MB Civic

    * 17:06 03 July 2008
    * NewScientist.com news service
    * 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
recognisable sounds.

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.

Scarecrow beam?

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 eardrums.

“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 of
Defence.

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