Re: Tone, Pitch, & Temperature


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Posted by Good post! on December 03, 2003 at 10:55:47:

In Reply to: Tone, Pitch, & Temperature posted by Matt Walters on December 03, 2003 at 09:44:18:

Good point, Matt!

Contrary to what some folks think, the hot-cold variation of pitch on a brass instrument does not arise because of the expansion/contraction of metal (which is only a few parts per million, but rather the effect that a cold instrument has on the temperature of the air contained within it.

In other words, a cold instrument will tend to cool the air within it (you're blowing warm air through it, right?), causing the speed of sound within it to change and lower the resonant pitch.

If you're bringing a cold instrument into a warm room, eventually the instrument will reach some sort of equilibrium temperature that is somewhere between the ambient room temperature and the temperature of your exhaled breath.

However, since a tuba is also a giant heat radiator, air circulation (drafts or lack of them) will have a definite effect on that equilibrium temperature. The same goes for absorption of radiated heat--for example, playing in the sun.

Unlike our small-brass friends, this effect of being a radiator or absorber can be quite significant and something we should be aware of.

It might be interesting to place a small temperature probe inside of a tuba to measure these phenomenon.

--Chuck(G)


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