How noisy are wind turbines really?
Posted by Graham Eastwick on 2 November 2009 at 9:50 am
When discussing noise and wind turbines it is important to be clear what size of turbine you are thinking about. The noise from large, commercial wind turbines is very different to that generated by smaller turbines installed at homes, offices and schools. The rotors on smaller turbines rotate much faster.
Data on noise from small wind turbines is often provided by the manufacturers. Ask them for it if it is not in their published data sheet.
As an example the Proven 6 kW wind turbine has the following noise profile published.
– 45 dBA at wind speed of 5 metres per second
– 65 dBA at wind speed 20 metres per second
These noise levels are measured at the turbine itself, and can then be calculated at varying distances from the turbine (noise level falls in proportion to the square of distance).
To give you an idea of how loud this is the following table gives the noise levels for some common situations:
- 30dB – whispering, leaves rustling very gently
- 60dB – normal conversation
- 90dB – in the middle of city traffic
- 120dB – rock concert
- 150dB – jet engine at 10m
The background noise in the local environment is also critical to understanding the impact of noise from any turbine. City centre locations are noisier than rural locations, windy days are noisier than still days. To ensure that noise is not an issue the turbines tend to be sited away from neighbouring properties. Typically 50m to 100m clearance is given from the nearest neighbours.
However, noise perception is also a subjective, psychological phenomenon. If people want to be disturbed by noise they are more likely to hear it and more likely to perceive it as loud. They are also more likely to be disturbed by noise that demands analysis (like conversation or music) than they are by random noise or noise related to wind, birds and similar.
Normal (horizontal axis) wind turbines have potential to generate low levels of noise because some parts of the rotors will be driven faster than the wind, so they create a gentle swish as they cut through the air. This is not true for vertical axis machines, which are silent as they travel at the same speed as the wind.
The only way to really get a feel for how noisy a wind turbine is in operation is to visit one and talk to the owners. A properly maintained and installed wind turbine does not generally cause a noise problem.
Photo by Alan Cleaver
If you have a question about anything in the above blog, please ask it in the comments section below.
2 comments - read them below or add one