A group of researchers from Adobe, Microsoft, and MIT have recovered audio from a video of a vibrating bag of potato chips. The algorithm developed by the researchers was also able to recover audio from videos of a plant, a bag of candy, and a pair of earbuds. The reason this works is that sound waves cause nearly imperceptible vibrations in whatever they hit. Using high-speed photography, the researchers were able to capture these vibrations and translate them into actual sound despite having no recording of the original stimulus in the video.
The researchers presented their findings at the recent SIGGRAPH 2014 conference. More on the work and resulting paper is available at MIT.