Initial Findings from the INWG Research
- Excessive Amplitude Modulation (EAM) is a Significant Factor. Noise complaints from wind farms are primarily related to a phenomenon called Amplitude Modulation (AM). This is commonly described as a ‘whoomp’, ‘swish’ or ‘beating’ type noise. It is the character of the noise that tends to make AM wind farm noise most intrusive. A recent Scottish study found that at 1-2km from the wind farm, 72% of those suffering audible noise strongly disliked the noise. When it becomes intrusive to people we call it EAM, or Excessive Amplitude Modulation. These noise components are not covered by the ETSU guidelines and we know of only one wind farm planning decision in the UK where a planning condition has been imposed for AM noise (Den Brook, Devon).
- There Have Been Decades of Deception. The wind industry has consistently denied the existence of EAM. Our research shows show that EAM is a frequent occurrence potentially affecting all industrial wind turbines, often for long periods of time and most frequently during the night time. A 2014 survey of Local Planning Authorities (LPAs), completed by Chris Heaton-Harris MP (Conservative, Daventry) and analysed by the INWG, shows that not only are incidents of EAM more frequent than the wind industry hitherto has claimed, the progress in resolving them is inconclusive and there are inconsistent approaches to dealing with it across the country. LPAs in the survey call for guidance on measuring and testing for EAM as well as nationally agreed standards that are consistently applied and provide effective mitigations for it. There is also anecdotal evidence of a ‘silent majority’ who suffer in silence without knowing how to complain, not wanting to get ‘involved’ or because of a fear of adverse implications; if, for example, they had to disclose any complaint should they wish to sell their house.
- Existing Legal Remedies are Found Wanting. We have found that the remedies available for wind farm neighbours affected by turbine noise are not fit for purpose. Statutory Nuisance has been actively advocated by the wind industry and supported by Planning Inspectors. Evidence however suggests that an Abatement Notice is not an effective control to protect nearby residents from EAM. Others such as private nuisance and similar legal actions have been considered but these place too much risk and burden on residents for a problem not of their making with likely long term adverse financial implications. In addition, there has been a recent trend of secondary operators forming individual shell companies for each wind farm. The impact of this was highlighted in July 2015 when David Davis MP (Conservative, Haltemprice and Howden) introduced a Bill in Parliament with the purpose of requiring wind farm developers to obtain public liability insurance for any nuisance that they may cause to nearby residents. In particular this is aimed at noise nuisance. One of his constituents had a problem with noise from a local wind farm but had found it impossible to sue because the wind farm operator was purely a shell company with very limited assets.
- Wind Turbine Noise Adversely Affects Sleep and Health. It is abundantly clear from the evidence examined by a world renowned expert in sleep medicine working with the INWG that wind turbine noise adversely affects sleep and health at the setback distances and noise levels permitted by ETSU. There is no reliable evidence that wind turbines are safe at these distances and noise levels, not a single study. In contrast there is an increasing volume of studies and evidence outlined to the contrary. There is particular concern for the health of children exposed to excessive wind turbine noise. The inadequate consideration of EAM is a major factor in the failure of ETSU to protect the human population. The denial of this by the wind industry is reminiscent of other health issues in the past. For example, the tobacco industry and the adverse effects of cigarette smoking.
- ETSU is Not Fit for Purpose. We show irrefutable evidence to discredit wind industry and government claims that ETSU provides a robust noise assessment methodology. This conclusion is supported by the recent Northern Ireland Assembly report, January 2015, into wind energy where it recommends, “Review the use of the ETSU-97 guidelines on an urgent basis with a view to adopting more modern and robust guidance for measurement of wind turbine noise, with particular reference to current guidelines from the World Health Organisation”.
