[R] How a quartz watch works

That is done too. It works in both directions. What you're describing is a microphone. A quartz crystal is vibrated and it generates an electric signal. If you play that electric signal back into the crystal it reproduces the sound, aka a speaker. The design of the two change obviously to improve quality for their purpose, but if you have a headset or something with a 3.5mm jack with separate mic/speaker inputs, try plugging them in the opposite way. Your mic will start playing sound and your speaker will produce input when it hears things.