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Wind turbine noise - the debate continues

The article by Dick Bowdler in the last issue of the Bulletin on the Institute's wind turbine noise good practice guide has generated a lively response, as we might have expected. Below we print a letter from Mike Stigwood and an article by Gwyn Mapp on the subject. The Institute recognises that there is still a long debate to be had about various issues concerning the assessment and acceptability of wind farm noise, and we will be continuing to discuss those issues through a series of technical meetings starting with a meeting in Edinburgh on 7 November, and further articles in the near future.

The IOA good practice guide, excess amplitude modulation and the failure of wind farm noise controls

In August 2013 at the 5th International Conference on Wind Turbine Noise in Denver, we presented extensive research which amongst other things identified that excess amplitude modulation is common and the main noise problem and source of annoyance caused by wind farms. Unbeknown to me prior to the conference, a major Japanese study looking at 34 wind farms had also concluded AM was common and warranted controls similar to those I have previously promoted with small peak to trough values1. The good practice guide (GPG) focuses on ETSU-R-97 (ETSU) as do councils investigating complaints about wind farm noise. This obfuscates the real problem and leaves communities unprotected. Focus on ETSU procedures rather than the main problem, EAM, provides a powerful distraction. Unfortunately, it remains necessary to continue debating the issues surrounding this distraction.
In 2009 a group of acousticians devised a new way of interpreting ETSU to address wind shear. They had not based this on any empirical data or published research and assumed that of the two options available to address wind shear both gave similar results. This was the thrust of a talk by one of the authors of the article which appeared in Acoustics Bulletin in March-April 2009. They were wrong. Our research comparing actual data from sites and then separate subsequent research by the Renewable Energy Foundation found repeatedly the method adopted allowed more noise, levels up to 5dB(A) higher.2,3 This equates to significant reductions in separation distance. Our research remains unchallenged and every wind farm site we have evaluated since that study provides the same results.
At best the article authors try to argue our research is flawed but do not contradict our findings with any meaningful research or data. Dick Bowdler has reiterated erroneous arguments in an article in the Bulletin (September-October 2013) to which I need and intend to respond. In short, predicted turbine noise referencing 10m standardised wind speeds can be directly compared to 10m measured wind speeds ("apples with apples"); it roughly approximates the situation where the wind shear between 10m height and turbine hub height (approx 80m) is equal to 0.16.
It is of interest that the same group of acousticians effectively concluded, in the same article, that low frequency noise was not an element of concern in wind farm noise impact despite emerging research demonstrating this was wrong. I had personally presented some evidence of low frequency impact at an IOA meeting two months earlier. The evidence of low frequency impact is now abundantly clear including an extensive Japanese study which has recently confirmed that these claims were wrong. Researchers have identified significant LFN issues in various papers since 2009. None of the authors has retracted their claims in the three and a half years since.
In 2012 the Institute of Acoustics selected a noise working group which was dominated by individuals who were party to the 2009 article, either originally or shortly after the article was released and before it was tested. They had effectively agreed to a method that allowed an increase in wind farm noise and from whatever position they approached the change, they had arguably compromised their future impartiality in that process. They had certainly argued the article was correct creating difficulty in any retraction. It is also of note that the majority of the working group are primarily employed by the wind industry, are promoting its aims or prosper from wind farm development. That is not necessarily unusual or disadvantageous, but it is not surprising that in these circumstances the new IOA working group endorsed their original idea, the article method shown to allow more turbine noise, in May 2013 in the GPG. Despite the lack of any contrary evidence to our research highlighting the issues with their method, the noise working group members defended their position.
The fact that the method does allow more turbine noise, including in their recommended prediction methodology, is also manifesting itself in reduced separation distances between turbines and housing. This is further testament that the method is allowing more noise. Simple comparison of sound power level versus separation distance demonstrates this in a simplistic way. A major problem with the change is that it has sidestepped the procedure in ETSU, and which is generally adopted for noise impact assessment, that would normally expose excess noise. The new method cannot enable investigation of noise levels under the conditions leading to complaint. Adopting the change recommended in the article gives the illusion that this is still achieved, but in reality it is now prevented as conditions are assessed at hub height and standardised to 10m height. They cannot determine the conditions or crucially the wind shear leading to complaints experienced at 10m height, the conditions people experience around their homes. We now see industry acousticians re-interpreting existing planning conditions that used 10m measured wind speeds as if standardised wind speeds were originally intended. This thereby allows a greater margin and minimises the likelihood that a breach will be shown.
Dick Bowdler is one of the original authors and he defends their position in his article in the Bulletin, arguing standardised wind speeds are better. The science is so complex on this issue that few understand it and many readily confirm they do not understand it. Phrases are then banded such as "like with like" and "apples and pears" attempting to imply one method is correct and the other incorrect as a way of deflecting from the significant noise increases standardised wind speeds now allow. Further deflection arises through implying the whole ETSU methodology is wrong. The latter may well be the case but it is arguably misguided when it allows more noise.
Dick suggests the Renewable Energy Foundation (REF) criticisms of the standardised method come from the MAS Environmental research. That assumption is wrong. REF undertook its own research without reference to MAS using different data and applied different methods. It led to similar conclusions; the standardised method allowed more noise.
