Re: Human Error in Tuba Making


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Posted by Gerald J. on February 06, 2001 at 10:54:38:

In Reply to: Human Error in Tuba Making posted by Mr. Curious on February 05, 2001 at 17:27:56:

Since I've formally studied acoustics engineering and radio engineering (the wave solutions for both use the same differential equations) I have an opinion. I think that the variations in path affect the acoustic resonance of the instrument. Blobs of solder and dents affect that path. Since the resonance requires standing waves with nodes and peaks of air motion, the position of an irregularity affects different notes differently. At a place where there's little or no motion because of a resonant node (which is different for each note) that irregularity (can be a dimple, blob, or expansion) has little effect, but half way between nodes any irregularity has the most effect. Valves and bends certainly add to the complication by acting as irregularities in the propagation path. I believe that it might be possible to adjust a bad horn by adding dimples at appropriate places. I don't know what those places are and its hard to take out dimples at the wrong places. Some corrections might take inserting flow changing collars to act like an orifice to achieve enough action. Too much restriction might make a beautiful horn on one note and prevent it playing on anything but harmonics of that note.

Gerald J.


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