Klarinet Archive - Posting 000076.txt from 1997/05

From: "Diane Karius, Ph.D." <dikarius@-----.edu>
Subj: Re: Air : amount,speed,presure etc.
Date: Fri, 2 May 1997 19:08:20 -0400

Jonathan Cohler wrote (in part):
> People have no conscious mechanism (to my knowledge) of controlling the
> temperature of the air that comes out of them.
True - once the air is inhaled, it is at body temperature (and fully
saturated with water vapor) before the inhaled air enters the
trachea. Since there are some detrimental effects associated with
not allowing the air to heat up, this is one of the things our bodies
won't give up. The air temperature will only change minimally until
it leaves the mouth.

> Furthermore, we have no direct mechanism of controlling air speed.
True (with a partial caveat): With the exception of the earliest part of expiration,
expiratory flow rate is "effort-independent" - meaning that increasing
muscular effort will not have any effect on the flow rate. During the
effort-independent part of expiration, the expiratory flow rate (and
therefore flow through the clarinet) is determined by the mechanics
of the system - airway resistance in particular (open/closed throat,
the clarinet would be part of this, etc...). We get around this
(here's the caveat) by exerting less than maximal muscular
efforts (even while playing), but no matter how gently we exhale,
we will eventually reach a point of "effort-independence".
The stronger and faster the contraction of the expiratory muscles
(which is certainly within our ability to control & we would think
give us the higher flow rates) brings us to the "effort-independent"
limit much sooner, although the initial flow rate is increased
(this increased flow will only last for the first second or so (I'm
making some serious assumptions about expiratory timing,
the level of motor activation etc... - it may be much shorter
(with higher flow rates) or a little bit longer (slower flow rates)).
Diane R. Karius, Ph.D.
Department of Physiology
University of Health Sciences
2105 Independence Ave.
Kansas City, MO 64124
email: dikarius@-----.EDU