Dick suggests either 10m measured or 10m standardised could have been adapted for wind shear, but this is a misconceived assumption as they both give very different results. In the standardised procedure wind shear effects are aggregated with a large number of other variables influencing background noise levels and so are effectively subsumed and diluted in the process. Using 10m measured controls wind shear effects are considered independently and influence wind turbine noise as a separate variable. This is why our research shows case by case that the article and GPG method allows more noise.
Dick asks if the GPG method gives less protection but this is already answered in both the MAS and REF research with a resounding yes. Every case compared has allowed more noise, a finding demonstrated in both the REF and MAS research using actual data from a number of sites. Every site we have considered since has produced the same results. It is a complex interaction of meteorology, acoustics, statistics and physics, and has taken us countless hours of analysis. In part this is why we conducted the research, to better understand the interactions.
Dick accuses me of perpetuating a scientific inaccuracy, which professionally I cannot allow to go unanswered. It is misconceived and incorrect, arising from a misunderstanding of the relevant principles. Our research was scrutinised by many including independent non UK-based acousticians who peer reviewed the work. We had to go overseas as most we approached in the UK did not have sufficient understanding of meteorology to comment. Incorrect assumption from a failure to fully read and understand the research is part of a wider problem, a common trap most of us have fallen into from time to time. It could be argued, from a cynical perspective, that wind industry acousticians have capitalised on those misunderstandings.
In as simple terms as I can express it:
•    The generation of power and hence turbine noise is related to the wind speed at the turbine hub height, whereas the background noise masking the turbine noise is related to the actual (not standardised) wind speed at or near ground level. The object of the ETSU methodology is to derive limits to protect residents in dwellings at ground level. Those limits should only rise in decibel level as the near ground masking noise rises. ETSU was not designed to derive limits that increase as the turbine noise rises whilst the background noise does not. This allows uncontrolled operation. The ETSU principle intends setting limits to control the level of turbine noise so that it does not emerge excessively above the background/masking noise. That is how context based limits and BS4142, on which ETSU was framed, work. In other words, we do not say "let us set noise limits to match the noise of the turbines" but "let us set noise limits which match the levels of masking noise present". The standardised wind speed approach adopts the former and departs from the latter. Adopting this approach abandons the basic mechanisms commonly applied to control any site noise.
•    High wind shear results in greater turbine noise and lower background masking noise than assumed in ETSU. The ETSU document discusses why it considered turbine noise would rarely exceed the background noise except by levels of up to 5dB and then only for a limited range of wind speeds. The standardised wind speed method abandons this concept by ignoring those circumstances when turbines emit maximum noise but background levels are low.
As a consequence of adopting standardised wind speeds, the GPG now mandates a sophisticated and deceptive averaging process for wind shear that fails to consider the periods when wind shear is higher than average. Unfortunately, this occurs at key times of the evening and night and as such is when complaints most commonly arise. The use of hub height wind speeds, recommended in the standardised method, does not differentiate high wind shear conditions. I am content that time will demonstrate those supporting the standardised method will be shown to have allowed significant noise increases and promoted a method that prevents assessment of actual conditions causing complaints. We are documenting this and will continue to publish the consequences of adopting this procedure. Residents who suffer the increased noise are not content and regrettably we are seeing a large increase in complaints. Ultimately it is our profession which is likely to be seriously tarnished.
The problem arises from a loss of sight of the purpose of assessment and controls. The assessment is not an exercise in determining the maximum energy that can be extracted from wind farms for a given decibel level, or through changing how that is defined to further allow more energy extraction, but what controls actually protect residents. To understand this latter point, we need to look again at decibel level objectives and also reflect on how these have become muddled to benefit developers.
In essence, there are two separate decibel control regimes with different aims and objectives.
Threshold levels. Protecting human health from excessive general environmental noise where that noise does not convey a message. We would normally consider this benign anonymous noise. I call this "general noise". General noise is normally considered to cause harm when it exceeds certain thresholds.
Context levels. These are used to protect amenity, welfare and sometimes health from noise which intrudes because of its character rather than its level. It is the message it imparts to the inadvertent listener. In other words, context levels are used for irritating noise that triggers adverse response because the noise conveys a message.
I call this "site noise" as it normally arises from a particular site or source. Site noise is generally considered unacceptable when it reaches a certain level of audibility or dominance.
The latter can equally impact upon health but not so much in terms of active damage, because of its energy levels, but in terms of a psychological stressor because of the psycho-acoustical responses of listeners. Naturally there is noise which falls within both categories and we may need to look differently at how we control this, especially if we seek to combine both objectives.
We can readily see examples of both. An example of the first is road traffic noise which we tend to filter out of our thought processes and so ignore any message it may impart. It is just there and many do not notice it. It may cause difficulty getting to sleep or lead to lower quality sleep but we are not consciously listening to it. An example of the second is noise from a party at a neighbour's which continues, albeit at low levels, into the core sleep hours. Commonly we cannot avoid listening to it and interpret messages such as the lack of care for neighbours' sleep by revellers, the irritating nature of an individual's laugh and so on. It can be quieter than the road traffic noise but impacts significantly more.
