Abstract
This paper presents results of an analytical and experimental investigation of wind turbine noise. Noise measurements are presented for solid and truss-type tower models with both upwind and downwind rotors. When the rotor is downwind of the support tower, the primary source of noise is the rapid change in rotor loading that occurs as the rotor passes through the tower wake. Upwind rotor configurations are significantly quieter than downwind configurations. This investigation was undertaken as a result of complaints from community members about noise associated with a MOD-1 wind turbine, a comparatively large turbine for its time, in North Carolina. Calculations and model tests indicate that placing the rotor upwind of the support tower minimizes the noise risk. The author states that it is difficult to extrapolate model results for the downwind configuration to full scale since all the parameters that affect wake affect generated noise. The inherent unsteadiness of wake flows may produce noise that is louder than would be expected from averaged measurements or calculations based on averaged wake characteristics.