Make that "every vibrating surface can be a potential microphone ..."

The laser on a hotel window experiment comes to mind.

	▲	srean an hour ago \| parent \| next [-]
		Or an adapted Theremin https://en.wikipedia.org/wiki/The_Thing_(listening_device)
	▲	spyder an hour ago \| parent \| prev [-]
		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