Klarinet Archive - Posting 000280.txt from 1996/10

From: Leonardo Fuks <leonardo@-----.SE>
Subj: Re: CO2 and Pitch
Date: Fri, 11 Oct 1996 05:59:04 -0400

Charette wrote:
>Most of the assumptions on pitch change concerned the CO2 in the
>clarinet air column changing the density. In reality, the amount of
>air expelled to produce a tone for a relatively short time is
>significantly smaller in volume than the air column contained in the
>clarinet. Therefore, diffusion of the CO2 over time would have to be
>taken into account, along with the effective length of the clarinet
>air column (which depends on the holes covered and exposed for the
>note).

Dear Mr. Charette:

The length of a clarinet is approx. 63 centimeters and the inside diameter
is in average lower than 1.5 cm .
The volume of air inside the instrument (bell and tone-holes would not add
too much) :
V@-----., d - diameter, ^2 - to
the power of two
V~ 111 cm3 ~ 0.11 liters

The air-flow through a clarinet reed (if no major leakeage is present), the
flow into the clarinet bore may assume tipically values that range from 0.12
to 0.40 liters per second (Bouhuys&Jonson, JASA 22:1086, 1967).

Your lungs contain very pessimisticaly 4.0 liters of vital capacity . Most
of healthy adults, males, higher than 5'9" - 1.75 m, breathing at sea
level, in a standing position, holding a black clarinet (:)), will have a
V.C. of more than 4.8 liters .

>From the former paragraphs you can conclude that the gas mass inside the Bb
clarinet will be "updated" almost every second, or even more often; that the
instrument will be filled dozens of time by every breath, with increasing
contents of CO2 (not in this message but I wrote about that some days ago).

CO2 is not a type of gas that diffuses as quickly as O2 or H2, in an
air-like mixture. So it is not likely to escape so quickly through your
clarinet holes.

I hope it makes sense.
Best regards,
Leonardo