Klarinet Archive - Posting 000492.txt from 1997/09

From: Jonathan Cohler <cohler@-----.net>
Subj: Re: Clarinet material
Date: Wed, 10 Sep 1997 02:25:09 -0400

Jerry Korten writes:

>In a message dated 97-09-08 16:11:16 EDT, Steve writes:
>
><<
> Jerry Korten,
>
> Why do you suppose, then, the sound going through a rosewood
> instrument will project less than that going through a grenadilla
> instrument.
>>>
>Not known to me. I must try them to find out. If the Rosewood is so soft that
>it does vibrate then that would account for the difference. But I bet the
>effect is psychological based on the weight of the instrument.
>
><<
>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.

><<
>Perhaps it's not the tone (darkness...sorry Dan) that the
> material affects but the projection of sound. Can softer materials absorb
> sound more than harder materials?
>>>
>Yessiree. If the material is really soft it will affect the sound.

Certainly, if the material is too soft, you won't even be able to make an
instrument out of it. But any reasonably hard material such as wood, metal
or plastic will work. FYI, the difference in thermal absorption between
copper, brass, silver and wood is very small. Between the metals there is
only a difference of at most .06 percent. Between the metals and wood
there is a difference of just over 2 percent.

Note that wood absorbs 2 percent less thermal energy than metal does.
However, because of losses due to porosity the combined losses of
thermal/porosity effects is slightly greater in wood than in metal. For a
highly polished, smooth dense wood, the difference from metal is in the 2
percent range, putting it just on the edge of detectability by the player
(not by the listener).

There are also viscous losses due the flow of the air through the tube.
Even if the surfaces are perfectly smooth, there will still be viscous
losses due, in essence to the air rubbing against itself and the smooth
walls.

Bottom line, once again, the material doesn make any difference in real life.

>
><<
>I always thought this was so. Part of
> "setting up" a clarinet is polishing the bore; does this affect the
> sound/timbre of the instrument? Again, I thought this was so. Please
> explain.
> >>
>Can't explain... Don't know enough! But I do know that some say the clarinet
>to buy is the one with a porous looking interior (see paper by Hite I believe
>at his web site on barrels).
>
>I do think that the level of polish on all commercially made professional
>instruments is sufficiently high enough to produce the same effect though. If
>there is such an effect, I would guess it would be affecting the way in which
>standing waves are reflected inside the bore. Much in the same way as frased
>holes affect the timbre of an instrument.
>

As I've mentioned in previous posts, having smooth surfaces and rounded
corners (which you refer to as fraised holes) is VERY important and has a
MAJOR effect on the playing character of a wind instrument. This is due to
turbulence caused by rough or jagged surfaces. But again, this is
independent of material.

--------------------------
Jonathan Cohler
cohler@-----.net