Acoustic sensor tech detects drones outside line of sight

German researchers have developed an intelligent solution that uses acoustic sensor technology to detect drones even when outside the line of sight. Furthermore, the technology can be combined with radar, camera and LiDAR to form a complete system.

When a drone (also known as an unmanned aerial system, or UAS) approaches a security-critical area without permission, it poses a potential threat — and as optical sensors, radio and radar can be disrupted by terrain, weather or technical measures, they cannot always reliably detect approaching drones.

Now, researchers at the Fraunhofer Institute for Digital Media Technology IDMT have developed an integrated acoustic sensor solution for drone detection and localisation that fills a crucial gap: it ‘hears around corners’.

Unlike purely optical and radar-based methods, which rely on line of sight, the technology enables drone operations to be detected even in built-up or forested areas. Furthermore, acoustics can be combined with radar, camera and LiDAR to form a robust sensor data network.

Fibre-optic-controlled drones or autonomous flying objects often remain hidden from radio reconnaissance, while high-resolution radar and camera systems require high costs and energy-intensive computing power. The acoustic solution from Fraunhofer IDMT, on the other hand, operates with low energy consumption, enabling autonomous operation with rechargeable batteries. The ability to wake up additional sensor components after acoustic contact also offers advantages.

The technology can achieve 360° coverage. Depending on the noise environment, the detection and localisation ranges are between 50 and 200 m, with a temporal resolution of one second. An extension to other acoustic events, from vehicles to gunshots, is conceivable. Thanks to their high availability, the acoustic sensors can be deployed across large areas.

“With our acoustic technology, we offer an inexpensive and low-maintenance addition to existing drone detection systems,” said Christian Rollwage, Head of Audio Signal Enhancement at Fraunhofer IDMT.

The target customers for the new technology are primarily companies in the defence and security sector that are already developing drone detection systems based on radar, optics or LiDAR, as well as system integrators who want their own sensor technology and drone manufacturers who want to detect signals from the air.

Image ©Fraunhofer IDMT/Leona Hofmann