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Wind Farm Noise Impact Assessment

Source and Characteristics – Different types of wind turbine

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• Higher frequenciesSwishing, lapping, hissing, whistling…

• Mid frequenciesTones, whines, roar…

• Lower frequenciesRumble, thumping…

Subjective noise from wind turbines

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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

controlledAerodynamic sources affected by air

inflow speed and turbulence

All sources affected by rotor speed and loading

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Aerodynamic sources(after Hayes, IOA 25-04-2006 and Lowson)

Separation (stall) noise Tip noise

Trailing edge noise Boundary layer noise

Dominant

Turbulence ingestion

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80

85

90

95

100

105

110

115

1 2 3 4 5 6 7 8 9 10 11

Wind speed at 10m height, ms-1

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(A)

Variable speed

Two speed (stall regulated)

Two speed (pitch regulated)

Speed changeover region for two speed turbines

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

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Evolution for a particular model

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Reduced noise modesCapacity 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

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Thank you