Regulations for wind turbines are generally based on A-weighted sound levels, and typical sound spectrums in the community from a localized source. Regulatory limits are based on levels believed to cause little annoyance. Large industrial wind turbines are a sound emitter that present a spatially distributed source principally arising close to the blade tips, rotating 50 to 150 metres overhead so that sound arises from a wide area. They pose a relatively new source of sound to communities, particularly the quiet rural communities where they are mostly located. Community experience shows that the same A-weighted sound limits that are acceptable for typical sound spectrums and localized sources give rise to a considerable level of annoyance from wind turbines. This paper sets out to identify the differences in the sound found at locations considered acceptable by regulators 500-600 m from wind turbines (about one-third of a mile), in spectrum, intensity, duration, and special characteristics, such as tonality or amplitude modulation compared to the sound levels at control sites distant by at least 5000 m (about 3 miles) from wind turbines. An explanation of the data collection method is given, as well as an analysis of extensive sound samples gathered.
Published by the Acoustical Society of America through the American Institute of Physics
Download original document: “Collecting data on wind turbine sound to identify causes of identified concerns ”