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the function of arching shape


reguz

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Dear All. Adjust me but my believe is that stress on structure is highly involved what frequency i may vibrate.

This tells at least me you must know the quality of that structure. For that reason, my research was finding structure with special quality I could do research on. I have shown above what I did. What was it You did?

No one thus far has given any response on my research on structure and function. I have a structure. You have a lot of instruments all with different structure. Since I am an amateur violin maker, I said to me solve it is better making one good instrument than 100 bad. I believe I have good success with the instruments I make with my geometric structure and I know what stress does with the instrument. I also know when I change the stress condition, I change the acoustic outcome. This tells me that stress is important just as stress is on a string.

Each violin maker has a lot of problems to deal with but there were a few 400 years ago that could make many instruments that today are probably the best. They must have worked out the plates with a specific method. What that method is no one know today. This forum certainly has not discussed that. I have tried to give an answer on the basic but you do not seem to be interested. Express your salve please!!

 

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13 hours ago, violins88 said:

I love it when humor overtakes a thread that is headed no where.

In the book “Into the Wild,” the author is walking in the desert in Wyoming. He meets a very bedraggled woman. He says “What are you doing here?” She says “Well everyone has to be somewhere.” 

It was funny at the time.

 

Like! :-)

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10 hours ago, martin swan said:

I genuinely was asleep in the garden, in spite of heavy and unruly bellringing practice at the cathedral!

Don't tell me you also live in Wells ...

Just visiting. My wife wanted to attend the rare plant fair in the Bishop's Palace grounds.

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1 hour ago, reguz said:

 

Just listen to what happens when stress conditions changes the accoustic aout come. at time 2:18 --- 2:30

Strss affect accoustic result.

Two problems: With the end panels on his test rig, he's changing the size of the resonant cavity when he bends them inward. Second, when you carve an arched plate, it's not under tension. The bass bar and soundpost support and distribute the pressure of the bridge, so there's nothing equivalent to the "demonstration".

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5 hours ago, reguz said:

I have tried to give an answer on the basic but you do not seem to be interested. Express your salve please!!

You may be talking to the wrong audience.  Try submitting your work to the JASA - they publish technical violin acoustics papers, where someone with expertise will take the time to read and evaluate your work.  If you've noted a lack of interest, then if you keep stumping it here I'd have to agree with Mr. Burgess that you're headed down the wrong path.

But I'll bite.  Given the diagram you presented to me earlier for example - it's correct, or close enough.  You can add the effects of sound post, bass bar, and ribs later - my question regarding the sound post was prompted because I expected you'd be starting with something closer to a complete violin instead of one of FiddleMkr's bridges.  So what's your next step?

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3 hours ago, FiddleDoug said:

Two problems: With the end panels on his test rig, he's changing the size of the resonant cavity when he bends them inward. Second, when you carve an arched plate, it's not under tension. The bass bar and soundpost support and distribute the pressure of the bridge, so there's nothing equivalent to the "demonstration".

Sorry FiddleDoug but you do not seem to understand the vector diagram at all. What is shown is that the curved shapes of the belly and back become more curved.by bending on the back and buckling on the top plate. That behavior produces stress conditions. When the instrument is bowed the acting forces on the end block changes constantly and thus the behavior and stress conditions on the curved shapes. These start function like a spring. On the violin the upper and lower bout shapes are different and we cannot expect them holding equal structural quality and behavior as springs. But my experince thave learned me to deal with that problem. I polish the varnish so the stress conditions and thus the spring function become more equal and so the quality of the sound.

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1 hour ago, Dr. Mark said:

You may be talking to the wrong audience.  Try submitting your work to the JASA - they publish technical violin acoustics papers, where someone with expertise will take the time to read and evaluate your work.  If you've noted a lack of interest, then if you keep stumping it here I'd have to agree with Mr. Burgess that you're headed down the wrong path.

But I'll bite.  Given the diagram you presented to me earlier for example - it's correct, or close enough.  You can add the effects of sound post, bass bar, and ribs later - my question regarding the sound post was prompted because I expected you'd be starting with something closer to a complete violin instead of one of FiddleMkr's bridges.  So what's your next step?

It always may be that there are person that cannot follow the technical quality and thus have difficulties understanding. If you are one of these people I expect you asking for explanation where you cannot grip what is shown. I am not the person saying you are stupid go else were. I always try do do my utmost be friendly and explain.

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1 hour ago, Dr. Mark said:

You may be talking to the wrong audience.  Try submitting your work to the JASA - they publish technical violin acoustics papers, where someone with expertise will take the time to read and evaluate your work.  If you've noted a lack of interest, then if you keep stumping it here I'd have to agree with Mr. Burgess that you're headed down the wrong path.

But I'll bite.  Given the diagram you presented to me earlier for example - it's correct, or close enough.  You can add the effects of sound post, bass bar, and ribs later - my question regarding the sound post was prompted because I expected you'd be starting with something closer to a complete violin instead of one of FiddleMkr's bridges.  So what's your next step?

