Plate Vibration Modes

[Shunyata]

WARNING: This thread covers material that some violin makers may find disturbing or objectionable.  With that disclosure (which won't deter passionate beratement of my question), on we go.

I have a just a few instruments and I avidly keep track of what i do and don't do each time.  I try to relate this to the quality of sound I produce.  I have noticed that when my thicknesses are reasonable, the plates have a "stretchy" flexibility, my tap tones are in the pitch neighborhood that other makers suggest, and the tap tones ring well (sustain) i wind up with a responsive behavior and powerful sound.  (I am a violinist and critical of my work.)

The latter - ringing tap tones - seems especially important when the other items are all in good order.

My question is this.  My mode 5 tone is around an octave higher than mode 1, and has far less ring.  Is this a natural result of the higher pitch, or should I be dithering with my thickness in the c bouts to increase flexibility and support the ring in the mode 5 pattern.

[Don Noon]

First, if your M1 and M5 are about an octave apart, you're in an unexplored zone.  I suspect you  mean M2 and M5, and will assume so.

"Ring" is a qualitative term, involving some personal evaluation related to decay time, with decay time a function of frequency and damping, and damping determined by material properties and how the mode shape involves the various properties and how the mode shape may or may not dissipate energy into other modes.  If modes have the same damping, a mode an octave below another will ring twice as long... so it's hard to really tell what's going on by ear, unless perhaps you have a LOT of experience and know what you're hearing.

If your damping is primarily a function of the wood, I think it can be very important... but as I mention above, it's really hard to tell where the damping is coming from.  An odd-shaped, arched shell is a complicated mess.  I prefer to judge the damping of my  wood when it's in the wedge, and things are simpler... but there can still be odd effects.

If the damping is more a function of the mode shape specifics, forget it.  The plate does not vibrate that way in the assembled instrument.  The modes might sorta kinda look about the same shape, but they're not really.

And I will repeat:  diddling with graduation concepts to get some prescribed "better" free plate taptones (or ring) has nothing to do with making a better instrument, and I personally believe it would be worse for it, especially  if you deviate too far from general good practice. (With decades of experience and dozens of instruments, maybe taptones could be used more effectively.)

 

 

[David Burgess]

9 minutes ago, Don Noon said:

If the damping is more a function of the mode shape specifics, forget it.  The plate does not vibrate that way in the assembled instrument.  The modes might sorta kinda look about the same shape, but they're not really.

And I will repeat:  diddling with graduation concepts to get some prescribed "better" free plate taptones (or ring) has nothing to do with making a better instrument, and I personally believe it would be worse for it, especially  if you deviate too far from general good practice.

Agreed.  at least from what I have leaned so far.

[Shunyata]

Yes, M2 and M5.  Thank ypu for correcting that!

I dont believe the modes tell us anything about the assembled instrument behavior.  But they tell us a lot about the structure, flexibility and density of the plate.  I think of them as a set of indications, not a prescription. 

In the original post I stipulated that all else is in normal ranges and I would not hunt off the ranch simply to modify tap tones.  My question was whether I should expect a higher frequency to damp more quickly.  I suspected "yes" due to the material, if nothing else.  But i wanted to make sure i wasnt looking at an indication of abnormality.

[jezzupe]

4 minutes ago, Shunyata said:

Yes, M2 and M5.  Thank ypu for correcting that!

I dont believe the modes tell us anything about the assembled instrument behavior.  But they tell us a lot about the structure, flexibility and density of the plate.  I think of them as a set of indications, not a prescription. 

In the original post I stipulated that all else is in normal ranges and I would not hunt off the ranch simply to modify tap tones.  My question was whether I should expect a higher frequency to damp more quickly.  I suspected "yes" due to the material, if nothing else.  But i wanted to make sure i wasnt looking at an indication of abnormality.

