pbcs.dll/article?AID=/20111226/NEWS/112260313
Be sure to read the comment by Sue Hobart, the owner of the home.
(2) I have a backup copy of the Cape Cod Online article at: http://windfarmrealities.org/wfr-docs/cconline-mcpherson-111226.pdf
I included the comment by Sue Hobart as part of this backup.
Alec Salt et al.
(1) The abstract to his article on PubMed, as sponsored by the NIH, entitled “Responses of the ear to low frequency sounds, infrasound and wind turbines”: http://www.ncbi.nlm.nih.gov/pubmed/20561575
(2) The direct link to his article on PubMed: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2923251/pdf/nihms214369.pdf
(3) I have a backup copy of the PubMed article at: http://windfarmrealities.org/wfr-docs/salt-nih-infrasound-wind-turbines.pdf
(4) The NIH had a press release about Salt’s article, at: http://www.nidcd.nih.gov/news/releases/10/Pages/07_28_10.aspx
(5) I have a backup copy of the press release at: http://windfarmrealities.org/wfr-docs/nihcd-salt-conventional.pdf
(6) Dr. Salt presented at the Society for Wind Vigilance’s (SWV) Picton conference, one of many fine presentations, listed on their site at: http://www.windvigilance.com/international-symposium/proceedings-first-international-symposium
I was privileged to have attended and posted about it at: http://windfarmrealities.org/?p=699
His presentation can be found on my web site as well as at the SWV’s. I also posted on his work when I first came across it, at: http://windfarmrealities.org/?p=400
Brian Howe et al.
(1) The paper I referenced was re-released by the government of Ontario with a
press release: http://www.ene.gov.on.ca/environment/en/resources/STDPROD_092087
(2) The paper itself is at: http://www.ene.gov.on.ca/stdprodconsume/groups/lr/@ene/@resources/documents/resource/stdprod_092086.pdf
(3) I have a backup copy at: http://windfarmrealities.org/wfr-docs/hgc-lfn-infrasound-report.pdf
(4) John Harrison wrote a critique of the latest Howe report, at: http://windfarmrealities.org/wfr-docs/harrison-response-hgc.pdf
Jorgen Jakobsen.
(1) I have a copy of the paper everyone quotes from at: http://windfarmrealities.org/wfr-docs/jakobsen-low-freq-noise.pdf
If you read that paper, you’ll find it was just another literature review.
Geoff Leventhall.
(1) I have a copy of the paper everyone quotes from at: http://windfarmrealities.org/wfr-docs/leventhall-canacoustics.pdf
If you read that paper, you’ll find the main topic wasn’t infrasound per se, rather it was about the confusion regarding infrasound.
CanWEA/AWEA Health Study.
(1) This is an example of what the industry calls a health “study”. Note they never talked to one victim, nor any attending doctor. http://windfarmrealities.org/wfr-docs/canwea-health-dec-2009.pdf
Eja Pedersen.
(1) The chart is from Pedersen & Waye (2004), “Perception and annoyance due to wind turbine noise – a dose-response relationship”, available at: http://windfarmrealities.org/wfr-docs/pedersen-dose-response-2004.pdf
(2) The industry has taken her generally competent work and stretched it beyond its original scope. An example is how Ontario has misused it, as detailed at: http://windfarmrealities.org/?p=1201.
Tyrrell Burt.
(1) The complete study would cost money. In lieu of that the abstract is at: http://ibe.sagepub.com/content/5/1/44
Burt was an early infrasound investigator.
(2) Other writings of his give an idea of the earlier one cited above: http://www.accessengineeringlibrary.com/mghpdf/0071450076_ar019.pdf
Paul Fuchs.
(1) Here is a summary of Fuchs’ work on signals from the OHC to the brain: http://www.sciencecodex.com/now_hear_this
(2) Here is the Johns Hopkins press release on his work: http://www.hopkinsmedicine.org/Press_releases/2009/10_22a_09.html
Wayne Gulden
windfarmrealities.org
December 26, 2011
Wind Turbines and Proximity to Homes: The Impact of Wind Turbine Noise on Health
A review of the literature & discussion of the issues ~~
This paper addresses not only the issues of wind energy policy where it violates the basic living environment of families and the adverse health effects ofwind turbine noise, but also assesses the considerable number of anecdotal reports from people living with wind turbine noise. As noted in the authors’ 2007 paper, although there are many who dismiss anecdotal reports as inconsequential or meaningless, these reports are from real people, living with real problems, often with no recourse: they put ‘the human face on science’. The authors also examine how this translates into a human rights issue, as government policy assigns more credibility to acousticians’ reports than to medical evidence, and assigns more importance to renewable energy policy than to the individual lives injured by that policy.
