Broad band sound from wind turbine generators

Sound spectra are characterized for the various types of wind turbine generators. Emphasis is placed on the broadband sound because it is an important component for upwind and downwind horizontal axis machines as well as for vertical axis machines. The various sources of broadband sound are identified and are rank ordered for the MOD‐2 machine which has 300‐ft‐diam blades and is rated at 2.5‐MW power output. The main sound sources for the MOD‐2 rotor are noted to be the inflow turbulence (30 to 50 Hz) and the interactions of the turbulent boundary layers with the blade trailing edges (800 to 1300 Hz). The MOD‐2 rotor radiates in all directions but the distant sound level contours are elongated in the downwind direction due to refraction effects of the wind. [Work supported by the NASA Lewis Research Center and the Department of Energy.]