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  • 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

Why do horns and musical instruments have this flared shape. To answer this question about a year ago

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世界最大のホーンがガラスを砕く (World's Largest Horn Shatters Glass)

  • 11 0
    彭成豪 に公開 2021 年 01 月 14 日
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