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.
This paper has highlighted that the wind farm noise limits stated in the EPA guidelines (2009) do not ensure adequate protection of the amenity of rural communities. In addition, 21-23 November 2012, Fremantle, Australia Proceedings of the concept of zoning has been challenged and background noise levels measured at each residence are proposed as a more suitable method for indicating acceptable noise limits at a given location. A dose response study specific to South
Australian rural areas is considered pertinent to provide further guidance for selection of a suitable noise limit. This study should take into account annoying characteristics such as tonality and amplitude modulation, which are not adequately
addressed in the EPA guidelines. The potential for background noise sources to mask wind turbine noise up to 5dB louder has also been questioned, particularly with respect to LFN. In addition, a more conservative method of predicting background noise for a given wind speed has been proposed, which is justified by highlighting the inherent difficulties associated with obtaining conclusive compliance measurements. The importance of separating out night-time and daytime background noise measurements for the purpose of establishing acceptable noise wind farm noise levels was also highlighted.
Measurements showed that consideration of the average noise level in a room is more accurate than relying on data from a single transducer. The transmission loss from outsideto-inside was found to be highly dependent on frequency.
While the overall transmission loss is close to specifications in the EPA guidelines, in some 1/3 octave bands there is very little difference in noise level from outside-to-inside. The difference in LCeq-LAeq > 20dB suggests that further analysis
of the data is required with respect to LFN.
This paper also highlighted the potential inaccuracy of using sound power level data from the manufacturer as an input for sound propagation models where the topography differs significantly from that used in the manufacturer’s measurements. In general, the influence of the surrounding topography on noise generation of wind turbines is not well documented and further research is necessary.