Development of a methodology for drone-noise investigation using phased-microphone arrays

Unmanned aerial systems (UAS), commonly referred to as “drones”, are employed for a wide range of applications, and their usage is likely to grow further in the future. Therefore, the problem of drone-noise pollution and annoyance to humans is becoming more relevant, especially in obtaining public acceptance of these machines. To address this issue, it is necessary to accurately characterize the aeroacoustic footprint of UAS in operative conditions since the radiated noise emissions strongly depend on the trajectories and maneuvers. However, current measurement techniques based on single microphones fail in achieving this objective because they cannot account for the varying distance between the drone and the receiver during the maneuvering, Doppler effect, and disturbances from sound reflections and spurious sources. In this project, we propose an innovative methodology based on phased-microphone-array techniques to localize the drone position during all the time instants of the flight and associate the corrected sound levels to its trajectory, filtering out unwanted noise sources. The method has been successfully validated using a synthetic acoustic source moving in a reverberant environment. Moreover, an experimental investigation was carried out in collaboration with the ID2move facility in Nivelles to elucidate the acoustic impact of different maneuvers of a commercial quadcopter drone and provide a dataset for applying the proposed methodology. Far-field microphone measurements were performed in a reverberant test hall, whose acoustic behavior was investigated and characterized. The facility is equipped with a system of tracking cameras that make it possible to accurately determine the drone’s location during the maneuvering. The results achievable with the proposed methodology can eventually be employed to define acoustic regulations for drone flight in populated areas and better understand the sound emissions radiated during the different flight conditions, which is instrumental for designing optimized sound-control strategies.