SCIENCE OF SOUND

sound used-drums

You have seen drums, but that many? Notice they all have a skin pulled tight over the drum body…

When you hit a drum it puts pressure on the air inside the drum.

That makes a SOUND WAVE that comes out of the bottom…

Big drums give a big low sound, small drums make a higher sound.

The sound wave is like a wave in the water, remember, if you throw a stone in a puddle or lake the wave it makes moves out in circles? The drum does the same in air and then…..

YOUR EAR PICKS UP THE SOUND 

HOW?

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ear schematic

This is a drawing of the inside of our ear, can you spot the EARDRUM?

It is called: TYMPANIC MEMBRANE, just a scientific word for the skin on a drum.

It gets moved by sound pressure waves that come from a recorder, a clapper , drum or any sound producing source: car horn, our voice …

From the eardrum some bony levers pass the movement on to the inner ear to tickle the nerves in our cochlear and then our brain makes sense of all this.

Enjoy the music!

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sound cup tele

You know how this works? 

Two paper cups or tin cans and a string… It only works when the sting is pulled tight….

sound science-projects-for-kids-producing-sounds-3

You speak in one cup and the sound of your voice makes the bottom of the cup move back and forwards. That makes the string move with it, it VIBRATES.

The string pullS the bottom of your friend’s cup back and forward, and the waves it makes are picked up by the eardrum of your friend.

Your VOCAL cords make the sound and its get moved by the string and picked up by the EAR DRUM. 

Now you can talk to each other, just say “over” when you are done and want to listen to your friend who speaks… Back and forwards, nobody else can hear!

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sound Early-Record-Disc

Have you heard or seen old fashioned record players? 

(By the way it is much like a modern CD that can be read by a laser)

Here is an antique player from your grandparents time.

Lets see how it works to make sound waves…

There is the record, the black disc; the turntable; the pick-up with the needle, which works like a lever that “tickles” the membrane of the pick-up; the hollow arm that guides the sound waves to the heavy metal horn under the turntable… that lets the sound into the room

You will see… first the record

sound gramophone sound record

Here is a old fashioned vinyl record.

The record has RECORDED the music on this disk by making a groove that wiggles sideways.

Every wiggle makes a sound wave through the pickup and the sound amplifier. Here we go…

sound gramophone sound record a

If you look good at this part of the record you can see all kinds of tiny wiggles especially in the left and right upper part.

sound gramophone-pin

And here the needle races through the groove picking up the wiggles, the needle  is like a lever with the fulcrum where the two screws are, the rest of the lever arm goes to the middle of the pickup and moves the skin or membrane back and forwards. That makes sound waves that are amplified through the  sound channel, below. 

sound gramophone sound path a

The “Royal” pick-up shows the membrane and the needle holder, can you see the needle holder as a lever that “tickles” the center of the membrane?

From there the membrane, like a drum skin, makes waves in the arm and from there through the black metal tube, that looks like a horn,  to the outside.

The sound is really loud, if can fill a whole room. The sound waves travel through the air to the eardrums of all the people in the room. It is great fun to hear these old gramophones play. 

The little dog listens through another type of horn to his master’s gramophone.

That horn looks like a…

sound trumpet

The gramophone sound amplifier looks much like a trumpet or horn…

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Wind instruments, like a trumpet, work different to make sound waves, have a look at this recorder.

This is the inside of a recorder and it is similar to the flute you made in the Flute Project. To see that project click here or look under Categories in the side bar.

When you blow into the flute the air goes through the wind way (B).

It is the space between the body of the flute and the block (A).

We used a cork in our flute with one side cut away . We pushed it into the plastic pipe and presto, you made a WIND WAY!

The air stream then hits the LIP (C), it is the sharp edge cut into the pipe. The location of the wind way and the lip are important!

sound recorder fipple

When the air stream hits the lip, here called “fipple”, it gets split and little whirls of air pass over the lip to the outside of the flute and to the inside, one whirl out and then one whirl in, and then all over again, in a very rapid motion.

This makes the air inside the flute VIBRATE. The vibrations in the body of the flute behind the lip cause PRESSURE CHANGES in the air inside the flute. And, those pressure changes move through the air and pick up that up with your ear, and now you hear sound as a TONE.

A good looking flute, made from a piece of electrical conduit. Read on...

With our flute you can make the VOLUME of air inside the flute larger or smaller by pulling the plunger out or pushing it in. Smaller air volume give a higher PITCHED sound, more air in the inside flute, when you pull the plunger out will give a lower pitch.

Now, build your FLUTE  and experiment. It will drive everybody “crazy” but it is great fun!

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You can make your own DRUM from scrap materials, an old bucket and some canvas or sun umbrella fabric and string….

You hit the skin that is pulled tight over the body of the drum and it makes air pressure waves that come out of the bottom of the drum and are picked up by your ears: BOOM BOOM…BOOM…BOM,BOM,BOM.

Strike the drum slowly and the rhythm is slow,  strike it twice as fast and the rhythm is double that is what makes the drum beat so important in all music.

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