How does a large car horn produce sound?
3 Answers
Car electric horns produce sound through the vibration of metal diaphragms. Horn composition: An automotive electric horn consists of an iron core, magnetic coil, contacts, armature, diaphragm, etc. When the driver presses the horn switch, current flows through the contacts to the coil, generating a magnetic force that pulls down the armature and forces 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 again and allowing current to flow through the coil once more, repeating the cycle. Horn classification: Automotive horns are divided into air horns and electric horns based on their sound power; by shape, they are classified into cylindrical, spiral, and disc types; and by frequency, they are categorized into high-pitch and low-pitch horns.
I've always been fascinated by mechanical principles, and the way car horns produce sound is quite interesting. It relies on the coordinated action of an electromagnet and a vibrating diaphragm. When you press the horn button on the steering wheel, electric current flows to the coil inside the horn, turning it into an electromagnet that attracts the armature. The armature is connected to the diaphragm, pulling it downward and causing it to instantly tighten and deform. Then the current is cut off, the electromagnet loses its magnetic force, and the diaphragm snaps back due to its own elasticity. This pull-and-release motion creates vibrations. The diaphragm can vibrate hundreds of times per second, and the vibrating air is amplified by the horn's trumpet-shaped resonator, producing the loud 'honk' sound. It's similar to how a drum produces sound when its head vibrates, except the car uses electromagnetic force instead of a drumstick.
I learned a few tricks from an auto mechanic before. The horn operation mainly depends on the electrical system. When you press the steering wheel, the button contact closes the low-voltage circuit, and the current first passes through the relay. This relay acts like a high-current switch—once it engages, it sends the high-voltage electricity from the battery to the horn. Inside the horn, there's a copper coil that generates a magnetic field when energized, pulling the central metal reed to repeatedly strike the resonance plate. The striking frequency is extremely fast, around 400 times per second. Additionally, modern cars are equipped with dual-tone horns, where high and low-pitch horns sound simultaneously, blending into a highly penetrating warning tone. If the horn stops working, it's most likely due to burnt relay contacts or a broken horn coil.
