Klarinet Archive - Posting 000161.txt from 2010/08

From: Tony Pay <tony.p@-----.org>
Subj: Re: [kl] About clarinet acoustics
Date: Mon, 16 Aug 2010 17:13:14 -0400

On 16 Aug 2010, at 21:29, Jennifer Jones wrote:

> Mike McIntyre wrote to Tony Pay:
>
>> The only way out I can see is that the textbook "cylindrical bore"
>> is at best an approximation -- especially near the mouthpiece?
>> If the bore cross-section varies along its length, then that
>> shifts the node-antinode pattern, of course, as
>> with the extreme case of oboes and saxophones. If you tell me how the
>> cross-section varies I could think about this a bit more.

What you subsequently write, applied to mouthpieces -- and oboe reeds -- I would say has only a small effect, which is why I didn't pursue it. (I couldn't see that it would reduce 8cm very much.) The main thing about oboes and saxophones is that the bore REMAINS conical as you continue down the instrument.

So I should have read Mike's '?' more seriously. He doesn't have to do with clarinets on a daily basis like us -- well, ME:-( -- you have proper jobs -- and so is not so immediately aware of the fact that the major departure from cylindricality in a clarinet is at the bottom end.

I think I shall find tomorrow that a precise determination of the pitch of a fingered low E without the bell gives a more plausible calculated position for the top node. (I have a suitable app on my iPhone:-)

Of course, really we need another method for determining it. If I said, for example, that I could remove the bottom flare with blutak and THEN do the experiment, you might say, well, hang on a minute, that's not a CLARINET. We'd need to know further that the postion of the top node doesn't change much with such a modification.

The fact remains, if I understand things correctly now, that having cylindricality is the only way that Diego's calculation method works.

What other methods are there for determining node positions?

Tony
--
Tony Pay
79 Southmoor Rd
Oxford OX2 6RE
tel/fax +44 1865 553339
mobile +44 7790 532980
tony.p@-----.org

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