What enables owls to fly silently?

Owls produce negligible noise while flying. Their wings make no noise while flying, enabling them to accurately locate their prey using their exceptional hearing ability while remaining undetected. While many studies have linked the micro-fringes in owl wings to their silent flight, the exact mechanisms have been unclear. Now, a team of researchers has uncovered the effects of these micro-fringes on the sound and aerodynamic performance of owl wings through computational fluid dynamic simulations. These trailing-edge fringes play a crucial role in suppressing the noise produced by wing flap-induced air movement. Simulations revealed that the trailing-edge fringes reduced the noise levels of owl wings, particularly at high angles of attack, and maintained aerodynamic performance comparable to owl wings without fringes. Researchers found that the fringes reduce the fluctuations in airflow by breaking up the trailing edge vortices, and they reduce the flow interactions between feathers at the wingtips, thereby suppressing the shedding of wingtip vortices. Synergistically, these mechanisms enhance the effects of trailing-edge fringes, improving both aerodynamic force production and noise reduction.