0:07:05 > 0:07:08This is Blue Peter but mini!
0:07:08 > 0:07:10Expect epic adventures,
0:07:10 > 0:07:11makes, bakes,
0:07:11 > 0:07:13badges, pets,
0:07:13 > 0:07:14presenters and your post.
0:07:14 > 0:07:18We've only got five minutes so get ready for your Blue Peter adventure.
0:07:18 > 0:07:21- Hi!- This is one of my favourite experiments...- Can't wait!
0:07:21 > 0:07:24- You look excited.- ..because this combines music and fire.
0:07:24 > 0:07:25Firstly, let's have a look at the piano.
0:07:25 > 0:07:27- Linds, you play the piano, right?- Sometimes.
0:07:27 > 0:07:30- Just give us a tinkle of the old ivories there.- OK.
0:07:30 > 0:07:32- So, just anything?- Yeah, anything.
0:07:32 > 0:07:33- Beautiful.- Tchaikovsky.
0:07:33 > 0:07:36Now, if you just hit one note for me, just one key. That's it, yes.
0:07:36 > 0:07:39So what's happening is you're actually moving a lever inside
0:07:39 > 0:07:42and it's causing this little hammer here to hit against the string.
0:07:42 > 0:07:44- Ah, OK.- And that causes that string to wiggle,
0:07:44 > 0:07:46it causes it to vibrate and it wiggles,
0:07:46 > 0:07:48it vibrates the air around it as well
0:07:48 > 0:07:51and that then vibrates the air molecules next to that
0:07:51 > 0:07:53and the ones next to that, all the way to your ear.
0:07:53 > 0:07:54Wow, that's how we hear it?
0:07:54 > 0:07:57- Yeah, if you think about dropping a stone into a pond.- Yeah.
0:07:57 > 0:07:59You drop it in and then you get ripples coming out,
0:07:59 > 0:08:01all those water molecules are vibrating the ones next to it.
0:08:01 > 0:08:03You get a wave.
0:08:03 > 0:08:06Sound is exactly the same but it's a wave in air, not water.
0:08:06 > 0:08:09- Ah!- So how exactly do you hear that wave though?
0:08:09 > 0:08:10How does it travel into your ear?
0:08:10 > 0:08:13So it comes towards your ear, that wave of sound,
0:08:13 > 0:08:17and it gets funnelled down into your ear canal here
0:08:17 > 0:08:20- and then it hits your eardrum, which I can pull out - ugh!- Gross!
0:08:20 > 0:08:23It sets your eardrum vibrating as well
0:08:23 > 0:08:26and then your eardrum actually vibrates all these little bones
0:08:26 > 0:08:29next to it and causes some fluid in your inner ear to vibrate
0:08:29 > 0:08:30and that sends a signal to your brain.
0:08:30 > 0:08:31So it's all about
0:08:31 > 0:08:34that sound is a wave and it's a series of vibrations.
0:08:34 > 0:08:36- Every time we hear something all of that goes on?- Amazing!
0:08:36 > 0:08:39- Unbelievable.- But I want to actually have a look at some sound.
0:08:39 > 0:08:42I know what you're thinking, "Greg, hang on a minute.
0:08:42 > 0:08:44"Sound travels through air, you've just said that,
0:08:44 > 0:08:47- "but air is invisible. How are we going to see this?"- Absolutely.
0:08:47 > 0:08:49Well, I don't want to put it through air, I want to put it through gas.
0:08:49 > 0:08:51- Yes!- Flammable gas.
0:08:51 > 0:08:53THUNDER RUMBLES
0:08:53 > 0:08:56- I love it.- Yeah!- OK.
0:08:56 > 0:08:59I'll never get bored of that but please don't try this at home,
0:08:59 > 0:09:00- for goodness' sake, stay safe. - Yeah.- Yeah.
0:09:00 > 0:09:02So, this is known as a Rubens' tube
0:09:02 > 0:09:05and at the end here I've got a speaker, and the speaker's
0:09:05 > 0:09:07- attached to a microphone that I've put inside the piano.- OK.
0:09:07 > 0:09:10- So just give us a few notes, a few chords.- Just anything?
0:09:10 > 0:09:13- Yeah. You can see it's dancing around.- What's happening?
0:09:13 > 0:09:17So what's happening is the speaker is vibrating back and forth
0:09:17 > 0:09:19and it's setting off those vibrations, a sound wave,
0:09:19 > 0:09:21all the way through the tube, but I've been clever,
0:09:21 > 0:09:23I've blocked the tube at the other end
0:09:23 > 0:09:27so the waves actually bounce back and they mix up inside the tube.
0:09:27 > 0:09:31Now, if we hit the perfect note on the piano we're going to be able to
0:09:31 > 0:09:35- freeze that sound wave made of fire in midair.- Wow!
0:09:35 > 0:09:38- So that's what we're going to try. - This is ridiculous, let's do it.
0:09:38 > 0:09:40So give us a low note if you can, please.
