Comparative Acoustic Examination of UAV Propellers

The reduction of aircraft noise is one of the major challenges of the aviation industry. This also concerns unmanned aerial vehicles (UAVs), since they will play an increasingly important role in everyday life. In the context of the presented project the energetic potentials of winglets at propeller tips ("proplets") were investigated in order to increase the aerodynamic efficiency and decrease the noise emission of propellers. Therefore it was necessary to determine the acoustic effects of the attached proplets. This paper compares the noise emission of a reference propeller with a proplet-equipped propeller for the first time. Except for the tips, they were identically designed. The acoustic power level of both propellers was determined and the results are assessed psycho-acoustically. Additionally an examination of the test pieces with a spaced microphone array ("Acoustic Camera") was conducted to visualize the localization of sound sources on the propellers. A rotational beamforming filter using a virtual array rotation was applied to precisely identify the positions of the rotating aero-acoustic sources. The results of the investigation provide an insight to the noise-reducing potential of using winglets in propeller design.