This is my suggestion, as we don't want to shun ya' 

Imo your line of thinking is on the right track, your way of envisioning things is in the right direction. However, let us say instead of you focusing on modes and tones, and the actual relationships and byproducts of those individual pitches and signatures, that instead,spend time focusing training your hands and muscles to do basically the same thing you are thinking, but instead of tapping,mics and software, your using flexibility, stiffness and  tap gradients as a replacement.

when I say that "tap tones may be detrimental" it's not so much the outcome of the instrument as it is the wasted time and energy doing something that just won't yield results.

I'm not saying that there are not some successful makers who would swear by "their" tapping "system" , but I do feel that in the long run, for most it just becomes a dead end, and somewhat like looking back at the pile of garbage that "we or one" may generate in a lifetime, tap tones and the entire "thing" seems to be something you can look back on and just see a pile of wasted time that could have been used making an instrument.

I will still state that my "theory of greatness" is the only one that is true,provable and statistically observable.

And that is simply a theory based on statistics and odds. The more instruments you build, statistically, based on odds, the more likely you are to 1. have some of those instruments sound really great 2. get better at what you do, thus increasing the chances of #1 happening.

The reason I steer people towards training their hands to be "flexy/pressure/drivers" and to simply use their ears in conjunction with that is that it is much faster, or the fastest way to get from point A to point B.

I think it is best to think of your ideas and thoughts as if they were entropy, eventually they will spread out and you will get to try "that" {whatever that is} on your next one, and in time you will see that you will be able to try ideas and different things and spread your intentions throughout your "violin universe" and as time goes by, if you are truly passionate about it, you will get results....and then right when you start to get some things figured out, that's about when it's time to die and it all become tears in the rain, and maybe if your lucky the violin gods will see to it that you get a blurb in some makers catalog book that no one reads... I know, it's a pretty glamorous lifestyle that's not for everyone.

[Marty Kasprzyk]

2 hours ago, Shunyata said:

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My question is this.  My mode 5 tone is around an octave higher than mode 1( corrected as 2), and has far less ring.  Is this a natural result of the higher pitch, or should I be dithering with my thickness in the c bouts to increase flexibility and support the ring in the mode 5 pattern.

It might have far less ring because Its vibration energy is being quickly transferred to the surrounding air (radiation damping from heating the air or producing sound).

Joseph Curtin mentioned that a Strad top plate he tested had a dull thud when tapped.  Maybe the often stated goal of having a long ring is incorrect.

 

[Greg Sigworth]

I learned violin making by my self in the 80's and C. Hutchen's work on tap tones was the forefront of making. The question is does this help? Maybe does in that it helps making the plate thickness not too extreme. I have noticed that the clear ringing tone mentioned on the #5 mode is almost always because the #2 mode is close to an octave below it. The plate is actually held where the two nodes cross. This reinforces the #5 pattern so that is rings longer. When the plates are continued to be worked on it is very difficult to keep these an octave apart and the clear ringing tone is less present. You are actually hearing two modes at once and gives the idea of a clear ringing tone. From the articles in Strad it seems that the Cremona instruments did not have this octave relationship with the #2 mode being lower than needed. I still check the patterns and write down the frequencies but not sure if it is a waste of time. 

[Marty Kasprzyk]

30 minutes ago, Greg Sigworth said:

I learned violin making by my self in the 80's and C. Hutchen's work on tap tones was the forefront of making. The question is does this help? Maybe does in that it helps making the plate thickness not too extreme. I have noticed that the clear ringing tone mentioned on the #5 mode is almost always because the #2 mode is close to an octave below it. The plate is actually held where the two nodes cross. This reinforces the #5 pattern so that is rings longer. When the plates are continued to be worked on it is very difficult to keep these an octave apart and the clear ringing tone is less present. You are actually hearing two modes at once and gives the idea of a clear ringing tone. From the articles in Strad it seems that the Cremona instruments did not have this octave relationship with the #2 mode being lower than needed. I still check the patterns and write down the frequencies but not sure if it is a waste of time. 

The  M5/M2=2, octave goal  came from the  Strad top plate Hutchens had a chance to study.  She warned people about the risk of using just one data point to make a conclusion.

