Ho John Lee’s Weblog

Although there’s no working system described in any articles I can find about this, the patent application that goes with this is filed on behalf of NASA, so it might not be total vaporware.

From Audio DesignLine:

At last, you think that you have a secure room for conversations. No windows to bounce laser beams off as a means to eavesdrop. The doors are sealed and air tight. But don’t rest too easy. Now there’s a new way of snooping using Gigahertz waves.
…
Reflected electromagnetic signals can be used to detect audible sound. Electromagnetic radiation reflected by a vibrating object includes an amplitude modulated component that represents the object’s vibrations. The new audio interception method works by illuminating an object with an RF beam that does not include any amplitude modulation. Reflections of the RF beam include amplitude modulation that provide information about vibrations or movements of the object. Audio information can be extracted from the amplitude modulated information and used to reproduce any sound pressure waves striking the object. Interestingly enough, the object can be something as unlikely as a piece of clothing. Thus, something as intensely personal as your heart beat can be intercepted by reflected RF waves in addition to audio sounds.

More from New Scientist, discussion at Slashdot, Bruce Schneier (see comments)

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