This is quite possibly one of the creepiest videos I've seen in a very long time. Scientists can now create audio from the slight motion caused by sound waves found in videos.
With high speed video of an everyday object like a plant of a bag of chips, computers can see the microscopic movement that the sound on an object produces. This software can then turn this movement back into sound.
Luckily most people don't have ultra high speed cameras that can shoot a thousand frames per second laying around but you don't have to. The "rolling shutter" issue that plagues digital cameras can also give a computer enough information to reproduce sound. Soon, video cameras will be to film us in public places and by simply looking at the objects around us, hear what we are saying.