No special treatment for wind turbine noise

"Though for now we know little about the health impacts of wind turbine noise, a lot is known about noise in general. The limits set on indoor noise levels are based on extensive international experience of the health hazards, and these limits have to be followed regardless of the noise source. That's why the sound in homes emanating from wind turbines must not exceed the set specifications," explains Senior Officer Vesa Pekkola.

There are now a little over 200 wind turbines in Finland. The aim is to increase the use of renewable energy rapidly, which means that in ten years time there may be many times more turbines. The pace of construction is increasing, and the complaints about wind turbines have underlined to the MSAH the importance of health impact assessments even at the planning stage.

"Inadequate planning often rebounds in the form of problems. Correcting them retrospectively is both complicated and expensive. It is much better to design a turbine from the outset so that difficulties don't arise," says Pekkola.

Measuring the noise from wind turbines is neither straightforward nor comparable to other environmental sounds. "The sound of a wind turbine varies greatly. In addition to the apparatus itself, there is the speed and direction of the wind and their variations, as well as air temperature conditions. The issue also concerns low frequency sound, which travels further and more easily through walls than high frequency sound."

Sufficient distanceIt is not easy to directly apply experiences from other countries, as developments are continually moving towards making larger wind turbines. The turbines now being constructed for Finland have three times more output than the average size wind turbines in Denmark, because interest in wind power developed in that country much earlier.

The best way to prevent detrimental noise is to construct turbines sufficiently far away from residential areas. The two-kilometre distance publicised in the media as recommended by the MSAH is not however a minimum distance set by the ministry. In Pekkola's view, the basis of planning must be that the levels of indoor noise abide by the Health Protection Act.

"Planning needs to take into account how far a building's outer shell curbs noise. This way, based on the determined level of outside noise, we can estimate the required distance of turbines from residential areas, according to the Ministry of Environment's guidelines for the modelling and measurement of the noise generated by wind turbines."

Pekkola also points out that the outcome of such modelling is a long-term average. "The result depends on the initial values that were set, which must be absolutely correct. But modelling does not tell us everything about the specific qualities of wind turbine noise, such as sound variations and intermittent throbbing that compound annoyance. It is important to bear in mind these uncertainty factors before drawing conclusions about outcomes. If they are not managed at the planning phase, the risk of exceeding indoor noise limits increases."

Wind power acceptabilityLast spring, the Ministry of Environment drafted a decree on wind turbine noise. Pekkola says that the MSAH is satisfied with the draft, which the proposed requirements concerning outdoor noise takes account of limits on indoor noise restrictions. The Ministry of Employment and the Economy, Finnish Wind Power Association and Finnish Energy Industries on the other hand take a different view. The fear is that restrictions seen as stringent will be disadvantageous to the whole economy and the construction of renewable energy.

A new draft decree is in preparation, which will probably be completed during the autumn. Pekkola says that the MSAH will not compromise on indoor noise restrictions. Wind turbine construction companies have pleaded that nowadays people should be prepared to put up with a certain amount of noise.

"That viewpoint has already been taken into account is the requirements concerning indoor noise. The fact is that noise can cause health problems. Even a low amount of decibels is enough to disturb one's sleep, and lack of sleep and stress can be harmful to one's health," says Pekkola.

There are already several examples where health authorities in Finland have intervened in cases of noise caused by wind turbines. But Pekkola is above all concerned about the situation in the future.

"In the long run, the acceptability of wind power by the public depends on the perceived disadvantages. If these are avoided through wise planning, its construction will be easier in the future."

Text: Mark Waller & Paula Mannonen