Klarinet Archive - Posting 001101.txt from 1998/11

From: George Kidder <gkidder@-----.net>
Subj: RE: [kl] Wagner; Fiume March; Helium and Pitch
Date: Sat, 28 Nov 1998 18:07:23 -0500

>> 6) And finally, while there is a difference in total density between
>> room air and expired air (what we blow into our instruments), this is
>> not due only to CO2. Expired air is also a) warmer, and b) saturated
>> with water vapor. Both of these will also change the density and
>> therefore the instrument's pitch.
>
>The difference I was referring to was not between room air and expired
>air. It was the difference between recently inspired air and air that
>had remained for a period of time in the lungs.
>
>Tony
>--
> _________ Tony Pay
> |ony:-) 79 Southmoor Rd Tony@-----.uk
> | |ay Oxford OX2 6RE
> tel/fax 01865 553339
>

However, when you breath in, the last air into the system never makes it to
the lungs, but remains in the trachea and oral cavity. Therefore, this
"dead volume" air, which is the first to be expired (whether into a clarinet
or otherwise) has not been subject to the alterations which occur in the
lungs - removal of oxygen and replacement with carbon dioxide, and (to a
great extent) addition of water vapor. This dead volume air resembles room
air much more closely than "end-tidal" air from later on in the expiration.
Thus, if the clarinet is sensitive to the composition of the air going
through it, as it seems to be, this composition changes during a normal
expiration from something resembling room air to a rather different mixture,
and this change can affect the intonation.

I think we are saying the same thing, really. I am just adding anatomical
"detail to an otherwise bald and unconvincing narrative." (G&S, Mikado)

George Kidder

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