Two notes exactly an octave apart  sounds very pleasant and clear and it seems reasonable to jump to a conclusion that the old makers might have wanted to achieve this with their plate tap tones. 

Recently however it has been found that other Strad violin plates had M5/M2 ratios around 2.3 or expressed as a fraction of about 9/7 .  Two simultaneous notes having this this ratio would be dissonant, rough or harsh.

So I think the goal of achieving a clear ringing tone when held at the M5 and M2 node cross lines is questionable.

 

 

 

[David Beard]

I'm not a big fan of tap tones and tuning them.

That said, I do tap the plates as I work. I like to hear a 'talkative' lively plate. But I'm more interested in ideas of flex versus unity.  After all, the plates end up moving and twisting in many ways.

But I do tap pitch as a rough tool to decide between "still too much wood on this plate" and "better stop tinkering with this plate now".

I'm not sure what people are meaning by 'clear' ringing.  I like hearing the plate "hold" some energy as the 'thwack' sounds. But I really don't want to hear a cleanly specific pitch emerge. I want to hear only a vaguely pitched wood perusion sound.  I'm not making a marimba.  If tap energy is going straight in to a really specific clean pitch, then the response as a violin will be too narrow.

 

[Peter K-G]

13 minutes ago, David Beard said:

 If tap energy is going straight in to a really specific clean pitch, then the response as a violin will be too narrow.

 

I would not agree on that, a clean pitch can also lead to a violin with a broad dynamic range

[Shunyata]

We are firmly in philosophical musings territory now.  So let's focus on what we actually know.

We know what reasonable graduations look like, but also know that they are not determinant and tweaking is needed.

We know twisting and bending flexibility is important but we don't have a good way to measure this.  We aim for a stretchy feeling that we learn by experience.  We further tweak and try not to distort the graduations too much.

Tapping the plate tells us a lot about the mechanical condition of the plate - overall density stiffness in key areas especially.  Working with tap tones allows us to recreate these mechanical conditions, but we don't clearly know how they matter.  Observation suggest that they do matter, but they are not determinant by themselves.

Tap pitches have no direct meaning to the finished product.  Gluing the plate changes all the vibration modes and pitches.  They are only useful as diagnostic tests for the other good work that has already gone into the plate, and provide information where more tweaking might be helpful.  

 

[Shunyata]

My most responsive instruments have consistently had clean tap tones, although with considerable variation in pitch.  

[David Beard]

14 minutes ago, Peter K-G said:

I would not agree on that, a clean pitch can also lead to a violin with a broad dynamic range

I violin is more soundboard breaking into patches of standing waves in support of driving signals from strings.

A violin will always have some charteristic ressonances that push some pitch areas, but there's no need to underline them.  

Obviously people don't agree on these points, but I tend to think that successfully emphasizing specific resonances will by its nature take more energy into these coloration pitches and away from the standing waves induced by the driving signal.  To me, those standing waves seem like they should be the main show.

The violin is not a marimba.

 

 

[Peter K-G]

Had to look up marimba and you are right they don't look like a violin 

[David Burgess]

7 hours ago, Greg Sigworth said:

I learned violin making by my self in the 80's and C. Hutchen's work on tap tones was the forefront of making.

Yes, it appeared that way at the time, but I'd put it more in the 60's and 70's.

I don't know of any really successful maker today who still works according to her theories, but I will acknowledge her for being a mover and a shaker, in her day.

[Marty Kasprzyk]

1 hour ago, Shunyata said:

My most responsive instruments have consistently had clean tap tones, although with considerable variation in pitch.  

What does a clean tap tone look like if you do a frequency analysis?

What's a dirty one look like?

[David Beard]

1 hour ago, Peter K-G said:

Had to look up marimba and you are right they don't look like a violin 

With marimbas, the parts that turn energy from playing action into pitched musical signal are objects with high Q resonances. And, the primary parts that support and radiate that signal also have high Q resonance.  At times it seems as if people think of the violin in similar terms.

But lute and harp family instruments aren't like that.  They still use high Q resonance objects to form the signal - strings.  But they use much lower Q objects driven into standing waves that follow instead of create signal to support and radiate the music.

