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TVTranscript
00:30Hello and welcome to Sigma Nava.
01:00Five.
01:04Thank goodness for that.
01:10Now, welcome to the show.
01:12As you see, what's happened is I rushed in and my microphone wouldn't work so I had to throw it away.
01:16And then without using any sound at all, I got this chap here to think of the same number that I had written on the card.
01:22Well, he didn't do it, the girl on the end did.
01:24Now, something else you may have noticed, although I appear to be talking, my lips aren't moving.
01:29That's because this sound was pre-recorded.
01:31But we can all understand what I'm saying because we're all used to listening to disembodied voices.
01:36Either on the radio.
01:41On record, record, record, record.
01:44Or on the telephone.
01:46Bring, bring.
01:48Hello?
01:50Wrong number.
01:51Wrong number.
01:52Now, this is a television programme.
01:54And television sounds without pictures are no good at all.
01:57But...
01:59So if somebody will give me a microphone that does work, we'll get on with the show.
02:04Firstly, one, two, three.
02:07Albert.
02:08Can you hear me in the back?
02:09Yes!
02:10What a funny place to have your ears.
02:13This is a megaphone helping us all.
02:16And to tell you what's on the show, we'll be seeing sounds you can see and hearing our ears here.
02:22We'll also be listening to loud sounds and some sounds.
02:27And we'll be finding out how to turn sounds into numbers to produce better recordings
02:32and how to turn words into numbers to produce synthetic voices.
02:37So what do you think of it so far?
02:39No!
02:40I happen to hear that.
02:43That's because a megaphone works both ways.
02:45It amplifies your voice when you sense sound in this direction,
02:49but at the same time it helps you to hear better when you hold it that way.
02:52But how can that be?
02:54If sound volume improves going in that direction,
02:57how can sound improve coming in this direction?
02:59Well, it's the quality.
03:01And then...
03:02Well, look at this ear.
03:12This ear is a human ear.
03:14And as you can see, it's almost the same shape as a megaphone.
03:20What happens is this.
03:23Your outer ear captures as much sound as it possibly can and channels it into this thinner channel here.
03:31So it's condensed the sound.
03:33The sound then reaches your eardrum.
03:35And there's the eardrum.
03:37And the eardrum is so sensitive that it can detect vibrations of just one one millionth of a centimeter.
03:46Next, the sound passes through this area here where there are three bones.
03:50The hammer, the anvil, and the stirrup.
03:53And they amplify the sound by 20 times and then pass the sound through an even thinner channel where it reaches the cochlea.
04:03And that's a Latin word for snail shell.
04:05And you'll see why.
04:06Now, the cochlea takes the sounds and determines the pitch of each sound.
04:12Low notes are picked up at the entrance of the cochlea.
04:15But high notes are picked up at the very interior.
04:18And there are little hairs that can detect a vibration of one one hundred millionth of a centimeter.
04:28Something else interesting about the ear.
04:30The ear.
04:31And that's this tube here.
04:33It's called the eustachian tube.
04:36Not the eustachian tube.
04:38The eustachian tube.
04:39And it's connected to the back of your throat.
04:41And air passes up into the inner ear so that the air pressure is balanced on each side of the eardrum.
04:47But because the tube's there, sound travels up it as well.
04:51So when you listen to your own voice, you hear it two different ways.
04:55The sound comes out of your mouth and around the corner.
04:58Or it comes up the eustachian tube.
05:00But there's another way that you hear your own voice.
05:03Try this.
05:04Close your ears off.
05:06And grind your teeth together.
05:12And you can hear it quite loudly.
05:14And that's because you're hearing through bone conduction.
05:16The sound is actually passing through your bones.
05:19Ludwig von Beethoven.
05:22Great composer.
05:23Ha, ha, ha, ha.
05:25And he was deaf as a post.
05:27But he could hear someone playing his piano music by jamming his walking stick against the end of the piano.
05:32And gripping the other end with his teeth.
05:35And luckily most of us have got two ears, haven't we?
05:38Yes.
05:39Let's find out what they're for.
05:40You've got blindfolds.
05:41Put them on, please.
05:42And that's what they're for, you see.
05:44Hooking your blindfold onto.
05:46Okay.
05:47And I'm going to flick my fingers and I want you to point to where you think my fingers are.
05:54Right.
05:55Keep pointing in the same direction and lift your blindfolds.
