Jump to content
Maestronet Forums

Plate tuning


fiddlewallop

Recommended Posts

The loudness of a resonance is proportional to Q/(m*f0) where the

m is the effective mass of that resonance and

f0 is the resonance frequency

Hi Anders, my limited knowledge of acoustics tells me that sound intensity produced by a vibrating plate is proportional to f^2. Where do you get the inverse dependence on f from?

Link to comment
Share on other sites

  • Replies 273
  • Created
  • Last Reply

Top Posters In This Topic

Hi Marty, I was thinking more along the lines of Q being generally defined as the product of the resonant frequency and the damping time constant, so the expression you derive for the amplitude at resonance (amplitude of driving force x Q) would surely need to be modified to include this?

He doesn't want to.

Link to comment
Share on other sites

Hi Anders, my limited knowledge of acoustics tells me that sound intensity produced by a vibrating plate is proportional to f^2. Where do you get the inverse dependence on f from?

I guess you are thinking about the general radiation efficiency (the acoustical one, not the wood property RR) which will rise with the frequency below the critical frequency. The admittance, however, will fall with the increasing frequency. I think the expression is for the admittance. For the limited frequency region the signature modes usually are found within, this expression also will explain the amplitude of the sound produced by the modes.

I got the relation from one of Bernhard Richardsons posters. He has been working on the guitar for a while. I do not know how he reached at that solution, but I am sure it can be found in one of his articles.

Using an intuitive approach, the vibration velocity over input force will go down for increasing frequencies due to the inertia of the vibrating mass. If you shake a body with a given mass it will be more and more difficult to vibrate it at the same amplitude for increasing frequencies.

Link to comment
Share on other sites

He doesn't want to.

I considered Q to be wood property and I chose to keep it as a constant (along with: length, width, outline shape, arches, edge constraints, varnish, fermentation temperature ...) and only varied the density (p), elastic modulus (E), thickness (t), and the tuning frequency (f).

The vibration amplitude at resonance is equal to the static deformation times Q.

If someone sees where I've made mistakes, please point them out to me. I'm not afraid of being wrong(again).

Link to comment
Share on other sites

I considered Q to be wood property and I chose to keep it as a constant (along with: length, width, outline shape, arches, edge constraints, varnish, fermentation temperature ...) and only varied the density (p), elastic modulus (E), thickness (t), and the tuning frequency (f).

The vibration amplitude at resonance is equal to the static deformation times Q.

If someone sees where I've made mistakes, please point them out to me. I'm not afraid of being wrong(again).

I wasn't criticizing ! It just seems a bit circular to me. I mean we knew those before starting.

Link to comment
Share on other sites

But why tap tones? It seems to me that reproducing the sound and response of the assembled instrument is more important than the particular means of getting there, and I'm not even convinced that reproducing tap tones is an effective means of getting there.

This plate tuning business reminds me of the cargo cults that emerged after the end of World War II: Following the departure of American solders from Tanna Island, members of one such cult built crude landing strips, bamboo air control towers, and coconut radio headsets, hoping in this fashion to attract the planes that used to deliver the cargo they had grown to appreciate.

I contemplate this general phenomenon often.

it might simply be that if you cannot control the outcome when manipulating physical objects (wood, tools, varnish, etc.) in order to arrive at a consistent specific outcome, perhaps it's easier to manipulate numbers or established ideas in order to arrive at a specific consistent outcome.

The fact that it (such results) may not relate to the actual object, often doesn't seem to be the crucial aspect of the discussion. As long as the "numbers crunch".

Link to comment
Share on other sites

On the other hand, if you build a crude landing strip, you have greatly increased the probability that an airplane will land, versus having no landing provision at all. ;)

Not having the correct explanation or understanding doesn't always preclude things from being effective.

But as Prof. Feynmann explained, you have done nothing to cause them to land.............

Link to comment
Share on other sites

But as Prof. Feynmann explained, you have done nothing to cause them to land.............

Nor will most conventional landing strips cause a plane to land. Yet planes sometimes do, for a host of reasons, one important reason being the very existence of the landing strip.

If the pilot isn't expecting or relying on radio communication from the ground, who cares whether the dudes are wearing coconut headphones? If a plane lands there due to emergency, or out of curiosity, something about the plan worked, even if some elements are ridiculous. Don't need to throw the whole thing out.

Same might be true of some fiddle schemes. Did Stradivari have complete technical understanding of everything he did? Probably not. But he may have had a system that worked, even if the explanation might sound like superstition or voodoo to us.

