[sasa999]

Вот такое прочитал, но всё ровно не всё понял. На зафуне это то же самое отверстие которое с низу большим пальцем закрывается? Как это отверстие на Вb инструменте может быть на "low А" ? На Вb инструменте же нет ноты "low А" так как самая низкая Bb.
Или же я что то путаю?
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Optimum proportions of speaker hole (cylindrical bore instruments)

For a cylindrical bore instrument, provided that the speaker hole serves only to produce the upper registers (i.e., that it does not also have to function as a tone hole for throat Bb), its optimum diameter vs. length proportions can be calculated from (adapted from Benade, 2nd ed., p. 45:

(d/D)² x L / (t + hd) = 0.7570

where
d = diameter of speaker hole
D = main bore diameter
L = acoustical length of the note for which the speaker hole is ideally located
t = length of speaker tube
h = approximately 0.75 (assuming a healthy pad opening height, which is not always the case!)

so, rearranging the formula,

t = [(d/D)² x L / (0.7570)] - hd


Example:

for a Bb clarinet with a bore diameter of 14.6mm, and with the speaker hole located ideally for low A (which has an acoustical length of 440mm), some optimum speaker tube dimensions are:

d = 2.1mm t = 10.5mm
d = 2.2mm t = 11.5mm
d = 2.3mm t = 12.7mm
d = 2.4mm t = 13.9mm
etc.

which agrees very well with, for example, the speaker tubes found on Reform-Boehm clarinets by German makers such as Wurlitzer; the speaker hole diameter is considerably larger on conventional clarinets, where the hole also produces throat Bb

http://www.sfoxclarinets.com/Mathematics.html#clspkr