- We Need an Effective Planning Condition for AM. The wind industry claims that an AM planning condition is not necessary and that the legal remedy of Statutory Nuisance provides adequate protection are thoroughly discredited by the evidence we have published. Without an AM planning condition there is no effective remedy for wind farm neighbours against excess noise. The relevance of EAM in causing noise complaints has driven the wind industry to ensure that an AM planning condition is not applied as standard planning practice. The application of an AM planning condition to the Den Brook (Devon) wind farm planning consent during 2009 presented a serious risk to the wind industry of a similar planning condition becoming the standard for future wind farm consents. The wind farm developer for the Den Brook wind farm has gone to enormous effort, at enormous expense, over an 8 year period to ensure first that an AM planning condition is not applied, then to have the applied planning condition removed, and finally to have it sufficiently weakened presumably to ensure it prioritises operation of the wind farm rather than provide the intended protection against EAM.
- There is a Lack of True Independence. The wind industry strategy of obfuscation capitalising on the trusted position of the Institute of Acoustics (IoA) as a scientific institution is discussed in our research findings. We find that the IoA through its wind turbine Noise Working Group, and latterly its specialist subgroup the AM Working Group devoted to the study of excess amplitude modulation, have consistently operated for the benefit of the onshore wind industry in the UK and to the detriment of local communities hosting wind turbines. This is also arguably against both the IoA Code of Ethics and that of the Engineering Council, its governing body. The effect has been to both obfuscate and hide problems related to wind turbine noise assessment from government and from the Planning Inspectorate.
INWG Recommendations to National Government
- Replace ETSU. Replace the use of ETSU, as recommended by the Northern Ireland Assembly report January 2015, with a procedure based on the principles of BS4142: 2014. This will bring wind turbine noise assessment into line with other industrial noise controls. New guidance of this type should be formulated in a Code of Practice that sets out a BS4142: 2014 type methodology that reflects noise character and relates impact to the actual background noise level and not an artificial average.
- Introduce an Effective AM Planning Condition. Based on the experience at Cotton Farm wind farm in Cambridgeshire, where there has been long term professional and independent noise monitoring, we recommend an effective AM planning condition should be part of every wind turbine planning approval unless there is clear evidence it is not needed. For assessing and controlling wind turbine noise AM, it is recommended that:
- Where wind turbine noise level and character require simultaneous assessment then BS4142:2014 should be used. The rated wind farm noise level should not exceed +10dB above the background noise level.
- Where only wind turbine noise AM requires assessment then a Den Brook type planning condition should be used.
- Continuous Noise Monitoring. Continuous noise monitoring of wind turbines should become a standard planning condition for all wind turbine planning approvals as recommended in the Northern Ireland Assembly report, January 2015. This should be funded by the wind turbine operator but controlled by the Local planning Authority (LPA) with the noise data made openly available to ensure transparency. The Cotton Farm community noise monitor describes an example of how this can be achieved. See: http://www.masenv.co.uk/~remote_data/ 
- Further Research into the Impact of Low Frequency Noise. There is a need to commission independent research to measure and determine the impact of low-frequency noise on those residents living in close proximity to individual turbines and wind farms as recommended in the Northern Ireland Assembly report, January 2015.
- Issues of Ethics, Conflict of Interest & Independence. The government should deal decisively with the ethical issues surrounding the Institute of Acoustics (IoA) wind turbine noise working groups. Government departments should disassociate themselves from the IoA until conflict of interest and ethics issues are resolved and full transparency is restored.
Download reports and publications:
The Fundamentals of Amplitude Modulation (AM) of Wind Turbine Noise 
Review of Reference Literature 
AM Evidence Review 
Study of Noise and AM Complaints Received by Local Planning Authorities in England 
Excessive AM, Wind Turbine Noise, Sleep and Health 
Den Brook Planning Conditions 
Draft AM Planning Condition, part 1 
Draft AM Planning Condition, part 2 
Legal Remedies 
Legal Issues Relating to Shell Companies 
Control of AM Noise Using Statutory Nuisance 
Informative: Wind Turbine Noise AM and Its Control 
Test of Institute of Acoustics AM Working Group Methodologies [not yet published]
Review of Institute of Acoustics Noise Working Groups 
Cotton Farm Monitor Experience 
Report Summary 
Terms of Reference 
Presentation to DECC Minister of State by Richard Cox 
Presentation to DECC Minister of State by Sarah Large 
Presentation to Institute of Acoustics by Richard Cox