Directional wind turbine noise prediction plots and prevalence histograms for community consultation

In Australia, wind turbine noise is predicted using international standards and guidelines with a set of conservative assumptions. For example, wind turbine noise predictions using the ISO 9613-2 method are based on a scenario in which each receiver is simultaneously downwind of every wind turbine. As such, winds that are outside of the downwind direction range will result in lower wind turbine noise levels than predicted using ISO 9613-2. These predictions are also based on the assumption that each turbine is simultaneously generating their maximum noise emissions, whereas variations in winds speeds across the site will frequently result in individual turbines producing lower noise levels than assumed in the modelling. The net effect of these conservative assessment choices is that actual wind turbine noise levels would be lower than presented in noise assessments in many cases. Providing an indication of how frequently predicted noise levels would likely occur can assist community consultation and provide useful context to noise modelling data. This paper presents analysis utilising directional noise modelling to assess the effect of wind direction, combined with an analysis of historic wind records, to determine the range of predicted noise levels and how frequently they may occur.