Acoustic Intelligence (ACINT)

For military forces protection, acoustic wave’s detection and processing can be key assets when no other detection clues are available.
It is the case obviously, since a long time in surface and underwater warfare, with the use of Sonars.
However, it is also the case for land forces and rotary wing air platforms used by land or air forces. To be efficient in many complex environments, these acoustic protection equipment need a processing type of the same kind of the one used in smart Electromagnetic Identification in dense and complex environments (such as “fingerprinting”).
To be able to distinguish a real threat out of a complex acoustic noisy environment, to identify the signature of a detected target with a low false alarm rate, the need of databases containing huge numbers of pre-recorded environments is key.
This is where ACINT becomes a key differentiator for the effectiveness of this protection.

ACINT is applied mainly in two different fields of modern warfare:

• UNDERWATER WARFARE:
  The acoustic signature of a surface ship or submersible is its identity card.
  We can find two types of signatures.
  The first is typical of the class of submarine (or surface vessel) to which the detected vessel belongs (this is justified by the fact that being built one after the other, the ships carry the same types of propulsion or energy generation equipment which makes them recognizable).
  The second is the typical signature of a ship or submarine; this signature differs from that of other ships in its class in the particularity of the ship.
  For example, a propeller cast slightly differently or with a defect on one of the blades will make that ship identifiable compared to others in its class that do not have that particular signature.

  • Submarines: Gone are the days when submarines were essentially sailing on the high seas.
    Today, submarines are increasingly occurring near coasts, in shallow waters, in complex and disturbed acoustic environments.
    Their missions are even more diversified: coastal surveillance, communications interception, intelligence.
    This change in employment conditions requires very high-performance acoustic systems in order to give the submarine the means to carry out its missions in the best conditions of safety and efficiency.
    These systems incorporate high-performance acoustic sensors.
    The combination of subsystems such as bow sonar, flank, obstacle avoidance, interception, and towed passive sonar allows the construction of solutions to ensure a panoramic view of the underwater environment to detect, locate and classify all short, medium and long-range targets and threats over a wide range of frequencies.

  • Surface ships: Variable Immersion Sonars (or Variable Depth Sonars) can detect, locate and classify increasingly stealthy and efficient submarines under all environmental conditions.

  • Mine Warfare ships: These systems consist of Hull Sonars, Variable Depth Sonar, and Synthetic Aperture Towed Sonar.

• SITES AND ARMY PLATFORMS PROTECTION

  • Sniper detection:
    Detection of enemy fire is an application of ACINT in the battlefield.
    Such acoustic equipment measures the shock wave at the exit of the gun barrel.
    The soldier can spot in a fraction of a second the origin of the shot, and thus retaliate by aiming.
    The drawback of this solution is that detection takes place after the fire has started.
    To anticipate the danger, a multi-spectral sensor with a data fusion engine can be used to locate the sniper before he fires.
    It is the coupling between acoustic detection and infrared cameras, seismic sensors or laser detectors (to spot the bezel of a rifle), which allows to obtain a highly efficient alert and anticipation system, with a low rate of false alarm, and reaction times compatible with the implementation of counter-measure and adapted response.
    The principles of this acoustic equipment are based on the comparison between two acoustic waves emitted by the ball, to determine its direction and the quality of the wave. An algorithm then compares the received wave with a huge catalogue of sounds, which allows knowing precisely what type of weapon it is.
    It is a kind of “enhanced ear” that allows to know where the enemy fire came from, and from what weapon.
    Being a man-portable equipment, it can be carried by the soldier anywhere in the field.

  • Protection of vehicles:
    protection of heavy and light armoured vehicles, as well as armoured police vehicles is available in the form of acoustic networks mounted on the roofs of vehicles.
    Such a system may also include a screen showing the origin and identification of the shot.
    It is operating during combat attacks with multiple threats such as small arms fire, RPGs and mortars.

  • Protection of sensitive sites:
    ground versions have also been designed to protect sensitive sites, whether permanent or temporary.
    A mission system following the monitoring approach offers a configurable and scalable suite consisting of 1 to 20 acoustic networks.
    The number of acoustic networks depends on the area to be covered.
    Data from the system and its sensors include GPS location of the threat, as well as azimuth, elevation and range.
    They can be deployed to improve surveillance and security of sensitive sites and events.
    These systems can be used in several types of operational configurations: military FOB, Border Control Post, Embassies, Personality Gatherings.

  • Protection of helicopters:
    helicopter crews are often the target of fire during missions, sometimes without even being aware of the threat until it is too late.
    This type of acoustic detection equipment (hostile fire acoustic indicator) is also used for the protection of helicopters.
    It warns pilots of the source of the shots, in less than a second, so that they can either take evasive action or engage.
    This system can be used as an autonomous hostile fire detection system or in conjunction with other threat warning systems to provide a comprehensive threat awareness capability.

In the context of the underwater missions developed above, we see the contributions of signal digitization (also seen in the fields of SIGINT and IMINT), and new information processing technologies (AI, deep learning, big data) both in terms of hardware (use of massively parallel computational techniques, as for High Performance Computing), and in terms of software.

These same needs and solutions are fully applicable for ground systems and the issue of fire detection, for the protection of ground vehicles, air vehicles (helicopters in particular) and sensitive sites.

Through ACINT, environmental and signature databases, powered by data collected during previous missions, are stored and processed to improve, mission after mission, the performance of on-board acoustic detection systems and contribute to force protection.