Quieter turbines

Noisy wind turbines are a problem. Not only for the residents who live next to them, but for their operators too.

If wind turbines clatter and whistle too loudly, they may only operate under partial load to protect residents living near them - but this also means they produce less power.

Now, German researchers have come up with a solution to the problem - they have developed an active damping system that cancels out the noise by producing counter-vibrations.

One source of noise from a wind turbine is from the gears that vibrate in the gearbox. These humming sounds are relayed to the tower of the wind turbine where they are emitted across a wide area.

'People find these monotone sounds particularly unpleasant, rather like the whining of a mosquito,' said André Illgen, a research associate at the Fraunhofer Institute for Machine Tools and Forming Technology in Dresden.

Passive damping systems have been used to address the issue, but the effectiveness of the systems has been somewhat limited: they only absorb noise at a certain frequency.