Re: a technical question


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Posted by Chuck(G) on July 16, 2001 at 20:20:14:

In Reply to: a technical question posted by Paul Scott on July 16, 2001 at 20:06:59:

The short reason isn't because the metal's expanding, it's the fact that cold metal is cooling the air going through the tuba, making the air denser and sound waves therefore propogate more slowly through air. So, your tuba resonates at a lower frequency.

For dry air, approximately
V (m/sec) = 331.5 + 0.6 T (celsius)

You can get the same effect by simply filling your tuba with a denser gas than air, say CO2 or Radon. Conversely, try filling your horn with helium and enjoy a never-before-imagined-of high range. Playing your horn outdoors in the fog will also lower the pitch, since moist air is denser than dry.

When going from freezing to a nice hot summer day (30C), the amount by which brass expands is infintesimal; certainly not enough to materially affect the pitch.



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