A new material that could make wind turbines and even aircraft quieter - by mimicking the design of owls' wings - has been developed by scientists.
The Cambridge University-led Anglo-American team studied the feathers of the stealthy nocturnal airborne predators to produce the coating.
"Many owls ... can hunt by stealth, swooping down and capturing their prey undetected," said Professor Nigel Peake of Cambridge's department of applied mathematics and theoretical physics.
"While we've known this for centuries, what hasn't been known is how or why owls are able to fly in silence."
Because of the noise they make, wind turbines are often braked to make them turn more slowly and quietly, but the team behind the new material say that it could enable the machines to turn faster and boost their output without increasing noise as a side-effect.
Using powerful microscopes, the team found that owls' wings have a "downy covering" to their flight feathers, as well as bristles on their on the leading of their wings and an "elastic fringe" on the trailing edges.
"No other bird has this sort of intricate wing structure," Prof Peake said.
"The structure of an owl's wing serves to reduce noise by smoothing the passage of air as it passes over the wing - scattering the sound so their prey can't hear them coming."
The discovery enabled the team to make a 3D printed plastic cover for a wind turbine, which reduced the noise it generated in wind tunnel tests by 10 decibels.
They believe it can be adapted for other types of wings and blades and want to move on to improve the coating further and test it on a working turbine.
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