Predictions of low-frequency sound from the MOD-1 wind turbine

The purpose of this project was to determine if aerodynamic noise mechanisms are associated with the acoustic noise situation that results from the operation of the MOD-1 wind turbine near Boone, NC. Acoustic measurements indicate that sound from the turbine produced structural vibrations in homes near the turbine site. The possible sources of aeroacoustic noise studied were steady blade loads, unsteady blade loads due to wind shear, and unsteady loads on the blades as they pass through the tower wake. Mathematical models that were used to study these noise sources are described. The results showed that the most significant source of impulsive, low-frequency sound was the unsteady loads that occurred when the blade passed through the tower wake. This problem might be resolved by operating the turbine at a lower rotor speed. This issue might also be resolved by changing the structural configuration of the tower to create an azimuthally smoother wake which would dramatically reduce the noise.