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jezzupe

energy storage and release

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Nothing special I just thought I'd start a topic for discussion related mostly i suppose about optimum stiffness and how that translates to a players feeling of feedback about ease of playability.

Thinking of the playing of a note as a time event, we have the hair contacting the string, that motion transferring to the bridge, that then to the plate and then into the entire corpus, and then we hear the note, all of this happening in a fraction of a second, all amplitude, velocity and dynamic range seemingly controlled by the player related to bow presure and intensity of the stroke.

Here we have a gigantic 84" gong, what seems so interesting to me is the way energy is slowly fed to it and it seems to store that energy and then use that to piggyback onto new energy input, with the end result being a slow crescendo to eventual ear blasting volume as the energy is slowly released or spreads.

I can't help but think that the science of whats going on here somehow applies to top stiffness, meh just something to discuss.

  

 

 

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32 minutes ago, jezzupe said:

Nothing special I just thought I'd start a topic for discussion related mostly i suppose about optimum stiffness and how that translates to a players feeling of feedback about ease of playability.

Thinking of the playing of a note as a time event, we have the hair contacting the string, that motion transferring to the bridge, that then to the plate and then into the entire corpus, and then we hear the note, all of this happening in a fraction of a second, all amplitude, velocity and dynamic range seemingly controlled by the player related to bow presure and intensity of the stroke.

Here we have a gigantic 84" gong, what seems so interesting to me is the way energy is slowly fed to it and it seems to store that energy and then use that to piggyback onto new energy input, with the end result being a slow crescendo to eventual ear blasting volume as the energy is slowly released or spreads.

I can't help but think that the science of whats going on here somehow applies to top stiffness, meh just something to discuss.

  

 

 

You need to also consider the reflections of the wave from the boundary.  Intuition is useless unless you actually can solve the problem.   At least,  I can see that there are two distinct resonators here;   a somewhat simlar situation is involved with those Carribean drums with the hollows beat into them.   

I suspect a good model and proper solution would be quite difficult.  Don't even try to think of an explanation.

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On 7/27/2019 at 7:40 PM, jezzupe said:

I can't help but think that the science of whats going on here somehow applies to top stiffness, meh just something to discuss.

There doesn't seem to be much discussion generated here yet, but this demonstration of a huge gong is quite fascinating, and there may be some (vague) implications for violin making.

But mostly in the way of what NOT to do.

The gong, especially in this demonstration, gets an excitation in a very low-frequency mode, and gradually transfers the energy into higher frequency modes due to non-linearities intentionally hammered into the shape, most likely small-scale convex and concave features.  This is exactly the wrong thing for a violin... you don't want string energy going in at one frequency, and coming out as a crashing noise at totally unrelated frequencies.

So, don't make a violin plate like a gong.  The damping of wood will be so much higher than the gong, so maybe there's nothing to worry about anyway, but it would seem like a good idea not to carve in lots of pimples and dimples that might create non-linearities and therefore a sound that is unrelated to the input.

Perhaps this it related to what I have heard from many experienced makers... make all the curves as smooth as possible, no abrupt changes.

 

 

 

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3 hours ago, Don Noon said:

There doesn't seem to be much discussion generated here yet, but this demonstration of a huge gong is quite fascinating, and there may be some (vague) implications for violin making.

But mostly in the way of what NOT to do.

The gong, especially in this demonstration, gets an excitation in a very low-frequency mode, and gradually transfers the energy into higher frequency modes due to non-linearities intentionally hammered into the shape, most likely small-scale convex and concave features.  This is exactly the wrong thing for a violin... you don't want string energy going in at one frequency, and coming out as a crashing noise at totally unrelated frequencies.

So, don't make a violin plate like a gong.  The damping of wood will be so much higher than the gong, so maybe there's nothing to worry about anyway, but it would seem like a good idea not to carve in lots of pimples and dimples that might create non-linearities and therefore a sound that is unrelated to the input.

Perhaps this it related to what I have heard from many experienced makers... make all the curves as smooth as possible, no abrupt changes.

 

 

 

Ya I just thought it was interesting the way it seems store and release energy. I'm of course thinking weird VSO thing that is basically a violin made of two gongs,just to see what it would sound like.Probably not like a gong and probably not like a violin either. Probably not that good :lol:

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21 hours ago, jezzupe said:

Ya I just thought it was interesting the way it seems store and release energy. I'm of course thinking weird VSO thing that is basically a violin made of two gongs,just to see what it would sound like.Probably not like a gong and probably not like a violin either. Probably not that good :lol:

Gong2 mass of center back.   

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3 hours ago, David Beard said:

Gong2 mass of center back.   

