Owls: Silent Fliers

Owls fly silently as they prepare to snatch their unsuspecting prey. They can fly more quietly and more slowly than other birds. What is it about their wings that allows them to glide through the air with hardly any sound?

Owls are nocturnal, meaning that they hunt at night. If they were hunting during daylight, they could be seen. Since they fly at night, the animals they hunt would be alerted by the sound of wings in the wind. Owls hunt small rodents which have hearing that is tuned to high-frequency sounds. The design of their wings reduces sounds at frequencies above 2 kHz.

Biologists continue to study this ability of owls to fly silently. One important factor is the design of the feathers. Owls generally have larger feathers than other birds. The feathers on the border of the wings have serrated edges which reduce air disturbance which reduces noise. The feathers also have a velvet-like surface which helps to absorb the sound.

Can we apply the same principles to reduce the sound of airplanes in flight, giant wind turbines, or even household fans? Researchers have been working on new materials inspired by owls which could reduce the sound that wind makes when moving across surfaces. They are studying the owl wing’s comb-like structure of evenly-spaced bristles with a porous elastic fringe. We intuitively think that smooth surfaces should provide the least friction to the air and therefore create less noise. The design of owl wings shows that is not the case.

This is another example of “biomimicry” where humans learn from and mimic biological designs in nature. The goal is to create a new material that can break up air currents into weaker flows that make less noise. When we realize that this design comes from a study of owl wings, we think the owls must have had a very intelligent Designer.
© Roland Earnst

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