Wind farm noise - what is a reasonable limit in rural areas?

Wind farms are a rapidly growing source of renewable energy, but can be a source of persistent noise complaints, despite compliance with the relevant wind farm noise regulation being achieved. This paper presents a review of wind farm noise assessment criteria and methodology with a focus on the South Australian guidelines. The results of this review indicate that the noise limits may not be appropriate for some locations which are characterised by very low background sound levels at night time. The assumption in the guidelines that background noise is capable of reducing annoyance from wind farm noise is also not necessarily borne out in reality. Measurements of the outdoor-to-indoor noise reduction for a typical dwelling, with the window open, show that the reduction is slightly lower than assumed by the guidelines, and varies significantly with frequency. Measured low frequency noise and infrasound complied with all criteria addressed in the literature with the exception of one. Reliable compliance measurements are often difficult to achieve for wind farm noise, therefore it seems appropriate to adopt a conservative approach in setting noise limits and predicting noise emissions.