You can also listen for audio simply by measuring any vibrating surface with a laser. Which goes all the way back to the late 40s, used by the USSR. |

Fun fact, it was invented by Leon Theremin. The inventor of the Theremin.

Yup: https://news.mit.edu/2014/algorithm-recovers-speech-from-vib...

https://en.wikipedia.org/wiki/The_Thing_(listening_device) is a fun read for people who haven't seen it before