Wind Farm Noise Uncertainty: Prediction, Measurement and Compliance Assessment

In most jurisdictions containing wind farms, base noise limits have been set by local regulatory authorities, with the intention of protecting the amenity of surrounding communities. It is a standard requirement that during the planning process for a new wind farm, the developer demonstrates that the proposed wind farm will comply with the relevant limits. At present, results from noise prediction models are commonly presented without uncertainty values, despite the fact that simplifications and approximations have been made in the models. Therefore, when prediction models indicate that the wind farm will generate noise within 3 dB of base noise limits, it is likely that these limits will be exceeded. Despite the fact that regulatory authorities often require that compliance measurements are taken to validate predictions of wind farm noise, it is very difficult to make substantial changes to noise emissions, without a corresponding reduction in electrical power output. Current methods of compliance assessment do not provide an indication of the amount of time that wind farms exceed allowable noise limits as they focus on ‘average’ levels only. Therefore, it is possible for wind farms to exceed allowable limits on a regular basis, and by significant margins. Hence, a more conservative approach is warranted during wind farm noise prediction and it is proposed that the upper level of the uncertainty estimate of the prediction model should not be permitted to exceed the allowable level.