Klarinet Archive - Posting 000128.txt from 2010/08

From: "Keith Bowen" <keith.bowen@-----.com>
Subj: Re: [kl] Location of antinodes of vibration in an air column
Date: Sun, 15 Aug 2010 07:45:32 -0400

Tony

It could be. The speed of sound does vary inside an instrument. You recall
correctly, it goes faster in a flaring section (not in a pure cylinder or
cone though). This is a big factor in the acoustics of trumpets, and also at
the bottom end of a clarinet. As you say, it's also affected by skin
friction. It will also be a factor at the mouthpiece end. How much, I can't
say without doing a lot more work, but I do have to get to grips with this!

How terrible, to be stuck in Siena!

Keith

-----Original Message-----
From: Tony Pay [mailto:tony.p@-----.org]
Sent: 15 August 2010 10:14
To: The Klarinet Mailing List
Subject: Re: [kl] Location of antinodes of vibration in an air column

On 15 Aug 2010, at 00:18, Keith Bowen wrote:

> I, too, am surprised that the distance from the reed tip to the antinode
is as much as 8 cm. This doesn't correspond with some quite detailed
measurements and calculations I made last year of bass clarinets to
determine their pitch (not being allowed to play museum specimens).

I think I see where the 8cm problem is. Diego has made the assumption that
the 'speed of sound' in the clarinet tube is the same as the speed of sound
in open air.

But we know that that speed can vary according to other parameters -- for
example, the 'shoelace-down-the-tube' experiment, that changes the pitch of
a clarinet as much as a semitone, demonstrates it. And I seem to remember
(stuck here in Siena without access to references) that there is something
about the diameter of even a theoretically smooth tube....

No?

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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