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Science gurus please help music teacher

(26 Posts)
twentypence Tue 05-Aug-08 10:14:03

Question from child

"So if you went into a room with a oxygen tank and then removed the air from the room and played a drum would it make a noise?"

As I had just tricked them into saying ds's 1/10th size cello would play higher than a full size one, by first showing a flute and a piccolo, I feel I need a full and complete answer for this one...

tortoiseSHELL Tue 05-Aug-08 10:16:13

No, sound can't be heard in a vacuum as their are no particles to carry the wave form. So you wouldn't hear the drum.

tortoiseSHELL Tue 05-Aug-08 10:16:43

(PS as one muso to another, what is the reason that a small cello isn't higher? I should know this but don't!)

Slouchy Tue 05-Aug-08 10:17:42

I'm not 100% sure of this but I believe sound can't travel through a vacuum, so the answer is no.

I think.

(Not a Science guru, as you may have guessed!)

juuule Tue 05-Aug-08 10:23:19

This any use to you?

twentypence Tue 05-Aug-08 10:39:13

Strings are same thickness, same as a grand piano and a tiny upright.

Whereas with a piccolo and flute it's the air inside that's important.

twentypence Tue 05-Aug-08 10:43:04

Love the bit about "when there is a battle in outer space you could see the explosions, but not hear them", I think as the battles are imaginary we will allow a further suspension of disbelief.

Thrilling that this was solved in 1660, by a combination of my ds and the surname of the boy who asked the question! Spooky.

IorekByrnison Tue 05-Aug-08 11:11:28

I'm still confused about the cello. If you have two strings of the same thickness and tension but one is half the length of the other, surely the shorter one will sound an octave higher? Is the tension of the strings lower on the smaller instruments?

snorkle Tue 05-Aug-08 11:15:53

twentypence, I'm not sure about the string thickness being the same on small cellos - I'm fairly sure it's advances in string technology that enables you to get low pitches on short string lengths. It's worth noting that a 1/10th cello is actually a lot bigger that 1/10th of a full size one as well. Very tiny cellists sometimes start on a viola with a spike added and these instruments do sound an octave higher.

MrsJohnCusack Tue 05-Aug-08 11:18:05

oooooh that is spooky
Well, I've learny something today - thanks all

MrVibrating Tue 05-Aug-08 11:54:55

Three things determine the pitch of a string:

Length - the smaller the instrument, the shorter the length and so the higher the pitch

Tension - the tighter the string, the higher the pitch

Linear density - the heavier the string, the lower the pitch

So on a smaller sized instrument, to keep the pitch the same the strings are made heavier by winding with heavier wire as much as possible. Using heavier wire means that the string doesn't have to be much thicker or tuned much looser than on a full scale length instrument, both of which have an impact on tone and the 'feel' of the instrument.

For a more detailed explanation see here or here for a bit more science

(Note: not a 'cellist but a guitarist and a scientist grin)

popsycal Tue 05-Aug-08 11:55:46


popsycal Tue 05-Aug-08 11:58:31

A couple of things I tell kids to rememver about pitch

Eg the shorter, narrower the string/vibrating object the higher the pitch - get them to remember it by thinking opf a tiny mouse <squeck squeak> and a huge elephant <ffffffffffffwwwwwwwwwwwwwaaaaaaaaaaaaaaaaaaaaaaa>
high pitch/low pitch little/big

also I tell my class that I often think of sending them to outer space as then they could be as loud as they want and I couldn't hear a thing
I say it to ds1 often too

popsycal Tue 05-Aug-08 11:59:22

the thing about tightening strings.......we ppicture a little mouse being stretched and his squeaks getting higer and higher

oh science is such good fun chez popsycal

twentypence Wed 06-Aug-08 01:08:14

His strings couldn't be thicker because they would then be impossible to press down with tiny fingers. They are not under a lot of tension though - tuning is very hard because the tiniest of turns can make the pitch go up a tone even on the fine tuners.

If he presses on hard with the bow, he can get a whole other note!

Like the idea of sending the children into space!

Blandmum Wed 06-Aug-08 20:31:10

No you wouldn't hear a sound diatnt from the instrument, as sound needs an atmoshere to travel in. However you would be dead if tyhere was no atmoshere in there, so it is a moor point any way!

If you filed the area with helium the pitch would =change because the speed of vibration of the drum/strings, would change and get faster, so the pitch would rise.

The fater the vibration the higher the pitch.

this is why you sound like Mickey mouse if you inhale helium, your vocal cords vibrate faster

twentypence Thu 07-Aug-08 01:02:39

I just loved that he thought to take an oxygen mask into the room with him.

Would having a vacuum affect his tank though?

snorkle Thu 07-Aug-08 10:00:47

A solid oxygen tank would withstand the (lack of) pressure OK I would think, but his body wouldn't - he'd explode unless wearing a spacesuit.

MrVibrating Thu 07-Aug-08 15:05:46

No he wouldn't explode, although his lungs would probably rupture if he tried to use the oxygen tank.

snorkle Thu 07-Aug-08 15:48:57

So in the scenario described the lungs would explode then.

snorkle Thu 07-Aug-08 15:48:57

So in the scenario described the lungs would explode then.

MrVibrating Thu 07-Aug-08 16:12:04

This is getting somewhat off topic, and I suppose it all depends what you understand from the word 'explode', but as the injury would be internal the word rupture is more appropriate IMHO.

IorekByrnison Thu 07-Aug-08 17:30:44

I love this thread

twentypence Thu 07-Aug-08 20:55:15

9 year old boys live off topic - I need all this info - keep going.

MrVibrating Fri 08-Aug-08 00:22:28

What else would you like smile?

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