Piezo crystals are reversible transducers, so they can be used either as transmitters or receivers. High voltages are generated by rather small vibrations, but the impedance is very high so the generated current is tiny.
Piezo crystals are reversible transducers, so they can be used either as transmitters or receivers. High voltages are generated by rather small vibrations, but the impedance is very high so the generated current is tiny.