Klarinet Archive - Posting 001095.txt from 1998/11

From: Clarguy3@-----.com
Subj: [kl] burping, helium and pitch
Date: Sat, 28 Nov 1998 11:05:37 -0500

The string about helium and CO2 and its relationship to pitch is interesting
and has a certain practical application. In fact, the density of a gas does
affect clarinet pitch--this is why the first note at the beginning of a breath
is sharper than a second or two later on. The tidal air (or so it is called
by the respiratory and pulmonary communities) is the same as outside air,
since it has only been in the body as far as the trachea, mouth and bronchi.
The air which emits somewhat later has been out in the avoeli, where the
CO2-Oxygen exchange takes place. After the tidal air is blown out, that which
has greater carbon dioxide saturation causes the pitch to settle downward
somewhat. This is due to CO2 being a heavier gas than oxygen and thus the
reed vibrates somewhat more slowly. You can demonstrate that this is true
with a tuner by taking a deep breath and blowing off the top small bit of you
breath, and then start the pitch. The initial rise in pitch will not be
present as it was when you only took a breath and played at the top of the
breath.

As to burping, yes, the pitch does drop, but only drops significantly if the
gas emitted is laden with CO2. Thus, if you're drinking a carbonated soft
drink or beer while playing any wind or brass instrument and then burp, the
pitch does drop. A garden-variety burp, as after a large meal, won't make the
pitch drop much at all by comparison.

And helium--being a very light gas (ref. the discussion on this string about
heliox and deep-sea diving), causes the voice to sound higher because the gas
is much lighter and the vocal folds vibrate more quickly in the lighter gas.
If you take some helium from a toy balloon into your lungs and blow it into
any wind instrument and you get a huge sharpening of pitch--like on the order
of a minor third or more. Incidentally, heliox is also used in hospitals for
severe asthmatics.

The practical application of the information that gas density affects pitch of
a wind instrument would be in reference to the tidal air at the beginning of a
breath. A whole secton of clarinets breathing at the same point will play
more easily in tune than one which staggers breathing. And the fingering one
can use for the first open G of Premiere Rhapsodie can be (and probably should
be) much more covered, thus flatter, than any open G following in these
phrases.

Chuck

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