What is the principle of a car horn?

[GavinLynn]

Car horns work by the vibration of a metal diaphragm to produce sound. An automotive electric horn consists of an iron core, a magnetic coil, contacts, an armature, and a diaphragm. Here is a related introduction to car horns: 1. When the driver presses the horn switch, current flows through the contacts to the coil, generating a magnetic force that pulls the armature, forcing the diaphragm to move. The movement of the armature causes the contacts to open, interrupting the current and causing the coil's magnetic force to disappear. The diaphragm, along with the armature, returns to its original position under its own elasticity and the action of the spring plate, closing the contacts and completing the circuit again. Current flows through the contacts to the coil, generating magnetic force, and the process repeats. 2. This cycle repeats continuously, causing the diaphragm to vibrate and produce sound. The resonance board, rigidly connected to the diaphragm, makes the sound smoother and more pleasant (i.e., the principle of an electromagnet).