How Do Car Horns Work?

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.

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.

SOURCES:

Popular Science 1951

[VapidVulpes]

By far the most memorable time I used my horn was in an old Saturn sedan I used to have. I had never used the horn, and when I took it to get a safety check renewed, they asked me to honk it to make sure it worked, so I did, and the most pathetic, squeaky noise came meekly forth like a bashful rodent attempting to gain the attention of all present with a polite cough...

Everyone in the garage stopped what they were doing and took turns honking it. It was hilarious :-D! They even gave me the safety check even though technically they said I should think about getting it replaced lol.

[sokra]

anyone else skip ahead a few seconds to avoid seeing their ridiculous and cringe worthy intros?

[daviddebroux]

It took you one minute just to get to the point. That is way too long just to tell people how a car horn works.

A 30 second edgy intro does not tell people anything about car horns and how they work, and is way too damn long.

A 30 second into with facts that almost have nothing to do with the topic being discussed in this video is way too long.

One minute full of nothing is too long to get to the actual topic being discussed in the video. This is *not* how you engage your viewers; _that_ is how you *_draw them away_* .

[Jefftaylor]

After that painful intro I dont even want to know how a car horn works anymore.

[TheUltraPingu]

I feel like cars should come with a few different horns to mean different things. Sometimes I beep it to get someones attention, or when they're not paying attention and the lights change, but it's not aggressive like when someone almost hits your because they're not looking where they're going.

[american_aviation]

Fun fact: the two horn versions are dual-tone and single-tone, the dual tone makes a strong, and loud horn while the single tone does a meep.

[Ratimus_]

I still don't understand how a car horn works. She said the diaphragm will continue to oscillate as long as current is applied. But speakers don't work that way; you get deflection in ONE direction as long as current is applied. So there must be something mechanically interrupting the current when the diaphragm extends past a certain point, which allows it to travel back to its starting position and complete the circuit again. But if there is an explanation of this in the video I must have missed it. To say "it continues to oscillate as long as current is applied" seems to be about as valid an explanation as
Q: how does a radio work?
A: it plays music as long as it's plugged in

[mstrainjr]

Males are more likely to honk their horns? My mother must be an anomaly.

[nsowers]

Remember as a child whenever a semi truck and trailer were going past, you'd wildly pump your arm up and down in an effort to get the driver to pull his horn? Where did that originate?

[Loudbicycle]

Snail shell car horns will have a flexible diaphragm like the one you showed, but with a metal piece that fits inside the coil otherwise it wouldn't have much power, and its movement wouldn't flip the switch. It make sound because the diaphragm springs back when the current is disconnected by the motion. If you apply a continuous current then you don't get sound, you just get a stressed piece of un-moving metal. Also, the horn graphics you used are disk horns, they don't have a flexible diaphragm, theirs is rigid, and directly connected to the coil too. Disc horns are not shaped like a megaphone which is why they sound more tinny than snail horns which sound more musical.
I would also be glad to explain more. Looking forward to part 2!

[FNHot]

I never honk when someone does something stupid, I honk when Im behind you and the light goes green, and in your fantasy world a red light means "Im done driving, time to dig through my car for that thing i lost".

[thomasstilp]

Its good to know that if i want to know where the sound of a horn comes out of, i can find a 3 minute long video on the internet of a random lady talking about hooks law.

[dkcknivekismyid]

Didn't know I wanted to know how a car horn worked until I saw the thumbnail and thought to myself, "gee, how does it work?"

Great video :)

[publicmail]

Starter then horn for current usage not even close, where do they get there info?

[PikachuJackskeling]

I used mine today because someone was taking to long to go at a clearly green light that was safe to pass through. (Which was why I came to this video I started to wonder how they work.)

[ClassicTycoon]

You said it makes a chord. What chord does it make? C#dim?

[MsterFancyPants]

HONKING MY HORN LAST NIGHT DURING THE 2019 RAPTORS NBA CHAMPIONSHIP WIN BABY LET'S GOOOO

[Dooality]

00:53. A chord requires at least three different pitches, not two. I haven't looked at the comments yet but I'm sure as hell not the only one to have pointed this out.

[vintagesimplexfirealarmsof]

My simplex mechanical horn works same way but a Edwards adaptahorn is 112 db but diaphragm is flat

[satan]

You push the steering wheel and the Car farts