Wind Turbine Noise Propagation

Abstract

The noise emitted by operating wind turbines will be influenced along its propagation to distant receivers by a large number of factors, including wind direction, wind and temperature gradients, atmospheric turbulence, and the ground effects arising both from the local acoustical properties of the ground itself and from screening or enhancement due to terrain. This chapter presents an overview of different environmental sound propagation calculation methodologies, of varying complexity, as applied to wind turbines. Available methods can broadly be separated into two categories: empirical or engineering methods and more complex numerical methods. The latter possess the ability to provide highly accurate representations of propagation for specific parameters in certain conditions, but are generally complex and computationally intensive. Their accuracy in practical use will be limited by the imperfect knowledge of the full range of atmospheric and ground conditions along the propagation path. However, they are successfully used to assess the parametric sensitivity of received noise levels and to isolate and better understand individual propagation effects. For most practical applications, engineering methods provide reasonably accurate predictions, provided they are applied correctly within their appropriate scope. Accuracy in this context should be interpreted within the context of the natural variability of environmental sound fields.