Acoustic Characterization of a Multi-Rotor SUAS as a First Step Towards Detection and Identification via Acoustic Signature

Abstract

In this study, the noise produced by a multi-rotor aircraft is recorded and characterized with the main goal to understand the signature for the use of detection and identification. The need for this technology spawns from multiple situations where sUAS are being used with malicious intent to perform illegal acts, such as delivering contraband to prisoners. The aircraft of choice is a small unmanned aerial system, the 3DR Iris+. The aircraft is tested in multiple different testing environments as well as different setups to investigate specific parameters and how they affect the acoustic signature of the system. The parameters under inspection are the following: rotor RPM, the number of rotors, distance and angle of microphone array from the noise source, and the environment. The aircraft is shown to be detectable in all the testing environments, while there are promising results for the identification. The results indicate that there are potential effects on the signature due to the aircraft structure, however, this requires further investigation. Also, there is no apparent effect on fundamental acoustic signature due to the environment. The significant factors that arise from this study are the operational state of the aircraft and the microphone location (or the directivity of the noise source). The results show that as the angle between the rotor plane and the microphone increases so does the overall sound pressure level of the system.