'Violins aren't marimbas' is just my short way of saying all that.

[Shunyata]

I don't use frequency analyzer tools, just my ear.  A clean tap tone is a pure tone without too much "texture" to the sound.

[Edward Byler]

I know not everyone would agree on this either but I think the weight of the finished plate to be as important as the mode pitches 

[Janito]

1 hour ago, Edward Byler said:

I know not everyone would agree on this either but I think the weight of the finished plate to be as important as the mode pitches 

Perhaps refined by 'distribution of the weight across the plate'.

 

[Don Noon]

2 hours ago, Edward Byler said:

I know not everyone would agree on this either but I think the weight of the finished plate to be as important as the mode pitches 

I am one who would definitely agree.  As I have mentioned many times, I look at the weight and taptones as I thin the plate; if the taptones are higher than normal, I'll go a few grams lighter, and vice versa.  I don't have any specific formula, nor will I deviate from my graduation pattern to try to get M5/M2 to anything specific or to make a clear taptone.  To me, that's silly.

Those other details might give you a hint about what the wood is, but it is what it is.  That's why I like to know as much as possible about my wood before I start.

 

 

 

[jezzupe]

I'll throw this unscientific blurb out there for what its worth....in general, the larger the surface area and the thinner the thickness dimensions the lower the pitch becomes...

so, in very simple terms what I try to do, regardless if it's "right" in any ones book, is that in general {particularly with the top} I try to carve a graduation scheme that makes the plate be as thin as possible without undermining it's structural capabilities to carry the load. 

And or quite simply I try to bring my tap pitch as low as possible without making a weak plate that will collapse. 

This of course is not done by uniform thicknessing, in the quest for the lowest tap pitch leaves some areas thicker and some thinner, and low and behold, not that far off from what we would see in any grad map, which is basically showing you in general where you can go thinner and where it needs to be thicker.

[Peter K-G]

On 6/13/2019 at 10:49 PM, David Beard said:

With marimbas, the parts that turn energy from playing action into pitched musical signal are objects with high Q resonances. And, the primary parts that support and radiate that signal also have high Q resonance.  At times it seems as if people think of the violin in similar terms.

But lute and harp family instruments aren't like that.  They still use high Q resonance objects to form the signal - strings.  But they use much lower Q objects driven into standing waves that follow instead of create signal to support and radiate the music.

'Violins aren't marimbas' is just my short way of saying all that.

Well, in any case more is more and less is less (less is not more). So I'll choose my wood blankets like best suitable for a marimba. High ring, clean ring, high Q.... this I know will be, the more the better later on for projection. 

You simply cannot make a soloist violin from dull wood and great wood will give a clean and strong M5 , nothing we can do about that (except for "dull" it down (the wood), if we want a less projecting violin, which surprisingly many fiddlers want.

[jezzupe]

On 6/13/2019 at 1:54 PM, Shunyata said:

I don't use frequency analyzer tools, just my ear.  A clean tap tone is a pure tone without too much "texture" to the sound.

Right! we'll have no ruffled, quilted, embossed, embroidered, lumpy or bumpy tones....just smooth tones....like jazz in the elevator! ...you know, in a purely scientific kinda way.

[David Beard]

22 hours ago, Peter K-G said:

Well, in any case more is more and less is less (less is not more). So I'll choose my wood blankets like best suitable for a marimba. High ring, clean ring, high Q.... this I know will be, the more the better later on for projection. 

You simply cannot make a soloist violin from dull wood and great wood will give a clean and strong M5 , nothing we can do about that (except for "dull" it down (the wood), if we want a less projecting violin, which surprisingly many fiddlers want.

Yes. The wood pick should be lively and talkative.  And in the traditional billet form it natirally and incidentally have clear pitch.     Just a matter of an elastic material and a shape that gives some mode enough freed to flex, good  'containment', and defined length.

But in making, seeking out well pitch defined resonances is counter to the main behaviors a  violin needs.  In my opinion.