The paper begins with a review of the acoustic impact of wind turbine noise reported by families and communities in the UK as well as similar cases in Japan, Australasia, the United States, Canada, and throughout Europe. This first chapter collates and details some of the evidence of recent reported cases and the extent of discomfort, distress, and health problems suffered by those families with prolonged exposure to wind turbine noise.
Chapter 2 examines the views of leading acoustic experts on the reasons that the acoustic ‘bombardment’ impacts people physically. This chapter also reviews the problems and complexities in interpreting the UK ETSU-R-97 guidance and subsequent apparent difficulty enforcing noise conditions that emerge from ETSU.
Chapter 3 discusses peer-reviewed medical research and reports from internationally recognised authorities, e.g., the World Health Organization, supporting the anecdotal evidence of health problems experienced by families living near wind turbines; these families endure the pulsating noise as well as prolonged exposure. There is also a growing body of evidence-based research substantiating the adverse health impacts of environmental noise pollution, particularly with extended exposure, of which wind turbine noise is an example.
As with many public health issues, the problems with wind turbine noise started with anecdotal reports where turbines were built too close to homes. These complaints emerged in a scattered pattern, because often the people affected did not associate the sudden onset of their sleep disturbances, headaches, or inability to concentrate with the noise. Most people were confident when told by the wind energy companies and their local officials that wind turbines were not intrusive, that the noise produced is easily masked by background noise, and that the noise compared favourably with familiar sounds, e.g., a home fridge, or a quiet conversation in the library. Initially, each affected person thought his or her new symptoms were unique.
As more complaints emerged from those who lived near newly operational wind turbine sites, and those who pinpointed the start of their newly identified health problems with the movement of the blades, some of those affected — and a few health professionals — suspected that the source of their problems might be associated with the noise generated by the wind turbines. This association seemed more likely because the victims’ symptoms were relieved when they were away from their homes or farms. Moreover, the symptoms recurred once they returned home. These patterns emerged only over time, and across many wind turbine areas, internationally. Chapter 3 also reviews several pilot studies conducted by physicians in order to assess the anecdotal reports of health effects from those living near wind turbines.
Chapter 4 considers basic international human rights, apparently sidestepped by Britain, as its environmental policy appears to assign greater priority to the protection of landscape, bats, dormice, and water voles (though the authors certainly applaud those efforts). The State appears to accord more importance to, and enforces with more stringency, those issues to the detriment of policy that protects the health and dignity of families. As a result, in their ambition to achieve renewable energy targets, public officials authorise what amounts to the degrading and inhuman treatment of families.
The influential wind energy industry and its lobbyists, public agencies, environmental organisations, and many media sources often employ pejorative labels, such as NIMBY – Not In My Backyard, to decry or stigmatise those who complain, as insensitive to environmental pollution and global warming, in order to dismiss these anecdotal reports. Yet, it is essential to remember that many of those affected by wind turbine noise were those same people who welcomed the wind turbine schemes and were skeptical of those who complained about potential or actual noise interference. Many early wind turbine noise studies focused on annoyance and identified sleep disturbance as a frequent problem, but these studies did not collect data on health effects. Public health problems often evolve gradually and become more evident only with the passage of time as more people are affected (duration of exposure).
UK government renewable energy policy has focused more on expanding the role of industrial wind turbines rather than ensuring the protection of the health of those exposed to wind turbine noise, i.e., the protection of the public’s health. Thus, the voices of those affected by wind turbine noise have grown more insistent as more wind turbine sites are located near homes and villages. The solution has always seemed transparently straightforward: locate wind turbines further from homes and other sensitive structures. Of course, one must then determine the optimum distance, and there lies the rub, with industry pushing for minimal distances, while many others seek a more precautionary stance, in an effort to protect health, well-being, dignity, and quality of life.
