Modelling sound propagation from a wind turbine under various atmospheric conditions

Abstract

Sound propagation from a wind turbine is investigated with the help of coupled atmospheric and acoustical simulation. Eight instants of time during nine diurnal cycles of idealized large-scale cases result in 72 meteorological situations for which the boundary-layer profiles of wind and temperature, the downstream wake flow of the rotor, and the sound propagation from the wind turbine into upwind and downwind direction were calculated. The resulting sound levels are evaluated relative to a non-refractive atmosphere to focus on the impact of meteorologically induced refraction. Within a range of 1 km from the turbine the sound levels vary stronger in upwind direction than in downwind direction, and the varying background wind speed at hub level causes a higher variability of the relative sound levels than the variations of the surface-layer stability. Surface-layer parameters turn out to be of only limited suitability for a meteorological classification of the wind-turbine noise impact.