Author: kdk ★2017
Date: 2020-11-10 19:19
Thanks, Luuk. I think I understood most of this intuitively (or based on the physics and acoustics I remember from school or I've been able to pick up without reference to advanced math). You've added clarity, especially as concerns the match between the reed and the vibrating air column.
My main remaining question has to do with the physical mapping of the vibrations. Obviously, i think, the whole reed must vibrate at the fundamental frequency. Where do the nodes occur physically *in the reed*? In the standard drawing of a vibrating string or air column, the divisions - the nodes - occur at discrete points along the full length, so, for example, the entire A string vibrates nominally at 440 Hz, but areas are also visible (at least in the drawings) in fractional portions along that length that are vibrating at 880 Hz, 1320 Hz, 1760 Hz, 2200 Hz, etc.. The string, if this isn't an illustrator's oversimplification, divides along its length.
The reed differs from a string (or even, I suspect the standing wave inside the tube of a wind instrument) in that it has a relatively larger width in proportion to its length, and the thickness of the reed varies in a controlled but substantial way along both the width and the length. How does the reed divide into partials? Along its length (from tip to the bark at the end of the vamp)? Along its width? Both? The crux for me is, what influence do the changes in thickness have on the location of the nodes and the strength of the partials they create?
One of the things I learned early about reed adjustment was not to create "fences," in one clarinetist's description (may have been in an article by Roger Salander decades ago), places where the change is abrupt from scraping too hard in one place. I assume those sudden bumps, whether natural or made-made, tend to compromise the integrity of the longer vibrations. But even a smoothly contoured reed can taper more quickly or more gradually both toward the side rails and toward the butt end. Those meat diagrams basically map where too much cane can cause specific problems - too dull, take out cane here; squeaks, take out a little cane there; too bright, thin this area, etc. I guess I'm interested in why thinning those areas (since you can't add thickness) does what it does. I'm assuming the location of the nodes that produce each harmonic has an important, if not determinative, effect on timbral character and, perhaps, response, that increasing or decreasing flexibility at those locations can encourage or damp the corresponding harmonics.
If one could (maybe this has been done) slow video of a vibrating reed enough to see the various harmonic sub-areas, where would they form? And, I suppose I should also ask, is this too esoteric to matter?
Karl
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