Acoustics researchers aim to make wind turbines quieter

Acoustics researchers at Adelaide University are investigating the causes of wind turbine noise with the aim of making them quieter.

They are also developing a computer model to predict the noise output from wind farms so they can accurately and quickly assess the effectiveness of potential noise-reducing designs and control methods.

Research leader Dr Con Doolan, from the university’s School of Mechanical Engineering, said the noise generated from wind turbines is ‘trailing edge or airfoil noise’ — the same sort of noise generated at the edge of aircraft wings.

‘We know generally what causes that noise — as the turbulent air flows over the sharp edge of the blade, it radiates sound much more efficiently, so the noise can be heard at some distance,’ said Doolan.

‘What we don’t yet understand, however, is exactly how that turbulence and blade edge, or boundary layer, interact and how that makes the noise louder.

‘If we can understand this fundamental science, we can then look at ways of controlling the noise, through changing the shape of the rotor blades or using active control devices at the blade edges to disrupt the pattern of turbulence and so reduce the noise.’

According to Doolan, further complicating factors came from the effects of multiple wind turbines together and the way the noise increases and decreases as the blades rotate — the blade ‘swish’. The model they are developing will look at the noise from the whole wind turbine and how multiple numbers of wind turbines together, as in a wind farm, generate noise.

‘Wind turbine noise is very directional,’ he said. ‘Someone living at the base might not have a problem, but 2km away it might be keeping them awake at night.

‘Likewise, this broadband “hissing” noise modulates up and down as the blades rotate, and we think that’s what makes it so annoying.’