David Lim wrote:Uilliam wrote:Now then lets hear all the sentimentalist arguments against....
uilliam
If you can feel the chanter vibrate in your hands then some of that energy from the vibrating column of air is passing into the wood (or other material).
This is certainly true. The resulting vibration of the timber doesn't have a direct effect on the sound, because the amplitude is dwarfed by the amplitude of the air vibrations, but as any good acoustics text will tell you, there are definitely damping effects associated with the wall material.
As for whether the differences in these damping effects are significant enough to account for discernible tonal differences, there is little agreement. To a "first or second-order" theoretical analysis it would seem that they are not, but the fact of the matter is that no one has really solved the relevant equations more rigorously. So those who point to a theoretical argument "against" wall material and/or microscopic roughness effects must concede that the effects usually categorized as "minor" or "tertiary" have never been quantified.
As I understand it, the complete equations are highly nonlinear, and so they are very difficult to solve, even numerically. Two of the things that are believed by theoreticians to make some of the usually-ignored effects more important are narrowness of bore and presence of a double reed. In other words, union pipes and oboes are among the most difficult woodwind instruments to model theoretically, whereas clarinets and flutes are much simpler.
(To my knowledge, all of the "empirical demonstrations" suggesting that wall material is acoustically unimportant have been carried out with flutes and clarinets.)
I have a strong interest in acoustics and a considerable background in the scientific field (admittedly as a numerical simulations/programmer type), and was pre-disposed to believe, from these theoretical arguments, that material didn't matter much. But my ears, and hands-on experiences, are telling me otherwise.
I did a bit of power-spectrum analysis of two chanters which are nominally "the same" (same reamers, tonehole spacing/size, chimney heights). One was made of violet rosewood (dalbergia louvelli) and one of ebony (diospyros sp.). (I could have used balsa and epoxy I suppose, but in my view the results of experiments like that are less interesting than trying woods that are already believed to be suitable.) The two chanters definitely sounded different with the same reed, and I recorded them under the same conditions on the same day, then did some spectral analysis of selected notes (the D major arpeggio from bottom D to third-octave-d). The initial results seem to bear out a consistent difference in harmonics, though I would concede that they are not by any means conclusive. A few notes show little difference harmonically, but overall the ebony chanter has a weaker fundamental relative to the harmonics (meaning a brighter, more harmonically rich sound), and in particular the ebony chanter often has stronger 4th and 7th harmonics than the rosewood chanter, and may have more harmonics represented overall.
Here's a dramatic example, showing the A4 (first octave A) note for the rosewood chanter:
and the ebony chanter:
Note: The vertical axes in the two plots are NOT to scale.
If you look at the vertical axes you can see that on the rosewood chanter, the fundamental is dominant, whereas in the ebony chanter the fourth harmonic dominates, for a brighter sound. Also, note in the top time-axis graph how the fourth harmonic "develops" over a period of 50 ms or so. The rest of the plots show similar general phenomena, though for some notes the differences are more subtle.
These plots illustrate a lot of other physical phenomena - for instance, cutoff frequency effects associated with tonehole sizes (thus, weaker harmonic content in the second octave), and the overall similarity in harmonic profiles reflects the basic similarity in the two bores. In other words, the chanters sound very "similar" in a familial way, but the rosewood one has a more muffled sound when compared side-by-side with the ebony. I believe that the semi-quantitiative results in the plots show the physical evidence of this subjective impression.
Another interesting point is the apparent importance of the seventh harmonic. In many instruments I believe the seventh harmonic is considered undesirably "dissonant" (as it corresponds to a flat minor seventh), but it is one of the strongest harmonics in the hard D and in some other notes, at least in my experiments. I suggest that perhaps the 'dissonant' seventh harmonic is one of the ingredients in chanter tone that gives it a "crack".
Have a look at this plot of the ebony hard D, for instance:
Note that the fundamental is very weak indeed!
If you want to look at all the plots, go to:
http://www.imagestation.com/album/pictu ... 1014&idx=2
I get the impression that very small bore deviations, on the order of a thousandth of an inch or less, and similarly quite small changes in tonehole size and undercutting, can have an appreciable effect on tone quality. For this reason, and the fact that my measurement and fabrication techniques are not good to the 0.01 mm accuracy, one would want to repeat this experiment with a collection of "supposedly-identical" chanters to have something statistically significant and/or conclusive. That said, I have made chanters from a number of woods, and the ebony ones have consistently seemed distinguishable from the others tonally (as well as in other ways).
David's comment below seems true to me, but in fact the theoretical arguments on both sides are presently mostly hand-waving, until someone can quantify them a bit better.
Bill
The nature of that material (including its surface) will control exactly which amounts of which frequencies are removed from the column of air. It may even put some altered energy back into the air column. And thus the material will have an effect on sound quality.
David