Klarinet Archive - Posting 000585.txt from 1997/11

From: njs5@-----.uk (Nick Shackleton)
Subj: RE: Clarinet Material Makes a difference - proof enclosed.
Date: Sat, 15 Nov 1997 11:52:59 -0500

I found this experiment very interesting. I have an idea what the
explanation may be.
Contrary to what is apparently learned in the University of Wisconsin, one
does not want to make the clarinet vibrate; one wants to make the air inside
it vibrate. I mentioned in an earlier posting that when we feel the barrel
vibrating this is a measure of the mouthpiece moving in response to the reed
vibrating and beating against it; we are wasting energy moving the clarinet
to and fro when the energy is intended to be transferred to the reed.
So my interpretation of this experiment is that when the clarinet body
vibrates in response to the reed, it oscillates to and fro about its centre;
the maximum to-and-fro movement will be at the ends. Thus the most effective
place to add weight in order to reduce this would be either at the
mouthpiece or at the bell.
If I'm on the right track, then this predicts that you'll also detect an
effect if you add the playdough on the mouthpiece, but that if you attach it
around the thumbrest it will have much less effect.
What I really like about how this experiment is described, is that Jerry
actually feels a change in how the instrument responds. I believe that this
proves that the effect is not related to any radiation from the vibrating
surface of the instrument (which, as I mentioned in an earlier posting, has
previously been argued to be negligible). Maybe the whole business of the
material of the body of the clarinet, and the material of the mouthpiece,
and the fancy designs of barrels, is related to which frequencies in the
reed vibration are preferentially absorbed by the mouthpiece/clarinet
vibration and which are transmitted to the air column.
Nick
>I'm reposting this cause AOL appears to be swallowing lots of my email to
>Klarinet. I think this is important enough...
>
>
>I have been listening, and reading, about the clarinet acoustic debate going
>on here on the list for a while now. Being trained in the sciences, I
>immediately took the side of the acoustician's and physicist's position that
>the physics of the situation dictate that material should have no effect.
>
>But one must remain a student of observation to be a scientist... So I
>decided to do an experiment.
>
>It always seems to me that when theories break down it has to do with
>boundary conditions. In fact when the Clarinet bore changes from cylindrical
>to the bell, such a boundary condition exists. (That is the physical location
>where the bore changes from cylindrical to conical.) The bell is also acting
>as an acoustic impedance coupling device. In a transitional geometry such as
>this I would expect that the theoretical math describing the acoustics and
>the actual situation may differ. In fact, this is where engineers make their
>money (and why mathematicians dislike engineers). Engineering involves
>observation and making up math to describe an observation. Fudging, of
>course, where necessary.
>
>So, I undertook a little experiment to see if material affects the acoustical
>performance of the clarinet. And in fact I have some surprising results. This
>is something that I hope each of you will try...
>
>Take a piece of playdough (approximately two ounces or a decent fistful).
>Plaster the playdough around the outside surface of your bell, just abover
>where the metal band around the largest diameter is.
>
>Now play an F major 7th arppeggio (lowest register) and a C major 7th
>arppeggio (starting at A440 or A44X what ever). Do some fancy articulation as
>well.
>
>Have a woman listen if you are male. They have better ears (even if they
>don't buy expensive stereo equipment).
>
>Then while playing these two arppeggios have your observer remove the wad of
>playdough.
>
>To me the differences in sound, are plain and simple. The playdough damps a
>high frequency component that adds richness and overtones to the sound. It
>also sounds this way to my wife and my brother. (I asked them to describe the
>difference before I told them what I heard.) The diferences are distinct and
>obvious.
>
>Now for the interesting part. Yes the sound is WAY DIFFERENT! But more
>interestingly to me the resistance of the right hand in the upper register
>(A440 and above) completely changes!!!
>
>What is happening here? The playdough is acting to damp vibrations in the
>bell of the clarinet. If the sound of the clarinet changes when the playdough
>is on it, then the clarinet must have vibrations that affect its sound.
>
>When I tried moving the playdough up the length of the clarinet, I could
>convince myself of some very minute changes in sound, but nothing of the
>order of magnitude of change as when the playdough was placed on the bell.
>
>Therefore, the material used to manufacture a clarinet DOES have an influence
>on the sound. But this influence is most likely to be felt in the very lowest
>(physically far away from your mouth) region of the clarinet.
>
>Now will someone please explain the change in resistance felt while doing
>this experiment?
>
>Jerry Korten
>NYC
>
>