 

3 hours ago, David Beard said:

Gong2 mass of center back.   

ya what he said...I'm envisioning something that has no ribs, but is coupled by a soundpost and where the blocks would be would be some type of thin spring loaded strut that would allow the gong plates to be free to move at the outer edges...probably best cello size

meh' just another of the million {WAI} weird ass ideas I've had, who knows, maybe one of these days. I just need to come up with an extra 30k so I can get myself a 80" gong, I can be in tune with the universe and bother the crap out of my neighbors, all at the same time:lol:

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On 8/9/2019 at 8:09 PM, jezzupe said:

Ya I just thought it was interesting the way it seems store and release energy. I'm of course thinking weird VSO thing that is basically a violin made of two gongs,just to see what it would sound like.Probably not like a gong and probably not like a violin either. Probably not that good :lol:

Hi Jezzupe, On the violin arching shapes a lot of energy become stored when string load to pitch is applied. Arching shape on both side of the sound post/bridge will bulge and energy become stored. Depending on the shape of the arching especially the bout shapes and the thickness of the bout shapes predict the amount of energy that become stored. I have studied how much the bout shape changes volume, thus deflect more, when very little energy by increasing string load on one string produces. You all have been able to see that picture.

Releasing that extra string load, the structure goes back and the figure than become completely black.

Playing the instrument, the bout shapes flex and many different stress conditions arises that all may answer spontaneous to e specific frequency. I’m quite sure that’s one of the secrets of the violins function. Mode shape respond extremely quick to the frequency played. Since the in the playing act the bout shapes constantly change bulging the respond time producing mode vibration is very short.

Without the loaded energy this will be much less quick. Graduating plate thickness improve the function and the acoustical quality.

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1 hour ago, reguz said:

On the violin arching shapes a lot of energy become stored when string load to pitch is applied.

......

I’m quite sure that’s one of the secrets of the violins function.

and I'm quite sure this is all has no significant influence on violin vibration and tone.

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The gong has very low damping, so the energy can be manipulated over a long period of time by various changes in geometry. As primary vibration modes are activated, non-linear effects become more prominent resulting in significant sub-harmonics.

One might expect violins with low damping to also exhibit complex tones due to changes in geometry, such as the garland/ribs. But my sense is that a gong is operating in a completely different realm of physical effects than a violin.

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21 minutes ago, reguz said:

Don, your replays are always the same. 

And will continue to be, every time there is a post regarding physics that I disagree with.  

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6 minutes ago, Don Noon said:

And will continue to be, every time there is a post regarding physics that I disagree with.  

Don, you may disagree. nothing wrong with that but it do not help the readers of  yor replay at any level. The best thing you can do is explain what your opinion is based on. People with be happy reading your explanations as I will.

 

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43 minutes ago, ctanzio said:

The gong has very low damping, so the energy can be manipulated over a long period of time by various changes in geometry. As primary vibration modes are activated, non-linear effects become more prominent resulting in significant sub-harmonics.

One might expect violins with low damping to also exhibit complex tones due to changes in geometry, such as the garland/ribs. But my sense is that a gong is operating in a completely different realm of physical effects than a violin.

No, the simple statement, y(x,t) = A sin(kx - ωt) + A sin(kx + ωt) = 2A sin(kx)cos(ωt), as well as the somewhat more complicated expressions describing a driven damped harmonic oscillator, remain true in both cases, but in practice, the geometry, the damping coefficients (plus other fudge factors), and the driving mechanism are all different.  Overdrive a violin, and you get things you don't want, such as wolf tones.  Violins, gongs, or earthquakes, it's all ultimately the same physics behind the waves, springs storing energy and weights bouncing around.  :)

 

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I know only a smattering of physics, and only the most basic, but that was a fascinating display of sound. I wonder how much energy would have been wasted if he had just whacked the gong as hard as possible?  The response time would’ve been every bit as slow, but the sound would’ve lasted much longer. But I wonder how much energy would’ve been lost immediately simply because it happened too quickly for the mass to react to it. It seems logical that because the shape, the material, and the type of stimulation are different, Nothing about this demonstration can be applied to violins.

Fascinating nonetheless.

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19 minutes ago, PhilipKT said:

I know only a smattering of physics, and only the most basic, but that was a fascinating display of sound. I wonder how much energy would have been wasted if he had just whacked the gong as hard as possible?  The response time would’ve been every bit as slow, but the sound would’ve lasted much longer. But I wonder how much energy would’ve been lost immediately simply because it happened too quickly for the mass to react to it. It seems logical that because the shape, the material, and the type of stimulation are different, Nothing about this demonstration can be applied to violins.

Fascinating nonetheless.

I think what Don said is accurate, it's like the anti-violin, my interest is the seeming increase in energy release {volume} well after, and or a delay in the swell where as it gets quite loader well after the last strike

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4 hours ago, reguz said:

The best thing you can do is explain what your opinion is based on. People with be happy reading your explanations as I will.

I doubt you are going to be happy...

My opinion is based on a lifetime in aerospace engineering, as well as a couple of decades of attention to violin acoustics.  More specifically, there is no theory or evidence that string tension does much of anything acoustically to the violin body, neither does the minuscule variations in string tension during vibration... which is how I read much of your theories.

