How does a doorbell button make a chime sound?

An electromechanical door chime has a button, an electrical supply, a coil and a movable metal plunger. Pressing the button completes a circuit. Current through the coil creates a magnetic field.

The field pulls the plunger toward a different position. As it moves, the plunger can strike a metal sound bar. The bar vibrates, setting nearby air vibrating and making the sound we hear.

A spring helps return the plunger when the circuit opens and the magnetic pull decreases. Some chimes strike a second bar during that return, giving a familiar two-note sound. The moving plunger and the vibrating bar have different jobs.

The button does not send sound through the wire. It controls an electrical connection that starts movement at the chime. This is one way to turn a small action at a doorway into a signal that people elsewhere in a building can hear.