UAV Passive Acoustic Detection

The proliferation of low-cost consumer Unmanned Aerial Vehicles (UAV) has enabled their potential nefarious use or negligent misuse, including intrusion into airspace used by emergency services or civilian aircraft, unauthorized surveillance, and delivery of harmful payloads. Passive acoustic sensors may permit the creation of low-cost means of detecting and localizing the unwanted UAV traffic. Experiments were conducted to characterize the emitted noise of UAVs of various sizes in an anechoic chamber while airborne and demonstrate the processing required to detect and find the direction toward the sound. An array of microphones arranged in two circular tiers, each with a radius of 1 meter, separated by 1.6 meters vertically was used for data collection in the tests at a local airport. Algorithms based on Generalized Cross-Correlation (GCC) were applied for direction finding including fusing time difference of arrival and steered power response with phase transform (SRP-PHAT). Detection distances of 294 m for the smallest UAS tested were demonstrated. An algorithm for tracking moving sources using microphones separated by about 19 meters was demonstrated, addressing the decorrelation due to the Differential Doppler effect.