Acoustic and aerodynamic performance evaluation of a commercial toroidal propeller compared to conventional propellers

Despite increasing interest in toroidal propellers and their potential for noise reduction, comprehensive peer-reviewed studies assessing their acoustic performance remain scarce and limited in scope. To address this gap, this study presents a comprehensive evaluation of the acoustic and aerodynamic performance of a commercially available 5-inch two-loop toroidal quadcopter propeller at hover conditions. We conducted measurements both on a static test rig and during in-flight operation, comparing the toroidal propeller with two conventional propellers of identical diameter. Test rig experiments enabled precise control of operating conditions, acoustic characterization at multiple emission angles, and direct determination of aerodynamic efficiency. Our results show that the toroidal propeller produced the highest A-weighted sound pressure levels at all typical hover thrust levels and emission angles. In contrast, the high-pitch baseline propeller exhibited up to 10 dB lower SPL, albeit at the expense of aerodynamic efficiency. The low-pitch baseline propeller showed higher efficiency than the toroidal design and still exhibited up to 5 dB lower SPL, depending on the thrust level. These results indicate that, at hover conditions, the tested toroidal propeller provides no noise or efficiency advantage over conventional propeller blades.