 The Clarinet BBoard
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Author: skygardener
Date: 2008-11-16 10:59
Okay, so I have very firmly been on both sides of the fence in regard to the great question "Does the material make a difference?"
Today, I have the real answer.
I saw this tube of foam in the hardware store, so I bought some of it. It is made in such a way that it is smooth on the inside and if you put it to your mouth and close of the far end with your hand, you can suck the air back and the tube will fold on itself just like a drinking straw. However, it is very soft and very flexible. It just happens to be a bit larger than 15mm inner diameter.
So I stuck a mouthpiece on it. Almost NO SOUND. Was there air leaking?? I covered the far end with my hand and pulled the air; suction is okay. Try again... Almost NO SOUND. Only the faintest grunting came out.
Mystery solved by a $1 tube!
Post Edited (2008-11-16 14:07)
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Author: Gordon (NZ)
Date: 2008-11-16 12:58
I think that everybody who claims that material is irrelevant means 'within reason'.
The logic behind the claim is that it is the vibrating air column that makes almost all the sound. Sure, the container of that air column vibrates a little as well, but amplitude is volume, and the amplitude of vibration of the container is so small as to contribute negligibly compared with the amplitude of vibration associated with the air column.
However your experiment concerns a totally different issue, and highlights how people can confuse the effects of different parameters.
The body of the instrument has the function of clearly defining the boundaries of the air column - its shape. To do this it must have a certain minimum level of rigidity as a material. Acoustic scientists have worked out what this minimum must be, and the thickness of different materials required to provide such rigidity.
So the body of plastic, timber, hard rubber, or concrete with walls a few mm thick thick has ample rigidity. And the metal clarinet with wall about 1 mm thick is amply rigid. They all function as containers of the air column. However your floppy foam tube is made of mainly air, and has so little rigidity that it could never pass the minimum criterion of rigidity, no matter how thick it was.
Perhaps the statement that material is irrelevant would be more accurately stated as "Material is irrelevant providing it has a known-to-be-suitable minimum rigidity, and has a suitable surface finish in the bore, and does not have unfilled grain blemishes across tone holes, and does not split, and does not melt in the midday sun, and is robust enough to mount mechanism on, and does not give off toxic vapours, and and and ......
But perhaps your post was simply said tongue in cheek. Nevertheless it begged a response lest the gullible here take it to be some sort of proof, or of profound significance.
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Author: clarnibass
Date: 2008-11-16 13:46
I just took a plastic tube that I happen to have. It's not as rigid as a clarinet body made of wood/plastic/metal/whatever but it's not very easy to squash with fingers (in the middle it';s pretty had and with a lot of force can squash slightly). It is about 13mm diameter bore. I wrapped some teflon on the end and put it inside a clarient mouthpiece (with enough teflon it just fits). It sounds pretty much like a clarinet. I think something a bit more rigid would be better. Of course because of the bore dimentions it doesn't sound exactly like a good clarinet but it's pretty close, and I've seen some clarinets with some notes that sound worse.
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Author: skygardener
Date: 2008-11-16 14:07
Gordon,
It is a bit of a joke, but a bit of serious. I really didn't know what ti expect, and I was not expecting no sound to come out. I did expected something, but I got nothing unless I forced it. I specifically thought about doing this with this material to find what happens to give a clearer picture. With PVC or ABS, the variations are so slight and variables in the bore can cause with variations in sound that it is almost untestable, except in large numbers. Some might think it is obvious (thinking "Of course it would be softer!"), but I wanted to see just how far the limit was. In the very extremes, what happens? Now I know. I note again that this material was air tight, not at all a porous material from the inside.
Maybe I should have added one more sentence to make it more sensible. Here goes...
"So with drastic changes in material, there are unquestionable drastic differences in resultant sound. It is not unimaginable to think that slight changes in material would produce slight changes in resultant sound."
Basically, that is my thought on it.
Post Edited (2008-11-16 14:21)
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Author: Mark Charette
Date: 2008-11-16 15:59
skygardener wrote:
> Maybe I should have added one more sentence to make it more
> sensible. Here goes...
