Microfiber coating as a noise-reducing device for aerial vehicles

A microfiber coating has been studied as a noise-reducing device for a propeller blade in small aerial vehicles. It is a hair-like structure attached to the trailing edge of a blade. To determine the optimal microfiber locations for a blade-noise reduction, the microfiber coating is placed symmetrically at different spanwise locations on each blade of the 15-inch diameter rotor. The Reynolds numbers based on the velocity and chord at the 75% span station is 7.4 × 10⁴. Sound level around the rotating blade is measured by using a sound-level meter in an anechoic chamber. When the coating is placed along the trailing edge of the outer portion of the rotor, the microfiber coating leads to noise reductions of up to 2.2 dBA. The location near the wingtip corresponded with larger noise reduction than the location close to the rotation center. The current status of this study as well as our future studies will be presented.