Psychoacoustic characterization of an isolated propeller at different inflowturbulence conditions and collective pitch angles
R. Merino Martinez (TU Delft - Operations & Environment)
L.N. Quaroni (TU Delft - Operations & Environment)
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Abstract
The far-field acoustic emissions of a six-bladed propeller were investigated in aeroacoustic experiments in an openjet wind tunnel. The propeller was operating in different isotropic inflow turbulence conditions generated by turbulence grids placed upstream of the exit plane of the wind tunnel nozzle. In addition, the collective pitch angle of the propeller blades was also varied throughout the measurements. A preliminary directivity analysis of different acoustic and psychoacoustic metrics was performed to investigate the influence of the inflow turbulence intensity and collective pitch angle on the noise emissions and sound perception. In general, increasing the inflow turbulence levels did not modify the conventional metrics recorded, e.g. equivalent sound pressure level. Nevertheless, it considerably increased the broadband noise emissions of the propeller, the loudness, and the overall psychoacoustic annoyance metrics. However, notable reductions in tonality (due to partial tone masking because of the higher levels of broadband noise) and sharpness were reported for increasing turbulence intensities. Overall, this analysis is valuable for the perception-influenced design of devices equipped with propellers, such as drones or urban air mobility vehicles, to account for installation effects.