Noise from wind turbines
Wind turbines emit a relatively weak but characteristic noise. The noise is mainly generated by the movement of the blades through the air. This produces a swishing sound in rate with the rotation of the blades, as well as noise from the turbine machinery. Machine noise can have a tonal character which is particularly annoying.
Noise limits are set for both weak and strong winds
Wind turbines must observe the noise limits in accordance with the Statutory Order on wind turbines. The noise limits apply to the total noise from all wind turbines and are set for both weak winds, when noise is found to be most annoying, and stronger winds. When the noise meets the noise limits it do not mean that the noise is inaudible. The limits have been laid down to ensure that no significant disturbance is experienced.
Download the Statutory Order (English translation)
Download noise thermometer (PDF, 120KB), which provides examples of noise generation at various decibel levels.
Noise is calculated, because precise measurements are difficult to achieve
The noise from wind in trees and bushes makes it impossible to take sufficiently precise measurements of wind turbine noise at neighbouring properties under the necessary wind conditions. In addition to the wind noise, traffic noise and sound from birds and from noise sources inside or near the dwelling may disturb measurement of the low noise levels in question. Regulations governing noise experienced by neighbouring properties therefore calculate noise annoyance based on the wind turbines' noise emission.
Noise emission is measured relatively close to the wind turbine using a microphone mounted on a large plate on the ground. Here there is much less influence from the background noise. At the same time the wind speed is measured or preferable derived from the produced power, as this corresponds better to the wind speed acting on the blades. The wind turbine noise emission is determined on this basis.
Noise emissions are measured under both very windy conditions (8 m/s at 10 m height) and less windy conditions (6 m/s) to reflect the two sets of noise limits.
The calculation of the amount of noise emitted to neighbouring properties is very simple, because the noise is emitted from a significant height. The calculation presupposes downwind sound propagation. The calculated noise level is almost always higher than actual noise experienced by neighbouring properties.
Modern turbines emit significantly less noise
The latest wind turbines are considerably quieter than the first models of the 1970s and 1980s. In particular, noise from the gears and generator has been reduced. The modern wind turbine's nacelle is noise insulated and the generator and gears are mounted so that noise is dampened as much as possible. The design of the blades has been developed to mitigate noise.
Noise from a modern wind turbine is commensurate with that of a tractor. A typical 1980s turbine generating 100 kW and a 1990s turbine generating 500 kW both emit approx. 100 dB. This is only slightly less than a typical modern turbine generating 2-3 MW.
Read more about regulations on noise from wind turbines