Music
Rabbits have very large ears which listen constantly for dangerous sounds.
Cats are also sensitive to dangerous sounds but some have learned to listen
for other things as well such as the opening the refrigerator door.
Hatches use their ears to help them survive in a complex jungle environment.
Human beings also use their ears to survive in their environment but they can do more.
They can understand and use sounds in the form of language.
That's what today's program is all about, how we hear and use the sounds which constantly surround us.
If a person had to go around for some time wearing a set of earplugs then that person would very quickly discover
how important hearing is. Our ears are able to pick up the sounds from the world around us
and we're able to make sense of those sounds. We're able to distinguish between different sounds and give them meaning.
Get out and stay out!
Oh I love you, I love you more than a flower loves spring, more than a brain loves honey, more than anything in this world.
If only you could understand just how much you mean to me, my darling.
In fact, in order for us to hear a sound something has to make sound.
Every sound is created by vibration.
When something vibrates it disturbs the air around it creating sound waves.
It's a bit like throwing a rock in a pool. The disturbed water forms waves which spread out from the original vibration.
In the same way any vibration will set off similar waves in the air.
In the water a small vibration creates small waves.
In the air a small vibration will set up sound waves which look similarly small on this oscilloscope.
Such waves are sounds of low volume, sounds which are not very loud.
Back in the water a larger vibration will create larger waves.
And similarly a larger vibration in the air will create sound waves which look larger on the oscilloscope.
Such waves are sounds of higher volume, that is they're louder.
If the distance between each wave is very great the sound will be of low frequency, that is of a low pitch.
If the distance between each wave is only small the sound will be higher in frequency.
So sounds can be low volume or higher volume at high pitch or low pitch.
But sounds have further qualities. Every sound has its own unique character.
Another instrument, the spectrum analyzer, allows us to see sound in a different way.
Notice the change in volume, the change in pitch, and the change in both.
It can also show us individual sounds.
Listen, you may pick up something new.
Listen, you may hear of something true.
Sit back, relax, let it take your cares away.
You can get some idea about the behavior of sounds from much more everyday machines than the ones we've been looking at.
An ordinary cassette tape usually has a VU meter.
The VU stands for volume units and the needles move as the volume goes up and down.
Of course, sound isn't very useful unless somebody can hear it.
This is where the ear comes in.
The outer part of the ear receives the sound waves which pass along the auditory canal.
The normal wax found here repels insects, moistens the canal, and protects the ear drum.
The sound waves strike the ear drum and set up a vibration like the one which started the sound going.
Let's have a closer look at the ear drum.
We could think of the ear drum seen underneath the middle ear in this position as being something like an ordinary drum.
A piece of skin tightly stretched across a frame.
Although we can't see the skin move when a sound is made, we can see the rice and cool light on the top move because of the vibration of the guitar string.
This vibration in the ear drum is passed on to the middle ear which magnifies the sound.
The sound is now passed on to the inner ear which will also pull out.
Through the tiny oval window facing you, then through the seashell like cochlea, and to the auditory nerve at the other end.
The vibration has been changed to a nerve impulse which is taken by the nerve to the brain.
The brain now tells us about the sound heard by the ear.
The human ear is very sensitive to middle frequency sounds.
In fact, if it were any more sensitive we would be constantly bombarded by the sounds of molecules colliding in the air around us.
On the other hand, it's not as sensitive to high frequency sounds as are the ears of some animals,
which explains why we can't hear a high frequency dog whistle.
And as well, our outer ears are only small and not shaped for catching sounds like the ears of some animals.
A cat, for instance, has fairly large external ears which can be pointed in the direction of a sound source.
And as a result, it's easier for a cat to hear low volume sounds more quickly than humans.
A sensitive hearing is extremely important for many animals.
It's one of their best ways of protecting themselves, especially when they're eating.
At such a time, their eyes have a very limited range of vision,
and they must be able to depend upon their ears to warn them of danger.
Bats, too, have large sensitive ears.
Their middle ears are very sensitive to echoes.
They're able to fly in the dark by listening to echoes of their own voices.
A bit like radar.
Dolphins, too, are able to locate themselves by listening to their echoes.
