Name: 世界上最大的喇叭打碎了玻璃。 (World's Largest Horn Shatters Glass)
Uploaded: 2021-01-14T11:18:45.000Z
Duration: 10 min 42 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

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

情態副詞

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

which shows there's more going on here than just focusing the sound in one direction

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

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

This actually isnt it, its that. The idea, now you can learn

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

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

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

That's the first time we've actually fired off and that's behind the horn

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

Yeah, we could hear it now we're a little nervous cuz you can hear it decently well

So for our second test we drove about a mile(1.6 Km) away and you can barely see the horn right here

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

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: 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

字幕列表影片播放

世界上最大的喇叭打碎了玻璃。 (World's Largest Horn Shatters Glass)

description

scale

effective

barely