Link to comment
Share on other sites

Not having the correct explanation or understanding doesn't always preclude things from being effective.

Exactly.

... then again, repeating what doesn't work, even if it sounds good (or reads well) - isn't very effective either.

So, although one might not understand exactly why something works the way it does, In my opinion, what proves to work in practice, should take precedence over incorporating an elegant, comprehensive theory that doesn't prove out.

In this case, what “works” and what “does not work” is more a point of debate than a point of fact. Probably something that everyone involved in a discussion of this nature should consider.

An earlier poster brought up a good point, I thought, when he mentioned that many of the recent posts were circular in nature - and that many posters were merely attempting to “prove” what everyone “already knows…”, an observation I tend to agree with.

Such a situation as this (for me) becomes not much more than a stage or an opportunity to highlight our “deep understanding” of the “scientific basics” and to be able agree with each other on specific concepts - much more than an attempt to point out specific methods that result in specific tonal consequences…that can accurately be engineered in or predicted. (an important consideration in my opinion ) - But that's just me.

It seems such discussions as this one, are rarely ever based on specific results of specific violins built using rigid methods in order to obtain highly engineered tonal properties - in other words, it‘s appears to be not much more than (well intentioned, perhaps) blowing into the wind….

PS - it did strike me, however, that since most people who are "pro-tuning" tend to talk about the methodology involved in a "knowing" way, as if these particular principals are obviously correct and entirely pragmatic, it might not hurt to also discuss the subject "as if" it was a forgone conclusion that none of it was proven - knowing all along that neither side has a real leg up.

Link to comment
Share on other sites

The concept I've kind of been working around to, and have found useful, is this:

When we've brought various people in to teach at Oberlin, who have demonstrated unusual accomplishment in various areas, I've always asked them to present a thought model behind what they do. I told them not to worry about whether it was technically correct, because the thought model is somehow producing good results, and the results are what most people are primarily interested in.

If someone has won a lot of VSA tone awards, and attributes it to eating three cans of asparagus per day, that's interesting to know, as opposed to not having that shared because it sounds ridiculous.

Vegetable splatter pigmentation? Changes in perspiration or urine chemistry? An example of a belief altering working methods?

If the belief of someone who is above-average successful, however ridiculous sounding, is never presented, it's hard to derive anything useful from it.

Link to comment
Share on other sites

If the belief of someone who is above-average successful, however ridiculous sounding, is never presented, it's hard to derive anything useful from it.

I won't argue with results either.

My only stipulation, before I will listen, is to insist on observing first hand - the "results" part.

As an example of something I have argued against in good conscience, is Vigdorchik's proposed theories and methods - and even then, I presented an argument from having read the material, and tried to prove that what he said is valid or invalid by virtue of what has been presented in the text, and by the same reasons given.

Which doesn't even mean that someone cannot use those same methods and not get great results.

Probably, I might still question the validity of the reasons..

Link to comment
Share on other sites

I totally don't get the Vigdorchik stuff either. But Tom Croen used it for a while, so I'm not willing to say it's garbage, or couldn't be useful, even if it may not be useful to me.

By coincidence I spoke with Mr Croen about exactly this point, back when I was actively involved with trying to understand the Vigdorchik method (long ago, on The Soundpost Online with a couple of other long time MN posters)- since I had been told that he was an advocate for the method.

At that time, he was not a strong advocate for the method as presented verbatim in the text, as much as he was an advocate for using some of the various techniques as usefull tools, for listening to the plates, and for keeping an open mind about what "works".

I wouldn't call the method garbage either - just as I wouldn't call Hutchins methods garbage...

But the other half of benefitting from an "open mind", is learning exactly what to embrace, and what not to embrace - and much of that depends on who you are, how you work, and exactly what you want to accomplish.

Link to comment
Share on other sites

At that time, he was not a strong advocate for the method as presented verbatim in the text, as much as he was an advocate for using various techniques as a usefull tool, for listening to the plates, and for keeping an open mind about what "works".

Let me add here, that although Mr. Croen was careful not to criticize the Vigdorchik method directly, (he was direct and very polite) - he did state that, over time, his views about the text and method had changed - and the assumption I made at the time, was that he may well have thought that the method broke down pretty much where I also found it to break down, via research of my own. (i.e. by cutting a top plate into diagonal strips and "testing" them individually...)

Link to comment
Share on other sites

Not having the correct explanation or understanding doesn't always preclude things from being effective.

Doing a rain dance will ALWAYS be effective... eventually. It just depends on how you define effectiveness (and who is providing the definition).

