1. Wind Farm Noise Impact Assessment
Source and Characteristics – Different types of wind turbine

2. Subjective noise from wind turbines
Higher frequencies
Swishing, lapping, hissing, whistling…
Mid frequencies
Tones, whines, roar…
Lower frequencies
Rumble, thumping…

3. 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

4. Separation (stall) noise
Aerodynamic sources
(after Hayes, IOA and Lowson)
Separation (stall) noise
Tip noise
Trailing edge noise
Boundary layer noise
Turbulence ingestion
Dominant

5. 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

6. Evolution for a particular model

7. Capacity of variable speed pitch-regulated turbines
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

8. Thank you