Owls fly so quietly that their prey never hear the end coming. This silent flight has long intrigued Geoffrey Lilley, a professor emeritus of aeronautics and astronautics at the University of Southampton in England, so he decided to study videos of owls in wind tunnels. He hopes a better understanding of owl aerodynamics will help engineers design quieter aircraft.
Serrated feathers on the front edges of owl wings, Lilley found, funnel air smoothly over the wings, reducing the noise of rushing air. Each wing has a scarflike, fringed back edge that prevents the abrupt air-pressure changes--and noise--produced by a plane's rigid wings. By adding serrations and fringes to wings, he thinks he can build a quieter plane. "We've done all we can with reducing engine noise," he says. "Any extra noise reduction has to come off the airframe."