Microfiber coating as a noise reducing device for a propeller blade

A microfiber coating has been studied as a noise reducing device for a propeller blade. It is a hair-like structure attached to the blade via an adhesive. To determine the optimal microfiber locations for a blade-noise reduction, the microfiber coating is placed symmetrically at different spanwise and chordwise locations on each blade of the 16-inch diameter rotor, and rotated at a range of wingtip speeds. Sound data is captured by a microphone placed 3 feet from the rotor and processed resulting in an average sound level in decibels and a spectral density plot over the relevant frequency range for each rotor configuration and wingtip speed. When the coating is placed along the leading edge of the inner portion of the rotor and the trailing edge of the outer portion of the rotor, the microfiber coating leads to noise reductions of up to 2.3 dBA. The low fiber density corresponded with larger noise reduction than the high fiber density for a given location. At the highest wingtip speeds of 72 to 83 meters per second, the high density fiber resulted in increased noise of up to 5.2 dBA relative to the baseline. Current status of this study as well as our future studies will be presented.