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? [IEEE Spectrum Online]