Bio-aerial Locomotion 2011

Biologists have discovered several different reasons for which owls are able to fly in silence. The specific shape of the wing and the feathers have a lot to do with the cancellation of noise.   The serrated edges on the front of the owls wing help in channeling air smoothly over the wings, which reduces the amount of noise produced. In addition, the owls back feathers have a velvety look and feel in order to prevent abrupt pressure changes which cause noise.

Serrated front edge

Fluffy back edge

The following are the three reasons why owls are able to fly in silence:

1. The primary feathers of the owl’s wings are  separated from each other, and the feather’s edges are serrated. In flight, the wings resolved the sound wave, which was produced after air passed the wings, changed the air flow status of its surface boundary layer, and inhibited the formation of air turbulence. This form has excellent performance in noise elimination
2. The smear feathers at the end of wings are spiciform and have no regular arrangement.
3. The soft feathers on owl’s wings can absorb surplus sound whose rate is over 2000 Hz. It’s the reason why prey cannot hear the owl.

Geoffrey Lowley has been studying owl flight and how it can be incorporated to improve on Quiet Aircraft Technology, specifically within the Vehicle Systems Program at NASA’s Langley Research center in Hampton, Virginia. Since some airports such as Chicago O’Hare and Heathrow have strict policies on noise restriction, engineers figured that reducing the noise can have more flights take off which would increase revenue. This may help the airline industry which has been struggling for fuel costs.

In order to accomplish a noise reduction, researchers proposed creating a retractable fringe for the plain that would mimic the owls’ trailing feather. They believe that putting on a velvety coating on landing gear will aid in the absorption of noise.

Sources:

• http://www.asknature.org/strategy/938e8c4d8e2bf786fa5c9922d181273e
• http://science.howstuffworks.com/environmental/life/zoology/birds/owl-fly-silently2.htm