Alex Constantine - July 29, 2008
MEDUSA: Microwave crowd-control raygun
As part of the U.S. Navy's investigation into futuristic nonlethal weaponry, the Sierra Nevada Corporation is building a microwave energy pulse gun that can produce a painful screaming sound inside a person's head from a long distance away. The inescapable sound, which is inaudible to untargeted bystanders, can be set to irritate, nauseate or even incapacitate people and animals that lie within range. Future applications may include crowd control, military use and even incapacitate people and animals that lie within range.
Future applications may include crowd control, military use and even shopping mall security, provided it proves safe from permanent side effects.
The science behind it also has the potential to give hearing to certain deaf people, or even projecting voices into peoples' heads.
The Sierra Nevada corporation has signed a contract with the U.S. Navy to follow up on successful recent testing of a non-lethal crowd control weapon that uses microwaves to project high-intensity sounds in the heads of targets, according to New Scientist magazine.
The MEDUSA (Mob Excess Deterrent Using Silent Audio) system makes use of the well-established Microwave Auditory Effect, in which microwave stimulation causes parts of the ear around the cochlea to expand thermally, which is interpreted as sound by the brain. The effect is a sound that appears to originate in the target's head, and can't be heard by anyone not directly in the beam's path.
This is not to be confused with Raytheon's Active Denial System, another crowd control weapon in development which uses a similar directed energy beam to cause unbearable but non-damaging heat pain in the top few layers of a target's skin.
Because MEDUSA's sound doesn't vibrate the eardrum itself, and thus the eardrum is not exposed to the damage potential that loud acoustic noise produces, traditional noise level limits don't have to apply with the MEDUSA system. So it's possible to dial in any level of sonic deterrent from mildly annoying up to physically and mentally incapacitating levels that the target has no way of blocking out of their head.
The MEDUSA system has the ability to be aimed at specific targets, multiple targets or even cover large areas with a broad beam, which will make it an effective security deterrent for the perimeters of protected areas. The same technology, on a smaller scale, could be used as an invisible sonic scarecrow to keep certain areas free from birds, as birds appear to respond to very low levels of microwave audio.
There are certain side effects - in 1961 testing of the first Microwave Auditory Effect system, Allen H. Frey noted dizziness, headaches and pins and needles in his subjects - and little is known about what further effects might occur when power levels are turned up to an incapacitating level. The potential for serious neural damage can't be ignored when you're effectively microwaving the inside of somebody's head - and if it does turn out to be lethal, the research may continue down that path and the technology may end up being used as a microwave death ray.
Beyond being used to generate an annoying high-pitched scream, the Microwave Auditory Effect has shown itself to hold interesting peacetime possibilities if it can be proven safe. By modulating the projected frequency, Sharp and Grove showed in 1975 that it's possible to "plant" voices, music and other sounds directly into the head.
Because the eardrum is not involved in the transmission of this sound, there have been hopes that patients with outer ear problems might be able to listen to music or voices through microwave transmission. On a more sinister note, it's easy to see how one might abuse the ability to direct "voices" straight into a person's head, as would appear to be feasible using the device described in this 2002 patent.
Still, the MEDUSA system is expected to be testable within one year and a mobile deployment unit built within another 18 months. And if it can be proven not to be harmful, it could be deployed within a few years in warzones, protest situations and shopping malls.
IEEE Spectrum Online
The MEDUSA crowd control ray gun we reported on earlier this month sounded like some pretty amazing—and downright scary—technology. Using the microwave auditory effect, the beam, in theory, would have put sounds and voice-like noises in your head, thereby driving you away from the area. Crowd control via voices in your head. Sounds cool. However, it turns out that the beam would actually kill you before any of that happy stuff started taking place, most likely by frying or cooking your brain inside your skull. Can you imagine if this thing made it out into the field? Awkward!
“Any kind of exposure you could give to someone that wouldn’t burn them to a crisp would produce a sound too weak to have any effect,” said Kenneth Foster, a bioengineering professor at the University of Pennsylvania. Foster knows what he's talking about, too. In 1974 he published the first research on the microwave auditory effect.
Fellow scientist and microwave research author Bill Guy agrees, citing some hard facts to support his conclusions:
Guy says that experiments have demonstrated that radiation at 40 microjoules per pulse per square centimeter produces sound at zero decibels, which is just barely in hearing range. To produce sound at 60 decibels, or the sound of normal conversation, requires 40 watts per square centimeter of radiation. “That would kill you pretty fast,” Guy says. Producing an unpleasant sound, at about 120 decibels, would take 40 million W/cm2 of energy. One milliwatt per square centimeter is considered to be the safety threshold.
Both scientists were in agreement about one other thing too: the MEDUSA just morphed from a crowd-control device into a monstrous weapon. We need more of those, right?