0:09:40 > 0:09:42- Let's start with a low note.- Like...
0:09:42 > 0:09:45- There we go.- Yeah, that's good. Lovely.
0:09:45 > 0:09:47Now what you can see is we've actually got a peak and a trough
0:09:47 > 0:09:49and a peak and a trough and a peak
0:09:49 > 0:09:53so we've got a wave kind of frozen in midair. Remember that one.
0:09:53 > 0:09:56- OK.- Now go to a higher note, jump right up.- Higher...
0:09:56 > 0:09:59- Oh, yeah.- There, there.- Perfect!
0:09:59 > 0:10:03So you get a peak and a peak and a peak and a peak
0:10:03 > 0:10:06so now the waves are a lot smaller, they're like that compared to
0:10:06 > 0:10:09being like that, like they were before, and this is all sound is.
0:10:09 > 0:10:13Music is just a series of waves. Big, long waves - a low note.
0:10:13 > 0:10:17Short, little waves are high notes, easy as that.
0:10:17 > 0:10:20There's actually something I've seen that's pretty cool
0:10:20 > 0:10:23and it's where you can use sound to actually break glass.
0:10:23 > 0:10:26- Can I put you on the spot? - Just a bit!
0:10:26 > 0:10:30- OK, so this is theoretically possible, right?- OK.- It can happen.
0:10:30 > 0:10:35- Yeah.- But it is so, so hard to try. - Is it?- Especially on a live show.
0:10:35 > 0:10:37- But I thought, why not try it?- Do it anyway. It's Blue Peter, isn't it?
0:10:37 > 0:10:40So what we need is a singer, a singer who can sing really,
0:10:40 > 0:10:43- really loudly.- Right. - We can do that.
0:10:43 > 0:10:45And hit a note and keep that note really perfect.
0:10:45 > 0:10:48- OK, well, that rules us out. - We can't do that, can we?- No.
0:10:48 > 0:10:51So I think we should welcome in a scientific singer, it's Helen.
0:10:51 > 0:10:53APPLAUSE
0:10:53 > 0:10:55- Hello, Helen.- Hello. - Welcome to the show.
0:10:55 > 0:10:57Thank you for coming on Blue Peter today.
0:10:57 > 0:11:00- Absolute pleasure to sing for science.- So here's the thing.
0:11:00 > 0:11:04If Helen was to sing actually at the glass like this,
0:11:04 > 0:11:08it could smash and that's dangerous so what I've done is I've set up
0:11:08 > 0:11:11a speaker here and I've put the glass above the speaker.
0:11:11 > 0:11:14So Helen's voice is going to go into that microphone,
0:11:14 > 0:11:17it's going to travel through to the speaker, speaker's going to vibrate,
0:11:17 > 0:11:19it's going to make the air vibrate
0:11:19 > 0:11:20and it's going to set the glass vibrating.
0:11:20 > 0:11:23- But she can't just hit it with any old note, right?- Uh-oh.
0:11:23 > 0:11:25This is the note that she's trying to go for.
0:11:25 > 0:11:28- If you flick a glass very carefully... - GLASS VIBRATES
0:11:28 > 0:11:30That is the note that a glass likes to vibrate with.
0:11:30 > 0:11:32Don't try that at home, OK? It's proper dangerous.
0:11:32 > 0:11:34You can flick a glass, you get a perfect note,
0:11:34 > 0:11:36we call that its natural frequency.
0:11:36 > 0:11:39Now, I've actually flicked this glass earlier and worked out
0:11:39 > 0:11:43that note that you need to hit this with and this is that note.
0:11:43 > 0:11:46NOTE PLAYS
0:11:46 > 0:11:49- OK?- Oh, yeah.- Now, I've put a ping- pong ball inside and that shows you
0:11:49 > 0:11:51when the glass is vibrating.
0:11:51 > 0:11:52The ball won't smash the glass, all right?
0:11:52 > 0:11:55It's Helen's voice that's going to smash the glass. So, guys...
0:11:55 > 0:11:58- Helen, do you think you can do this? - It's live, you get one chance.
0:11:58 > 0:12:01- I'm ready, is the glass ready? - Yes!- Yes, I like that answer.
0:12:01 > 0:12:04- Ear protection, eye protection, guys.- OK.- Helen's all set as well.
0:12:04 > 0:12:07We should say one more time - do not try this at home.
0:12:07 > 0:12:10Helen is a pro, as is Greg, so please don't do this at home.
0:12:10 > 0:12:13- Right, here we go. - So, Helen, here's your tone.
0:12:13 > 0:12:17NOTE PLAYS, HELEN HUMS
0:12:19 > 0:12:31# Ah... #
0:12:31 > 0:12:34- CHEERING - Yes!
0:12:34 > 0:12:36- My goodness, Helen!- You legend. Awesome!
0:12:36 > 0:12:40That was amazing, Helen, well done!
0:12:40 > 0:12:43- Wow!- Wow!- That is the power of sound.
0:12:44 > 0:12:47Join in every Thursday on CBBC.