06:11And nearly all of you are right.
06:14Amazing.
06:15It was easy, wasn't it?
06:16This time, put the blindfolds back on.
06:18I fooled you.
06:20And close off one ear.
06:21Stick a finger in one ear and close it off.
06:23Or put your hand over it.
06:24Really close it off.
06:25And now point to where you think the clicks are coming from.
06:46Keep pointing and lift your blindfolds.
06:48You're pointing over there.
06:49He's pointing over there.
06:50Some of you have got it right.
06:52But most of you seem to be a little bit off.
06:55And that's because we hear in stereo.
06:58And although the difference in time that the sound reaches the ear is very small,
07:02it just takes 0.005 of a second for sound to get from here to here.
07:06That's enough for your brain to evaluate where the sound's coming from.
07:10And in this way, you can determine from which direction all the sounds of the earth reach you.
07:14All the sounds.
07:15The beautiful sounds.
07:17A chuffing.
07:20Or the not-so-beautiful man-made sounds.
07:39This is Concorde.
07:41Without doubt, the most beautiful and advanced passenger aircraft in the world.
07:45But there are problems.
07:46It's noisy.
07:47Not just on take-off and landing, because all aircraft are noisy on take-off and landing.
07:51Some much more than Concorde.
07:53Concorde's noisy because of the speed at which it travels.
07:57Sound travels at 1,100 feet per second or 0.32 of a kilometre.
08:02But so does Concorde.
08:03And when it's travelling at that speed, the sound it makes can't get away.
08:07So a front of sound is built up in front of the aircraft.
08:10And as Concorde goes faster than the speed of sound, there's a great kaboom.
08:14A double bang.
08:15And the sonic boom from Concorde travels back from the aircraft in a sort of a cone.
08:20And it's very similar to the wave a ship makes as it breaks through the water.
08:25The wave stretches behind it.
08:28Sometimes Concorde's sonic boom can travel for 200 miles.
08:33Now, Krakatoa, the volcano in 1883, when it blew up, produced sound that could be heard 3,000 miles away.
08:41Which is much more than Concorde's 200 miles.
08:44Nevertheless, Concorde's sonic boom is quite alarming.
08:51Don't panic! Don't panic!
08:58It's an alarm bell!
08:59And I can't get in the glass case to turn it off.
09:01How else can I turn it off?
09:03Smash the glass.
09:04No, no.
09:05I can do this.
09:06Somebody say, this is a pump.
09:09And it's pumping the air out of the glass.
09:14And the sound is diminishing.
09:18Because sound cannot travel through a vacuum.
09:25See, sound needs a medium through which to travel.
09:31Like bone, or water, or air.
09:34And it causes a vibration.
09:36And the vibration causes the molecules in the air to knock against each other.
09:40And they knock on.
09:41And they travel out.
09:42The sound travels out like ripples on a stream.
09:45Rather, like waves.
09:48Now, every note has got a particular pitch.
09:52And that pitch doesn't vary.
09:55Or does it?
09:56Who's got the tube?
09:57Can you come out?
09:58Yeah.
09:59You stand there.
10:00And can you just give the tube a quick blow?
10:02See what it sounds like.
10:04It's not a kettle.
10:05It's a whistle on the end.
10:06Okay.
10:07And if you hold that down there.
10:08And start swinging it round your head.
10:10Let me get out of the way.
10:11And then, give a long whistle.
10:13And you'll...
10:14And we're listening through my microphone.
10:18See?
10:19So, do it again.
10:20And see if you can give it a longer whistle.
10:22Get it spinning.
10:23And then, big breath.
10:28And you can hear the whistle rising and falling in pitch.
10:31Can you?
10:32Can you hear it?
10:33What's happening is this.
10:34The sound is travelling through the air at 1,100 feet per second.
10:37But, when the whistle is in front of her, it's travelling towards me.
10:41And because it's coming towards me, the pulses of sound are arriving a little more frequently.
10:46So, the frequency has increased.
10:49And therefore, the sound seems to rise.
10:51Now, when the whistle is behind her and travelling that way, the sound is still travelling at the same speed towards me.
10:57But, because the whistle is travelling away, the pulses are spaced out a little bit.
11:02So, I don't hear them quite as frequently.
11:04The frequency drops, so the note drops.
11:06And we get what is called the Doppler effect.
11:09Have another go.
11:17Great!