This ability is something like sonar devices in submarines.
But dolphins are unique in another way as well.
More than any other animal, apart from humans, they're able to communicate.
They appear to have distress calls, the cries of lost babies, angry claps, and playful whistles.
Scientists are sure that they have many more signals as well.
Human beings can use their hearing like animals to avoid danger.
But for us, the most important thing about hearing is that it enables us to hear our language.
From a very early age, children learn language by listening to others.
Once they're capable of understanding their language,
then they have the potential to learn much, much more.
In a very important sense, it's much easier for blind people to learn things than deaf people,
because blind people find it much easier to communicate to find out what others know.
I've brought this watch along to try a little experiment.
If I put it there, where you can hear it, then I can make this point.
If we could always listen to all the sounds that were being made, it would be very confusing.
One of the things that makes us able to learn is our ability to pay attention,
to concentrate on the sounds that we think are important.
For instance, at this moment, you're probably shutting out sounds in your school or your home
to concentrate on the sounds of the television set.
And not only that, you've probably shut out the sounds of the watch
to concentrate on the sounds of my voice.
Honestly, it's been ticking all this time.
And here's another interesting thing.
What we hear can make a difference on how we look at something.
What do these sand yachts do?
Let's look at the same picture all over again, but with a different soundtrack.
I don't know what you felt.
But to me, it was like looking at two different actions.
And this use of music to suggest the action that's going on in a film or a television program
is being used all the time.
And here's just one more thing to think about.
Of all the sounds that are made in this world, there's something very special about rhythmic sounds,
sounds that are repeated, sounds which have a beat.
It's interesting to think that one of the first sounds we hear, even before we're born, is a heartbeat.
After we're born, all kinds of everyday activities have their own rhythm.
It's no wonder then that when we listen to music, we expect to hear a beat.
In fact, when you watch this group performing, it's possible not only to almost hear a heart-like beat,
but to see a heart-like beat.
Is there really a connection between a heartbeat and a rock beat?
Well, it's an interesting thought.
But here's something that's a bit more factual.
Rock groups are just one of the many modern sounds which are sometimes heard at a very loud volume.
There are many industries which are very noisy and people have to work in them.
It's very difficult to say just how loud noise affects people over a long period of time,
but experts suspect that it can create extra stress for some people at least.
It's a problem which is causing some concern.
But before anything can be done, people have to know just what kind of sound is being made.
The volume of sound can be measured, and scientists use the term decibels to describe how loud a sound is.
And to give you a very rough idea of how it works,
35 decibels would be the amount of sound in a quiet house in the middle of the night.
65 decibels would be the sound made by a television set at normal volume.
90 decibels can occur in some noisy factories,
and if a person was only 20 meters away from a jet plane taking off,
the sound could easily reach 120 decibels.
In spite of the fact that the ear has two small muscles to protect it from loud sounds,
bursts of noise in excess of 130 decibels can be painful and damaging to the ear as well.
Longer periods of noise between 100 and 130 decibels can have the same effect.
To understand how a loud noise might damage the ear,
let's look again at how sound waves are transferred to the fluid in the cochlea.
Movement of this fluid stimulates tiny hair cells inside,
which change the movement into impulses which are passed on to the brain.
Very loud sounds can damage these hair cells, and thus damage the ability to hear.
A noise dose meter can be used to check how noisy sounds might be,
giving a reading in decibels.
This one is being used to check another common source of sound pollution, traffic.
Meter readings in this traffic reached 88 decibels at times.
Aeroplanes have been another source of sound pollution,
and the Concorde has been criticized more than most.
Governments have been keeping a close check on the Concorde's noise levels.
Some people see the Concorde as just one of the many noisy parts of an unnecessarily noisy world.
They feel that too much emphasis is placed on machinery,
and that we could all live much more simply.
If we did live more simply, they feel there wouldn't be the problem with pollution which we now have.
It's an argument that has its appeal.
If there were more bicycles around, cities would certainly have less air and noise pollution.
On the other hand, how many motorists would be willing to give up their cars?
There seems to be no easy solution to the problem.
But if you can use your ears to learn, who knows?
Maybe one day you'll be the person who solves it all.
Thank you.