Owls are often considered nature's stealth fighters, and it turns out their ability to silently is a result of a unique wing structure not found in any other bird. Now that researchers know the owl's secret, they can make lots of stuff silent — everything from bedroom ceiling fans to massive wind turbines.
What contributes to a noisy wing or fan blade as it slices through the air is the turbulence from its trailing edge. But once a team of researchers from the University of Cambridge, Virginia Tech, Lehigh University, and Florida Atlantic University put an owl's wing under a microscope, they discovered that its flight feathers had a unique soft downy covering, a flexible array of bristles along its leading edge, and a porous fringe coming off the trailing edge.
Working together, these three unique characteristics smooth out the air as it passes over an owl's wing while also scattering the sounds produced — like how a stealth fighter scatters radar signals — so that it can catch its prey unawares.
To replicate this structure on a wind turbine, for starters, the researchers first experimented with covering those massive blades with a fine mesh material that was similar to what's used in wedding veils. It succeeded in reducing the blade's surface noise by a whopping 30 decibels, but ultimately proved impractical for real-world use.
As an alternative, the researchers created a custom prototype material using 3D printing techniques that reduce noise in wind tunnel tests by as much as 10 decibels, without sacrificing aerodynamics. And as this technique is further tested and refined, it will make those giant blades even quieter.
But in addition to reducing the amount of noise pollution generated by a massive wind farm, the new coating could allow wind turbines to actually run at higher speeds, making them more efficient and increasing their power output. And while applying the material to a plane's wings is a little more challenging given the speeds they travel at, it has the potential to make an air craft more fuel efficient and also more comfortable and quieter for those riding inside.
Photo by Shutter Stock/Matt Gibson