Noise and infrasound
While modern wind turbines are designed to minimise noise levels, they still produce some noise.
Wind turbine noise can be attributed to two main sources. Mechanical noise comes from components within the turbine itself, such as the generator or gearbox. Advanced engineering means that this is not a significant feature of the total noise emissions. The main source is aerodynamic noise originating from the wind passing over the blades, making a ‘swish’ sound, the levels of which depend on the wind speed. These noise levels diminish with distance from the wind farm and may be masked considerably by the background noise environment, especially from the wind passing though trees and around buildings. Near to the wind farm, it may be audible at times depending on the location and factors such as the number of turbines operating, wind speed and wind direction and other atmospheric conditions like temperature or humidity. Importantly, the noise levels at surrounding dwellings are restricted according to government regulations and/or planning conditions protecting the amenity of the surrounds.
In Australia, we communicate with landholders, neighbours and communities about wind farm noise emissions generated by wind farms, including our design approach and compliance requirements, through our community consultation program. During the planning stage, independent acoustic consultants prepare noise impact assessments, including background noise monitoring, to demonstrate compliance with the government regulations and/or planning conditions.
Once construction is complete, we conduct additional noise monitoring to ensure that compliance with the regulation is achieved. We also have a formal complaints procedure which can be used by members of the community if they have concerns relating to Pacific Hydro, including issues relating to noise.
There has been recent debate about infrasonic emissions from wind farms. Infrasound can be generated by natural sources such as waves, waterfalls and wind, or man-made sources including vehicles, air-conditioning systems and wind farms. In the interests of informing the debate, in November 2010 we commissioned an acoustic consulting firm, Sonus, to measure and compare infrasound levels from two of our wind farms with other common environmental infrasound sources, both natural and man-made. Their report found that the infrasound generated by wind turbines is well below established guideline perception thresholds and also below levels produced by other natural and man-made sources. The full Sonus report can be found here.
The recent Australian Senate Inquiry on ‘The Social and Economic Impacts of Rural Wind Farms’ found that there was no direct link between adverse health effects and wind turbines. In fact, no scientific peer reviewed literature suggests that infrasound produced by wind farms causes any health impacts. International and national health bodies, government departments and medical professionals reject a link between the two.