"Wind turbines generate noise from multiple mechanical and aerodynamic sources. As the technology has advanced, wind turbines have gotten much quieter, but noise from wind turbines is still a public concern. The problems associated with wind turbine noise have been one of the more studied environmental impact areas in wind energy engineering. Noise levels can be measured, but, similar to other environmental concerns, the public's perception of the noise impact of wind turbines is in part a subjective determination.
Noise is defined as any unwanted sound. Concerns about noise depend on 1) the level of intensity, frequency, frequency distribution and patterns of the noise source; 2) background noise levels; 3) the terrain between the emitter and receptor; and 4) the nature of the noise receptor. The effects of noise on people can be classified into three general categories (National Wind Coordinating Committee, 1998):
1) Subjective effects including annoyance, nuisance, dissatisfaction
2) Interference with activities such as speech, sleep, and learning
3) Physiological effects such as anxiety, tinnitus, or hearing loss"........
prepared by the Renewable Energy Research Laboratory Center for Energy Efficiency and Renewable Energy Department of Mechanical and Industrial Engineering University of Massachusetts at Amherst