ETSU assessed wind turbine noise as primarily falling in the general noise category. An element of context is recognised in the application of a penalty for tonality and relationship to background noise. The first and most serious error was to assume wind farm noise did not or still does not contain substantial psycho-acoustic messages other than tonality. Unfortunately, even the tonal element of wind farm noise considered in ETSU and its adjustment assumes that impact can be applied to general noise thresholds, rather than relate it to its dominance or audibility. That is a fundamental error of analysis and is one reason why wind farms that are considered compliant cause so many complaints.
In summary, it all promotes bad science allowing more noise by varying the procedure increasing the margin of error. The graph below shows a comparison of context; the background noise level in a bedroom without turbine noise and the turbine noise inside the bedroom post development but which complies with ETSU.
An example confirming the bad science of ETSU is the Bilberry Farm planning inquiry in 2012. A small turbine had been built in the wrong place without a noise control. It caused a tonal nuisance and statutory nuisance action was taken. Planning enforcement action was also taken and appealed. All experts for all parties at the appeal agreed it caused nuisance. Works were being implemented to reduce the tonal noise content and decibel levels but were not completed by the time of the appeal hearing. Nuisance was not continuing as the turbine had been parked for some considerable time. Tests during the inquiry showed nuisance level noise continued. The appellants proposed a condition based on the lowest levels in ETSU, including its tonal penalty, to control the noise in the event that the inspector approved the new turbine position. It was promoted on the basis it would render the turbine compliant with ETSU. Cross-examination of the evidence confirmed the ETSU-based condition did not prevent the noise that had already been judged a nuisance. In other words,
the ETSU controls permitted undisputed statutory nuisance. The failure of the condition was acknowledged by the inspector but it is instructive it was not specifically identified as an ETSU condition in the decision letter. That would amount to an open criticism of ETSU by a government inspector.
Returning to the issue of the noise working group and interpretation of ETSU, no published research supports the standardised procedure. It cannot as the change introduces an averaging process. not originally envisaged by the authors, which effectively subsumes the effect of wind shear averaging it with other influences and thereby losing its effect. The outcome of the IOA GPG working group is very helpful for the wind industry and the acousticians who work for it. Arguably it is also procedurally convenient; it avoids an argument about how it gives a false illusion of protection.
The harm of all of this process is ultimately to the profession. We see politicians vilified and a number of other professions also. Acousticians who promote procedures that give a false illusion of protection must expect the same attacks on professionalism but from which we will all suffer.
The simple fact is that proportionately a huge number of wind farms cause noise complaints but almost every wind farm causing complaints has been deemed to comply with ETSU-R-97. Only in one case has a wind farm been confirmed to marginally exceed limits that I am aware of. There is an obvious anomaly in that. Either we have a very high percentage of unreasonable/abnormal people in society living near wind farms, the controls and those who devised them are wrong, the method of applying those controls and those who apply those methods are wrong or it is a combination of all of these factors. It is of note that many complainants were in support of the wind farm development before it became operational.
We need to learn from this problem and so it is now a matter of documenting the harm caused, who said what, who endorsed those processes and procedures causing that harm and who allowed those promoting an erroneous approach to wind farm noise to do so. Currently we see environmental statements confidently claim that excess amplitude modulation is only a rare problem. In reality it is the main problem with almost all the wind farms that cause complaints. We are in the process of documenting these cases. Some difficulty has arisen as wind farms are not built for several years allowing a time lapse before the evidence emerges that decision makers have been misled. Many of the sites approved in 2009-2011 are now being completed and are leading to widespread complaints.
We need to return to environmental noise assessment basics and look at the principles we have abandoned in wind farm noise assessment without any research to support that abandonment. We need to look at why bad science prevails and before it is too late. In the words of the World Health Organisation, only one third of noise nuisance is due to the decibel level. We need to properly evaluate the other two thirds. We need to stop averaging the quietest 10% of the source of noise for comparison with the average of the background noise. We need to stop assuming noise with substantial psycho-acoustic character can be assessed as if it is benign and anonymous noise.
In the acoustics profession we assess noise generally by:
•    Looking at short term noise impact and not long term averages
•    We are interested in the impact at a moment in time and the disruption that it causes, such as sleep disturbance on a particular night, and not what the average noise is.
If we looked at average speed on a journey it would not tell us if inappropriate speed was applied in relevant circumstances, whether the driver was too close to the car in front or drove erratically and dangerously. In the same way the average of the noise during periods when it was not excessive does not inform us of adverse impact. The averaging now applied by those using the standardised method was not the original intent of ETSU or, if its authors now claim it was so, meant to be worded that way and it does not mean what it literally says (as they have claimed in relation to wind shear) then the intent was clearly wrong.
We assume too much in acoustics. It was assumed thalidomide would not be passed genetically but this was a serious error. It was assumed the people of Liverpool would ultimately accept repeated inquiries using individuals with known persuasions with a view that they were responsible for the Hillsborough disaster but this was wrong. It is wrong to assume people will accept the noise they suffer from wind farms, accept disturbed sleep and associated heath effects and move out of their homes just because it meets an illusionary standard. The growing evidence is they will not. The sooner we recognise the failings and get back to basics the better.
Mike Stigwood, MAS Environmental Ltd (MAS)

