Prediction of broadband noise from horizontal axis wind turbines

A method is presented for predicting the broadband noise spectra of horizontal axis wind turbine generators. It includes contributions from such noise sources as the inflow turbulence to the rotor, the interactions between the turbulent boundary layers on the blade surfaces with their trailing edges, and the wake due to a blunt trailing edge. The method is partly empirical and is based on acoustic measurements of large wind turbines and airfoil models. The predicted frequency spectra are compared with measured data from several machines, including the MOD-OA, MOD-2, WTS-4, and U.S. Windpower Inc. machine. The significance of the effects of machine size, power output, trailing-edge bluntness, and distance to the receiver is illustrated. Good agreement is obtained between the predicted and measured far-field noise spectra.