Klarinet Archive - Posting 000566.txt from 1997/11

From: Roger Shilcock <roger.shilcock@-----.uk>
Subj: RE: Clarinet Material Makes a difference - proof enclosed.
Date: Fri, 14 Nov 1997 15:35:07 -0500

The tube in Sean's discussions and experiments is presumably deemed to be
a weightless tube of non-vibrating material - at least, as regards
discussion of the basic principles. Sound waves are also held to propagate
longitudinally; this does not mean that they inevitably propagate
lengthways along a wind intrument, however. It would be interesting to
know (maybe somebody does) just what the shape of the wavefront is like,
both during attacking a note and when a note is being sustained; if the
wavefront is not perpendicular to the longitudinal axis of the tube at all
points, then reflection from the inner surface is bound to occur - and,
possibly, the setting up of some sort of vibration in the wall*. It still
has to be determined what kinds of vibration these might be - and whether
they could affect the perceived tone spectrum of the instrumental sound.
Jerry Korten's "playdough" experiment may involve damping of reflected
waves.

Roger Shilcock
*Nobody seems worried about the alleged spherical curve of the wavefront
in
oboes and saxophones....

On Fri, 14 Nov 1997, SEAN TALBOT wrote:

> Date: Fri, 14 Nov 1997 08:28:29 CST
> From: SEAN TALBOT <talbotse12@-----.edu>
> Reply-To: klarinet@-----.us
> To: klarinet@-----.us
> Subject: RE: Clarinet Material Makes a difference - proof enclosed.
>
> >Now will someone please explain the change in resistance felt while doing
> >this experiment??
>
> I'm just going to take a stab at this, no idea if it is correct. It seems
> that when you push air through the instrament, you are working to vibrate
> the entier instrament-----air, wood, posts, keys----in a complex but stable
> mannor. When you added the playdough, this made it more difficult to
> set the instrament in motion. It is comparable to adding more stain to
> a violin. You add stain and it changes how the air inside the box vibrates
> oddly enough. Take the lacquer off the sax and it changes the playing
> characteristics. It seems that if the wood doesn't vibrate as easily, the
> air doesn't vibrate as easily, and if the air doesn't vibrate as eaily you are
> going to have to put more energy into the system to make it vibrate causeing
> more resistance.
>
> At least that is what I learned in my Physics of Sound and Music class here
> on campus when we discusses the reflection/refraction characteristics of a
> closed end cylindrical tube which is what the clarinet is.
>
> Sean Talbot
> University of Wisconsin - Whitewater
>