Noise assessment at Carland Cross wind farm site

A propagation model is necessary to predict noise levels resulting from a wind farm at nearby dwellings. These levels depend upon the site's topography and the local meteorology. The most commonly used model is that proposed by the IEA, which considers solely hemispherical spreading and air absorption. Several more detailed models exist, for example ENM (Environmental Noise Model), a proprietary software package specifically designed for the prediction of noise levels resulting from multiple noise sources in a complex environment, and CONCAWE, a model developed by the Oil Companies Study Group for the Conservation of Clean Air and Water. To assess the performance of these models a loudspeaker has been used to broadcast noise across the Carland Cross site in the UK and noise level measurements made at a number of locations. These data have been compared with predictions obtained from the IEA, ENM and CONCAWE models. Wind farm noise may have an audible tonal content in the near field. By broadcasting noise with a tonal content similar to a Windane 34 and measuring narrow band noise spectra at increasing distances from the source the audibility of the tones have been assessed using critical bandwidth analysis. The results suggest that such tones will not be audible in the far field. A brief discussion about the mechanism by which this happens is also included. (author)