Klarinet Archive - Posting 000157.txt from 1997/03

From: "Diane Karius, Ph.D." <dikarius@-----.EDU>
Subj: Re: Clarinet bores (was: barrels)
Date: Tue, 4 Mar 1997 17:42:40 -0500

James Pyne wrote (in part):
...> tube/instrument that I constructed to experimentally evaluate the pitch
> drop associated with decreasing bore size relative to length. That
> instrument is one half inch longer than my Buffet R-13. They compare as
> below:
>
> A. Buffet R-13, cylindrical bore @-----.575, with the normal small expansion at
> inlet and large expansion at outlet (Bb clarinet mouthpiece and reed).
>
> B. Tube/instrument, cylindrical bore @-----.500, no modifications to bore
> shape.
> (Eb soprano clarinet mouthpiece and reed)
>
> The closed tube (all tone-holes covered) Buffet R-13 produces, of course, a
> clarinet-pitch low E3 while the tube/instrument produces a somewhat flat
> clarinet-pitch low D3. This is more than a whole step pitch drop in an
> instrument that is 1/2 inch shorter!
>
> Amazingly the smaller bore tube/instrument easily produces a very loud and
> stable sound, rich in harmonic content. In my experience blowing resistance
> and loudness do not always parallel each other in as predictable a way as
> one would hope. Partly this is because, from a perceptual standpoint,
> loudness and sound pressure level are not the same. As Diane Karius
> indicates the changes in blowing resistance should be easy to accommodate:
>
> "Increasing the length of the tube doesn't have nearly that great of an
> effect - doubling the length of the tube will only double the
> resistance to
> airflow - well within the range of the human respiratory musculature
> assuming a normal person"
>
> Intuitively one would expect stuffy resistance from the small-bore
> tube/instrument that I constructed, but that is clearly not the case. It
> produces a robust and very clear tone with, seemingly, little effort.
> Possibly the return (feedback) we get, especially in terms of richness of
> tone quality, is somewhat related to perceived, as well as real effort.
>
I agree with Dr. Pyne's suggestion that respiratory sensation
is (at least in part) at issue here. Based on some of the different
bores that have been posted, I calculated the
relative change in resistance to airflow through the different instruments
(including the "tube" described above) (I always knew that PhD would
come in handy for something...). The largest change in resistance
was between the "tube" and the R13 - its airway resistance hadn't even
doubled (Resistance of tube is sbout 171% of that in the R13).
Noticeable to anyone, but not insurmontable. However, the
pereception produced by a change in resistance is extremely variable -
the sensation of dyspnea (difficulty in breathing) is extremely powerful,
very subjective and does NOT strongly correlate to any of the measureable
indices of pulmonary mechanics (like airway resistance). Whole
dissertations have been written trying to correlate respiratory sensation
to objective measurement (no, mine was not one of them...)
Diane R. Karius, Ph.D.
Department of Physiology
University of Health Sciences
2105 Independence Ave.
Kansas City, MO 64124
email: dikarius@-----.EDU

   
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