UAV Noise Emission—A Combined Experimental and Numerical Assessment

Noise emission will be a significant obstacle to the widespread uptake of unmanned aerial vehicles or UAVs. The assessment and mitigation of UAV noise will require validated modelling approaches. The European Union has recently mandated an UAV sound power measurement procedure based on a procedure for measuring machinery or equipment. It is not clear if this legally mandated noise assessment will provide useful data for environmental noise modelling of UAVs. This research aimed to determine the sound power level of a UAV according to the legally mandated ISO 3744 and to investigate the suitability of commercial implementations of ISO 9613 for modelling noise emission from UAVs. A class C1 UAV was used for the investigation which also included controlled flyover tests. Several different operating conditions were measured and modelled and the results compared. The small scale UAV used had a sound power of 86.8 dB (A) and modelled flyover tests agreed with experimental values within ±2.1 decibels at distances up to 30 m and within angles of 45–90° of the receiver. The validated model was then used for a case study of UAV noise emission in an urban setting. The model demonstrated the potential for UAV noise emission to significantly exceed urban background noise levels by up to 10 dB. It was found that flight altitude relative to building height had a significant impact on the number of allowable UAV operations within WHO LDEN guidelines