Klarinet Archive - Posting 000684.txt from 1998/09

From: "Dee Hays" <deerich@-----.net>
Subj: Re: [kl] Pitch standard confusion
Date: Sat, 19 Sep 1998 20:16:45 -0400

-----Original Message-----
From: Bill Hausmann <bhausman@-----.com>
Date: Saturday, September 19, 1998 11:04 AM
Subject: Re: [kl] Pitch standard confusion

>At 09:48 AM 9/19/98 -0500, Dee Hays wrote:
>>If the change were due to changes in the instrument length, they would get
>>longer in the heat (i.e. flatter) rather than sharper as is the case in
the
>>real world. Notice how much players have to pull their barrel or tuning
>>slide on a hot day to match an electronic tuner. They don't push them in
>>unless they have pulled them too far in the first place.
>>
>Right. The change thermal expansion causes is NOT so much in the length of
>the instrument, but in the diameter of the bore. When the wood expands,
>the diameter SHRINKS. Only a very small change is required to be
>significant, relative to overall length.

The circumferential change is still proportional and on wood is very much
less than the 0.07% that I calculated for aluminum. For a 1/2 inch diameter
that is less than 0.00035 inches in aluminum. Again wood is even less.
Thus diametrical or circumferential changes in dimensions due to thermal
expansion are NOT enough to change the pitch of the instrument and the
controlling phenomenon is the sound wave moving out of the horn into the air
with the different density.

By the way a hoop expands on both the inside diameter and outside diameter
when heated so the bore gets larger when warmer not smaller. Remember that
to loosen a metal cap on a jar, you run hot water over the cap. If the
inside diameter got smaller, the cap would get tighter not looser.

Dee Hays
Canton, SD

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