Wind turbine noise is a form of and another cause of environmental noise pollution. Recent studies, both medical and acoustic, offer data to assist with the decision on where to site and how to design wind turbine arrays. Notably, wind energy developers often assert that there are virtually no studies on wind turbine noise and no evidence of its ill effects. However, there are not only studies specifically on the adverse effects of wind turbine noise, there are also studies on noise with similar or shared acoustic characteristics. Wind turbine noise is especially complicated because of the ‘cocktail’ of physical acoustic characters that comprise the noise pollution. The pulsating noise, characteristic of wind turbines, can be more intrusive than other types of noise, and the pulsations include both audible and inaudible components, i.e., low frequency noise, infrasound, and vibration. Noise with these characteristics is more intrusive, and the World Health Organization (WHO) guidelines recommend lowering the permissible decibel levels when noise contains these characteristics. WHO makes these recommendations not merely to reduce annoyance or nuisance. WHO makes these recommendations because epidemiological studies indicate clearly that environmental noise is prejudicial and injurious to health. [WHO 1999, 2010, 2011]
WHO’s impartial reports are particularly compelling because they undergo periodic review and updating by its international panel of experts from diverse, related fields. Moreover, the panel’s findings and reports undergo a process of stringent review internally amongst the panelists, as well as externally, by reviewers not on the panel. Most recently WHO issued Night Noise Guidelines for Europe 2009, and the Burden of Disease from Environmental Noise 2011, which, with EU directives and guidelines on noise, offer policy-makers and other invested parties with descriptions of how health is adversely affected by noise, as well as with methodologies to ameliorate or to prevent injury to health from environmental noise.
Those affected by wind turbine noise could be your relatives, friends, neighbours, and even — at some point — you. Often these are people who know austerity intimately, who understand the dilemma of balancing environmental issues such as energy supply and global warming with current policy and future demands. Instead, they are marginalised and made to feel doltish and selfish. They also feel disenfranchised and abandoned by those in whom they have placed their trust. This cynicism is not unfounded, as many are left financially impoverished as they seek advice and support in order to make their voices heard. The issue of wind turbine noise is about real people, who are genuinely suffering degrading and inhuman treatment.
Planning for industrial estates near dwellings is more restrictive on noise control, with those facilities rarely operating daily, 24/7, than the noise controls on wind turbines. Selecting a minimum distance of 2km as a buffer between homes and the placement of a wind turbine — though an even greater distance may be required — is not excessive when the lives and well-being of those affected are taken into account. There is still ample opportunity for developers to site their schemes more appropriately and for government to redress errors in policy that allow these untoward, unpredictable, and unacceptable effects.
Barbara J Frey, BA, MA (University of Minnesota)
Peter J Hadden, BSc (Est Man), FRICS
January 2012
Response to HGC Literature Review
Source: Harrison, John
Response to “Low Frequency Noise and Infrasound Associated with Wind Turbine Generator Systems – A Literature Review”
Also see: “Compliance Protocol for Wind Turbine Noise – Guideline for Acoustic Assessment and Measurement”
Introduction
The low frequency report, prepared by Howe Gastmeier Chapnik Ltd. was commissioned by the Ministry of the Environment (MOE), released in draft form in August 2010, released in final form to MOE in December 2010 and to the public in August 2011. Why MOE is issuing it now as a press release is a mystery. This response will address the report itself and the news release from the Ministry of the Environment.
A glaring omission from the report and the news release is the motivation for the commission to HGC. The motivation of course is that a large number of residents living in proximity to wind turbines are suffering from annoyance, sleep deprivation and resulting adverse health effects. The root cause of the annoyance is the noise generated by wind turbines.
Not only does the report and news release avoid mention of the motivation for the commission, neither MOE, the Ontario Chief Medical Officer of Health nor HGC made any attempt to interview those suffering from adverse health effects
The commission focused on low frequency audible sound and infrasound because at a distance of several hundred metres from a turbine much of the high frequency sound has been absorbed by the atmosphere.
The annoyance associated with turbine noise is considerably larger than noise of a similar sound pressure level generated by traffic or industrial noise. For instance field studies by Pedersen, van den Berg, Bakker and Bouma (referenced in the report) show 15% and 27% of a population are annoyed by sound pressure levels in the ranges 35 to 40 dBA and 40 to 45 dBA respectively. [Pedersen et al. consider five reactions to turbine noise: do not notice; notice but not annoyed; slightly annoyed; rather annoyed; and very annoyed. They group rather and very annoyed together under the heading “annoyed”.] These numbers are to be compared to 3% of a population annoyed by traffic noise in the same sound pressure level range. The present Ontario noise limit is 40 dBA; the noise limit before the Green Energy Act was 51 dBA in a sufficiently high wind. As noted below the Ontario noise limit is based upon prediction with significant noise contributions to the prediction not considered.
Possible reasons for the difference in response to turbine noise and road or industrial noise is the predominance of low frequencies in the turbine noise and the characteristic amplitude modulation of turbine noise at the blade passage frequency; this amplitude modulation draws continual attention to the turbine noise in the way that a dripping tap does. The wind industry and its lobbyists make much of the contribution of attitude to wind turbines to the annoyance. However, it is difficult to think that the attitude to industrial plants or road noise would be any less benign. In addition, while Pedersen et al. show a linear dependence of annoyance on the turbine sound pressure level there is no similar study showing a linear dependence of annoyance on attitude!