References

1. Several papers have resulted from the study, see for example
Tachibana, H., Yano, H., & Fukushima, A. (2013). Assessment of wind turbine noise in imission areas. 5th International Conference on Wind Turbine Noise. Denver.
2. 2 http:/ /www.masenv.co.uk/publications
3. 3 Renewable Energy Foundation (REF) (2012) A Critique of the IOA Treatment of Background Noise for Wind Farm Noise Assessments. Available online:
http://www.reforg.uk/attachments/article/255/ref%20info%20note%20120403%20IoA%20Shear%20Methodology.pdf

The following article is included out of interest

Wind farm noise - all blown over?

By Gwyn Mapp

Introduction

On 20 May 2013 the IOA published a good practice guide to the
application of ETSU-R-97 for the assessment and rating of wind turbine noise.
The guide was commissioned by the Department of Energy and Climate Change (DECC) who also endorsed the guide along with the Welsh and Scottish Governments. The Department of the Environment of Northern Ireland issued a holding response. It is agreed by the endorsements that the good practice guide would improve the consistency of application of ETSU-R-97.
So, everything is going to be fine then, right? Well, not quite. Criticism of the good practice guide has been vociferous in some quarters'.
In order to understand why the issue of wind farm noise is still proving to be controversial it is necessary to understand how the planning system method of dealing with wind farms fits in with the law of the land.

What are the legal rules for noise in the UK?

