Recovering speech from vibrations of a potato-chip bag

Washington Post : Video footage of a potato-chip bag, the surface of a liquid in a glass, or the leaves of a potted plant can reveal what is being said by people speaking nearby. As people talk, the sound waves strike objects in the vicinity and cause them to vibrate. Researchers at MIT have been working to capture those tiny vibrations on film and, through the use of an algorithm, convert them to an audio signal. Interestingly, an ordinary digital camera can be used because of a design quirk called rolling shutter , which captures scenes by recording visual information one row of photodetectors at a time and assembling the rows into a single image, rather than taking a snapshot of the entire scene at once. “It kind of turns a two-dimensional low-speed camera into a one-dimensional high-speed camera,” says Abe Davis, coauthor of the group’s paper, which will be presented at this year’s Siggraph computer graphics conference.