An acoustic and psychoacoustic assessment on the noise control of propellers in distributed propulsion configuration using phase-synchronisation

Distributed electric propulsion is widely recoginised as a promising propulsion configuration for next-generation aerial vehicles, including short-to-medium-haul passenger aircraft and urban air mobility vehicles. The presence of multiple propulsors gives rise to additional aerodynamic noise sources and yet, opportunities to novel noise control strategies. The present work examines the application of phase syncrhonisation technique to a DEP configuration, represented by two side-by-side propellers mounted to the leading-edge of a wing. Both the aeroacoustic and psychoacoustic analyses are performed on the far-field acoustic information. The results clearly show that when a relative phase difference is introduced between the two propellers, significant reduction of the tonal component at blade passing frequency can be achieved, accompanied by minor modifications to the directivity pattern. Moreover, such reduction leads directly to the reduction of loudness, a key indicator for the psychoacoustic annoyance. However, interestingly, the impulsiveness and sharpness indicators yield greater levels when the relative phase angle is increased. The findings from the work suggests that there could exist optimal phase angle for which the DEP configuration produces the least noise and psychoacoustic annoyance.