 The Clarinet BBoard
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Author: Amanda S
Date: 2004-10-16 03:52
I needed a science fair project that I was interested in, so my bio teacher gave me this idea: How does the intonation of plastic vs. wooden clarinets vary in the cold and hot? At first, she wanted me to put my wooden clarinet in the FREEZER for 2 hours, but I put my foot down there. I asked her if I could just play it in the could outside. I live in Texas, and the coldest I would take ny horn outside would be 30 degrees...would this crack my wooden clarinet?? My teacher doesn't know much about this subject, so would any of this hurt it? (i'm not to worried about my plastic horn...it seems indestructable...)
Thanks for the help,
Amanda
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Author: GBK
Date: 2004-10-16 04:04
Warm air into a cold wooden clarinet? You're asking for trouble ...GBK
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Author: EEBaum
Date: 2004-10-16 04:20
Perhaps with a garage sale junk instrument I'd carry out this experiment, but with nothing more valuable.
Also, since intonation varies greatly between different models of clarinets and even individual instruments, I'd personally find it hard to come to a conclusion about plastic vs. wooden without a decent sample size.
-Alex
www.mostlydifferent.com
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Author: Phat Cat
Date: 2004-10-16 13:32
Your bio teacher had an episode of fuzzy thinking. There are many factors that affect the intonation of a given instrument. The “intonation of a clarinet” actually consists of the intonation of all the notes on the instrument, each of which can be affected differently by the change of a given factor.
In order to make a meaningful experiment, you would have to keep all other variables the same and measure the change of intonation due to a given change in the temperature. This is difficult to do for a single instrument, but in your case you would need to have a plastic and wooden clarinet that are identical in all aspects, the most important being bore/tone-hole geometry and bore smoothness. This is practically impossible. The closest you could come is probably a Buffet R-13 and a Buffet Greenline R-13 manufactured at nearly the same time.
Assuming that you could find two identical instruments, you’ll have to measure the intonation for different temperatures. This isn’t as easy, since there at least three ways in which air temperature affects the intonation of a given instrument.
First, the actual physical dimensions of the instrument will change with temperature. In the case of a wood body, the relative humidity of the air will also cause the body to change shape/size as it absorbs water. Many “experts” cite physical size change with temperature as the reason the instrument intonation changes. The problem is that a warmer clarinet body would expand, and a longer instrument should play flatter. However, as every player knows, a clarinet gets sharper as it “warms up”. So if the change in physical dimension isn’t what’s changing the pitch, what gives?
Second, the speed of sound in air is proportional to the square root of the absolute temperature ( i.e., in degrees Kelvin). We have just seen that the physical dimension of the internal resonance chamber of the clarinet doesn’t change appreciably with temperature, which means that the wavelength of the note produced inside the clarinet bore for a given fingering doesn’t change. The fundamental formula regarding sound waves is that frequency (i.e., pitch) times wavelength equals velocity (i.e., speed). So, we can see that what gives in our case is pitch, which must also increase since the wavelength is constant and the speed of the sound wave inside the bore is greater for warmer air.
Third, the speed of sound is inversely proportional to the square root of the average molecular mass of the air. Humid air is less dense than dry air (water molecules are lighter than the nitrogen/oxygen mix they displace). So as the air in the bore becomes saturated from the humidity in your breath, the air becomes less dense and the speed of sound increases.
How large a difference does the temperature and humidity of the air in the bore make? A lot. A semitone is roughly 6%. The change in speed due to temperature is approximately 0.17% per °C (which is also °K). And the humidity can account for another 0.1 to 0.2%.
See the following link for a not-too-complicated discussion of this and other interesting topics related to acoustics:
http://www.phys.unsw.edu.au/~jw/musFAQ.html
And don’t ever put your wood clarinet in the freezer and then play it. The drastic change in temperature and humidity between the air in the freezer and your breath will put great stress on the wood. When wood can’t relieve stress gradually, it cracks.
