A burning question for all you science and physics geeks

[JP-]

"You wouldn't be able to hear the guitar. As soon as it came out of the case it would be used to build a fire."

Great responses! Thanks. Yes, definitely this would be a most appropriate carbon-fiber situation!

Since someone brought up starting a fire -- just curious, could you build a fire with a carbon-fiber guitar? Do they burn? Would it be like igniting charcoal? They are carbon and perhaps some type of petroleum by-product? Right?

I would guess that in a really desperate survival situation, this might give you a small momentary edge. I can see someone writing this storyline into the next "plane crashes into the artic surrounded by angry wolves" movie.

[djg]

Originally Posted by musicman1951

The temperature can drop as low as -30 to -60. I think you might have bigger problems than tuning.

Yeah, I'd keep the mitts on. People lose fingers up there. Among other things.

[Edgar Poe]

What about expansion due to altitude.
If you take an empty water bottle and seal the lid at 4000 feet. When you hit sea level the bottle will be completely collapsed. I would think that may have some effect on play ability.

Ed

[ac]

Originally Posted by JP-

"You wouldn't be able to hear the guitar. As soon as it came out of the case it would be used to build a fire." . . . .

Great responses! Thanks. Yes, definitely this would be a most appropriate carbon-fiber situation!

Since someone brought up starting a fire -- just curious, could you build a fire with a carbon-fiber guitar? Do they burn? Would it be like igniting charcoal? They are carbon and perhaps some type of petroleum by-product? Right? . . . .

Unfortunately (or fortunately, depending on your point of view) you wouldn't build much of a fire with carbon fiber.


However, the resin might burn if hot enough, but the smoke would be worse than the cold!

[Howard Klepper]

The frequency of a vibrating string is determined by length, tension, and mass per unit length. Temperature and air density and gravity are not in there. Temperature does affect pitch, a lot actually, because it changes tension, but I take the OP to have said to ignore that and assume it is controlled.

That the gas in which the string is vibrating and its density has nothing to do with frequency of a note on a guitar can be understood this way: the frequency of the note is about the length of the string and the speed with which a wave propagates in the string. The speed of propagation of a wave in the string is dependent on its mass and how tight it is. Once you have a speed of propagation, then the length of the string will determine how long a standing wave in the string can be before it bounces off the ends of the string. Speed divided by wavelength will then give you frequency.

Friction effects of the air the string is moving in are so tiny as to be irrelevant, but I suppose they might be measurable with good laboratory equipment at extremes of air density.

The speed of sound in the gas in which the compression wave caused by the guitar top moves will not change the frequency of the string's vibration, and hence won't change the frequency with which the guitar top moves to create those compression waves in the gas, or the frequency of those waves. However, the length of the compression wave in the gas will be changed--it will be longer if the speed of sound is greater, shorter if it is less. This won't change the pitch of a guitar in open air (or some other gas). But what it will do in wind instruments (like the voice) is make the wavelengths of lower pitches too long to resonate in the air column where the sound waves are generated. Hence the lower pitches of the voice get cut off in helium and we hear only vocal cord overtones for most common voice pitches.

One other thing: The speed of sound in air at higher elevations is lower than at sea level, not higher. Some comments have taken the helium example to mean that the speed of sound must be higher where air is less heavy. This confuses two things: The density of the gas molecules (how many per unit volume) and the mass of the gas molecules. Helium has the same density of molecules as air at a given pressure; but its molecules have much less mass so they are accelerated more when bumped by the adjacent molecules and a compression wave in helium propagates faster. But either gas will have a slower speed of sound wave propagation when the gas is less dense, because collisions of the molecules are take longer to occur because they are further apart. Because those collisions are fewer, the amount of sound pressure the wave carries is less, and the sound won't be as loud.

Hey, you asked for geekery.

[Athens]

Sorry, I'm late to the party on this one.

The only thing I want to comment on is speed of sound at altitude. Howard is right. Speed of sound decreases. Anyone who is a pilot will explain this to you. Google coffin corner and see what you find.

[cotten]

Originally Posted by JP-

...If I could transport a guitar to the top of Mt. Everest...

I'm weird, I know, but I can't get past this question: Why?

cotten

[Howard Klepper]

Originally Posted by Inyo

Note that the poster has answered his own question to his own satisfaction.

Note that if you read one more sentence of that paragraph, he hasn't. He clarifies that his question is about air density, not temperature.

Originally Posted by JP-

Obviously, it is so cold at the top that my fingers would quickly freeze. Also, my steel strings would contract, thus changing the pitch. But discounting these matters – do strings vibrate faster in rarified air? And is perceived volume diminished?

[random works]

I assume the frequency at which a string vibrates would be the same if plucked in a vacuum or at sea level or on a mountain top.

[woody70]

I once played mandolin with a group in minus 20 celsius degrees at a ski sport event. My fingertips went slightly blue, and i had to play with gloves on. The accordion player couldnt play much because the buttons were frozen. After one song we just had to stop and wait for the sun and temperature to rise. Mount everest would be so cold you probably dont even want to try it.

[murrmac123]

Originally Posted by Edgar Poe

What about expansion due to altitude.
If you take an empty water bottle and seal the lid at 4000 feet. When you hit sea level the bottle will be completely collapsed. I would think that may have some effect on play ability.

Ed

I am surprised that nobody has picked up on this one already.

Your premise appears to be similar to that of the many who think that consigning a guitar to the hold of an airliner is hazardous because of the decreased air pressure.

Leaving aside the fact that there actually is no decrease of air pressure in the hold of a modern airliner, the question then becomes "does an acoustic guitar (made of wood) suffer in any way if the ambient air pressure is significantly decreased" ?

I will go out on a limb here and say that you could put any acoustic guitar, strung up to pitch, into a vacuum chamber and extract all the air to make as perfect a vacuum as possible, leave it there for hours, days or months, and it would come out of the (re-pressurized) chamber in exactly the same condition as it went in.

[JeffreyAK]

Well we're off topic now, but if you actually put a wood guitar in a vacuum chamber, what will happen is every bit of moisture will evaporate out of the wood, and you will be left with the driest guitar you've ever seen. That will cause structural changes (warping) that probably won't fix themselves after you re-humidify the guitar.

[murrmac123]

Originally Posted by JeffreyAK

Well we're off topic now, but if you actually put a wood guitar in a vacuum chamber, what will happen is every bit of moisture will evaporate out of the wood, and you will be left with the driest guitar you've ever seen. That will cause structural changes (warping) that probably won't fix themselves after you re-humidify the guitar.

And this has been experimentally verified ?

[JeffreyAK]

It's just physics, below about 5 torr liquid water cannot exist.


As it evaporates, it is pumped out of the tank by vacuum pumps, so little by little all the moisture goes away. Vacuum drying is pretty common in some industries, though probably not in wood guitar manufacturing.

[murrmac123]

Originally Posted by JeffreyAK

It's just physics, below about 5 torr liquid water cannot exist.


As it evaporates, it is pumped out of the tank by vacuum pumps, so little by little all the moisture goes away. Vacuum drying is pretty common in some industries, though probably not in wood guitar manufacturing.

OK , gotcha.

I was more interested in the question of why the vacuum process would inevitably result in irreversible damage to the guitar ...

That will cause structural changes (warping) that probably won't fix themselves after you re-humidify the guitar

Which is why I wondered whether there had actually been any experimental verification of your hypothesis.

Hey, I am just surmising here ... my guess is that there would be no adverse effects, but I am quite happy to be proved wrong (based on experimental evidence).