Measurement and characterization of multirotor unmanned aerial system noise

The acoustic flight test and data analysis procedures developed for the reliable characterization of noise from multirotor Unmanned Aerial Systems (UAS) are described. In contrast to conventional aircraft, multirotor UAS provide a unique challenge due to their small size and sensitivity to disturbances, the use of fixed-pitch variable speed rotors, and of multiple electric motors to provide both propulsion and flight control. In combination, these factors lead to increased variability in the magnitude and directionality of the radiated noise. UAS acoustic flight test procedures are developed to quantify the variability in UAS noise across a range of flight conditions, including flyovers, hovering flight, approach and ascent. These procedures are applied to collect and analyze an extensive set of acoustic flight test data for a multirotor UAS. Some representative acoustic data are presented, showing typical variations in measured acoustic characteristics. These data will be used to develop guidelines for the repeatable characterization of UAS noise.