Not in sight, but within earshot: Fraunhofer IDMT’s solution detects and locates drones outside the field of vision using intelligent acoustic sensor technology. Photo: Fraunhofer IDMT/Leona Hofmann

Fraunhofer IDMT in Oldenburg has developed an intelligent sensor solution that detects drones even outside the line of sight. The acoustic detection 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 authorisation, it poses a potential threat. In some cases, optical sensors, radio and radar are disrupted by terrain, weather or technical measures and cannot reliably detect a drone.

The Fraunhofer Institute for Digital Media Technology IDMT in Oldenburg has developed an integrated acoustic sensor solution for drone detection and localisation. In view of the increasing threat posed by unmanned aerial vehicles in security-critical areas, the system fills a crucial gap: it can ‘hear around corners’. Acoustics can be combined with radar, camera and lidar to form a robust sensor data network. 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 wooded areas.

Since 2016, the Hearing, Speech and Audio Technology department has been advancing the acoustic detection of drones in the publicly funded joint projects AMBOS (BMBF) and ALADDIN (H2020). Twelve partners led by the Fraunhofer Institute for Communication, Information Processing and Ergonomics FKIE were involved in the AMBOS project. For ALADDIN, 18 partners from nine European countries joined forces, including the CS Group as project manager. The algorithms and system components were continuously refined in numerous internal projects. Today, in addition to easily integrable algorithms for detecting and localising UAS, researchers can also draw on a fully integrable system solution.

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 metres, 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 a wide area.

‘With our acoustic technology, we offer an inexpensive and low-maintenance addition to existing drone detection systems,’ explains Christian Rollwage, group manager for ‘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.

Fraunhofer IDMT has published a video on its YouTube channel about the detection and localisation of drones:

PROFILE: Hearing, Speech and Audio Technology HSA at the Fraunhofer Institute for Digital Media Technology IDMT in Oldenburg

Founded in 2008 under the direction of Prof. Dr. Dr. Birger Kollmeier and Dr. Jens-E. Appell, the Hearing, Speech and Audio Technology HSA division of the Fraunhofer Institute for Digital Media Technology IDMT stands for market-oriented research and development with a focus on

• speech and event recognition
• sound quality and speech intelligibility, as well as
• mobile neurotechnology and systems for networked healthcare.

With their expertise in the development of hardware and software systems for audio system technology and signal enhancement, the employees at the Oldenburg site translate scientific findings into customer-oriented, practical solutions. Through scientific collaborations, the institute is closely linked to Carl von Ossietzky University, Jade University of Applied Sciences and Emden/Leer University of Applied Sciences. Fraunhofer IDMT is a partner in the ‘Hearing4all’ cluster of excellence and in the ‘Hearing Acoustics’ collaborative research centre. Further information is available at www.idmt.fraunhofer.de/hsa.