Dr. Mark my next step was getting sfficient proof that the sound post is the center of "rotation". Two student at the University of Lund, Sweden did their master on this problem. That reoirt you can find here on Maestro.

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3 hours ago, FiddleDoug said:

Two problems: With the end panels on his test rig, he's changing the size of the resonant cavity when he bends them inward. Second, when you carve an arched plate, it's not under tension. The bass bar and soundpost support and distribute the pressure of the bridge, so there's nothing equivalent to the "demonstration".

You are correct. No stress condition on the free plate. But it is to understand there will be. That is the problem to deal with. I have tried to find an answer on that problem. Thinner plates become more stress but to thin means they will deform and get creep and do not work well after some time. It is to find the balance with the wood available. What we know for sure is that the instruments of the old master start directly they need not much energy starting. Modern instruments at least may need quite much energy starting. The plates are to thick. So I have also studied what area is possible graduating so no creep arises but make an instrument that start easy.

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3 minutes ago, reguz said:

It always may be that there are person that cannot follow the technical quality and thus have difficulties understanding. If you are one of these people I expect you asking for explanation where you cannot grip what is shown. I am not the person saying you are stupid go else were. I always try do do my utmost be friendly and explain.

Yet your comment could be taken as some pretty unfriendly innuendo, so I'll ignore it.  Have you submitted to JASA?

3 minutes ago, reguz said:

Dr. Mark my next step was getting sfficient proof that the sound post is the center of "rotation". Two student at the University of Lund, Sweden did their master on this problem. That reoirt you can find here on Maestro

Were you applying some external force, or are you talking about the balanced torques of the equilibrium condition?

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8 hours ago, reguz said:

 

Just listen to what happens when stress conditions changes the accoustic aout come. at time 2:18 --- 2:30

Strss affect accoustic result.

I do not think the stress is the main cause of increased sound level here. It is just a better contact between the tuning fork and the wood. The resonance of the plate increases, so maybe a modal overlap fitting happens there between the fork and the bent wooden plate. Tension is not the cause of the sound level increse per se.

The thickness, surface mass and plate size influences sound levels. Normally curvature of plate supresses the viobration energy into stretching of the plates and thus giving the opposite effect, a reduction of sound producing vibrations as some of the vibrating energy goes into non sound producing stretching energy. 

Edited by Anders Buen
Spelling error corrections and slight rephrasing
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25 minutes ago, Anders Buen said:

I do not think the stress is the main cause of increased sound level here.

Me neither.  This is a promotional video, not a scientific one.  My take is that the flat board resonance is way below the pitch of the tuning fork.  When the plate is bent, the curvature stiffens the low modes and brings the pitch up to match the tuning fork.

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23 minutes ago, Don Noon said:

Me neither.  This is a promotional video, not a scientific one.  My take is that the flat board resonance is way below the pitch of the tuning fork.  When the plate is bent, the curvature stiffens the low modes and brings the pitch up to match the tuning fork.

I agree on that and we may asume that the complex bout arching shapes respond on the many frequancy imput that come produced under the bridge feet. It certainly is complex.

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23 hours ago, Dr. Mark said:
23 hours ago, reguz said:

It always may be that there are person that cannot follow the technical quality and thus have difficulties understanding. If you are one of these people I expect you asking for explanation where you cannot grip what is shown. I am not the person saying you are stupid go else were. I always try do do my utmost be friendly and explain.

Yet your comment could be taken as some pretty unfriendly innuendo, so I'll ignore it.  Have you submitted to JASA?

23 hours ago, reguz said:

Dr. Mark my next step was getting sfficient proof that the sound post is the center of "rotation". Two student at the University of Lund, Sweden did their master on this problem. That reoirt you can find here on Maestro

Were you applying some external force, or are you talking about the balanced torques of the equilibrium condition?

We can continue this conversation or not - your choice.

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21 hours ago, Anders Buen said:

> Normally curvature of plate supresses the viobration energy into stretching of the plates and thus giving the opposite effect, a reduction of sound producing vibrations as some of the vibrating energy goes into non sound producing stretching energy. 

I agree that shallower arches produce less energy wasting in plane stretching.  I suspect that is one why the Strad and DG violins were often preferred and why classical guitars and pianos still use essentially flat plates. 

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1 hour ago, Marty Kasprzyk said:

I agree that shallower arches produce less energy wasting in plane stretching.  I suspect that is one why the Strad and DG violins were often preferred and why classical guitars and pianos still use essentially flat plates.

It seems intuitive since we'd expect applied vertical force at the bridge to be more normal to the plate surface with a flatter plate, and more tangential to the plate surface with higher arch.  I think it's a bit more complicated than that since, regardless of arching, most plates become horizontal at the ribs.  Will anyone commit to correlating plate flatness to either a specific quality of tone, or loudness?  Or playing characteristics?  Any takers?

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1 hour ago, Marty Kasprzyk said:

I agree that shallower arches produce less energy wasting in plane stretching.