11:18Three round of applause.
11:19Thanks very much.
11:26Now, you've all heard the Doppler effect, haven't you?
11:28With fire engines and police sirens.
11:30But, astronomers use the Doppler effect because all stars emit radiation at a certain frequency.
11:35And by examining that frequency, and studying the changes in it, in the variations, you can tell whether a star is moving away or coming towards us.
11:43So, let's transmit a few frequencies ourselves.
11:50This is a milk bottle.
11:51You knew that, didn't you?
11:53Alright, watch this.
11:54Now, what I want you to do in the audience, you've got milk bottles, and I want you to hold them to your ear, so you can hear, rather like listening to seashells in the sea.
12:07Now, hold it away from your ear now.
12:10Alright?
12:11And when I blow and make the note, I'll move my hand in, and that'll tell you to move the bottle close to your ear.
12:17Here we go.
12:19Now, did you notice any difference?
12:26It got louder.
12:27You tell me.
12:28Louder.
12:29When the bottle was near to your ear, it got louder.
12:31That's exactly what happens.
12:33Why does it happen?
12:34Well, when you blow over a milk bottle,
12:36you cause the air in the bottle to vibrate.
12:40And this produces a note, which is transmitted at that set frequency.
12:45So the note reaches you, it's the same note when it reaches you.
12:48Now, your milk bottles are the same size, so they contain just as much air, and they also resonate at the same frequency.
12:55So when the note travels over the top of your milk bottle, it causes the air in your milk bottle to vibrate.
13:00Try it once more.
13:08Right?
13:09So milk bottles can transmit and receive one frequency.
13:13Actually, if you could blow harder, you could get two or three frequencies out of a milk bottle.
13:17However, if milk bottles could transmit and receive all the frequencies, they wouldn't be milk bottles.
13:23They'd be radios.
13:24And if you connected them with cable, you could say they'd be telegraph or telephone.
13:30On the way out, can you put that on the step?
13:33Now, this man did a lot of early work on telephones.
13:52His name is Thomas Edison.
13:55And in his life, he only went to school for three months.
13:59And yet, when he died, he'd patented 1,033 different patents.
14:05And perhaps the most important of all was this one.
14:17Edison was working on the telephone receiver.
14:20As you can see, this looks like a telephone receiver.
14:22And he's trying to improve the quality.
14:24So he attached a needle to the diaphragm on the inside.
14:29And then, he got a cone to amplify his voice.
14:32And shouted into the receiver while touching the needle.
14:36Hello!
14:39The vibration was so great that it pricked his finger.
14:42And he fell asleep for a hundred years.
14:44No, no, no.
14:46He realised that if he could capture this vibration, he might be able to capture sound.
14:52So he designed this equipment.
14:56There's a long barrel there with a weight on the end so that you turn it rather smoothly.
15:01In the middle, there's a cylinder.
15:04When you place the needle so that it's touching the cylinder,
15:09you can turn and scratch the tin foil.
15:13Now, I'm going to shout into the cone.
15:21Mary had a little lamb!
15:25Did it pick it up?
15:28Well, when Edison first tried this, you can imagine.
15:31How he held his breath as he wound it back.
15:34Then try it again.
15:37I'm going to put the cone back.
15:39And this time, you should be able to hear through my microphone.
15:43He'd recorded sound.
15:53Immediately, this became number one in the hit parade.
15:56Basically, because it was the only one in the hit parade.
15:58You could say that Edison was the father of music.
16:02Or if you like, the pop of pops.
16:04But ever since then, sound has been recorded using a vibrating needle or a vibrating cutting edge to produce recorded sound.
16:14That is, until recently.
16:21This equipment here is an oscilloscope.
16:26And as you can hear, when I'm talking into this microphone, I'm affecting the scope every time I speak.
16:32And when I whistle on one note, I create a waveform.
16:42And if I switch this down, I can capture that waveform.
16:48What's this?
16:52Captured.
16:55Captured.
16:58And can you see, the higher the pitch, the closer the waves are together.
17:02It shows the frequency has risen.
17:06Now then, this machine does something else.
17:12It examines that waveform.
17:14And then...
17:18It cuts it up into bits.
17:21But incredibly small little bits.
17:23Up to 32,000 little bits in a single second.
17:28Now, it's possible to give those individual points a coded binary number.
17:37And you can see, as I press, we get a different sort of wave line up here every time I press the switch.
