Klarinet Archive - Posting 000214.txt from 2010/08

From: Jennifer Jones <helen.jennifer@-----.com>
Subj: Re: [kl] About clarinet acoustics
Date: Tue, 17 Aug 2010 17:16:13 -0400

Below, I consider complex measurement of end effects in clarinet.

-Jennifer

On Tue, Aug 17, 2010 at 10:15 AM, Keith Bowen <keith.bowen@-----.com> wrote:
> Jennifer
>
>>The node location estimate for notes with open tone holes in
> cylindrical bored portions of clarinets seems to be missing a
> parameter. =A0The equation you sent looks like it is only the end
> correction. =A0Where does the length of the clarinet come into it? =A0The
> simple calculation was L + 0.6a where a =3D radius. =A0Is the complex
> calculation something like L+C?.
>
> The length of the clarinet only comes into it for the fully-closed notes.
> The equation isn't missing a parameter.

Now that I look at how the flute/cylindrical tube end correction
again, I see the form in which it was given matches the form that you
presented the end correction for notes with open tone holes; just the
end correction is given, so if I understand correctly, the end
correction is added to the length of the tube. In the case of the
whole flute, it is the full length (L) from top to bottom plus 0.6 *
radius (a). Whereas in the case of the tube with open tone holes, I
assume, the length from the mouthpiece tip to the open tone hole
counts as L which is added to the end correction C, noted in the
previous email.

> On 16 Aug 2010, at 22:40, Keith Bowen wrote:
>
>>> The end effect must be taken into account as it can be more than the
> distance between tone holes. The correction formula is on >page 450 of
> Benade (Fundamentals of Musical Acoustics) and is also given in my master=
s'
> thesis that I sent you recently.
>
>>>"The acoustic length is longer than the physical length to the last clos=
ed
> tone hole by the amount
>
>>>C =3D z/2{sqrt[1 +(4/z)(t+hd)(D/d)^2]-1}
>
>>>where z is the distance to the next open tone hole, d is the diameter of
> that tone hole, D is the bore diameter at the open tone hole >and t is its
> depth. h is a factor that may be taken as 0.75 for a completely open hole
> and 1.0 for an average padded hole."
>
>>This can be used to estimate the first node location without removing
> the bottom of the clarinet, but it requires a narrow ruler that can
> get in through the tone holes...
>
> Well I didn't say that you could use a ruler. I used a vernier caliper wi=
th
> depth gauge. There are accurate plastic ones available (used in the car
> industry for measuring without scratching), which are the types that one =
is
> allowed to use on museum specimens. Using a ruler would be taking bad data
> :-).

Well, dang! I gotta get me one a those!-)

-Jen
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