If you have any tests or evidence to back up your theories, fine... but diagrams and verbal arm-waving won't do it for me, as it just looks far off the mark.   

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7 hours ago, reguz said:

On the violin arching shapes a lot of energy become stored when string load to pitch is applied. Arching shape on both side of the sound post/bridge will bulge and energy become stored.

Hi Reguz,

Although it's true that tightening the string stores energy as potential energy, my layman's understanding would be that this is not released when the string is bowed.  what is released is the energy just imparted by the bow.  But at different tensions there MAY be some difference to how a violin responds to this immediate stimulation.  Like Don says, we have not seen any evidence of this...

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Yeah.  I think you'll find most of the energy that eventually radiates as the musical signal has passed through a number of stages of oscillating between storage as mass in motion and material in either flex or compression.

Even though more mass takes more engergy to get moving, it also holds more energy once going.

 

 

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11 hours ago, violinsRus said:

Hi Reguz,

Although it's true that tightening the string stores energy as potential energy, my layman's understanding would be that this is not released when the string is bowed.  what is released is the energy just imparted by the bow.  But at different tensions there MAY be some difference to how a violin responds to this immediate stimulation.  Like Don says, we have not seen any evidence of this...

 

11 hours ago, violinsRus said:

Hi Reguz,

Although it's true that tightening the string stores energy as potential energy, my layman's understanding would be that this is not released when the string is bowed.  what is released is the energy just imparted by the bow.  But at different tensions there MAY be some difference to how a violin responds to this immediate stimulation.  Like Don says, we have not seen any evidence of this...

Hi violin Rus, thank you for letting me know your opinion. However, try to come to an understanding what happens when the already applied string load increase when you bow the string. The re arises an increasing of the action on the end blocks and the bout shapes deflection increases. This is not a one for all increasing but a dynamical moment arises. The stress conditions on the bot shapes increase/decrease and when a specific frequency played is in conformity with the stress condition on the bout shape a mode shape vibration start. I have tested changing stress condition on bout shapes improving the dynamical result of spontaneous reaction for many years on the same instrument with very good result. So, I have evidence that stress condition and dynamic behavior are possible improving by polishing the varnish or by scraping the wood surface. I also have learned where to do this over the many years of experience. What evidence are you asking? Have you done any such work improving? In this process unbalance in the interaction of the bout shapes may arise. This may produce wulf tones. But by knowing in what step (polishing the bout shape) the improvement goes in wrong direction its easy reducing stiffness on the other one. This is all about the stress conditions that become produced. From the beginning stage nothing happened polishing/scraping. So, we may say there was too much structure. Continuing the process when changes became positive it became important to let the structure rest so the stress conditions that changes became stable. At the same time later on the sound quality was recorded with Audacity that verify the changes of the amplitude and frequency spectra. Is there any reading this having own experience just let us know so we may discuss and let other learn how to understand!!

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It seems plausible that static load might affect the response of a violin body to external stimuli. 

A simple analogy would be the influence of a DC bias on the small signal AC response of an electrical circuit, which can either be negligible, huge, or somewhere in between, depending on the linearity of the system at the operating point.

Not a hill I’m particularly interested in dying on.

just chewing the fat, like,

 

 

 

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2 hours ago, JohnCockburn said:

It seems plausible that static load might affect the response of a violin body to external stimuli. 

A simple analogy would be the influence of a DC bias on the small signal AC response of an electrical circuit, which can either be negligible, huge, or somewhere in between, depending on the linearity of the system at the operating point.

Not a hill I’m particularly interested in dying on.

just chewing the fat, like,

The key is "linearity of the system at the operating point".  If it's non-linear, like the gong, then you can get all kinds of strange things going on, including influences from static loading.  

As far as I know, nobody has demonstrated any non-linearities in the violin structure vibration, nor significant influence of static loading on vibration behavior.  I know folks might bring up soundpost tightness to refute this statement... I'd love to see some objective results and analysis about this, but up to now all I have heard is anecdotes with no physics-based explanation (it's on my long list of things to do, but not near the top).

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1 hour ago, Don Noon said:

nobody has demonstrated any non-linearities in the violin structure vibration

Hi Don,

Not to derail the thread, but can you tell me briefly why vibrations in a gong is non-linear and in a violin it's linear?   Sure, if you want to raise the pitch of a violin string you tighten it, that's a very linear relationship.  But if you want to get rid of a wolf tone, or eliminate some harshness, or make another tone 'adjustment', what do you do?  You tweak any of the 1000 variables, some work, some don't.  Doesn't sound linear to me. 

Or take bowing, we all know there is a 'sounding point' or sweat spot that works.  If you move the bow closer to the bridge the tone crunches into a bunch of random noise, which I assume one would call non-linear vibration.  

Just askin'

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