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The effect of noise on adjacent populations is the reason for concern about noise. Mainly in the case of wind turbines this concerns human populations. However, underwater propagation of sound from offshore wind turbines may need to be kept in mind with respect to marine animals but is very unlikely to be as significant as it is for tidal stream turbines. Noise effect on adjacent populations is normally defined by a geographical noise footprint based on contours of perceived noise (PNdB). In drawing these up account has to be taken of the different efficiencies of propagation of noise at different frequencies, in particular that low frequency noise travels much farther than high frequencies, and of the non‐uniform sensitivity of the ear over the audible frequency range. Because of the major issues surrounding aircraft noise and the siting of runways, there is a great deal of research published on this.

This Section 3.19 on aerodynamic noise has only attempted to summarise the main issues and research into the subject where it concerns noise arising from wind turbine rotor blades. In practice this is the most important source of noise from a wind turbine, and because noise has become one of the major planning constraints for siting wind turbines, it is likely that the industry will continue considerable effort into the development of methods to suppress it. An excellent reference on the theories describing aerodynamic noise and the sources, radiation, and propagation of sound is the book by Richards and Mead, Noise and Acoustic Fatigue in Aeronautics (1968).