Question about flute bores

Bigbore · Post by **Bigbore** » Mon May 17, 2004 3:43 am

I've been reading some of the old posts here, and looking at various sites, and noticed a couple references to Rudall Rose flutes having complex bores - that multiple reamers were used to give a smaller bore in one spot, larger in another. Why'd they do that? To tune 'em up, or effect the tone in a certain way? And was this unique to them? I've read that uilleann pipe chanters show this as well.

glauber · Post by **glauber** » Mon May 17, 2004 6:20 am

Bigbore wrote:Why'd they do that? To tune 'em up, or effect the tone in a certain way?

Yes.

djm · Post by **djm** » Mon May 17, 2004 7:03 am

You can't directly compare UP bores with flute bores. While some flute bores can be conical, most are cylindrical, whereas UP bores are always conical. Where it gets complicated is that the rate of change in the slope of the UP bore is quite often changed at several points. Many flutes start cylindrical, but then become slightly conical in the top fifth of the bore, usually by about ten percent. Many individual makers will play/modify the bore at different points to tweak it further.

djm

dcopley · Post by **dcopley** » Mon May 17, 2004 9:22 am

Some makers seemed to stick close to a simple conical design, maybe with a flare out for the bottom 1.5 inches or so, where others had more complex changes of taper along the bore. I have a Hawkes and Son, 1895-ish model with a very complex taper, including a 3 inch long cylindrical section part way down the bore.

You can make local variations in the bore diameter and taper to affect the intonation and volume of certain notes, and to correct weakness of some notes. A particular note may be weak because the fundamental (first octave) note, and the first harmonic (second octave) do not have the correct 2:1 frequency ratio. If you enlarge the bore at the right place you can lower the fundamental frequency and raise the harmonic frequency at the same time. If you reduce the bore diameter, the opposite happens. This gives you a method to correct the harmonic ratio, and get a louder note with better intonation. There is a good discussion of this in A.H. Benade's "Fundamentals of Musical Acoustics". I don't know how much of the variation was done as part of the instrument design, and how much was a post-manufacture part of the voicing of individual instruments. Probablya mixture of both. Maybe our flute historians have more information from documents of the time.

Dave Copley
Loveland, Ohio

Nelson · Post by **Nelson** » Mon May 17, 2004 12:34 pm

You have asked a very complicated question. Here goes. The influence of bore geometry on the standing wave in, and sounds coming out of a flute is well known but can be explained only using advanced calculus. I will give you a general feel for what changes what. If anyone wants the advanced treatment, I can send you the references in the engineering literature.
(1) Bohem and pre-Bohem wooden flutes all have a wavie taper. The wavie taper in the Bohem is in the head joint. The wavie taper in the Celtic is in the other end. To the sound, it makes little difference where the taper is, and has very little to do with the coupling our.
(2) With no finger holes to complicated things, there are only two kinds of geometries of a pipe in the whole universe that will have overtones that are harmonicly related. This is most important to understanding standing waves in a pipe. Do you know what these two shapes are? They are a cylincer and a cone. It is proved mathmatically in one of the flute physics books. For those of you with a math background, another way to say this is that the only harmonicly related solutions to the second order differential equation are sine functions and Bessel functions. Sine functions for cylinders and Bessel functions (sin x / x) for cones. In all other shapes, the first over tone of D will not be d, and the next will not be d''. For example in a globe, the famous Helmholtz resonators, the overtones are way up there and go crazy and can be ignored in experiments.
(3) You trouble makers that put finger holes and embrochures in a pipe and want to know what this does to the sound, cause us physicist a royal mess! Finger holes cause the overtones to not be harmonic. Espacially with chimnies. So how are you going to get the overtones back into harmony with the fundamentals? Answer, make the right wave in the bore. The only two choices you have are the cone and the cylinder. Here is the punch line: (a) waves in a cylinder are practiaclly hard to make. Your boring tool gets stuck like a dog gets stuck in a bitch. (b) waves in a cone are pratically easy to make. You can get your tool out.
(4) A little off the subject, any slight change in geometry, sharp edged, tuning holes, under cut holes, espacially twist and eliptical cross-section from wood drying and wetting, cause a difference in sound.

I hope this helps,
Nelson McAvoy

Post by **Nanohedron** » Mon May 17, 2004 1:22 pm

djm wrote:While some flute bores can be conical, most are cylindrical...

I suppose that's true if you're talking about all flutes worldwide. All my trad flutes have a conical bore, wider at the upper register and narrowing toward the foot. Headjoints are cylindrical on these.

It's a problem I have; I keep forgetting that "trad" design ain't the only one being discussed here.

andrew · Post by **andrew** » Mon May 17, 2004 1:28 pm

Thank you Mr McAvoy .
Are there any readers out there willing to join me in asking the Moderator to introduce translation facilities ?

Post by **Nanohedron** » Mon May 17, 2004 1:33 pm

Well, I certainly thought I was clear enough, Andrew. What's not to understand? Your command of English has proven to be adroit. I should think that you of all people would have no problem.

McAvoy? *translator, please*

Post by **Nanohedron** » Mon May 17, 2004 1:47 pm

Aha. My use of the word "register", likely. Mea culpa. Upper toneholes, then.

Alan · Post by **Alan** » Mon May 17, 2004 2:02 pm

"Ouyay avehay askeday..."

No, this will just take too long. Someone more fluent will have to translate.

Loren · Post by **Loren** » Mon May 17, 2004 4:15 pm

Nelson wrote:(2) With no finger holes to complicated things, there are only two kinds of geometries of a pipe in the whole universe that will have overtones that are harmonicly related. Nelson McAvoy

My calculus isn't so good, and perhaps I'm misunderstanding, but square pipe geometry seem to work as well (plenty of square organ pipes and recorders, plus the odd whistle), so what am I missing?

Loren

andrew · Post by **andrew** » Mon May 17, 2004 4:31 pm

I'm sorry , Nanohedron .I hadn't noticed your contributions .
What I did notice the other day was Mr Carte , writing of the (re)introduction of cylindrical bores , saying that they got rid of the need for chambering .
If your flutes include Rudall & Rose , for example , you will find that the taper of the conical bore is not regular .

Post by **Nanohedron** » Mon May 17, 2004 4:32 pm

Oh, my. If I'd only just read other's posts fully...didn't get Nelson's surname. Sorry.

andrew · Post by **andrew** » Mon May 17, 2004 4:40 pm

I don't doubt that Nelson's contribution is all good stuff ,but beyond me, with it's abstruse references . ( Which don't quite address the art of chambering , which I suspect nobody has yet reduced to mathematics useful to a flute borer , and doesn't in practice seem to rely on waves ).

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