You can use a window or any large panel as a microphone without even touching it by observing its vibrations. You can bounce a laser off it, or even go fully p

You can use a window or any large panel as a microphone without even touching it by observing its vibrations. You can bounce a laser off it, or even go fully passive using a camera with some sensitivity tricks: I recall a paper that reconstructed a remote conversation by watching a houseplant through a window.