 The Clarinet BBoard
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Author: Buster Brown
Date: 2005-07-05 12:25
Had an interesting technical discussion with my fellow musicians (some of them brass players). Why, as your horn warms up, do you go sharp? When tuning, you make the horn longer by pulling out barrel or other joints (slides for brass) to lower pitch. Yet as horn warms up (horn should get longer-especially brass) the pitch goes up. Is it air density (like helium makes you sound like Donald Duck)? Would one of you help me understand the science? It's driving me nuts, and I'm too lazy to Google it. Thanks in advance.
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Author: WorldIRC
Date: 2005-07-05 12:40
Warm means particles moving faster (faster vibrations)...faster vibrations mean higher notes.....maybe thats why
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Author: Synonymous Botch
Date: 2005-07-05 13:59
Wooden instruments suffer from minute dimensional changes as they change temperature. The wood near the top heats up first, and the center part of the horn wants to move outward (radially) while the outside part is still at room temperature.
The overall length of the instrument may also change, a more pronounced example being a trumpet taken from a cold car into a warm concert hall.
My teacher will take the barrel and mouthpiece off her instrument to warm in her pocket between sets.
It's MUCH worse for oboes - the top part of the instrument has a tiny hole in the middle, and cracking is a common occurence with them!
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Author: clarinetist04
Date: 2005-07-05 14:53
I was just thinking about this...
Seems like a logical explanation would be that, as we heat the instrument up, the wood swells (which it does) thus making the air tube minutely smaller...thus as the air goes down the instrument it has less area to cover and the frequence of the resulting sound becomes higher.
In fact, physics lends an equation that explains exactly how this happens. I can't remember the name or equation but basically it says that as you add heat to a system (i.e. warm air from the body) the system will increase or decrease in size (increase for input of heat, decrease for input of negative heat). So as that relates to the question, when the tube increases in size radially (a better description would be swelling) the tube becomes smaller and the air comes out at a higher frequency than when you started playing and the clarinet had not swelled.
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Author: archer1960
Date: 2005-07-05 17:06
clarinetist04 wrote:
> I was just thinking about this...
>
> Seems like a logical explanation would be that, as we heat the
> instrument up, the wood swells (which it does) thus making the
> air tube minutely smaller...thus as the air goes down the
Nope, the inside of the tube gets bigger just as the outside does - think of the piece of wood which was removed from the center; it would swell as well.
The real answer was one of the early ones: as fluids (both gases and liquids) warm up, the sound velocity through them increases and their density decreases. Humidity also decreases the density of air because water vapor is lighter (on average) than air molecules. These effects cause you to be sharp in hot humid weather, and cause you to go sharper as you warm up.
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Author: Don Berger
Date: 2005-07-05 17:44
We have had several discussions of cl acoustics here on the BB, and several references to web sites/articles of "learned character" which GBK can list for you in his ?spare time?, yer velcome, Glenn. Don
Thanx, Mark, Don
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Author: David Peacham
Date: 2005-07-05 18:47
It seems to be universally accepted that clarinets get sharper as they warm up because sound travels faster in warm air than in cold. But there is something I have never understood about this, all the same.
Surely the temperature of the air inside the instrument is determined almost entirely by the temperature of the player's breath, and in turn by his blood temperature? This should be pretty constant whatever the ambient temperature. In this case:
1) A clarinet should warm up to operating pitch within a few seconds.
2) Its operating pitch should be the same whatever the ambient temperature.
But these predictions do not accord with reality.
Why?
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If there are so many people on this board unwilling or unable to have a civil and balanced discussion about important issues, then I shan't bother to post here any more.
To the great relief of many of you, no doubt.
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Author: archer1960
Date: 2005-07-05 19:34
David Peacham wrote:
> It seems to be universally accepted that clarinets get sharper
> as they warm up because sound travels faster in warm air than
> in cold. But there is something I have never understood about
> this, all the same.
>
> Surely the temperature of the air inside the instrument is
> determined almost entirely by the temperature of the player's
> breath, and in turn by his blood temperature? This should be
> pretty constant whatever the ambient temperature. In this case:
> 1) A clarinet should warm up to operating pitch within a few
> seconds.
Part of the air column will be cooled by the walls of the instrument until it gets up to "operating" temperature; that would take longer than a few seconds.
> 2) Its operating pitch should be the same whatever the ambient
> temperature.
I'm not sure about this one, but the temperature and humidity of the air just outside the tone holes might have an effect. Also, the thermal conductivity of the material making up the body of the instrument will affect the temperature of the inside wall of the bore.
>
> But these predictions do not accord with reality.
>
> Why?
>
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Author: Gordon (NZ)
Date: 2005-07-05 22:01
If I am playing LOUDLY in an orchestra pit, without heating, on a cold (for Auckland) night, then significant warm breath is going through the instrument that I am able to compensate for the effect of the air column being colder than it would be on a warm night.
