Seppo Hakola, Head of TCM at Ilmatar, is responsible for the technical management of Ilmatar’s wind farms:
“In the initial planning of a wind farm, we do noise modelling, identifying the 40 dB noise level boundaries around the site, which is the normal limit for wind power in the Nordic countries. This data is used as an instrument for further planning to ensure that no neighbouring homes are within the noise zone. In the direct proximity of the turbine, the noise can, of course, be higher and will fluctuate in relation to wind conditions,” he explains.
Wind turbine noise is categorised into two main types: aerodynamic and mechanical. Aerodynamic noise is the whooshing sound generated when the wind moves over the turbine’s rotor blades and varies depending on factors such as blade design and wind speed. Mechanical noise is generated by the machinery itself, i.e., generators, gearboxes, and such. It should be noted that older wind turbines are noisier, while modern wind turbines normally cause less mechanical noise.
“Thanks to technological developments by our turbine suppliers, it has been possible to multiply the power output while noise levels have not increased,” says Seppo Hakola.
One of these technological developments is Vortex Generators, small devices that attach to the blades and trim the power output of the turbine aerodynamically without increasing noise levels. The control automation of wind turbines is also constantly evolving to improve turbine efficiency. This means that the pitch angles of the blades are more precisely controlled, that they operate optimally, and that they generate less noise.
“At Ilmatar, we always choose the latest possible type of turbines and all the equipment that can be used to reduce noise. We also regularly inspect the blades using drone images and repair any potential damage, as broken blade surfaces can also increase noise levels,” says Seppo Hakola.
Infrasound studies show no effects
Another type of sound often mentioned when discussing wind power is infrasound, which can be explained as sound below what we can perceive with our ears, with a frequency below 20 Hz.
Some of the symptoms reported as a result of infrasound from wind power include headaches, nausea, dizziness, sleep problems, fatigue, tinnitus, high blood pressure and more. As a result of this criticism, several studies and analyses of wind turbine noise have been conducted, including the report ‘Infrasound Does Not Explain Symptoms Related to Wind Turbines’ published as part of Finland’s energy and climate strategy until 2030, in which the research group could not identify any factual links between infrasound from wind turbines and effects on the body, and instead concluded that other mechanisms must cause the symptoms.
The Swedish Environmental Protection Agency’s research programme Vindval thoroughly maps the impact of wind power on people, nature and the environment. In their fact sheet ‘The impact of wind power on people’s interests’, it is stated that the current guideline level for wind power noise of 40dBA is reasonable in terms of disturbance and health. It also refers to a study of 2,400 residents near wind turbines in the United States, Germany and Switzerland, which showed that the levels of disturbance and stress experienced also seem to depend on factors such as the perceived fairness in the wind farm development process and the person’s overall attitude towards wind power.
Communication is key
Although the experienced symptoms cannot be empirically attributed to wind turbines, and despite the technological advances in wind power and the urgent need to reduce our dependence on fossil and non-renewable energy, the fact remains – that some people living near wind farms experience inconvenience and disturbance from wind power. So how do we move forward? Jussi Mäkinen is VP of Project Development at Ilmatar:
“Balancing the societal value versus the impact on local residents is complicated. However, one must keep in mind that despite the potential change a wind farm can bring to local residents, it is also a major contribution to the clean energy transition. Resistance seems often based on the feeling of not being heard. Therefore, open dialogue and involvement of the local community in wind farm development are crucial. If the local community can have a say if we as an energy company are ready to adjust our project design, and if it is also made clear how the local economy can be strengthened by, for example, property taxes – that’s when we can move forward,” he says.
“This is why we regard interaction with stakeholders, authorities, local residents and the public through open consultation meetings as an essential part of the democratic process and a tool to find the best possible way forward. We organise these meetings for all our projects, even though they are not always legally required. The transition to fossil-free energy is the most challenging endeavour in human history, yet we have to take it on. Because the alternative is even worse.”
WHO noise guidelines (average noise level)
From car traffic
Daytime maximum 53 dB.
Night time max 45 dB.
From train traffic
Daytime maximum 54 dB.
Night time maximum 44 dB.
From air traffic
Daytime maximum 45 dB.
Night time maximum 40 dB.
From wind turbines
Daytime max 45 dB.
No specific recommendation at night due to low evidence of risk of exposure.
Noise guidelines for wind turbines in Finland and Sweden
Finland: The Wind Power Noise Decree (1107/2015) states that the maximum noise levels from wind power near residential and holiday homes are 45 dB during the day and 40 dB at night.
Sweden: The Swedish Environmental Protection Agency’s guidelines for noise from wind power state that the outdoor noise level at homes should not be higher than 40 dBA. This applies to both permanent and holiday homes.
Comparing turbine sound to other noise sources
20 dB: Whispering conversation.
40 dB: Maximum noise of wind farm in the Nordics.
45-60 dB: Dishwasher.
60 dB: Normal conversation.
70 dB: Vacuum cleaner.
90 dB: Motorbike.
100 dB: Helicopter.
110 dB: Rock concert.
120 dB: Ambulance siren.
130 dB: Jet plane starting.
