World's Largest Horn Shatters Glass

  Why do horns and musical instruments have this flared shape. To answer this question about a year ago I decided I would take this and scale it up to this But I've never actually made something this big for my channel before so as usual we decided to make a smaller prototype Model to see what we could learn about the challenges that would come from scaling it all the way up So we started by creating a plaster mold with the right curvature then you cover that with a gel coat and then we put three layers of fiberglass and Polyester resin and then when you pop it out of the mold, you're left with this We're immediately struck that there is in fact something really special about this shape So I'm going to switch over from my lav mic to my shotgun mic for this demo Here's my voice normal. here's my voice while using the tube which shows there's more going on here than just focusing the sound in one direction Here's my voice using the horn You can even hear me whisper... which is creepy So this was proof that the curved shape of the horn had a significant effect on amplifying the input sound But I still wasn't sure why, so now it's time to really scale things up to the big monster horn 

Which we did by applying all the same principles We 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 inside I thought it was only appropriate to open it with my friends Dan and Lincoln from the popular YouTube channel What'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 vibrate 110 times in a second which causes a corresponding pressure wave to shoot out here and down the throat of the horn So after a few hours, everything was finally set up and it was the moment of truth since after 8 months None of us had actually ever heard it fire yet and Lincoln hadn't even seen the thing because we made him wait in the car Mark: "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 it We need to first talk about how hearing works and what I eventually learned about why horns have that curved shape Let's say this jello block represents a volume of air molecules if that horn diaphragm hits the jello molecules over here 

There's a chain reaction of jello molecules crashing into each other Until finally you see movement on the other side of the jello block and this is where your eardrum is So it moves back and forth at the same rate as the horn diaphragm because of all of these collisions of the jello molecules in between this is called a pressure wave and it's how sound travels through air and so if the horn diaphragm is hitting the air molecules at A high frequency or very frequently our brain decodes that as a high pitch But if the crashes are happening at a low frequency or less frequently than our brain decodes that as a low pitch. Okay But why the curvy horn shape? Well that has to do with something called impedance matching Basically, the horn diaphragm is very solid and strong and it pushes against the air which doesn't offer much resistance It's not very effective like trying to break a piece of paper by punching it So without the curvy horn portion as the diaphragm moves back and forth It interfaces with the air sort of like this. You can still see the jello is moving on the opposite side Just not that much because the air is just too thin and weak over this small of an area So to have a better interface with the air you put a big curvy shape right after the diaphragm You can see now your eardrum is moving back and forth much more vigorously because the interface is so much better so the sounds louder with a curved horn not because you're amplifying the sound but because you're conserving the sound this makes sense because Amplifying means you're adding power to the system and there's no battery or  plugs at the curve section of a horn It's passive So by impedance matching you give yourself a much larger area to push against all the air at the outlet which makes for a more effective chain reaction of molecules crashing into your eardrum And now the horn Isn'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 gosh Just like eight months of work That's the first time we've actually fired off and that's behind the horn Dan: I could feel the vibrations Yeah [?] be in front of that thing We're gonna go see what it's like on the other side. All right So this is we're about two football fields away from the horn. We have no idea how loud this is gonna sound here All 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 well Alright, 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 here Alright, Ken fire. [Air horn firing] Lincoln: We can still completley hear it, that's crazy You can hardly see that massive horn, but it's still super loud. So let's just drive keep going We're gonna go real far So from satellite view This is where the horn was Here was the first spot and then the second spot and then here was the third spot two and a half miles[4 Km] away Okay, so the horn is now super far away. I literally can't see with my naked eye. Dan: It's so far away Dan: I can barely see it. It's right at the crest of the hill. There's a little tiny speck and it's right there We're gonna do an experiment and we're gonna test the speed of sound We should hear it on this walkie-talkie and then some amount of time later 

We might be able to hear it from this distance Lincoln's gonna measure the time on his stopwatch and then we should be able to calculate from there what the speed of sound is We're ready when you ar bwowwwwwwwwwww [temporary silence ] Mark:Wait for it Vmmmmmmmm That's crazy! How long. It took 11 seconds for the sound of the horn to get here It's so clear. Like I feel like we can go 10 miles further Think 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 other Until they made it all the way down here and bumped into the air molecules in our ear canals which then bumped into our eardrums Hi! Wait, what if I scream? [Screams] So the Sun was quickly going down But before we went home We wanted to try and break some glass and if you want to break glass with what is essentially little puffs of air the trick Is to find out its resonant frequency. You actually know all about this If you've ever used one of these I can make Eliza go really high With 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 fun But if I apply that force equal to the timing of the natural frequency of the swing those little pushes add to each other Go higher Mark Rober And so in this case the resonant frequency increased our fun, but if engineers don't take this into consideration It could lead to disaster such as when wind gusts going at just the right rate destroy the Tacoma Narrows Bridge It's also why soldiers don't march in unison when crossing a bridge So if you measure the natural frequency of the glass with an accelerometer like this Then you just need to make sure your horn fires at that exact frequency or a multiple there of Or 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 investigated What's inside an old Japanese air-raid siren for their video? It's a totally different way to make a really loud sound So you should go check that out using the link in the description 

This horn is easily the largest thing I've ever built for my channel and it took eight months of coordination with my former NASA buddy Ken to pull it off The problem is that Ken lives way down here by NASA but I live 400 miles up this way So I partnered with Portal from Facebook to better collaborate on the design and build process So he put a portal in his workshop and I set up a portal plus in mine and besides the high fidelity audio And the HD video. I think the coolest thing about portal is the smart camera feature, which you see in action here So as I would move around my workshop and Ken moved around his the camera frames the video to keep us both centered and this Is great for us because we're not constantly moving the cameras around or tied to just working in one spot and smart sound enhances our voices as we move about so we Can 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 deal So with a single tap portal will allow you to disconnect both the camera and the microphone or if you prefer an analog solution They provide a camera cover Also, 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 us So 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 watching Don't forget to Like, comment down below and subscribe for more