Posted by Rick Denney on April 18, 2002 at 13:56:50:
In Reply to: Re: Re: Re: diaphragm placement/bore size? posted by answers... on April 18, 2002 at 12:48:21:
These answers do not fit with what I observe of my own body.
When I hold my lungs partly or fully filled, I can do so while leaving my glottis open. If I close my glottis, then I can relax inhalation muscles and create pressure. When I leave the glottis open, I must leave the inhalation muscles in the expanded state, allowing a free change of air through the glottis, which in turn requires atmospheric pressure only in the lungs.
This does not get at the question of which muscles do what, but clearly I can do what Klaus suggests without using the glottis.
I'm not persuaded by Klaus's argument, though, in that it seems that my diaphragm is capable of only one sort of movement, and that can control air flow (either in or out), but not air speed. From physics, assuming little or nearly additional zero pressure, flow equals velocity times cross-sectional area. Flow is the volume per unit time. Moving the diaphram (or whatever muscle we should be talking about) creates a cavity into which the lungs are compelled to expand. This expansion creates a volume of emptiness that draws air into the lungs. If the mouth and glottis are open, then the pressure change will be very slight, in which case the speed will be a direct function of the flow. Increasing the speed (in order to control pitch), it seems to me, can only be done by changing the flow, or by changing the cross-sectional area. The only place where the latter can be done during play is the embouchure, and the only place where the flow can be changed is by the diaphragm (or whatever muscle I should be describing). But it seems to me that control over exhalation is what we do to control dynamics, not what we do to control speed, unless there is a compensating alteration of the aperture in the embouchure. In managing this coordination, it seems to me, too much conscious thought is likely to cause more problems than it solves.
Rick "not an anatomist but a careful observer of his own body" Denney