 The Clarinet BBoard
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Author: Bob
Date: 2002-06-16 16:54
A recent post re the thickness of reeds got me to thinking about how a reed vibrates and how that vibration affects total sound. Some of the reed vibration must be transmitted to the instrument itself vis a vis the air column. The ligature,lips and teeth must have dampening effects. The "critical" area must be the tip opening but what affect do the side rails have? I've searched the board but don't find specifics on the above. Anyone know of any papers or have factual information on the subject(s)?
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Author: Don Poulsen
Date: 2002-06-17 14:21
I know of no papers, but I can make an educated guess.
In case you are not familiar with why a reed vibrates, let me explain that it is due to the Bernoulli effect. As air passes over the reed, the air pressure on the mouthpiece side of the reed decreases, causing it to deflect in that direction. As the reed closes the gap between its tip and the mouthpiece, the air flow stops and the pressure inside the mouthpiece equalizes to that on the outside, allowing the reed to spring back, reopening the gap and starting the cycle over again.
Knowing this, we can hypothesize that if you thickened the side rails inward, the low pressure area on the mouthpiece side of the reed would decrease, meaning that a lower pressure (force per unit area) would be needed to create the same amount of differential force on the reed in order to deflect it. Bottom line is, there would be more resistance and you would either need to blow a little harder or use a softer (less stiff) reed.
Now, if you were asking about the effect on tone quality, that is the type of question that is best answered through empirical means. In other words, it's easiest to try it out to see what happens.
If you are asking about the curvature of the side rails, I would guess, without having any experience in mouthpiece manufacture or modification, that ideally you would want them to curve smoothly to the tip in such a way that when the reed closes, it contacts each point on the rails and the at the tip at the same moment. Not enough curvature, and you will have gaps between the sides of the reed and the rail. Too much curvature and the tip of the reed will never close against the mouthpiece.
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Author: Mark Charette
Date: 2002-06-17 16:03
I've seen analysis of reed vibrations (movies, analytical) from both Guy Legere and another presenter at ClarinetFest. The modes are numerous and relatively complex (not a nice, simple, vibration mode).
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Author: Ken Shaw
Date: 2002-06-17 18:07
Bob -
I have several hand-made mouthpieces from various makers (Kaspar, Miller, Matson, Wells, Morgan, Kanter, Opperman, Genussa). Each maker except Kanter has made the flat area on rails and tip quite narrow. When I asked about it, they said that more width makes the response stuffy and the sound dull.
Best regards.
Ken Shaw
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Author: Bob
Date: 2002-06-18 15:11
Thanks all and welcome any additional comments. So what happens to the vibration state that causes squeeks...assuming that's what causes them?
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Author: Burt
Date: 2002-06-18 23:02
The rails form a boundary that limits the reed vibration. The curvature of the rails affects the range of vibration which, in turn affects things such as the strength of overtones and how hard you have to tongue to close off the reed. There's lots of room for individuality on the curvature. If the curvature of two rails is not the same (as might happen with a poor re-facing job), some of the vibration modes will be crosswise to the clarinet, which is very undesirable.
Don described the effect of making the rail wider in the direction of the other rail. If the rail is made wider by adding material to the outside of the rail, there should be no impact (only the inside edge of the rail is important).
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Author: Mark Charette
Date: 2002-06-19 00:05
Burt wrote:
>
> If the
> curvature of two rails is not the same (as might happen with a
> poor re-facing job), some of the vibration modes will be
> crosswise to the clarinet, which is very undesirable.
There are a number of fine mouthpiece makers who purposely make asymmetrical curves on the rails, so, at least for some people, asymmetry is not automatically a "bad thing".
The reed has cross-vibrational nodes even on a symmetrical facing.
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Author: Bob
Date: 2002-06-19 14:50
Thin metal alloys are used for various kinds of reeds including the harmonica. Has anyone ever heard of metal being used for clarinet reeds?
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