Not for nothing do the following health and other experts propose setbacks well beyond those allowed by the Ontario Ministry of the Environment:
The HGC report gives considerable prominence to the Colby et al. health study and to the Chief Medical Officer of Health, Dr. Arlene King, health study. The one was commissioned by the Canadian/American Wind Energy Authorities and the other by the Ontario Government which is far from unbiased with respect to wind energy. Both are seriously flawed, notably in having no interest in the numerous people suffering from adverse health effect and in emphasizing the absence of direct health effects. Generally the adverse health effects are indirect: sleeplessness and annoyance leading to stress-related illnesses. This is recognized by the World Health Authority which considers annoyance and stress as adverse health effects. A recent paper by Dr. Carl Phillips, a noted epidemiologist, offers a detailed critique. The King report is marred by an erroneous quotation from the 2009 Pederson et al. paper of the number of people annoyed by turbine noise. Dr. King has yet to acknowledge this error/deception.
Technical Review
As must be, much of the HGC report concerns technical aspects of noise generation and sound propagation. Here there is a fairly complete literature review. However, this section fails to emphasize that the turbine manufacturers are aware that the future of widespread acceptance of wind energy will depend upon reducing noise and low-frequency noise. To quote:
“The acoustic noise radiating from wind turbines continues to be the dominant design driver that must be incorporated into the design process. The tip speed of many turbine designs is limited by the amount of noise created by the blades passing through the atmosphere.” Moriarty (NREL, USA) et al., AIAA Conference Proceedings (2005).
“… noise emission … has become one of the most important environmental impacts of wind energy.” (Romero-Sanz and Matesanz (Gamesa Spain), Wind Engineering, 32, 27-44 (2008))
As stated in the report a major cause of turbine noise is aerodynamic trailing-edge vortex creation. There has been theoretical and wind-tunnel research to investigate the effect of different blade cross-sections on TE noise.
Perhaps of far more importance for low frequency and infrasound noise is the work on inflow turbulence. HGC, the Ministry of the Environment and CanWEA continue to bury their heads in the sand concerning this issue. This important noise source has been brought to the attention of MOE and the Canadian acoustics community by bringing to light the early work at the National Renewable Energy Laboratory (NREL) in the USA. This work demonstrated through theoretical work based upon the mathematical modelling by Amiet and through experimental work with the NREL CART up-wind test turbine that turbulent inflow considerably enhances the low frequency noise emitted by turbines. More recently, Dr. Moriarty has brought to my attention their continuing work, in collaboration with Dr. Guidati, well-known as a co-author of the Wagner et al. treatise on wind turbine noise.
On July 8th, 2011, The National Laboratory for Sustainable Energy, Risø, Denmark placed the following description in an advertisement for a scholarship: “Noise is an interesting concern for wind turbine manufacturers and communities living near wind turbines. These concerns are exacerbated by the constant increase of wind turbine sizes and the cost advantages of placing turbines close to the consumers. The design of low-noise turbines requires the use of validated and accurate engineering models. The main sources of noise generated by a wind turbine have been identified as turbulent inflow noise and trailing edge noise”
If still not convinced then Figure 32 of a recent report by K.D. Madsen and T.H. Pedersen should be enough (“Low Frequency Noise from Large Wind Turbines” DELTA report AV-1272/10 (2010)).
Other work not referenced concerns measurement of turbulence intensity. This work is being done because turbulence increases dramatically low frequency noise, because it puts stress on the turbine blades and because, with associated wake loss, it decreases the capacity factor of downwind turbines. A list of references that needed to be addressed is as follows:
Lange et al., “Modeling of Offshore Wind Turbine Wakes”, Wind Energy, 6, 87 (2003).
Barthelmie et al., “Modeling and measured Power Losses and Turbulence Intensity …”, Wind Energy, 10, 517 (2007).
Wagner et al., “Influence of Wind Speed Profile on Wind Turbine Performance Measurements”, Wind Energy, 12, 348, (2009).
Barthelmie et al., “Off-Shore Wind Turbine Wakes Measured by Sodar”, J. Atmos. Oceanic Tech., 20, 466 (2003).
Bertaglio, “NACA0015 Measurements in LM Wind Tunnel and Turbulence Generated Noise”, Risø National Laboratory for Sustainable Energy (2008) (report # Risø-R-1657(EN))
In Europe, the European Commission is supporting turbine research through the SIROCCA Project: http://www.ecn.nl/nl/units/wind/projecten/sirocco/
Propagation of Low Frequency Noise (Section 3.2)
The report makes important points concerning the propagation of turbine noise: The cylindrical decrease in sound energy, the acoustically hard character of ground for low frequency sound, the low absorption by the atmosphere for low frequency sound and the ready penetration through residence walls. These points needed to be emphasized in the executive summary, the conclusions and the recommendations. At present they are not acknowledged by the Ministry of the Environment. This is especially important as guidelines are drawn up for off-shore wind energy.
