If you watch an owl flapping or gliding, it's like viewing film footage with the sound on 'mute'—they are so silent. That's because their wings have velvety surfaces, comb-like serrations (see photo) at the leading edge, and trailing-edge fringes that dramatically suppress the sound of air rushing over the wings.
Therefore the owl's prey (mice and voles) can be taken by surprise.
Also, with wing noise suppressed to a level below the owl's own hearing range, they can better hear (and thus locate) prey while flying—crucial for hunting at night.
These features have caught the attention of researchers in the dramatically-expanding field of biomimetics, whereby engineers copy biological design.
Owl wings have already inspired quieter fan blades in computers. More recently researchers using wind tunnel facilities have studied the leading-edge serrations. Each is "the tip of a single barb, having a very complicated 3D shape", and its size and orientation differ according to its position.
The owl wing design also efficiently resolves the trade-off between effective sound suppression and aerodynamic force production. Biomemetics hopes to use those design aspects. For example, so the blades of multi-rotor drones can 'chop' the air more quietly, without unduly sacrificing lift; similarly in other aircraft, wind turbines, and fluid machinery in general.
Which raises the question: how did owls come to have such enviable design characteristics in the first place? Design implies, well, that they were designed, which of course, implies a Designer. However, when it comes to crediting the Creator, many today would rather that be kept as silent as an owl in flight (see Romans 1:18).•