United Kingdom

United Kingdom

Research not even needed -- Aerodynamic noise

Amplitude modulation of aerodynamic noise (AM), a phenomenon associated with wind turbine blades, is not a problem for the UK's wind turbine fleet, concludes a study by Salford University. AM describes noise that is greater than the normal degree of fluctuation in the "swish" of wind turbine blades. Complaints about AM from residents near wind farms have likened it to the noise of a distant train or piling operations. The government-commissioned study looked at operational wind farms across the UK and found that the incidence of AM from operational turbines is low. AM, however, cannot be fully predicted as yet and its causes are not fully understood.

The work follows a 2005 study by Hayes McKenzie into noise from wind turbines which found no evidence of health effects from low frequency sound, but noted that in some isolated cases aerodynamic modulation was occurring in ways not anticipated by earlier government guidance on siting. The Salford team surveyed local authorities for the 133 wind farms operating at the time of its study. It found that complaints about noise had been lodged for 27 sites over the past 16 years since the first UK wind farm began operating. The 239 complaints were lodged by just 81 complainants, with 152 of the complaints (64%) associated with a single site. The team found that most cases were caused by mechanical noise; at only four sites was AM identified as at least part -- although not always all -- of the problem. Another eight cases were marginal.

Complaints have subsided at three of the four wind farms -- at one after remedial action. It had received the largest number of noise complaints of all the sites. Now a control system shuts down the three most offending turbines at times when the wind is from a particular direction. The remaining case is a recently-built wind farm where investigations are ongoing.

Salford University's report concludes that the number of cases and people affected by AM is too small to make a case for more research funding. This appears to satisfy the government, which says it does not intend to carry out any further research at this time.

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