The noise characteristics of the U.S. Windpower 50-kW wind turbine generator were measured at various distances from 30 m to 1,100 m and for a range of output power. Generator noise is affected by the aerodynamic wakes of the tower legs at frequencies below about 120 Hz and the blade trailing edge thickness at frequencies of about 2 kHz. Rope strakes and airfoil fairings on the legs did not result in substantial noise reductions. Sharpening the blade trailing edges near the tip was effective in reducing broad band noise near 2 kHz. For multiple machines, the sound fields are superimposed. A three-fold increase in the number of machines (from 1 to 3) results in a predicted increase in the sound pressure level of about 5 dB. The detection threshold for 14 machines operating in a 13-20 mph wind is observed to be at approximately 1160 m in the downwind direction.