1. A transducer consisting of a set electrode and a movable electrode, charged electrostatically in opposite polarity.

The motion of the movable electrode changes the capacitance between the electrodes and so makes the applied voltage change in proportion to the amplitude of the electrode's motion.

2. A transducer which consists of a capacitor, at least one plate of which can be set into vibration.

Its operation depends on the interaction between its electric field and a change in its electrostatic capacity.