Detecting gunshots has always challenged the military and law enforcement agencies. Two principal approaches are used – detecting the acoustic signature of the gunshot and spotting the visible signature of the event. A new approach combining a new approach to acoustic detection, developed by the Dutch company Microflown Avisa has now matured and is introduced for use on unmanned aerial vehicles.
Microflown Avisa is displaying two applications of its gunshot detector at ISDEF 2011, an artillery fire locator capable of detecting artillery and mortars firing events at ranges of 30km and a new airborne gunshot detection system, that can be mounted on a mini UAV and offer detection ranges up to seven kilometers.
The proprietary Miniature Electro-Mechanical System (MEMS) vector sensor developed by Microflown measures temperature differences in the cross-section of two extremely sensitive heated wires, to determine acoustic particle velocity. Assembling three orthogonally placed sensors in one single point, a very compact acoustic vector sensor is produced. The integrated processor computes these parameters to provide bearing, and elevation at the firing source, at angular accuracy of 0.25-2 degrees. Further algorithms and additional acoustic vector sensor allows distance to be measured (by triangulation).
Actual performance depends on weather and humidity conditions, but the sensor can operate effectively even under 100% humidity as well as extreme high or low temperatures. The sensors can detect and report multiple sources of fire simultaneously, even in complex acoustic situations such as urban environments or on noisy platforms such as UAVs.
The company is now offering UAV acoustic sensors to equip miniature UAVs. At ISDEF Microflown highlights the sensor integrated on a Aerovironment Raven, offering effective situational awareness for small units operating the miniature drone. According to John Bremner, business development manager at Microflown, the sensor weighing about 200 grams can be best integrated in the mini UAVs employing pusher propellers, as it offers a clean environment for the system. The sensor can also be integrated on aerostats, typically operated on force protection missions.