There are two elements to the law that applies to noise in the UK. These elements are civil law and criminal law.
Under the civil system noise can be considered to be a tort, i.e. a civil wrong, if it is considered to be a private nuisance. A private nuisance is the unreasonable interference with the use and enjoyment of land or some right in connection with it. Case law provides a range of issues that should be considered when judging whether a noise is unreasonable. These issues include give and take between parties, particular sensitivity of the complainant, motive of the defendant, time of day of the disturbance, duration, frequency and intensity of the disturbance, nature of the area and the importance and value of the activity to the community'. In order to claim under private nuisance, the complainant needs to have some property rights in the land that is being affected.
Under the criminal system noise can be considered to be a crime by two main routes. The first is for the noise to be considered a public nuisance. A public nuisance is defined as a nuisance which materially affects the reasonable comfort and convenience of life of a class of the public who come within the sphere or neighbourhood or its operation4.
The second way noise can be considered to be a crime would be for the noise to be considered a statutory nuisance as described by Part III of the Environmental Protection Act 1990 (as amended). Noise is considered a statutory nuisance if it is either prejudicial to health or a nuisance. Nuisance in this context is not defined but is taken to mean either private nuisance or public nuisance'. It should be noted that there are some technical differences between private nuisance in tort and private nuisance in statutory nuisance, the most important of which is that there is no need for a complainant to have a proprieto¬rial interest in the land if statutory nuisance is being used to deal with the noise6. There is also no such need to have proprietorial interest in order to take action under public nuisance'.
The planning system as provided by the Town and Country Planning Act 1990 (as amended) is frequently used proactively to manage noise and could be considered to be all conquering due to its sheer ubiquity. However, the planning system is fundamentally a political system that operates under the law. As such, the planning system is required to avoid permitting potentially illegal activities in both civil and criminal law.' In fact, it has been established that public officials who permit a criminal offence to occur or recur are acting ultra vires.9 This means that, in effect, the planning system needs to avoid permitting criminal or civil offences that affect all neighbours at all times. This requirement cannot be over-ridden by the social or economic benefits of the development.