My Benade "Principles" isn't around right now, but in there is a statement about requirements for wall rigidity & smoothness (the walls had to have some level of rigidity and the smoothness had to be equivalent).
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Author: Bob Phillips
Date: 2008-11-16 16:05
Sounds (sorry, I mean "It seems") like your foam tube has the properties of a glass-pack muffler.
Bob Phillips
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Author: Gordon (NZ)
Date: 2008-11-16 21:43
Skygardener wrote:
"I note again that this material was air tight, not at all a porous material from the inside."
NO, it was not porous in a DC (thinking electricity here) sense, but where sound is concerned, the AC sense that just as important.
For example, if you wrap a thin rubber membrane (eg surgical glove or dental dam) around every tone hole to make 'seals', instead of using pads, then I doubt that low notes would play. That is because although you made a DC seal you did not make an AC seal... There is a lot of "acoustic loss".
The rubber allows the oscillating air pressures inside the bore to communicate with the air pressure of the ambient air outside the instrument, and therefore acts as open tone holes. The material you chose does the same thing, but to a lesser degree, over the entire body.
It is this phenomenon that suggests that come pads may have a different sound from others, depending on the acoustic loss that they allow.
Post Edited (2008-11-16 21:44)
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Author: skygardener
Date: 2008-11-16 22:17
One more thing I didn't expect was that the reed did not vibrate except when I used a lot of air to get the faint grunt. One would think that the result would be a vibrating reed and a faint sound, but the reed did not vibrate.
Yes, it does draw the question about pads. If 4% of the surface of the bore is a super soft pad, then do you lose 4% of sound?
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Author: tictactux ★2017
Date: 2008-11-16 22:29
skygardener wrote:
> Yes, it does draw the question about pads. If 4% of the
> surface of the bore is a super soft pad, then do you lose 4% of
> sound?
If it is super-duper soft (as in 'air') then you may lose everything - well it is an open hole. If there is little that would reflect the the pressure back into the bore, you might get the same effect as a smaller or bigger leak.
BTW I liked Gordon's analogy with the AC and DC filter very much. Just because a glove over a tonehole is airtight it doesn't make it pressure-wise or acoustically inert. In that light I understand why saxophones have resonators on the big pads (why some people go crazy about their shapes or materials is beyond me, however), and maybe a clarinet would profit from resos as well, but I think they're too tiny to have a discernable effect. Plus, don't forget that the clarinet tonehole chimneys are relatively long, and a lot of lazy air hangs in there that dampens the effect of the material used for pads. But I digress, and a lot is gut feeling based on "real world" analogies.
--
Ben
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Author: clarnibass
Date: 2008-11-17 04:31
>> So with drastic changes in material, there are unquestionable
>> drastic differences in resultant sound. It is not unimaginable
>> to think that slight changes in material would produce slight
>> changes in resultant sound.
If Gordon is right, and I assume he is, it is possible (and more likely) that once the material passes that minimum rigidity required it has no more affect on the sound at all. The fact that this minimum exists makes it obvious that a material with less rigidity will have an effect on how the instrument plays, but it has nothing to do on how a material will affect the instrument after it is rigid enough.
I added a very small "tone hole" a few cms from the end of the plastic tube, and added a bell (funnel from my kichen). When I left the "tone hole" uncovered the note only played when I blew very strong. It was a leak but blowing strong allowed to play over that leak. So it seems that your instrument is essentially playing like it has a leak that is impossible to overcome.
Post Edited (2008-11-17 10:09)
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Author: Gordon (NZ)
Date: 2008-11-17 09:51
For the electrically minded, the analogy can be continued...
A rubber membrane pulled so it 'seals' over a tone acts like an electrical capacitor, blocking DC power and allowing AC to pass.
But what the instrument needs at a tone hole is the equivalent of a switch, able to block both DC and AC. And what it needs for the body of the instrument is the equivalent of an insulator, blocking both the DC and AC. The foamy tube 'clarinet body' acted as a capacitor.
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Author: rtmyth
Date: 2008-11-18 18:35
Harry Olson's Dynamic Analogies is a book given over to acoustic, mechanical, and electrical circuit analogies. His other books have some relevant material also.
richard smith
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