DASAM [the Danish Society for Occupational and Environmental Medicine] has with interest read the proposal for a new executive order on noise from wind turbines. DASAM welcomes that low frequency noise from wind turbines are now being subjected to the same limits as low frequency noise from other industries during the night.
DASAM believes however, that the executive order not sufficiently protects against health risks due to noise and therefore recommends:
- The noise limits should be lowered from 39dB (A) to 35 dB (A).
- A health based assessment on the effects of introducing up to 1000 wind turbines in Denmark should be performed.
Based on current knowledge about the relationship between noise from wind turbines and effects on humans, and the raised critic on the quality of the proposed noise measurements, for example from researchers from Aalborg University, we are concerned whether the proposed noise limit values for wind turbines will sufficiently protect the Danish citizens against annoyance of living close to wind turbines.
A number of original papers and several reviews show that between 10% and 40% of citizens living close to wind turbines feel annoyed or extremely annoyed by the noise, and it is shown that the number of annoyed people rises sharply when the noise exceeds 35 dB [1-7]. Generally, it has not been possible to distinguish between nuisances from noise and low frequency noise respectively. Some of the studies also suggest that living near a wind turbine affect sleep quality and the most recent review concluded that “Wind turbine noise is causing noise annoyance and possible also sleep disturbance, which means that one cannot completely rule out effects on the cardiovascular system after prolonged exposure to wind turbine noise, despite moderate levels of exposure” .
Some case studies describe vibroacoustic disease and wind turbine syndrome in persons living close to wind turbines, but these findings have not been confirmed by more systematic studies.
The current noise limits that are unchanged in the new revised proposal is 44 dB(A) at 8 m/s (open land) and 39 dB(A) at 8 m/s (noise sensitive land use). Actually, the noise load can be considerably higher, due to 1) no enhanced noise limits in the night, even though it is well documented, that the noise reduction can be lowered 3-15 dB at night [8,9] and 2) that the noise level can increase at higher wind speeds.
As something new, an indoor noise limit value of 20 dB for low-frequency noise is proposed, but it is accepted, that the noise limit value will be exceeded in 33% of households living close to wind turbines. Basically DASAM finds this approach unacceptable. The Environmental Protection Agency’s calculation of the insulation capability of houses against low frequency noise – including the acceptance of the large number of exceedings – and the controversial use of measurement variability in the control measurements for noise has been strongly criticized by international experts in noise and acoustic . In the proposed executive order the noise insulation numbers are increased compared to earlier, resulting in calculated indoor levels of low frequency noise below 20 dB, despite the fact that the real levels are well above 20 dB. We refer to  and to the statement on the executive order from Aalborg University for further details.
We estimate that with the current noise limit values for wind turbines, an unacceptable proportion of citizens in the vicinity of wind turbines will be annoyed or strongly annoyed by the noise. In the suggested noise limit values it has not been taken into consideration that susceptible subjects due to e.g. pre-existing disease can be more sensitive to noise compared to the general population .
No studies so far have investigated the magnitude of the problem in Denmark, but based on studies from mainly Sweden and Holland DASAM recommends that the noise limit value is decreased from the current 39 dB (A) so in the future no more than 35 dB is allowed at residences at a wind speed of 8 m/s. It is also recommended to use 35 dB as the noise limit value in noise sensitive land use – today it is covered by the 44 dB noise limit value. By doing this the Danish noise limit values will become comparable to the Swedish  and the New Zeelandic  noise limit values. Based on present knowledge, this means that less than 10% of citizens living close to wind turbines will be annoyed by the noise.
DASAM finds it relevant that a health-based assessment is made of the effects of introducing as planned up to 1000 wind turbines in Denmark. DASAM can propose a person capable of performing the task, including suggestions on how effects of wind turbines may be monitored and estimated in the future.
Chairman, Danish Society for Occupational and Environmental Medicine
Associate Professor, MD, specialist in occupational medicine
Department of Public Health, Section for Environmental and Occupational Medicine
Aarhus University, Denmark
Tlf: +45 8617 8022 / +45 2899 2499
- Sammenhæng mellem vindmøllestøj og helbredseffekter. DELTA, marts 2011
- Infrasound and low frequency noise from wind turbines: exposure and health effects; Environ. Res. Lett. 6 (2011) 035103 (6pp)
- Health aspects associated with wind turbine noise – results from three field studies. Noise Control Eng J 59(1) 2011
- Perception and annoyance due to wind turbine noise—a dose–response relationship; J. Acoust. Soc. Am. 116 (6), December 2004
- Wind turbine noise, annoyance and self-reported health and well-being in different living environments; Occup Environ Med 2007;64:480–486
- Response to noise from modern wind farms in The Netherlands; J. Acoust. Soc. Am. 126 2, August 2009
- Evaluating the impact of wind turbine noise on health-related quality of life; Noise & Health, Sept-Oct 2011; 13:54,333-9)
- Effects of the wind profile at night on wind turbine sound; Journal of Sound and Vibration; doi:10.1016/j.jsv.2003.09.050
- Schneider, C.P. Accuracy of Model Predictions and the Effects of Atmospheric Stability on Wind Turbine Noise at the Maple Ridge Wind Power Facility, Lowville NY.2007
- Henrik Møller, Christian Sejer Pedersen, Steffen Pedersen, ”Miljøstyrelsens mystiske beregninger”, Kronik, Berlingske, 15. juni 2011
- New Zealand Standard. Acoustics – Wind farm noise DZ 6808. REPORT DRAFT