I don't see much difference between wasting energy in plate stretching vs. wasting energy in bending.  The main difference is that curved plates with in-plane stretching are stiffer and mode frequencies are higher than flat plates.

There is also the possibility of getting very efficient sound radiation from a "ring mode", which only happens with curved plates, and is an artifact of in-plane stretching.

36 minutes ago, Dr. Mark said:

Will anyone commit to correlating plate flatness to either a specific quality of tone, or loudness?  Or playing characteristics?  Any takers?

I built a flat-plate violin once, compensating with greater thickness to offset the less-stiff flatness.  Amazingly, I ended up with signature modes fairly normal, and it was reasonably loud... but the loudness was mostly centered around the 1 kHz or so region, and sounded fairly crude.  

In observing response plots from various violins over the years, it is apparent to me that higher arching (more curved) suppresses the 1 kHz zone for a more refined tone.  Sam Zygmuntowicz has also expressed this observation, and perhaps there is a slight enhancement to the higher frequencies.

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2 hours ago, Marty Kasprzyk said:

I agree that shallower arches produce less energy wasting in plane stretching.  I suspect that is one why the Strad and DG violins were often preferred and why classical guitars and pianos still use essentially flat plates. 

I rather think this preference is related to their greater stability to humidity cycles than the higher arched instruments, rather than the sound. Maybe it is a combination. Other makers made shallow arches too, like Bergonzi and Guadagnini, I believe. I haven't studied this in detail, though. The guitar is kind of a strange instrument, with the low bridge and sideways excitation. Seen against the light there are some tension arch there. And lots of bars under the plates. 

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31 minutes ago, Don Noon said:

There is also the possibility of getting very efficient sound radiation from a "ring mode", which only happens with curved plates, and is an artifact of in-plane stretching.

I wonder if the "ring modes" are able to build up around a violin with the sharp corners where the plates meet the ribs. I am sure there is energy going there, but in a tube this is supposed to be a travelling compression wave, the ring frequency is the first "ring mode" stretching the tube and compressing it successively. 

Above the ring frequency a pipe and a tube behve more like a flat plate with less or no stretching, mostly bending. 

We see clear effects of the ring frequency for tubular ventilation pipes. The sound insulation of a pipe, or circular tube, is way better than for square, or rectangular, ventilation tubes below the ring frequency. The rectangular ones leak more low frequency noise and tend to rumble more, equal to the sound we hear by tapping them. The stiffer circular tubes sound more mid and high frequency. 

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On 9/16/2023 at 11:50 AM, reguz said:

Dr. Mark my next step was getting sfficient proof that the sound post is the center of "rotation". Two student at the University of Lund, Sweden did their master on this problem.

Why should we care what a couple of University students  somewhere think? Did either of them have the surname "Einstein"  or "Stradivari" or somethin'?

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5 hours ago, Don Noon said:

In observing response plots from various violins over the years, it is apparent to me that higher arching (more curved) suppresses the 1 kHz zone for a more refined tone.  Sam Zygmuntowicz has also expressed this observation, and perhaps there is a slight enhancement to the higher frequencies.

So the takeaway is that there's a correlation between higher arching and suppression of power near 1 kHz.  Since 1 kHz is pretty close to the maximum sensitivity of human hearing, then w/o compensation elsewhere we'd expect a decrease in loudness and 'refinement of tone' (like 'sweeter'?) with increasing suppression of the ~1 kHz power, i.e. increased arching - at least up to a point.

So Mr. Noon - what you mean by high arching - is Mr. Darnton's description correct? : "What are called "highly arched" violins have a cross-section across the top which is closer to circular. "Flat" ones' arches are shaped with more curve in the center, flattening towards the outside. If you look at a "flat" violin from the ends the rising slopes of the top and back appear almost straight. The bad version of a highly arched instrument seems to have the greatest curve towards the edges, not the center, where it's more flat, so that "ate a cinder-block" description is perfect" (from Highly Arched Violins, thread begun by Mr. Huang, July 2000)

In the same thread, Ole Bull wrote"In my experience highly arched violins make a sweet but small (in general) sound. The flattER [sic] models of mid-to-late Strad and del Gesu have a richer, perhaps earthier quality that carries well in large halls. I don't think it's true that they are necessarily brighter, just more powerful" which seems consistent with your observation, but tonally maybe not.

...C.B. Fiddler, in the same thread and apparently with some experience, states "I honestly question any general statement on the projection of an instrument based on the its arching".  He describes his violin as 'highly-arched modern...looks like a football from the side' (ascribed to Robert D. Kimble).

...and finally Beriot: "My friend has a probably Tyrolean violin-- no label, BIG arching, and a somewhat large body with a golden varnish. His teacher got it for him at an auction for 3k; i don't know which auction. I don't know if he had any major adjustments done, but it has a gorgeous tone. It was soooooo loud too. " - more food for thought

The above comments are cherry-picked and should be read in context.

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