Abstract

When hunting many, but not all, species of owl manage to fly almost silently in the audible frequency range of both themselves and their prey. A complete understanding of how this is done has yet to be found, but it is believed that three rather unusual features of the owl wing and feathers play a significant role. These features include a leading-edge comb of barbs, a porous and flexible trailing edge brush, and a particularly unusual microstructure in the feathers which leads to a velvet-like wing suction surface. Although the first feature is found on other raptors, the second two are quite unique to owls which hunt in acoustic stealth. In this talk I will describe a range of theoretical and experimental research which has been conducted to attempt to understand these mechanisms. It is well-known in other contexts, including aircraft landing noise and wind turbines, that a turbulent boundary layer passing over a wing trailing edge is a potentially potent source of noise, and so a particular focus of our work has been to investigate the ways in which the owl’s adaptations may have weakened this noise mechanism. An owl-inspired trailing-edge noise control device will be described.