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World’s Largest Horn Shatters Glass

I might upgrade my car horn to this. Shoutout to Portal from Facebook for their support on this video. Learn more and get yours at:

Watch the What’s Inside video here:

Here is a behind the scenes video from the day:

High Speed camera courtesy of They rent high speed cameras at killer prices. Hit them up.

ELI20 version: I answered why you want a large outlet area but not necessarily why it curves like that. Anytime you have a sudden change in cross-sectional area in the horn you will get waves reflecting back at the source. You don’t want that because that is wasted energy that could have moved forward. Even if it goes from a small cross-section to a larger, if you do it suddenly you get those wasted waves. So you want the horn to basically be asymptotic at the exit so you never have a jump in discontinuity when it exits to the wide open air. So a directors cone isn’t as good as the curved shapes I showed because it still has the sudden change when it dumps into the open air.

0:10- Arrow- Andrew Applepie –
1:08- Dance- Danijel Zambo-
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7:30- Ceral Killa- Blue Wednesday –
8:47- Q- Blue Wednesday –
9:46 Too Happy to be cool by Notebreak-

Summary: I made a huge horn and broke glass with it and explored why horns are shaped the way they are.

They are soft-



I make videos like this once a month all year long while supplies last:





Video transcription:

Why do horns and musical instruments have this flared shape. To answer this question about a year agoI decided I would take this and scale it up to thisBut I've never actually made something this big for my channel before so as usual we decided to make a smaller prototypeModel to see what we could learn about the challenges that would come from scaling it all the way upSo we started by creating a plaster mold with the right curvaturethen you cover that with a gel coat and then we put three layers of fiberglass andPolyester resin and then when you pop it out of the mold, you're left with thisWe're immediately struck that there is in fact something really special about this shapeSo I'm going to switch over from my lav mic to my shotgun mic for this demoHere's my voice's my voice while using the tubewhich shows there's more going on here than just focusing the sound in one directionHere's my voice using the hornYou can even hear me whisper… which is creepySo this was proof that the curved shape of the horn had a significant effect on amplifying the input soundBut I still wasn't sure why, so now it's time to really scale things up to the big monster hornWhich we did by applying all the same principlesWe learned on the prototype and then we headed to the most desolate location we could find on Google Maps to put it together[Some cool music]Mark's assistant: "Can you hear me"Mark's assistant: "Hello over there!"Mark: "It feels like you're like right on my shoulder"As you know, the base of the horn is what's responsible for creating all the sound so to see what's insideI thought it was only appropriate to open it with my friends Dan and Lincoln from the popular YouTube channelWhat's Inside. And it turns out it's pretty simple: the key is this thin metal circular plate or diaphragm.So the air comes in here at 100 psi and passes around this diaphragm in such a way that it causes it to vibrate110 times in a second which causes a corresponding pressure wave to shoot out here and down the throat of the hornSo after a few hours, everything was finally set up and it was the moment of truth since after 8 monthsNone of us had actually ever heard it fire yet and Lincoln hadn't even seen the thing because we made him wait in the carMark: "This is the big reveal"Mark: "You Ready?"One two, here it is[high pitched air horn]Isn't that pretty loud?Lincoln: "Wow, that's so cool!"This actually isnt it, its that. The idea, now you can learn[Lincoln:] Oh my!Before we fire itWe need to first talk about how hearing works and what I eventually learned about why horns have that curved shapeLet's say this jello block represents a volume of air molecules if that horn diaphragm hits the jello molecules over hereThere's a chain reaction of jello molecules crashing into each otherUntil finally you see movement on the other side of the jello block and this is where your eardrum isSo it moves back and forth at the same rate as the horn diaphragm because of all of thesecollisions of the jellomolecules in betweenthis is called a pressure wave and it's how sound travels through air and so if the horn diaphragm is hitting the air molecules atA high frequency or very frequently our brain decodes that as a high pitchBut if the crashes are happening at a low frequency or less frequently than our brain decodes that as a low pitch. OkayBut why the curvy horn shape? Well that has to do with something called impedance matchingBasically, the horn diaphragm is very solid and strong and it pushes against the air which doesn't offer much resistanceIt's not very effective like trying to break a piece of paper by punching itSo without the curvy horn portion as the diaphragm moves back and forthIt interfaces with the air sort of like this. You can still see the jello is moving on the opposite sideJust not that much because the air is just too thin and weak over this small of an areaSo to have a better interface with the air you put a big curvy shape right after the diaphragmYou can see now your eardrum is moving back and forth much more vigorously because the interface is so much betterso the sounds louder with a curved horn not because you're