London, July 4 : Researchers at a US-based company have invented a microwave ray gun, which can beam sounds directly into people's heads.
Lev Sadovnik of the Sierra Nevada Corporation has revealed that the device called 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.
The researcher says that a series of pulses can be transmitted to produce recognisable sounds.
Although the company has made the device for military or crowd-control applications, Sadovnik says that it may have other uses too.
Sadovnik says that the microwave auditory effect MEDUSA involves is "loud" enough to cause discomfort or even incapacitation.
According to him, normal audio safety limits do not apply because the sound does not enter through the eardrums.
"The repel effect is a combination of loudness and the irritation factor. You can't block it out," New Scientist magazine quoted him as saying.
As regards MEDUSA's non-military applications, Sadovnik says that birds seem to be highly sensitive to microwave audio, and thus the new technology may be used to scare away unwanted flocks.
James Lin, a researcher in the Department of Electrical and Computer Engineering at the University of Illinois in Chicago, believes that MEDUSA is feasible in principle.
He says that impressed by his own work on the technique, the music industry once discussed with him how to use microwave audio to enhance sound systems.
"But is it going to be possible at the power levels necessary?" he asked.
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. You might see neural damage," Lin said.
Sierra Nevada says that a demonstration version could be built in a year.