Re: ATT: Rick Denney


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Posted by Joe Baker on October 16, 2003 at 11:27:21:

In Reply to: ATT: Rick Denney posted by tim on October 16, 2003 at 03:57:29:

That depends; that 'C' would be open 4th partial on a C tuba, or first-valve 5th partial on a Bb (I leave it to the reader to figure it out for other key tubas & alternate fingerings). The tube length could be MANY different lengths.

There are other factors we would have to either choose to ignore or simulate with MUCH more complicated mathematical models. So to simplify: assuming a tuba-playing automaton who blew room-temperature air into the mouthpiece, who could not listen and adjust his embouchure -- and would therefore have to account for temperature changes ONLY with slide movement -- the ratio of wavelength/tube length would be constant. So you could only answer the question if you knew the actual tube length. Since the tube length is undoubtedly MUCH longer than the wavelength (262 CM is a little shorter than a trombone), the amount pulled out would be proportionally greater than the increase in wavelength (but then divided by 2, since you've got two stretches of tube being shortened).

In the simplest case, open bugle of a C tuba, then, the wavelength is 1/2 the tube length (1/4 of the tuba's fundamental wavelength, since it is an open pipe). So if you want to shorten the wavelength by 1/2 CM, you'd have to shorten the bugle by 1 CM; but you would do that by pulling out only 1/2 CM.

Joe Baker, who thinks some problems are better solved empirically than mathematically.


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