[Cryptography] "The Visual Microphone: Passive Recovery of Sound from Video"

[Sergio Lerner]

Incredible!
Also you can recover the audio by filming an object with a camera, and
then recording the high-frequency sound the camera makes while filming
the object with a microphone, and then detecting the EM radiation of the
microphone with a radio, and finally detecting the temperature
fluctuations of the radio with a thermostat.  :)

Seriously, very interesting work.