April 2012

Rheinmetall Defence Electronics develops advanced Acoustic Shooter Locating System

Special microphones protect soldiers against ballistic threats

Military activities frequently involve noise. So what could be more obvious than to use noise to locate the source of action?

Over the years, Rheinmetall Defence Electronics (RDE) in Bremen has acquired a wealth of experience with the acoustic detection, localisation and classification of different noise sources that are of relevance from a military standpoint. The latest result of such efforts is the Acoustic Shooter Locating System (ASLS).

ASLS was developed to enhance the ballistic protection of vehicle crews. Practical experience has shown that the crew in the vehicle is often not aware of fire from individual snipers – frequently because personnel inside the vehicle are separated from the ambient noise. The objective of related development activities supported by the German Bundeswehr was therefore to design an automatic shooter locating system.

Microphone antenna for locating shooters (left) and Situational Awareness System (SAS) with compact ASLS variant (right)

Microphone antenna for locating shooters (left) and Situational Awareness System (SAS) with compact ASLS variant (right)

Rheinmetall Defence Electronics was able to draw on its long-standing experience with acoustics for reconnaissance applications: ranging from classical artillery localisation to the detection and tracking of low-flying helicopters that are difficult to acquire by radar or opto-electronically, through to spatially distributed and networked acoustic sensor systems for the reconnaissance of vehicle movement in the terrain.

ASLS is based on microphones since two distinct acoustic occurrences are automatically associated with gunfire: the muzzle blast and the projectile blast. The muzzle blast occurs as soon as the projectile leaves the barrel; in flight, the projectile itself produces a projectile blast – if and for as long as it is travelling at ultrasonic speed. Microphones reliably register both these sounds.

Microphone antenna for locating shooters

Microphone antenna for locating shooters

A compact microphone antenna was developed and tested especially to allow localisation of shooters. This antenna has eight special microphones designed for very high sound pressure levels. Conventional microphones cannot detect the sonic boom of the projectile sufficiently well. Combined with signal processing, the RDE design reaches 360° coverage by relatively simple means.

Data acquisition and signal processing are performed by a compact, energy-efficient electronic evaluation system, integrated with an accumulator in the base of the microphone antenna (also referred to as a cylinder antenna due to the cylindrical arrangement of the microphones). This design also allows lengthy mobile or dismounted operations, independent of the vehicle. The signal evaluation routine based on proven sonar processes like directional procedures allows high-precision localisation (direction and distance) of shooters. The false alarm rate is low, even in the disrupted zone around the vehicle.

Energy-efficient electronic assembly integrated both in the vehicle and in the hand-held variant

Energy-efficient electronic assembly integrated both in the vehicle and in the hand-held variant

Individual system performance features are definitely superior to the human ear. ASLS can, for instance, perceive frequency ranges beyond the hearing ability of individuals. The system can also reliably register momentary events in the millisecond range, and is thus able to detect the two blast events even in the presence of high ambient noise levels – something that the human hear is incapable of.

ASLS is additionally equipped with integrated attitude sensors and a compact GPS sensor. These sensors are used to detect and compensate for vehicle movement so that the shooter position on the control and display panel remains accurate

even while the vehicle is on the move. The display incorporates a history feature that enables ready access to previous events, enabling the subsequent evaluation of all recent events.

Thanks to the extreme energy efficiency of the electronic and signal processing components, power consumption is much less than one watt.

When a shot is fired, the ASLS alerts the crew acoustically and visually so that it is not necessary for personnel to concentrate on the system all the time. The result provided includes exact azimuth, elevation and range data.

ASLS users are already kept busy with routine jobs. The demands on intuitive operation were therefore high. The user is given various display options: either on an independent control unit that can also be used as a mobile unit, or by means of an integrated display on a C4I device. Symbol displays in electronic devices (augmented reality) are likewise possible.

Shoulder-mounted shooter locating device

Shoulder-mounted shooter locating device

Thanks to the flexible design, the system can easily be fitted in small or non-military vehicles. The same applies to the adaptation of the microphone antenna. Since the evaluation electronics and accumulator pack are integrated in the antenna base, additional integration tasks like e.g. connection to the vehicle’s electrical power supply are therefore not necessary although they are nonetheless possible.

ASLS offers high growth potential. A combination with opto-electronic components like the Situational Awareness System (SAS) will be available soon. A soldier-borne shooter detection device is being developed alongside the ASLS for vehicles and systems.

Hearing is important for soldiers when they stop and listen to their surroundings or listen and watch at night. The ASLS developed by Bremen-based Rheinmetall Defence Electronics supports and alleviates soldiers in the performance of their duties, thus enhancing the protection of life and limb.

RDE develops advanced Acoustic Shooter Locating System (ASLS) Special microphones protect soldiers against ballistic threats.

Over the years, Rheinmetall Defence Electronics (RDE) in Bremen has acquired a wealth of experience with the acoustic detection, localisation and classification of different noise sources that are of relevance from a military standpoint. The latest result of such efforts is the Acoustic Shooter Locating System (ASLS).

Gunnar Becker

Rheinmetall AG

Head of Press and Public Relations
Oliver Hoffmann
Rheinmetall Platz 1
40476 Düsseldorf
Germany
Phone: +49 211 473-4748
Fax: +49 211 473-4157

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