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, and 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 with the tube to show that there's more going on here than just focusing the sound in one direction and then here's my voice using the horn. You can even hear me whisper, which is creepy, so this was proof that the curve 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.

Could you hear me hello over there? 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, danny 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 eight 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. This is the big reveal you ready, yeah one two here it is: is that pretty loud wow, that's so cool. Is that pretty good? This actually isn't hard? It's that, oh behind you now you can look, oh my god, but 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, then 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 jellos 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 inner face is so much better. So it sounds louder with the 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 curved 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 is that pretty loud wow, that's so cool.

Is that pretty good? This actually isn't hard, it's that behind you now you can look. Oh my gosh. This is like eight months of work. That's the first time we've actually fired off and that's behind the horn.

I could feel the vibrations yeah not even in front of the thing we're gon na 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 gon na sound here, all right, ken fire, the normal air horn yeah. We could hear it now we're a little nervous because you can hear it decently, well, all right firing.

So for our second test we drove about a mile away and you can barely see the horn right here, all right, ken fire. Now i mean you can hardly see that massive horn, but it's still super loud. So let's just drive, keep going all right. We're gon na go real far so from a 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 away. Okay, so the horn is now super far away. I literally can't see it with my naked eye. It's so far away like 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 gon na do an experiment and we're gon na 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 or lincoln's gon na 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 are okay, i'm ready wait for it. That's crazy! How long it took 11 seconds for the sound of the horn to get here? We can still hear it so clearly, 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. 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 elisa, 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, 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, destroyed 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 thereof. Or you can just change the natural frequency of the glass to match your horn by adding weights in the right spot, you're, so fun.