Acoustic Source Localization From Multirotor UAVs

In this article, we address the problem of acoustic source localization using a microphone array mounted on multirotor unmanned aerial vehicles (UAVs). Conventional localization beamforming techniques are especially challenging in these specific conditions, due to the nature and intensity of the disturbances affecting the recorded acoustic signals. The principal disturbances are related to the high-frequency, narrowband noise originated by the electrical engines, and to the broadband aerodynamic noise induced by the propellers. A solution to this problem is proposed, which adopts an efficient beamforming technique for the direction of arrival estimation of an acoustic source and a circular array detached from the multirotor vehicle body in order to reduce the effects of noise generated by the propellers. The approach used to localize the source relies on a diagonal unloading beamforming with a novel norm transform frequency fusion. The proposed algorithm is tested on a multirotor UAV equipped with a compact uniform circular array of eight microphones, placed on the bottom of the drone to localize the target acoustic source placed on the ground while the quadcopter is hovering at different altitudes. The experimental results conducted in outdoor hovering conditions are illustrated, and the localization performances are reported under various recording conditions and source characteristics.