Why does the car horn sound twice when opening the door?

[DelOlive]

The car horn sounds twice when opening the door because the vehicle was locked with the remote but not unlocked with it, causing the car to automatically enter anti-theft mode. Conditions for the vehicle automatically entering anti-theft mode: If the car door is opened but not locked, and the key isn't turned on within a certain period, the vehicle will automatically activate the anti-theft system. Working principle of car horns: An automotive electric horn produces sound through the vibration of a metal diaphragm. It consists of an iron core, electromagnetic coil, contacts, armature, and diaphragm. When the driver presses the horn button, current flows through the contacts to the coil, generating magnetic force that pulls down the armature and forces the diaphragm to move. The armature movement then breaks the contacts, interrupting the current and eliminating the coil's magnetism. The diaphragm returns to its original position along with the armature due to its own elasticity and the spring plate, allowing the contacts to close again and restart the circuit. This cycle repeats continuously, causing rapid diaphragm vibrations that produce audible sound.