Silent Owl Wings: Trailing-Edge 'Micro Fringes' Behind the Mystery of Silent Flight of Owls [Study]

Owls are solitary birds and are known for being nocturnal animals, which means they sleep during the day and are active at night. Belonging to the order Strigiformes, which consists of more than 200 species where most also prefer to live in isolation, owls have several unique features. We know them as having tube eyes and as efficient predators that can adapt to nearly all of Earth's ecosystems.

However, one of the remarkable traits of owls is they can fly quietly, unlike other birds where we can hear their wings flap as they move it up and down (before or during flight). The silent owl wings had been a mystery for a long time. It is also one of the reasons why these large-eyes, nocturnal birds can sneak inside homes and target their prey without the latter noticing it.

If silent flight is comparable to running without making any noise, then there must be a hidden mechanism behind it. Now, a new study led by scientists in Japan has examined a mechanism behind silent owl wings, called trailing-edge "micro fringes" or TE micro fringes. While previous studies have evaluated these fringes, their interaction with the feathery wings of owls remains unclear.

Silent Owl Wings

Using numerical simulations, the Japan-led research paper unravels the secrets behind silent owl wings by investigating the aeroacoustic mechanisms that suppress the sounds coming from true owl wings. The recent scientific report not only aims to solve the silent flight mystery but it also opens the possibility of its application to mechanical aircraft, drones, and even flying cars in the future.

The study, which was published in the journal Bioinspiration & Biomimetics in November 2023, shows that silent owl wings are made possible since TE micro fringes enable aerodynamic force produce and noise suppression. Using an owl wing model, researchers from Chiba University in Japan believe that these fringes play a critical role in the silent flight of owls.

Trailing-Edge Micro Fringes

Based on the owl wing model used in the study, the researchers constructed two 3D owl wing models, one with TE fringes and one without TE fringes, based on the structure of real owl wings. The research team found that the fringes on owl wings can suppress aerodynamic noise while flying. On the other hand, wings with no fringes are unable to suppress sounds emitted from true flight.

Following the results of the two owl wing models, the Japan-led study acknowledges the validity and feasibility of applying owl-based TE fringes in low-noise fluid machinery, just like an owl's feathered wings. Furthermore, the researchers also said that their findings further deepen our understanding of TE fringes in real owl flight, including gliding.

So far, there are no other known birds that can fly with mechanisms of noise suppression just like the silent owl wings.