Klarinet Archive - Posting 000104.txt from 1996/10

From: Jordan Selburn <jselburn@-----.EDU>
Subj: Re: odd comment (acoustics)- CO2
Date: Sat, 5 Oct 1996 00:16:34 -0400

Does anybody know offhand how the varying CO2 content affects pitch? If the
speed of sound in CO2 is markedly different than in whatever the rest of
what we exhale (mainly N2???), than the pitch should change as we play a
long note/phrase.

I'm probably at A@-----.

Jordan
and glad to be back on the list

>Excuse-me if I am dropping on the list a little late for this discussion, I
>could not make use of my net for a whole week.
>I am doing research on breathing/blowing habits in reed woodwinds and this
>theme interests me a lot.
>I have been measuring the CO2 contents in exhaled air during playing the
>oboe and I got some preliminary
>ideas and data so far :
>
>- The percentage of exhaled air during normal respiration (no instrument
>connected to your mouth)
>usually ranges from 2.5 % to 3.5 . If you take more time to complete the
>exhalation phase, the final amount of CO2 should increase.
>- As you start playing (I just measured oboe until now) the percentage of
>CO2 raises continuously from the above values and depending on the duration
>and remaining air volume in the lungs, being this slope positively
>dependant on time (the more-the more) and negatively to instantaneous volume
>(the least volume, the fastest the increase of CO2).Values close to 8% were
>found while 1 subject (myself) played Schumann's 2nd Romance, during the
>long phrases, without circular breathing, of course.
>- A measurement with 4 subjects, showed (preliminarly) that if a small flow
>of air is produced through a
>small opening, at aprox. 30 cm H2O mouth pressure, the maximum bearable
>condition corresponded to aprox. 8% in
>all of four subjects.
>-If you quickly breath in or perform a circular breath, the %CO2 quickly
>returns to the low levels.
>-The maximum tolerable percentage of CO2, before you faint is of about 10%
>according to some sources. Of course you will die if this condition
>persists...
>
>Well, as I told before, this is just a first glance on the CO2 presence and
>I am planing to write a paper on that later on. I will turn to the problem
>by the end of the year and would like to keep in touch with the
>"green-house effect watchers" in woodwinds.
>
>I used an equipment called "Capnograph", which measures the CO2 content
>through the infra-red method. The model used was :
>Capnograph , CD-3A Carbon Dioxide Analizer (I don't have the name of the
>manufacturer now)
>
>A fresh air for all,
>Leonardo
>
>Music Acoustics PhD Programme
>Royal Institute of Technology
>BOX 70014 , Drottning Kristinasvag 31
>S-10044 - Stockholm - SWEDEN