The Science of Sound Blue Peter Bite


The Science of Sound

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This is Blue Peter but mini!

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Expect epic adventures,

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makes, bakes,

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badges, pets,

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presenters and your post.

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We've only got five minutes so get ready for your Blue Peter adventure.

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-Hi!

-This is one of my favourite experiments...

-Can't wait!

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-You look excited.

-..because this combines music and fire.

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Firstly, let's have a look at the piano.

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-Linds, you play the piano, right?

-Sometimes.

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-Just give us a tinkle of the old ivories there.

-OK.

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-So, just anything?

-Yeah, anything.

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-Beautiful.

-Tchaikovsky.

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Now, if you just hit one note for me, just one key. That's it, yes.

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So what's happening is you're actually moving a lever inside

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and it's causing this little hammer here to hit against the string.

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-Ah, OK.

-And that causes that string to wiggle,

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it causes it to vibrate and it wiggles,

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it vibrates the air around it as well

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and that then vibrates the air molecules next to that

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and the ones next to that, all the way to your ear.

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Wow, that's how we hear it?

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-Yeah, if you think about dropping a stone into a pond.

-Yeah.

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You drop it in and then you get ripples coming out,

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all those water molecules are vibrating the ones next to it.

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You get a wave.

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Sound is exactly the same but it's a wave in air, not water.

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-Ah!

-So how exactly do you hear that wave though?

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How does it travel into your ear?

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So it comes towards your ear, that wave of sound,

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and it gets funnelled down into your ear canal here

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-and then it hits your eardrum, which I can pull out - ugh!

-Gross!

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It sets your eardrum vibrating as well

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and then your eardrum actually vibrates all these little bones

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next to it and causes some fluid in your inner ear to vibrate

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and that sends a signal to your brain.

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So it's all about

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that sound is a wave and it's a series of vibrations.

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-Every time we hear something all of that goes on?

-Amazing!

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-Unbelievable.

-But I want to actually have a look at some sound.

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I know what you're thinking, "Greg, hang on a minute.

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"Sound travels through air, you've just said that,

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-"but air is invisible. How are we going to see this?"

-Absolutely.

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Well, I don't want to put it through air, I want to put it through gas.

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-Yes!

-Flammable gas.

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THUNDER RUMBLES

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-I love it.

-Yeah!

-OK.

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I'll never get bored of that but please don't try this at home,

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-for goodness' sake, stay safe.

-Yeah.

-Yeah.

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So, this is known as a Rubens' tube

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and at the end here I've got a speaker, and the speaker's

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-attached to a microphone that I've put inside the piano.

-OK.

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-So just give us a few notes, a few chords.

-Just anything?

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-Yeah. You can see it's dancing around.

-What's happening?

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So what's happening is the speaker is vibrating back and forth

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and it's setting off those vibrations, a sound wave,

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all the way through the tube, but I've been clever,

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I've blocked the tube at the other end

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so the waves actually bounce back and they mix up inside the tube.

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Now, if we hit the perfect note on the piano we're going to be able to

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-freeze that sound wave made of fire in midair.

-Wow!

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-So that's what we're going to try.

-This is ridiculous, let's do it.

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So give us a low note if you can, please.

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-Let's start with a low note.

-Like...

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-There we go.

-Yeah, that's good. Lovely.

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Now what you can see is we've actually got a peak and a trough

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and a peak and a trough and a peak

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so we've got a wave kind of frozen in midair. Remember that one.

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-OK.

-Now go to a higher note, jump right up.

-Higher...

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-Oh, yeah.

-There, there.

-Perfect!

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So you get a peak and a peak and a peak and a peak

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so now the waves are a lot smaller, they're like that compared to

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being like that, like they were before, and this is all sound is.

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Music is just a series of waves. Big, long waves - a low note.

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Short, little waves are high notes, easy as that.

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There's actually something I've seen that's pretty cool

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and it's where you can use sound to actually break glass.

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-Can I put you on the spot?

-Just a bit!

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-OK, so this is theoretically possible, right?

-OK.

-It can happen.

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-Yeah.

-But it is so, so hard to try.

-Is it?

-Especially on a live show.

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-But I thought, why not try it?

-Do it anyway. It's Blue Peter, isn't it?

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So what we need is a singer, a singer who can sing really,

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-really loudly.

-Right.

-We can do that.

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And hit a note and keep that note really perfect.

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-OK, well, that rules us out.

-We can't do that, can we?

-No.

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So I think we should welcome in a scientific singer, it's Helen.

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APPLAUSE

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-Hello, Helen.

-Hello.

-Welcome to the show.

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Thank you for coming on Blue Peter today.

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-Absolute pleasure to sing for science.

-So here's the thing.

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If Helen was to sing actually at the glass like this,

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it could smash and that's dangerous so what I've done is I've set up

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a speaker here and I've put the glass above the speaker.

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So Helen's voice is going to go into that microphone,

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it's going to travel through to the speaker, speaker's going to vibrate,

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it's going to make the air vibrate

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and it's going to set the glass vibrating.

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-But she can't just hit it with any old note, right?

-Uh-oh.

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This is the note that she's trying to go for.

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-If you flick a glass very carefully...

-GLASS VIBRATES

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That is the note that a glass likes to vibrate with.

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Don't try that at home, OK? It's proper dangerous.

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You can flick a glass, you get a perfect note,

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we call that its natural frequency.

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Now, I've actually flicked this glass earlier and worked out

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that note that you need to hit this with and this is that note.

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NOTE PLAYS

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-OK?

-Oh, yeah.

-Now, I've put a ping- pong ball inside and that shows you

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when the glass is vibrating.

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The ball won't smash the glass, all right?

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It's Helen's voice that's going to smash the glass. So, guys...

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-Helen, do you think you can do this?

-It's live, you get one chance.

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-I'm ready, is the glass ready?

-Yes!

-Yes, I like that answer.

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-Ear protection, eye protection, guys.

-OK.

-Helen's all set as well.

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We should say one more time - do not try this at home.

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Helen is a pro, as is Greg, so please don't do this at home.

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-Right, here we go.

-So, Helen, here's your tone.

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NOTE PLAYS, HELEN HUMS

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# Ah... #

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-CHEERING

-Yes!

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-My goodness, Helen!

-You legend. Awesome!

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That was amazing, Helen, well done!

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-Wow!

-Wow!

-That is the power of sound.

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Join in every Thursday on CBBC.

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