Quadcopter propeller noise and its control

Abstract

Simple scaling analysis is used to show that truly significant reductions in propeller noise are possibly by increasing the propeller diameter while reducing its rotational speed, thereby reducing its blade tip speed, while maintaining a given level of static thrust. The scaling analysis is also used to show that efficiency improvements accompany the reductions in radiated noise. The significant reductions in noise and the increase in efficiency predicted were verified experimentally by measuring the radiated noise and power requirements for both large, slowly rotating propellers and small, high speed propellers, at equivalent static thrusts, where the large propellers serve as possible replacements for the small propellers in typical quadcopter applications. The bulk of the noise reductions offered by large and slowly rotating propellers compared with small, high speed propellers is shown to be maintained at equivalent net force (thrust minus weight conditions), as required for practical implementation into a quadcopter, even using readily available hobby grade components. Further significant noise reductions are possible with lightweight and custom engineered components.