Klarinet Archive - Posting 000657.txt from 1997/09

From: Jrykorten@-----.com
Subj: RE: Clarinet Materials
Date: Fri, 12 Sep 1997 17:57:07 -0400

I Certainly never assumed a brass and copper bell were attached to an air
column! Most bells that I know of are suspended and sounded by a clapper, as
in a church or a ship. In this case the material is vibrating and generating
the vibrating air column.

The issue of material for a trumpet type of instrument was demonstrated in
the late 1800's (see Stubbins book in appendix on materials) where a
demonstration showed that a wooden trumpet was indistinguishable from a metal
trumpet.

On the issue of material, there is one issue that still needs to be addressed
and this is a passing comment made by O. Lee Gibson that certain low
frequencies are "launched from the bell" of the clarinet. If so this could be
a determining factor in the selection of material for that part of the
instrument. Although I am not so sure of this as it has not been documented
by research that was cited in Mr. Gibson's book.

Jonathan, concerning your statement about fraising and turbulence/viscosity.
At the low flow rates of the air through the column - does this really have
an effect? Or is it the air speed in the vibrating air column that is
interacting with the smoothness of the surface?

And speaking of books, when is Jonathan Cohler going to write a more
comprehendible book on clarinet acoustics than those currently on the market?
It seems like a natural....

Jerry Korten
NYC

In a message dated 97-09-10 01:58:26 EDT, you write:

<< >A brass bell rings with a different sound (not pitch) than a
> pure copper bell.
>>>
>Different sounding mechanism. Here the body of the instrument vibrates (not
>the air column) which generates the sound. So the material has an effect on
>the sound. Just like a piano or a violin - the wood material and its
>preparation make a BIG difference in sound because they are vibrating.
>

NOT TRUE. Wall vibrations do not contribute audibly to the sound of a brass
instrument. The air column vibrations create the sound in a brass
instrument. This is TOTALLY different than the sound mechanism on a
violin, which works as follows:

* bow pulls across string causing string to vibrate
* string vibrations are transmitted through bridge to the top plate
of the violin
* top plate vibrations are transmitted to the back plate by the
sound post
* back plate vibrates moving a large mass of air and creating most
of the sound

On a brass instrument, the libs vibrate and excite the air column to
vibrate. That's why these are also called "lip-reed" instruments.

>>