Wind Turbine Aerodynamics - 9 - Noise Emission 2
22 August 2026, Pascal Weihing
Design of Noise Optimal Modes
noise reduced operation modes have
- usually reduced speed at maximum power
- often reduced maximum power output
- other power curves (less yield)
pitch curve has to be chosen in a way that stall is avoided, slope of curves also depend on the controller characteristics. at rated power, pitch has to be increased for increasing wind speeds to keep power constant.
Steps for Design
- determine target sound power level
- estimation of required rpm with Hagg model: $SPL = 50 log(V_{tip})+10 log D-4$ if the sound power level of another mode of the same turbine is already known: $\Delta SPL = 50 log(\frac{V_{tip, 1}}{V_{tip, 2}}$
- choose rated power and estimate contribution of secondary noise sources
- if neccessary: adjust rated power and / or rpm
- detailed design for maximum AEP (long lambda-opt region) by considering boundary conditions of controller
- verify assumptions by detailed noise simulation
Emission Measurements
measurements are done in accordence with IEC 61400:
- turbine is assumed point source
- A-weighting is applied
- ...
| emission measurement | immission measurement |
|---|---|
| good reproducability | direct assessment of noise impact at dwellings |
| relatively independent of the season of the year | directivity, shielding or other propagation effects considered imlicitly |
| signal to noise ratio mostly good | -- |
| result directly comparable with the values from the manufacturer | -- |
| -- | -- |
| reference point features TE noise | signal to noise ratio often bad |
| no consideration of directivity | no transfers between different wind farms possible - more effort |
Conditions for successfull measurements: no rain, no background noise, volatile wind: 0,8-1,3 times the wind speed at 85% rated power has to be measured
Measured Values
- sound pressure level
- wind turbine power
- rpm
- pitch
- temperature
- air pressure