Microwave ray gun controls
crowds with noise
Microwave ray gun controls crowds
by David Hambling
A US company claims it is ready to build a microwave
ray gun able to beam sounds directly into people's heads.
The device - dubbed MEDUSA (Mob Excess Deterrent Using
Silent Audio) - exploits the microwave audio effect, in which short microwave
pulses rapidly heat tissue, causing a shockwave inside the skull that can
be detected by the ears. A series of pulses can be transmitted to produce
The device is aimed for military or crowd-control applications,
but may have other uses.
Lev Sadovnik of the Sierra Nevada Corporation in the
US is working on the system, having started work on a US navy research
contract. The navy's report states that the effect was shown to be effective.
MEDUSA involves a microwave auditory effect "loud"
enough to cause discomfort or even incapacitation. Sadovnik says that normal
audio safety limits do not apply since the sound does not enter through
"The repel effect is a combination of loudness and
the irritation factor," he says. "You can't block it out."
Sadovnik says the device will work thanks to a new
reconfigurable antenna developed by colleague Vladimir Manasson. It steers
the beam electronically, making it possible to flip from a broad to a narrow
beam, or aim at multiple targets simultaneously.
Sadovnik says the technology could have non-military
applications. Birds seem to be highly sensitive to microwave audio, he
says, so it might be used to scare away unwanted flocks.
Sadovnik has also experimented with transmitting microwave
audio to people with outer ear problems that impair their normal hearing.
Brain damage risk
James Lin of the Electrical and Computer Engineering
Department at the University of Illinois in Chicago says that MEDUSA is
feasible in principle.
He has carried out his own work on the technique, and
was even approached by the music industry about using microwave audio to
enhance sound systems, he told New Scientist.
"But is it going to be possible at the power levels
necessary?" he asks. Previous microwave audio tests involved very "quiet"
sounds that were hard to hear, a high-power system would mean much more
powerful - and potentially hazardous - shockwaves.
"I would worry about what other health effects it is
having," says Lin. "You might see neural damage."
Sierra Nevada says that a demonstration version could
be built in a year, with a transportable system following within 18 months.
They are currently seeking funding for the work from the US Department
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