Klarinet Archive - Posting 000153.txt from 2010/08

From: Jennifer Jones <helen.jennifer@-----.com>
Subj: Re: [kl] About clarinet acoustics
Date: Mon, 16 Aug 2010 16:07:49 -0400

On Mon, Aug 16, 2010 at 11:53 AM, Tony Pay <tony.p@-----.org> wrote:
> On 15 Aug 2010 at 11.15, Jennifer Jones wrote:
>
>> It appears there are some end effects that make the (L+2a) approximation=
not quite
>> correct in the presence of a bell, as indicated by the section "End
>> corrections are more complicated in real instruments" at (4)
>> http://www.phys.unsw.edu.au/jw/musFAQ.html#end. =A0It states that bells
>> are more complicated and links the reader to clarinet acoustic
>> impedance. =A0It appears the end correction is non-linear in the
>> presence of a bell.
>
> On 15 Aug 2010, at 17:43, Diego Casadei wrote:
>
>> I cannot explain the 8 cm, I simply measured it. =A0My measurement does =
not claim to be as precise as 1 mm but it should be at least within 1 cm fr=
om the true position. =A0It would be good if the real experts with the need=
ed equipment could make this measurement, repeated over different tones. =
=A0Unless I made big mistakes, I have experimentally shown that the node is=
far from the vibrating edge of the reed.
>
> What happens if you take the bell off, and measure it again, Diego?

My clarinet, is 67 cm, end of bell to mouthpiece, so 68 cm taking into
account the L+2a, (where a is the bore radius) end correction.
Without the bell, my clarinet is something like 58.3 cm. The
diameter of the end of the lower joint is 2.4 cm, making the effective
length of the clarinet without the bell 60.7 cm [58.3 + (1/2)*2*2.4].
This puts the node a couple centimeters below the tip of the
mouthpiece. I don't have a ruler small enough to fit into the
mouthpiece, but it looks like my baffle extends about 3.5 cm below the
tip. This puts the node in the conical portion of the mouthpiece.

Suppose the first node is somewhere between 2.5 and 8 cm from the tip?

Surely the node is lower than 2.5 cm, since the effective length of
the clarinet with the bell should be longer than the clarinet without
the bell. (This is supported by the extreme sharpness of low E
without the bell.)

-Jennifer

Alas my tuner is packed away in a box and I cannot check the tuning of
my clarinet.
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