However if I am playing a long QUIET passage, there is nowhere near enough air going through the instrument to keep the air in the bore anywhere near breath temperature. I sure do notice the additional chaos this plays with tuning.
Furthermore, if most of the notes played are in the throat region, then there will be little heating of the air in the lower part of the instrument, which plays havoc with the tuning of these notes relative to the throat notes, which may use more heated air.
As a rough guide, from http://mmd.foxtail.com/Tech/soundspeed2.html ,
"The main rule is: In dry air the pitch of flue pipes will rise with temperature 3 cents per centigrade, 1.7 cents per deg F. Equivalently, a quarter semitone (25 cents) per 8 degrees centigrade or per 15 deg F. "
This site also discusses the rather irrelevant effects of temperature and humidity on the timber of woodwind instruments.
The effects of varying proportions of carbon dioxide in the air (both on account of the player and the audience) is discussed in http://www.speech.kth.se/music/publications/leofuks/IIIbism97co3.html
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Author: Buster Brown
Date: 2005-07-06 12:02
Very interesting. Some seem to say sound moves faster in warm air. Physics tells me that's not true. The more dense the medium, the faster it moves. Molecules closer together bump into each other quicker. Sound moves faster in water than in air.
I think it obviously has more to do with frequency of vibration than with speed. Therfore, the warm ait must vibrate a little faster. Not move through air faster. Fot example if cool air vibrates at 440, maybe warm air (full of moisture) vibrates at 440.05.
Anyway, thanks. This has proved to be an interesting discussion (at least for me).
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Author: archer1960
Date: 2005-07-06 13:06
Buster Brown wrote:
> Very interesting. Some seem to say sound moves faster in warm
> air. Physics tells me that's not true. The more dense the
Physics also says that temperature (= speed of molecular motion) has its own effect on sound velocity independent of density, and in the opposite direction. The effects of temperature and density are both in operation here, but the temperature effect in one direction is stronger than that of density in the other direction.
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Author: David Peacham
Date: 2005-07-06 16:17
Buster, if you look at:
http://hyperphysics.phy-astr.gsu.edu/hbase/tables/soundv.html#c1
you will see:
a) The speed of sound in air increases with temperature.
b) At a given temperature, the speed of sound in hydrogen is faster than that in helium, which in turn is faster than that in air. You will, I think, agree that air is denser than helium (otherwise helium balloons would not rise). Therefore your contention that "The more dense the medium, the faster it moves" is just plain wrong when applied to gases.
In fact, the speed of sound in solids does tend to increase with density, but other factors are at work. For example, sound travels faster in aluminium that in iron, and much slower in lead than in either.
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If there are so many people on this board unwilling or unable to have a civil and balanced discussion about important issues, then I shan't bother to post here any more.
To the great relief of many of you, no doubt.
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Author: archer1960
Date: 2005-07-06 16:32
David Peacham wrote:
> a) The speed of sound in air increases with temperature.
> b) At a given temperature, the speed of sound in hydrogen is
> faster than that in helium, which in turn is faster than that
> in air. You will, I think, agree that air is denser than helium
> (otherwise helium balloons would not rise). Therefore your
> contention that "The more dense the medium, the faster it
> moves" is just plain wrong when applied to gases.
But if you compress the gas, the speed of sound _will_ increase in it. It's just that the speed of motion of the molecules over-rides the density effect in most cases when you change either the temperature or the composition of the gas.
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Author: David Peacham
Date: 2005-07-06 16:58
Archer9160 wrote:
"if you compress the gas, the speed of sound _will_ increase in it"
Will it? Reference, please?
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If there are so many people on this board unwilling or unable to have a civil and balanced discussion about important issues, then I shan't bother to post here any more.
To the great relief of many of you, no doubt.
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Author: archer1960
Date: 2005-07-06 19:23
David Peacham wrote:
> Archer9160 wrote:
> "if you compress the gas, the speed of sound _will_ increase in
> it"
>
> Will it? Reference, please?
Yes, it will. I'll dig out my college physics textbook tonight if I think of it.
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Author: archer1960
Date: 2005-07-06 19:45
archer1960 wrote:
> David Peacham wrote:
>
> > Archer9160 wrote:
> > "if you compress the gas, the speed of sound _will_ increase
> in
> > it"
> >
> > Will it? Reference, please?
>
> Yes, it will. I'll dig out my college physics textbook tonight
> if I think of it.
I must apologize: I've been talking out my a** wrt pressure effects. Further research indicates that within normal ranges that humans can tolerate, changes in pressure do not affect the speed of sound; only the temperature and to a small extent the humidity. At a constant temperature, the speed depends on the gas characteristics (chemical makeup: humidity, CO2 content, etc) and not much else.
Sorry for the mis-information.
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