Renewable UK has published (16th December 2013) an extensive study into the acoustic phenomenon known as ‘Amplitude Modulation’ or ‘AM’. This effect has long been cited by wind energy objectors as a major cause of disturbance to residents living near Wind Farms and has resulted in a high profile court case. The case was settled out of court so developers have been unable to draw definitive conclusions on the potential effects of AM – further uncertainty that the industry does not require.

The Renewable UK study has identified two types of AM – Normal AM (NAM) and Other AM (OAM). NAM is explained as the general aerodynamic ‘swishing’ sound created by the turbine blade as it passes through the air. This has long been identified and modeled to support prospective wind energy developments. OAM, the findings suggest, is a deeper less frequent noise created as the blade ‘stalls’ momentarily part way through its rotation in certain wind conditions.

The findings in the study have allowed Renewable UK to conclude that the problem of OAM only exists in specific circumstances and can be remedied by software alterations that regulate the operation of the wind turbine. The trade organisation has also proposed a planning condition that should protect residents in the event that OAM should be identified.

This is positive news for the industry and step in the right direction. It should allow developers and planning authorities more certainty over the issue of AM. However, there is sure to be criticism of this work by anti turbine campaigners. Developers should also take care to be aware of the implications of any planning condition, of how easily any turbine software alterations can be implemented and at what this is likely to cost in energy yield.

The full Renewable UK Press Release and Study can be found here.