17:54Because at the moment of pressing, we catch the wave band in a different place.
17:58And all those blobs, 32,000 to a second possibly, all those blobs are converted into a waveform like this, which is composed of noughts on the bottom line and ones on the top line.
18:11It's converted it into a digital number.
18:13And those numbers, at 32,000 to a second, can be stored in a computer.
18:21And then, played back later, and there's absolutely no loss in quality.
18:27Now, if you can break sound up into so many small bits and feed them into a computer, perhaps, instead of taking them back in order, you can get the computer to select those little bits of sound and put them in a new order.
18:44Any new order.
18:46And in doing that, you could create a synthetic voice.
18:51Have a look at this.
18:56This machine can read books.
19:03And it told us what it's doing.
19:07It's looking for the first line.
19:09Well, we're playing around with it because it hasn't even got a book, so I've stopped it.
19:12And now, I'm going to give it a book.
19:15It can read any book in the English language.
19:17This isn't just any book.
19:18This is the Think of a Number book.
19:20Let's see what it makes of this.
19:25Have you ever wondered what it must be like?
19:30Zero travel at 600 miles and taller?
19:35Well, at this very moment, while you are reading,
19:39it is good, you are probably travelling at our lives at speed.
19:46Could you understand what it was saying?
19:49It's difficult at first, isn't it?
19:51But that's because you haven't heard it before.
19:52You see, it's a totally synthetic voice.
19:54The more you hear it, the more you get used to it.
19:58This is what it's doing.
20:00There's a camera, which is looking at the page through this lens here.
20:04And it's getting images, which it translates into letters or couples of letters.
20:11And these it feeds into its computer and looks for the minute bits of sound that make up words.
20:19Then it puts them in order and groups them together.
20:21And it tries to make sense of the words.
20:25Now, of course, it's not a real brain.
20:27And it can't really think, am I making sense?
20:30But it can discern between words like trough, though, enough and bow.
20:36But it can only do it because it's been told to do it.
20:40Let's let it read some more.
20:42And this time, see if you can understand it a little better.
20:44Have you ever wondered what it must be like to travel at 600 miles an hour?
20:56And there you are.
20:58And this machine can read any book in the English language.
21:01So imagine it. Blind people can now read any book in the English language
21:05if they have access to a machine like this.
21:08Not only that, with adjustments, the whole programming could be changed
21:11so that the book could read any other language and talk in any other language
21:16once you tell the machine what to do.
21:18So, we've got one machine that's turned sounds into numbers to produce perfect recording
21:24and another machine that's turned pictures into numbers to produce
21:29a synthetic voice that can read any book.
21:33Let's have a puzzle.
21:35OK, you've got a tray there, haven't you?
21:37And there are some articles like key, ruler, pencil, cork, whistle, and an envelope.
21:43Now, I've got a supersensory hearing.
21:46So what I want you to do, I'm going to turn my back and I want you to select one of them,
21:49hold it in the air, and then write its name, cork, whistle, whatever, on the piece of paper.
21:56OK, off you go.
21:58Tell me when you've done it.
22:00Because although I can hear everything you're doing, I'd like to know that you're ready.
22:04OK, count the letters in the word.
22:09And multiply that number by five.
22:13Write the answer down.
22:18OK.
22:20Now, I've done this six times before and I've always got it wrong.
22:23So add seven to your number.
22:28And double the new number.
22:35Right, now to really confuse me, the person next to you is going to whisper in your ear.
22:42And I want you to select any number between nought and nine and whisper it in her ear.
22:45OK.
22:47Quietly so that I don't hear.
22:51Have you done that?
22:53Right, add that number onto your number.
22:55I said quietly, but with my supersensory hearing I can hear everything.
22:59If you tell me the number, the total.
23:02Can you tell me the total you've got?
23:04One hundred.
23:06That means you chose the envelope and you whispered in your ear number six.
23:15Trick, isn't it?
23:17Of course it's a trick.
23:18And if you'd like to know how the trick's done or anything else about the programme, drop us a line.
23:22Here's the address.
23:23Johnny Ball.
23:24Think of a number.
23:26BBC Television.
23:28London.
23:29W1A.
23:301AA.
23:32Until next week, keep your ears peeled.
23:35Sounds really amazing.
23:37And we hope we'll be hearing from you.
23:40Bye.
23:53Bye.
23:54Bye.
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