Every capacitor can be a potential microphone ...
Make that "every vibrating surface can be a potential microphone ..."
The laser on a hotel window experiment comes to mind.
Or an adapted Theremin
https://en.wikipedia.org/wiki/The_Thing_(listening_device)
with a high speed camera any vibrating reflective object like a potato chips bag can become a weak microphone if you have line of sight even behind a soundproof window: https://www.youtube.com/watch?v=FKXOucXB4a8
Make that "every vibrating surface can be a potential microphone ..."
The laser on a hotel window experiment comes to mind.
Or an adapted Theremin
https://en.wikipedia.org/wiki/The_Thing_(listening_device)
with a high speed camera any vibrating reflective object like a potato chips bag can become a weak microphone if you have line of sight even behind a soundproof window: https://www.youtube.com/watch?v=FKXOucXB4a8