Researchers reconstruct human speech by recording a potato chip bag

This, plus a camera and computer, is all you need to listen to remote sounds.

Flickr user TheFoodJunk

Watch enough spy thrillers, and you'll undoubtedly see someone setting up a bit of equipment that points a laser at a distant window, letting the snoop listen to conversations on the other side of the glass. This isn't something Hollywood made up; high-tech snooping devices of this sort do exist, and they take advantage of the extremely high-precision measurements made possible with lasers in order to measure the subtle vibrations caused by sound waves.

A team of researchers has now shown, however, that you can skip the lasers. All you really need is a consumer-level digital camera and a conveniently located bag of Doritos. A glass of water or a plant would also do.

Good vibrations

Despite the differences in the technology involved, both approaches rely on the same principle: sound travels on waves of higher and lower pressure in the air. When these waves reach a flexible object, they set off small vibrations in the object. If you can detect these vibrations, it's possible to reconstruct the sound. Laser-based systems detect the vibrations by watching for changes in the reflections of the laser light, but researchers wondered whether you could simply observe the object directly, using the ambient light it reflects. (The team involved researchers at MIT, Adobe Research, and Microsoft Research.)