The ding dong sound of the doorbells signifies the presence of someone at the door. Although there are many doorbells available in the markets today with a variety of sounds, the ding dong doorbell still has its share of the market. What makes them interesting is how do they produce this ding dong sound?The ding dong doorbells use the magnetic force produced by an AC solenoid to force an iron rod (called the plunger) to hit against aluminum sheets placed at both sides of the solenoid. This in turn produces the ding dong sound. The DC and AC solenoids are different. The doorbell uses an AC solenoid. When current flows thorough the coil of an AC solenoid, a magnetic field is produced. This magnetic field produces a magnetic force and pulls the plunger in its direction.