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Wind Farm Noise Impact Assessment Source and Characteristics – Different types of wind turbine. Subjective noise from wind turbines. Higher frequencies Swishing , lapping, hissing, whistling… Mid frequencies Tones , whines, roar… Lower frequencies Rumble , thumping….
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Wind Farm Noise Impact Assessment Source and Characteristics – Different types of wind turbine
Subjective noise from wind turbines • Higher frequencies • Swishing, lapping, hissing, whistling… • Mid frequencies • Tones, whines, roar… • Lower frequencies • Rumble, thumping…
Principal Sources of Noise Aerodynamic sources • Motion of air around the blades • Various sources, complex mechanisms Mechanical sources • Motion of mechanical & electrical components • Sources are more easily identified and controlled • Aerodynamic sources affected by air inflow speed and turbulence • All sources affected by rotor speed and loading
Tip noise • Separation (stall) noise • Boundary layer noise • Trailing edge noise • Aerodynamic sources • (after Hayes, IOA 25-04-2006 and Lowson) Turbulence ingestion Dominant
Comparison of sound power outputs of different wind turbines…. • Turbine sound output levels are wind speed dependent • Actual variation with wind speed is turbine specific • Common now for large turbines to be pitch-regulated variable speed
Reduced noise modes Capacity of variable speed pitch-regulated turbines • Most turbines offer reduced noise mode operation • Speed restriction or pitch setting change • Cost is power generation loss but can be restricted to specific conditions