Non-nationally significant wind farms

The usual way that the planning system manages to avoid permitting criminal or civil offences for noise from all noise sources is to assume a restrictive approach that protects the rights of individual neighbours unless there is a nationally significant reason for
the development.
In practical terms, a standard methodology is adopted that can be used to design out the potential for nuisance claims. This has typically meant the application of BS4142 to determine, on a case by case basis, as to whether a proposed noisy activity is likely to provide an indication as to whether complaints are likely. The indication of the likelihood of complaint is used as a proxy to estimate the presence of nuisance, whether in the civil or criminal legal systems.
Legally, non-nationally significant infrastructure project (non-NSIP) wind farms should be considered in the same way as other non-NSIP noise sources, such as factories or air conditioning units. Wind farm developments, however, are required to apply the methodology of ETSU-R-9710. This document describes how to assess and rate noise from wind turbines for the purposes of planning applications. Justification for this departure from the status quo for wind farms is found in ETSU-R-97 itself which states that:
"A literal interpretation of how B54142 should be applied to wind turbine noise assessment is difficult and its use may be inappropriate and problematical."11
The ETSU-R-97 document sets out a framework that creates a variable noise limit based upon background noise, in a similar fashion to BS4142, albeit at the permissive end of what BS4142 might be considered appropriate. However, for low background noise levels, and more controversially, at night, ETSU-R-97 creates an absolute noise level that is applicable regardless of local conditions. The noise limit applied at night of 43dB LA90, 10 min is frequently described as being unique in the world as it is higher than the daytime noise limit.
There are a couple of problems with the noise limits contained within ETSU-R-97. The first is that the concept of an absolute noise level, i.e. a noise level where the non-acoustic factors have been harmonised to a national level, is incongruous with the principles of nuisance. Absolute noise limits, applied nationally, penalise the wrong people at the wrong times. They penalise neighbours of new developments in quieter areas by imposing less noise controls than appropriate while at the same time they penalise developers introducing new noise sources in noisier areas by insisting on a level of noise control that may not be necessary, or at least it should be the case, but ETSU-R-97 changes from an absolute noise level to a variable noise level once the background noise level gets within 5dB of the absolute noise level.
Secondly, the noise level chosen for the night noise limit is too permissive. According to the National Noise Incident Study of 2000 (NIS)', the ETSU-R-97 night limit provides a positive indication that complaints are likely, using the methodology of BS4142, at approximately 50% of properties in England and Wales'. This percentage includes all properties in England and Wales, urban and rural. It is likely that this figure would be significantly higher if only rural properties were considered. Incidentally, by using the same methodology it was estimated the percentage of properties where the ETSU-R-97 night limit would provide a positive indication that complaints were unlikely was less than 5%.
As a result, it can be argued that the ETSU-R-97 night noise limit might be appropriate for the noisiest 50% of the dwellings in England and Wales under certain circumstances, but probably would not be appropriate for the quietest 50% of the dwellings in England and Wales. Either way, it could easily be said that the ETSU-R-97 night noise limit is too permissive as it does not protect all of the neighbours, all of the time, thereby leading to the argument that Government officials, planning officers and by extension environ¬mental health officials are acting ultra vices in applying this document to the assessment and rating of noise from non-NSIP wind farms.
Nationally significant wind farms
Up until 2008 there were no circumstances where wind turbine developments could be considered to be nationally significant. This changed when the Planning Act 2008 was given Royal Assent. Section158 of the Planning Act 2008 extended the defence of statutory authority in "civil or criminal proceedings for nuisance" to developments that received development consent using the streamlined system introduced by the act. Onshore wind farms in England and Wales with a capacity of greater than 50 megawatts and offshore wind farms adjacent to England and Wales with a capacity of greater
than 100 megawatts are considered to be Nationally Significant Infrastructure Projects (NSIPs), therefore qualifying them for the use of the defence, in line with other NSIPs such as railways, roads
and airports.
In applying the defence of statutory authority to large wind farms the Government is effectively saying that these developments are so important that individual rights in relation to noise and other nuisances are suspended and they are allowed to generate noise levels that would otherwise be unacceptable as the development is in the national interest. However, Government cannot simply remove the rights of an individual without offering compensation, to do so would invite challenge via judicial review and/or the human rights provisions. To resolve this, neighbouring land owners of NSIPs are entitled to compensation under the "injurious affection" route provided by section10 of the Compulsory Purchase Act 1965.
In developing the procedures for the streamlined planning system in the Planning Act 2008, the Government produced a suite of National Policy Statements (NPSs) that set out how key issues are highlighted, how these issues were to be evaluated and what mitigation (if any) might be expected to be applied if the issues were not adequately dealt with. It should be noted that the NPSs underwent public consultation and parliamentary scrutiny prior to publication' and the process of review lies with the Secretary of State, who may revoke part or all of the documents if they are no longer appropriate for decision making".
When discussing onshore wind farms NPS EN-3, the policy statement for Renewable Energy Infrastructure, states that when considering noise developers "...should use ETSU-R-97, taking into account of the latest industry good practice. This should include any guidance on best practice that the Government may from time to time publish"". It is this paragraph that allows the Good Practice Guide to be adopted as current operational practice.
Paragraph 2.7.58 continues by stating that: "Where the correct methodology has been followed and a wind farm is shown to comply with ETSU-R-97 recommended noise limits, the IPC may conclude that it will give little or no weight to adverse noise impacts from the operation of the wind turbines."
The reliance of the NPS EN-3 upon ETSU-R-97 might initially seem sensible, but the whole point of providing the defence of statutory authority to NSIPs is to allow these developments to make more of an environmental impact than would otherwise be considered reasonable as they are nationally significant. Imposing the same noise limits upon NSIP wind farms as non-NSIP wind farms significantly restricts the generating capacity of wind farms that Parliament has considered to be vital to the wellbeing of the country and denies neighbours of proposed wind farm developments the opportunity to apply for compensation so that they may move from the area without incurring financial penalty, should they wish to do so.

Health impacts from wind turbine noise

If it is accepted that NSIP wind farm developments should be allowed to generate more noise than currently allowed, what would be an appropriate methodology?
In the absence of the threat of civil or criminal action in nuisance, NSIP wind farms could be controlled by an absolute noise level, which could be considered alongside the social and economic benefits of the development.
Discussions between stakeholders on how noisy the absolute noise level could be could be framed in terms of seeking to "avoid significant adverse impacts on health and quality of life" as described by the Noise Policy Statement for England16. This discussion would undoubt-edly involve the development of a Significant Observed Adverse Effect Level (SOAEL) for NSIP wind farms.
By introducing a health and quality of life element to the discussions of acceptable noise limits from NSIP wind farms, the debate could build upon the research by Eja Pedersen and others17 and address directly the concerns of some about a possible "wind turbine syndrome".