I suspect that the makers who do produce consistently better tone (as determined by impartial judges) may not credit trial and error for their success, but it really is an important part of what they do... more of what works, less of what doesn't, and then develop a theory that makes sense of it, to them. The theory might be total garbage, but behind it is a method that works.

I totally don't get the Vigdorchik stuff either. But Tom Croen used it for a while, so I'm not willing to say it's garbage, or couldn't be useful, even if it may not be useful to me.

I'd be willing to say I think it's garbage.

I wouldn't call Hutchins methods garbage...

Better than nothing, I suppose. But can be counterproductive when relied on exclusively and religiously, when there may be more important things to pay attention to.

Link to comment
Share on other sites

The concept I've kind of been working around to, and have found useful, is this:

When we've brought various people in to teach at Oberlin, who have demonstrated unusual accomplishment in various areas, I've always asked them to present a thought model behind what they do. I told them not to worry about whether it was technically correct, because the thought model is somehow producing good results, and the results are what most people are primarily interested in.

This is wonderful. Thank you. So many makers I've met are indignant about others' thoughts on sound, or varnish, or the reasons to produce sound or varnish a certain way. And yet, if your set of tools works, or your system functions, why bother with the idealogical clashes between different tools and systems?

All roads lead to Cremona, I think they used to say.

Link to comment
Share on other sites

This is wonderful. Thank you. So many makers I've met are indignant about others' thoughts on sound, or varnish, or the reasons to produce sound or varnish a certain way. And yet, if your set of tools works, or your system functions, why bother with the idealogical clashes between different tools and systems?

All roads lead to Cremona, I think they used to say.

In a way, yes - this is true.

Interestingly, in the real world, we can observe firsthand that it only usually works that way when people "agree" with each other.

Being indignant about the thoughts of others, is something where the onus is always on the person being indignant.

Because, when presenting ideas, an honest person must be able to present his or her views with regard for results only, and not "popularity".

On the other hand, "Idealogical clashes" are simply going to happen in any circumstance where ideas are at odds - that's sort of the whole idea behind a free exchange of ideas. It is something that, as you infer above, we should all welcome...

It only become problematic if and when personal intolerance makes a showing.

Intolerance in either party, (on the part of the person or persons presenting the idea, or on the part of the person(s) on the receiving end) when either "side" has an immovable, personal bias or "denominational belief", and where they tend to then make a "personal judgement" - not about the idea, but about the person or persons holding an idea that they do not agree with.

Link to comment
Share on other sites

Doing a rain dance will ALWAYS be effective... eventually. It just depends on how you define effectiveness (and who is providing the definition).

Sure, but there are examples with better outcomes. When the Native Americans taught the Pilgrims to place a small fish next to the seed when planting corn, maybe they thought it worked because of a synergy between the corn spirit and the fish spirit. Doesn't matter. It was one of the things which helped the Pilgrims grow crops in the poor soil, and make it through the second winter with far fewer people dying.

I suppose the Pilgrims could have rejected that, along with other valuable Native American survival teaching, on a theoretical (and religious) basis, and because it came from "uneducated heathens". (insert "violinmakers" :D )

Link to comment
Share on other sites

Having had a number of tone winning speakers at Oberlin did you find any commonality, a consistent theme?

For instance I've heard some say they try to construct an instrument with no 'stress' built in. (not sure what is meant by that.

Oded

Oded, I'd need to review five days of presentations to give a good answer. What I remember is that most (all?) of them used tap tones to some extent, and I think there was one (Chicago School graduate) who used what he described as the Vigdorchik method. I think most of them were also using tactile flexing of parts, and there was one who trimmed the bar by placing the outside of the violin top, near the bridge location, against a flat surface, pushed on the ends of the bar as if to straighten the arching, and watched for a certain flex gradient along the length of the bar.

I think the "no stress" concept had to do, for instance, with building a rib assembly in such a way that it would maintain it's shape when removed from the mold. This might involve overbending some parts initially, to compensate for some eventual springback.

Of people who post here, Wallin and Pasewicz were present that week, and Wallin was one of the multiple tone award winners who presented, so maybe they can add to that or correct it. Some of the time, I was running around doing administrative things, so I didn't catch everything.

Didn't one of our presenters, Mark Womack, also give a presentation to the Acoustics Workshop, and were you there that year? He claimed to have learned much of what he knew about sound from having regraduated thousands of factory-type instruments when he was employed by an outfit which did a lot of that. Any recollections?

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
  • Recently Browsing   0 members

    • No registered users viewing this page.



×
×
  • Create New...