amplifying the sound but because you're conserving the sound this makes sense becauseAmplifying means you're adding power to the system and there's no battery or plugs at the curve section of a hornIt's passiveSo by impedance matching you give yourself a much larger area to push against all the air at the outlet which makes for a moreeffective chain reaction of molecules crashing into your eardrumAnd now the hornIsn't that pretty loud?Lincoln: "Wow, that's so cool!"Is that pretty good?This actually isnt it, its that. The idea, now you can learn[LOUD Horn sound][LOUD Horn sound][laughter]Oh my goshJust like eight months of workThat's the first time we've actually fired off and that's behind the hornDan: I could feel the vibrationsYeah[?] be in front of that thingWe're gonna go see what it's like on the other side. All rightSo this is we're about two football fields away from the horn. We have no idea how loud this is gonna sound hereAll right Ken, fire the normal air horn(Air horn firing)Yeah, we could hear it now we're a little nervous cuz you can hear it decently wellAlright, firing[BIG horn firing][laughs]So for our second test we drove about a mile(1.6 Km) away and you can barely see the horn right hereAlright, Ken fire.[Air horn firing]Lincoln: We can still completley hear it, that's crazyYou can hardly see that massive horn, but it's still super loud. So let's just drive keep goingWe're gonna go real farSo from satellite viewThis is where the horn wasHere was the first spot and then the second spot and then here was the third spot two and a half miles[4 Km] awayOkay, so the horn is now super far away. I literally can't see with my naked eye.Dan: It's so far awayDan: I can barely see it. It's right at the crest of the hill. There's a little tiny speck and it's right thereWe're gonna do an experiment and we're gonna test the speed of soundWe should hear it on this walkie-talkie and then some amount of time laterWe might be able to hear it from this distanceLincoln's gonna measure the time on his stopwatch and then we should be able to calculate from there what the speed of sound isWe're ready when you arbwowwwwwwwwwww[temporary silence ]Mark:Wait for itVmmmmmmmmThat's crazy! How long. It took 11 secondsfor the sound of the horn to get hereIt's so clear. Like I feel like we can go 10 miles furtherThink about what this means?It took an unbroken chain of two and a half miles of air molecules 11 seconds to all collide with each otherUntil they made it all the way down here and bumped into the air molecules in our ear canals which then bumped into our eardrumsHi!Wait, what if I scream?[Screams]So the Sun was quickly going downBut before we went homeWe wanted to try and break some glass and if you want to break glass with what is essentially little puffs of air the trickIs to find out its resonant frequency. You actually know all about thisIf you've ever used one of these I can make Eliza go really highWith just a little force now if I apply that force at random intervals, it doesn't do very much. It's not fun, huh?No, it's not funBut if I apply that force equal to the timing of the natural frequency of the swing those little pushes add to each otherGo higher Mark RoberAnd so in this case the resonant frequency increased our fun, but if engineers don't take this into considerationIt could lead to disaster such as when wind gusts going at just the right rate destroy the Tacoma Narrows BridgeIt's also why soldiers don't march in unison when crossing a bridgeSo if you measure the natural frequency of the glass with an accelerometer like thisThen you just need to make sure your horn fires at that exact frequency or a multiple there ofOr you can just change the natural frequency of the glass to match your horn by adding weights in the right spot[Glass break]Shoutout to Lincoln and Dan from What's Inside for helping me out. We actually investigatedWhat's inside an old Japanese air-raid siren for their video?It's a totally different way to make a really loud soundSo you should go check that out using the link in the descriptionThis horn is easily the largest thing I've ever built for my channel and it took eight months of coordination with my former NASAbuddy Ken to pull it offThe problem is that Ken lives way down here by NASA but I live 400 miles up this waySo I partnered with Portal from Facebook to better collaborate on the design and build processSo he put a portal in his workshop and I set up a portal plus in mine and besides the high fidelity audioAnd the HD video. I think the coolest thing about portal is the smart camera feature, which you see in action hereSo as I would move around my workshop and Ken moved around his the camera frames the video to keep us both centered and thisIs great for us because we're notconstantly moving the cameras around or tied to just working in one spot and smart sound enhances our voices as we move about so weCan still hear each other regardless of other shop noise[Diaphragm drop off][Laugh]And of course when it comes to any device in a home, privacy is a big dealSo with a single tap portal will allow you to disconnect both the camera and the microphone or if you prefer an analog solutionThey provide a camera coverAlso, the smart camera uses AI technology that runs locally on portal not on some remote servers.At the end of the day, it's a great piece of hardware and it worked really well for usSo if you want to learn more about Portal or maybe even get your own just go ahead and use the link in the video description.Thanks for watchingDon't forget to Like, comment down below and subscribe for more


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