Microflown Technologies BV

over the world. The sensors have properties which make them beneficial for the defence industry, as source (target) locating sensors, enhancing situational awareness.

The particle velocity sensors can be used as extremely compact Acoustic Vector Sensors (AVS), capable of detecting, localising, identifying and tracking sound sources in 3D space.

Microflown’s sensors are already established in the automotive industry, but the Dutch company has now secured their bridgehead in battlefield acoustics, in the detection of gunshots, mortars and aircraft.

The Breakthrough

At any point in space, a sound field can be described completely by its two dimensions. The scalar value sound pressure is well known and well measured. But the other quantity in acoustics, the vector value acoustic particle velocity, only recently became a directly measurable quantity with the invention of the Microflown sensor.

Acoustic Vector Sensor

Acoustic Vector SensorAssembling a sound pressure transducer and three orthogonally placed Microflown sensors in one single point, a very compact (5x5x5mm) AVS can be created. The amplitude differences across the Microflown sensors provide the direction and elevation of sound sources.

Merging and Improving Existing Systems

Until now, acoustic detection systems have been used for the detection of either snipers, or artillery and mortars.

Acoustic vector sensors merge the performance of these systems whilst improving their performance, e.g. in terms of improved detection range and lower susceptibility to meteorological conditions, and especially improved elevation measurements, as AVS are not susceptible to ground reflections like traditional systems are.

This allows Microflown Technologies to develop a system which incorporates gunshot localisation, artillery localisation and additionally, aircraft and vehicle tracking, all in one compact and lightweight package.

3D Situational Awareness

Quite some progress has been made in detecting a large number of sound sources simultaneously in a 3D space. AVS also allow the amplitude information of the sound field to be exploited, allowing improved source separation while drastically reducing the footprint of a traditional acoustic detection system.

3D Sniper Detection

3D Sniper DetectionGiven the AVS’ small size and weight, extremely compact and light-weight man or rifle mounted sniper detection systems can be realised.

AVS can detect small arms fire up to 2km distance, and, as they are less susceptible to ground reflections and echoes, can be used for sniper detection in an urban environment.

The maximum value can be extracted from the presence of a fully networked walking array (soldier mounted).

Rockets, Artillery and Mortars

In addition to gunshots, and as was proven on several European firing ranges, AVS are able to detect the launch and impact positions of mortars and artillery with high accuracy up to 10km.

Passive Radar

Particularly in uninhabited areas, border lines are difficult to protect against low flying aircraft. An autonomous version of the AVS was developed for that purpose, capable of detecting the speed, direction and altitude of a low flying airplane or helicopter.

Kept in a dormant mode to save power until alerted by a sound source, the AVS incorporates local processing and as such, needs to transmit only very small data packets to command & control.

An example scenario was an aircraft detected and localised during a measurement on a shooting range, with shooting noise from numerous weapons in both south west and north east locations, and with a truck engine idling nearby.

Using newly developed software algorithms which can separate static and transient sources, the gunshots and truck engine noise were automatically removed from the audio signals, so only the aircraft signal remained.

Analysis of the aircraft signal showed the bearing, elevation, speed and closest approach distance of the propeller driven airplane.

Using such a system, an array of AVS nodes with around 10km intermediate spacing can be used to create an acoustically tight perimeter or border protection system that works unmanned, at close range (where normal radars can struggle) and under all weather conditions.

Intelligence, Surveillance and Reconnaissance (ISR) + Sense & Avoid for UAVs

Due to its light weight and compact size, AVS can be incorporated in even the smallest UAV for the purpose of intelligence, surveillance and reconnaissance, capable of detecting acoustic events and steering the UAVs other sensors. The AVS have the ability to detect gunshots and artillery on the ground, and even tell whether the gunshots are aimed at the UAV or not, all despite the presence of both wind and the UAV’s own engine noise.

Aside from the detection of ground based acoustic events, AVS can be used as a mid-air anti collision system, detecting any flying objects approaching the UAV from any direction, so long as they make noise of course. Using novel signal processing techniques, a large number of sound sources around the UAV can be simultaneously localised, and if necessary, can be avoided.


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