Noise Annoyance (Sections 3.5, 3.6 and 3.8)
Laboratory studies have their place. Nevertheless, for reasons that Dr. Leventhall gives, as referenced in section 3.6, far more weight needs to be given to field studies in comparison to laboratory studies. Missing from Section 3.6 is consideration of the amplitude modulation. This is typically 5 dBA but higher values have been reported. Dr. Leventhall himself has written: “A time-varying sound is more annoying than a steady sound of the same average level and this is accounted for by reducing the permitted level of wind turbine noise”. As we are well aware, the Ministry of the Environment refuses to do this.
Section 3.8 quotes the work of Pawlaczyk and Luszczynska. It was only fair to have quoted also the work of Persson Waye et al. (“Low Frequency Noise “Pollution” Interferes with Performance”, Noise Health, 4, 33, (2001)). This paper comes to the opposite conclusion for low frequency noise at the 40 dBA level.
Health Effects (Section 3.11)
The Colby et al. and King reports were dealt with above. Turning to the discussion of Dr. Pierpont’s work, the report is bizarre. There is no mention of the bulk of the work on the medical study of a large number of people suffering adverse health effects resulting from wind turbine noise. This work analyses the range of symptoms and finds reason to treat them collectively as a syndrome. Separately, there are hypotheses for the cause of the syndrome. Hypotheses are not proofs; scientifically, the presentation of a hypothesis is reason to study the problem and to demonstrate proof or otherwise. Whether the hypotheses are correct or not is irrelevant to the fact that there are adverse health effects. The energy devoted by Colby et al., King, CanWEA to denigrate the medical and diagnostic work of Dr. Pierpont is reminiscent of the methods we saw some decades ago used by the tobacco industry! Again, I recommend a reading of the Phillip’s report on the power of crossover analysis in understanding the reality of adverse health effects from wind turbine noise. There is a reference to Leventhall (2010) missing from the bibliography; nevertheless, I know that Drs. Leventhall, Colby and King are not epidemiologists!
Conclusions (section 5.0)
1) Although turbine noise is broadband, at a distance of 500 metres, much of the high frequency sound has been absorbed. Distance enhances the low frequency component as does turbulent inflow.
3) Reference needs to be made to the Salt study demonstrating other pathways for the perception of very low frequency sound.
4) This conclusion is wrong and is a red herring. Turbine noise in the range 35 to 45 dBA causes annoyance and sleep disturbance. These are adverse health effects and in turn lead on to other adverse health effects. 100 people reporting adverse health effects and more than a dozen families abandoning their homes in Ontario alone gives the lie to this conclusion.
5) Non-trivial (a derogatory and unworthy expression) has no place in a professional report. It should be replaced by about 20% being annoyed.
Recommendations (Section 6)
Given that the review of current technical literature in the HGC report has missed completely research dating back to Amiet and forward to detailed comparisons between theory and experiment on turbulent inflow noise, the first recommendation needs to be revised. MOE does need to revisit its guidelines to include turbulent inflow noise, to treat the ground parameter as hard for low frequency sound, to reconsider spherical spreading, particularly for off-shore sound propagation, to address the uncertainty in the prediction of sound at a residence and, given the accepted enhancement of annoyance due to amplitude modulated noise, to apply a penalty for amplitude modulation.
Response to Backgrounder: Low Frequency Sound and Infrasound Report
What kind of noise do wind turbines produce? Turbines do indeed produce a wide range of frequencies. However, the noise 550 metres or more from the turbine is skewed towards low frequency noise because of selective absorption of the high frequencies by the atmosphere.
Is wind turbine sound harmful? The Minister of the Environment writes that there is no direct health risk. However, field studies have demonstrated that 15 to 27% of people exposed to turbine noise at the Ontario regulated limit will suffer annoyance. This is an adverse health effect and in time leads on to other adverse health effects such as stress, tinnitus, headaches and sleep disturbance.
Are Ontario’s rules to control wind turbine sound stringent enough?
The minister writes that at the Ontario regulated setback much of the sound that turbines produce lays outside the range that people can hear. This is untrue. Field studies show that at the regulated setback, 80% of people can hear the turbine noise. Also, the minister fails to note that Germany, with its more extensive experience with wind energy, has a lower night-time noise limit than Ontario.
John Harrison, harrisjp/physics.queensu.ca