Conclusion

it is too early to say whether the good practice guide has made
significant improvements to the application of ETSU-R-97, it is endorsed by Government departments and is here to stay. However, the controversy surrounding wind farm noise assessments appears to be on-going.
Legally, wind farms can be split into two distinct groups, those that are not considered to be nationally significant, which are bound by nuisance law, and those that are considered to be nationally signifi¬cant, which have a defence of statutory authority against civil and criminal action in nuisance.
ETSU-R-97 is the Government-approved method of assessing and rating noise from wind turbines. Despite the IOA good practice guide intending to improve the methodology of ETSU-R-97, the noise limits are unchanged.
The ETSU-R-97 noise limits are applicable to both groups of wind farms, and can easily be argued to be too permissive for non-NSIP wind farms and too restrictive for NSIP wind farms. Therefore, if ETSU-R-97 does not properly benefit either side of the debate, what is the purpose of persisting with it?

References

1. http://www.reforg.uk/press-releases/295-new-wind-farm-noise- guidance-is-inadequate-and-increases-risk-of-harm-to-neigh-bours
2. Rogers (Ed.); (2010); Winfield & Jolowicz on Tort; 18th Edition; Sweet & Maxwell.
3. Hunter vs. Canary Wharf Ltd (1997).
4. Rogers (Ed.); (2010); Winfield & Jolowicz on Tort; 18th Edition; Sweet & Maxwell.
5. McCracken, Jones and Pereira; (2012); Statutory Nuisance; 3rd Edition; Bloomsbury Professional.
6. Ibid.
7. Rogers (Ed.); (2010); Winfield & Jolowicz on Tort; 18th Edition; Sweet & Maxwell.
8. Cullingworth Nadin; (2006); Town and Country Planning in the UK; 14th Edition, Routledge
9. R (Smeaton) vs. Secretary of State for Health (2002) as discussed in Bingham; (2010); The Rule of Law; Penguin Books.
10.Paragraph 2.7.55 of National Policy Statement for Renewable Energy (EN-3) (https://whitehall¬admin.production.alphagov.co.uk/government/uploads/system/u ploads/attachmentdata/file/37048/1940-nps-renewable-energy¬en3.pdf) which are to be considered as material considerations in planning decisions not using the Planning Act 2008, according to Paragraph 3 of the National Planning Policy Framework. (https://www.gov.uk/government/uploads/system/uploads/attach mentdata/file/6077/2116950.pdf)
11. DTI; (1996); ETSU-R-97: The Assessment and Rating of Noise from Wind Farms; DTI.
12.http://infrastructure.planningportal.gov.uk/legislation-and¬advice/national-policy-statements/
13.DECC; (2011); National Policy Statement for Renewable Energy Infrastructure (EN-3); DECC; Paragraph 1.6.1.
14.DECC; (2011); National Policy Statement for Renewable Energy Infrastructure (EN-3); DECC; Paragraph 2.7.56.
15.It should be noted that the IPC mentioned in this paragraph refers to the now defunct Infrastructure Planning Commission. The IPCs functions were transferred to the Planning Inspectorate in 2012.
16.https://www.gov.uk/government/uploads/system/uploads/attachmentdata/file/69533/pb13750-noise-policy.pdf
17.Eja Pedersen, Frits van den Berg, Roel Bakkerand Jelte Bouma; Response to noise from modern wind farms in the Netherlands; J Acoust Soc AM 126
2, August 2009.
i http://www.bre.co.uk/pdf/NIS.pdf
ii positive indication of complaints being likely requires the source noise to be at least 10dB(A) higher than the background noise. If the source noise is 45dB(A) LAEQ (43dB(A) LA90) then the background noise levels at the dwellings would need to be 35dB(A)
LAEQ or lower, which according to the NIS was present at approximately 50% of dwellings in England and Wales in 2000.

Acoustics Bulletin November/December 2013

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