Login / Register

How Do Car Horns Work?

Thanks! Share it with your friends!


You disliked this video. Thanks for the feedback!

Sorry, only registred users can create playlists.

Channel: BrainStuff - HowStuffWorks
Categories: Science   |   Technology  
 Find Related Videos  added


The next time you honk your car horn at that jerk who cut you off, you’ll understand how it uses physics to get the job done.

Learn more at

Share on Facebook:
Share on Twitter:
Visit our site:

My name is Lauren. My world is fire and blood. Once, I honked the horn of my Interceptor Pursuit Special.

It was hard to know who was more crazy… me… or everyone else.

No, really. When people honk car horns they’re pretty freaking aggressive. Research shows we’re more likely to do it when it’s hot outside, when it’s a weekday… and if you’re male. That’s right, war boys.

Here in the U.S., your run-of-the-mill car horn is 110 decibels of sustained noise. While the vehicle horns of yesteryear had different combinations of notes, today they’re mostly regulated to sound the same. And the law requires you to have a car horn.

If they’re so important, let’s talk about how car horns work.

Typical car horns these days are electromechanical. There are two horns per vehicle, usually, each sounding at a different pitch to produce a chord.

These horns generally consist of a spring steel diaphragm, a coiled wire, a switch, and housing that amplifies sound like a megaphone. All of this is mounted somewhere behind your vehicle’s grille.

So, when you slam your hand on that steering wheel button with the little trumpet symbol? It sends an electrical current through a relay and on to a copper coil that supplies electricity to the horn.

To create such a loud sound takes a lot of energy. In fact, the only accessory that uses more juice in your War Rig is the starter.

The electrical current surging into the horn creates a magnetic field. This field causes the flat, circular diaphragm inside to oscillate.

The oscillation is set up by the diaphragm flexing to its mechanical limit and then releasing back past its neutral position, only to be pulled forward again.

This functions by using the basic law of elasticity, also known as “Hooke’s Law” because it was formulated in the 17th century by an English scientist named Robert Hooke.

The law states that “the strain of a body is proportional to the stress applied to the body.” What this means for the car horn is that its diaphragm will oscillate continuously as long as the current is applied.

There are also other types of horns used in vehicles: air horns, klaxons, whistles similar to organ pipes, and even sirens like we see on emergency vehicles. But the electromagnetic car horn is the most common one you’re going to find out there in the Wasteland.

Popular Science 1951

Post your comment


Be the first to comment