Renewable Energy Foundation

  • Increase font size
  • Default font size
  • Decrease font size

IoA Consultation on AM Noise

REF submitted a response to the consultation carried out by the Institute of Acoustics (IoA) on Amplitude Modulation (AM) noise of wind turbines. We made a number of general remarks on the consultation process and further comments on the detailed questions raised by the IoA.

IoA Consultation Process Flawed

1. This is the third consultation on wind turbine noise carried out by the IoA in recent years. The first two were a) that for the Good Practice Guidance (GPG) and b) the Supplementary Guidance Notes (SGN).

2. The process adopted by the IoA for these earlier consultations was flawed. It is a normal requirement following a consultation that a consultation response document is produced in which the specific points raised by consultees are addressed. Where a consultee has made a recommendation or criticism of the original document, the IoA, as a professional body, must explain either what adjustment to the guidance was made to accommodate the point, or, on what evidential basis the point was rejected. The IoA has not done this.

3. Instead, the IoA has argued that reports made by planning inspectors following planning inquiries provides sufficient detail to explain why the IoA does not need to respond to technical criticism of acoustic issues contained within IoA Guidance. (See This position is absurd and untenable; no other professional, let alone scientific body would delegate the responsibility of technical rebuttal to a planning inspector whose own expertise is in Town Planning.

4. We urge the IoA to respond to the current consultation with a professional consultation response document that explains what regard has been paid to the consultation responses and why.

5. We further note that the consultation responses to both the GPG and SGN reports are not apparently available on the IoA website in spite of an earlier statement that they were to be published. This should be rectified, and the responses to this AM consultation also published.

6. In spite of our organisation, the Renewable Energy Foundation, having responded to both the GPG and SGN consultations, and having produced original work on AM that is cited (inaccurately) in the IoA AM Discussion Document, REF was not notified of this consultation by the IoA. This suggests that other individuals and organisations who have responded to the earlier consultations might similarly have been ignored in this consultation process. This undermines confidence in the IoA’s ability to carry out a proper consultation exercise.

7. In summary, the process for earlier IoA consultations has been seriously and significantly inadequate; there are worrying signs that the current consultation will be no better. The pattern that is emerging does no credit to the IoA and must be rectified if reputational harm is to be avoided.

Selection of NWG Members

8. In any exercise involving recommendations of how to define a potential noise nuisance, it is important that the participants involved in formulating the recommendations are seen to have no vested interest in the outcome, or that the recommendations are framed in such a properly scientific manner that they are seen to be reasonable and not to unfairly serve any interest.

9. There is a long history related to AM noise nuisance. Following the 2006 DTI report by Hayes McKenzie Partnership (HMP) which highlighted the fact that UK wind farms were producing AM noise at levels that exceeded what is accounted for in the ETSU-R-97 guidance, a NWG was set up by the then Department of Trade and Industry (DTI). Many of the same members and or organisations in the IoA NWG and AM subgroup were represented in the 2006 DTI NWG.

10. The draft minutes and emails relating to the meetings of the 2006 NWG were released under a Freedom of Information request.

11. It is clear from these released documents that there was wholesale resistance to the idea of limiting AM noise even though it was recognised that AM levels of 15dB had been measured as long ago as 1997. It is also plain that the concerns of neighbours and objectors were treated by some members with disdain. It is also plain that considerations other than purely acoustic issues coloured the judgement of some members of the group.

12. No empirical AM data was collected nor were any attempts to limit AM problems made as a result of the efforts of 2006 NWG. In fact, the situation nine years later is unchanged from when the last NWG group was convened.

13. The fact that the same people and/or organisations have been chosen to form the 2015 NWG is profoundly alarming and unlikely to generate confidence or improve the prevailing public opinion of the IoA as an appropriate organisation to formulate robust and fair wind farm noise guidance.

Lack of real world evidence

14. The 2006 DTI report by the Hayes McKenzie Partnership (HMP) gathered AM data at three sites. One of the sites, Far Old Wind Farm at Askam in Cumbria could be considered a benchmark site for AM noise problems. It is the wind farm site in the UK with the most neighbour complaints about AM noise and has been causing these complaints for 14 years since April 2001. We find it surprising that no effort has been made to test the suggested methodologies by quantifying the AM measured by HMP that actually triggered the AM debate.

15. We need to understand how the different methodologies proposed by the IoA would quantify AM at the wind farm sites with incontrovertible AM problems, such as Askam and Deeping St Nicholas for example. REF has carried out the exercise on the Askam data for both the original Den Brook AM condition and the RUK AM condition and shown that the former condition would be breached and the latter not breached at Askam.

16. This is definitely the sort of exercise that the IoA NWG should be carrying out.

17. There is a clear bias in the document towards a penalty mechanism which we could not possibly endorse for the reasons spelled out below in the answer to the time interval question in Section 5. However, if the reader was provided with the quantified AM level under each of the proposed methodologies for Askam and other sites with outstanding long-term AM complaints, it would be possible to see if a penalty scheme would result in a breach or no breach.

18. Without provision of real world data of this sort, the document seems likely to result in another decade where wind farm developers can build too close to neighbours and generate AM noise with impunity. This would suit wind farm developers, but would amount to a professional betrayal of lay members of the public to whom the IoA has a professional duty of care.

For the full REF response to the IoA AM noise consultation, click on the document link below.