ABSTRACT
Wind turbines generate sound by both mechanical and aerodynamic sources. As the technology has advanced, wind turbines have become quieter; however sound remains an important criterion used in the siting of wind farms. Although sound levels can be measured accurately, the perception of the acoustic impact of wind turbines on people is sometimes subjective. A sound level measurement that combines all frequencies into a single weighted reading is defined as a broadband sound level. Low frequency sound consists of pressure fluctuations that can be heard near the lowest end of the frequency response of the human ear, namely from 10200 Hz. Infrasound propagates farther, with lower levels of dissipation, than higher frequencies. Wind turbines generate four types of sound characteristics: tonal, broadband, low frequency, and impulsive. In general, as sound propagates without obstruction from a point source, the sound pressure level decreases. The ability to hear a wind turbine in a given installation also depends on the ambient sound level.
