U.S. Marines with Battalion Landing Team, 1st Battalion, 6th Marine Regiment, 22nd Marine Expeditionary Unit (MEU), hold riot shields to prevent injury during a simulated riot at Camp Lejeune, N.C., Jan. 22, 2016. The Marines participated in the course to ensure mission readiness and to improve their ability to maintain control during a riot. (Credit: U.S. Marine Corps)
The alleged attack on U.S. State Department officials in Cuba has made weapons that use sound a national conversation.
Acoustic weapons are not just in the arsenals of countries unfriendly to America. The U.S. military and American companies have developed some of the best of this kind of sonic weaponry.
Like rubber bullets, acoustic weapons tend to fall within the category of “non lethals” or “less lethals.” The general idea is that they exploit the sense of hearing to apply force in a way that will stop a target, but without causing permanent harm or taking a life.
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The LRAD sound cannon is one of the better-known acoustic weapons designed to disperse crowds or disable a hostile target. It emits bursts of loud, irritating sounds that can discourage violent behavior.
Aside from being annoyed from an ear walloping, those targeted can also experience effects like headaches and nausea.
Sound as ammo
Since acoustic weapons use sound, these weapons deliver what could be described as “invisible” attacks.
One interesting twist in acoustic weaponry is Raytheon’s research into a "sonic shield." Towards the end of 2011, Raytheon filed a very interesting patent for this weapon.
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Both shield and weapon
The Sonic Shield looks and functions like the riot shield that military and law enforcement use - but this shield is also a weapon.
Typically, acoustic weapons use sound against a target’s sense of hearing. But rather than target the ear, this acoustic weapon targets the lungs.
It would unleash this invisible “ammo” in a way that can cause the sensation of suffocation. So if you were a target, you would suddenly have a sense of suffocation but have no idea what was causing it – because the beam can not be seen.
The user can choose the intensity and unleash the invisible acoustic “ammo” at a level meant to warn and deter through to one intended to “temporarily incapacitate.”
Blasting wall of sound
According to the patent, Raytheon also aimed for a bunch of shields to be able to coordinate and work together to deliver a wall of sound.
The networked shields would provide a powerful combined beam. One shield could be designated as the lead or "master" shield, with the others being subserviant. The master shield would direct and coordinate the beam patterns.
A team of shields would deliver a more sophisticated beam with better power, range than the capabilities of a single shield.
For example, they could be used to create a more effective perimeter in a large riot scenario when trying to contain a dangerous situation.
How does it work?
The sonic shield looks and functions like a riot shield. It is a fortified “shell” with one side for the user and the other to face the target.
There is an acoustic horn as well as a sonic pulse generator built into the physical shell of the shield. This sonic pulse generator creates the acoustic pulses that blast out through the horn directed at the target.
When the user fires, the shield triggers the sonic pulse generator to generate a shot. The shot can include a burst of multiple pulses at a repetition rate fixed (or varied) for each of three settings: Warn, Stun or Incapacitate.
The shield could also be equipped with a sensor that measures the distance to the target. If the target moves, then the weapon could automatically adjust to maintain the same pressure.
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Heads up display for targeting
From behind the shield, the user can manage targeting and firing using a Heads Up Display (HUD). It could provide visual targeting, beam width and other data to the operator.
The HUD, for example, could provide color-coded “target-of-interest” dots indicating how effective a blast would be.
It could tell the user which target is closest and warn if a target is moving out of range.
The patent also details another targeting option, head-tracking goggles. Worn by the shield user, the goggles would follow the user’s head movements and display the most likely achievable beam in three dimensions.
What does it do to human targets?
According to the research presented in the patent, the sound waves emitted from the shield won’t damage eardrums. The shield does not merely make a loud noise.
Raytheon submitted in the patent that the company had conducted extensive testing to ensure safety.
Through testing on human subjects, the company identified thresholds for the three settings. Raytheon cited “warn/discomfort” at approximately 172 decibels, “stun/disorient” at approximately 176 decibels and “incapacitate” at approximately 182 decibels in the patent.
Their research showed that a pain threshold occurs at approximately 145 decibels.
Eardrum rupture threshold for overpressure events shorter than 400 milliseconds occurred at approximately 185 decibels.
The lung damage threshold ranged from 194 decibels to 205 decibels, depending on duration ranging from 3 milliseconds to 400 milliseconds.
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Safety features
The shield could incorporate a range of safety features to prevent accidental firing, firing by unauthorized persons or firing too close for safety.
For example, the shield may be provided with a biometric interface that would restrict firing to only the programmed user. This would prevent someone from picking up a shield and blasting away.
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