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Author: Amanda S
Date: 2004-10-16 13:40
Thanks everyone...I definently wasn't going to put my clarinet in the freezer, but i wasn't sure about the cold weather. Thanks for the info. I'll find a safer project!
Amanda
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Author: Hank Lehrer
Date: 2004-10-16 16:12
Amanda,
Check out this thread for some temperature/pitch ideas.
http://test.woodwind.org/clarinet/BBoard/read.html?f=1&i=124476&t=124394
I can still see a science fair project though that could be performed with a plastic clarinet and a comparison between specific notes on the clarinet and determining if a graph of the numbers for pitch change is linear or not. You'd need several test and the research should probably be performed outside so that the clarinet is working in a somewhat uniform temperature (as spoken before, eliminate the variables is the only way).
Perhaps a comaprison of tests done with several different models of plastic clarinets or even saxophones. Why not get some band pals that play brass to participate?
HRL
PS If you can find a cold storage locker in your community ...... :-)
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Author: Dee
Date: 2004-10-16 16:43
It is far more likely that it is the radical humidity variations that cause a wooden instrument to crack. If you will search the bulleting, you will find that I showed a calculation of the stresses in a clarinet going from below freezing to 100°F. They are under 100 pounds per square inch. The weakest hardwood for which I could find data has a strength of 1000 pounds per square inch parallel to the grain (the weakest direction) unless there is a flaw in the wood. Dimensional changes due to temperature aren't even measurable over this range.
Now humidity is quite a different story. Most of us have had loose bell rings and/or tenon rings in the winter at one time or another. This is a signficant change in the dimensions.
However, I wouldn't willing put my good instrument in the freezer either.
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Author: Jim E.
Date: 2004-10-17 04:02
My stand mate in a community band was leaving her Bundy in her car all day this summer on rehearsal days. It was almost too hot to touch. WOW was she sharp!
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Author: Hank Lehrer
Date: 2004-10-17 09:45
Jim E.,
This is from my earlier post and clearly shows the problem.
"I went to the libray and got Accoustic Foundations of Music by John Backus, W.W.Norton, 1977 and on page 156 found the following information. "A rise in temperature will flatten the strings. On winds and brass, however, the increased speed of sound at higher temperatures produces a considerable increase in pitch. It amounts to 3.0 cents for each degree Celcius (1.6 cents for each degree Fahrenheit)."
So, it looks like a 10 degree increase in C will raise the pitch 30 cents. I could not find the mention of standard temperature but my recollection is about 72 degrees F."
So, if the clarinet was "too hot to touch" you can see that half of a semitone (half-step) would only take about 30 degrees F above standard using a rate of 1.6 cents per degree F. It would seem that 102 degrees F would be easily achieved; maybe even more.
I always have a 68 mm barrel with me for those summer outdoor concerts, as well as winter rehearsals in a very warm room. I don't think people realize the great effect of temperature on musical pitch (or airplane performance which we call density altitude). It's all the same physics.
HRL
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Author: Gordon (NZ)
Date: 2004-10-17 13:14
Dee wrote "...The weakest hardwood for which I could find data has a strength of 1000 pounds per square inch parallel to the grain (the weakest direction) unless there is a flaw in the wood. "
This is pretty meaningless when we are dealing with a piece of timber that is riddled with flaws.
1. Those inherent in the particular piece of timber. Very little of the timber harvested is good enough to even consider making a clarinet from. A fair bit more is lost because of more flaws discovered during production. A whole lot more undiscovered ones must remain in many pieces of timber.
2. "Stress raisers" are any locations where the shape of the material creates a place where a fracture may more easily begin. They are effectively "flaws" created during production, and can DRASTICALLY reduce the effective strength of the material. Examples include:
a. Tone holes
b. Holes for posts, screws, key guides.
c. Compression exerted by screws, posts, tone hole inserts, key guides when they are of a tight fit. (And don't forget these forces increasing as the timber shrinks around the metal, or expands towards it.)
d. Areas where the timber is thinner, such as at a tenon.
e. Spring grooves.
But I agree with the rest of the post.
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