Prediction of Urban Air Mobility Multirotor VTOL Broadband Noise Using UCD-QuietFly

Abstract

This paper investigates broadband noise of multirotor urban air mobility (UAM) vertical take-off and landing (VTOL) vehicles. Based on an earlier single-rotor trailing-edge noise prediction method, a multirotor broadband noise prediction program is developed, where the multirotor coordinate transformation is included, and the amplitude modulation capability is introduced. Thereafter, the program is used to predict broadband noise from three UAM VTOL conceptual designs and a vertiport conceptual design. It is found that UAM VTOL vehicles' broadband noise is important in the high-frequency range, where the community background noise level is typically low. For the same mission specifications, broadband noise is found to be higher for VTOL designs with more rotors. UAM vehicle noise is compared to conventional helicopter noise. It is found that the amplitude modulation of broadband noise of a single rotor is insignificant when the observer distance is larger than four rotor radii. Multirotor vehicles at the same rotational speeds have weaker amplitude modulations than a single rotor, which demonstrates the benefits of using multiple rotors in terms of noise annoyance. Finally, noise contours from a vertiport design show an increase in the broadband noise level when multiple VTOL vehicles are operated simultaneously.