Scientific investigations of Stradivarius violins--an updated review article


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A floor mic has an interesting property. It does not color the recorded sound. The signal becomes a little louder. However, it is probably a little suseptible to "floor noise".
In Hardanger fiddle music, or many other folk fiddle traditions, foot percussion is a part of the experience. 

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4 hours ago, Don Noon said:

I'm not sure how well I can explain it... but if you have been around new and old wood and cut some shavings and look at them, it is obvious that wood becomes darker and more opaque with age, with some possible photo-bleaching depending on age and exposure.  Or look at old violins where the varnish is worn down to the bare wood and then polished over, and compare it to a similarly finished new piece of wood.

I recall a video (which I can't immediately locate) where Robert Cauer was checking for a Strad authenticity, and the first test was to shine a light on the top and look inside to see how much light came through.

As for the chemistry and mechanisms for opacity, I can only point to exposure to light, air, and other natural chemical reactions.  Your paper points out chemical reactions that occur spontaneously with time, and if chemistry changes, optics can change with it.

I am astounded that someone in chemistry writing articles about old violins would be unaware of this fundamental fact.

 

 

Strad tops (2.0-2.8 mm in the center) are also thinner than average modern violins (2.9-3.0 mm). Strad also has a thin and transparent varnish. Both can affect the amount of light being transmitted, in addition to wood properties. 

I found a good explanation of light transmission on the internet: https://light-measurement.com/reflection-absorption/

"Reflection is the process by which electromagnetic radiation is returned either at the boundary between two media (surface reflection) or at the interior of a medium (volume reflection), whereas transmission is the passage of electromagnetic radiation through a medium. Both processes can be accompanied by diffusion (also called scattering), which is the process of deflecting a unidirectional beam into many directions. In this case, we speak about diffuse reflection and diffuse transmission (Fig. II.14). When no diffusion occurs, reflection or transmission of an unidirectional beam results in an unidirectional beam according to the laws of geometrical optics (Fig. II.15). In this case, we speak about regular reflection (or specular reflection) and regular transmission (or direct transmission)."

Old wood looks more opaque either because it absorbs more light or causes more diffusion/scattering. Old wood becomes more yellow due to lignin oxidation. I have seen woods carved out from deep parts (>4 mm deep) of guqin plates that are 500-1200 years old. They certainly get more yellow over time. Guqin tonewood over 2000 years old are not yellow but dull grey at all depths (I have seen two), but these may have come ancient burial sites.

Yellow color is probably due to stronger absorption around 450 nm. To increase scattering, perhaps more internal pores are needed. After 200-300 years for hardwoods or 1000 years for softwoods, noticeable degradation can occur with hemicellulose. But I am not sure if this will actually create nanopores that enhance scattering. 

Old wood becoming more opaque may be due to lignin oxidation and blue-light absorption. This is not particularly important for the appearance of Stradivari's varnish because other old violins would be similarly affected. Moreover, it is easy to cause artificial yellowing of wood by baking or staining.  

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15 hours ago, Bruce Tai said:

This is new to me. Can you explain a bit more? 

Is old wood more opaque before varnishing or after varnishing? 

Why is the cause? Is it because if yellowing?

Don is correct on older wood being more opaque, based on assembled instruments I have observed so far. Would wood newly cut from the center of large old beam exhibit similar opacity to a much thinner fiddle of similar age? I don't know.

I suspect (but don't know) that this has to do with a change in the refractive index of the wood, versus the entrained air, over time. It seems to hold true for both varnished and unvarnished wood.

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23 hours ago, Peter K-G said:

Oops, You woke the Viking!

First 200 kg, is nothing to him., for every poke it doubles (no offence Anders)

Vikings are the strongest/smartest people on this planet ever lived.

(except for Finns)

 

They studied the Romans. That's how they became Normans. 

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15 hours ago, Bruce Tai said:

While it may not be apparent to some readers in this thread, what we having here is a healthy debate between old acquaintances but not quarrels of any sort. I have been sharing my research articles on this forum since 2007 (my first VSA varnish review). Different kinds of criticism have shown me many new ways to look at the problem. Through my interactions with the knowledgeable members of this forum, I have been educated on many aspects of violin making and violin properties. 

Based on personal experience, there are believers and non-believers in the superlative qualities of Strads. Some believe in the "blind tests," but I also pointed out in my article that these are flawed and cannot really address the tone quality problem. 

Instead of getting trapped in the "Strad vs. best modern" violin debate, we could compare Strad vs. other old Italian. I think it is universally accepted that Stradivari and del Gesu were a class above other old Italian makers. If so, then why? What are the acoustic correlates of the favorable tonal qualities described by soloists and collectors? If we can actually answer these questions, we would be making great progress. 

 

Was Cremona a very competitive place for violin making? 

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20 hours ago, avandesande said:

 

This is from the article...

"First, fewer than 20% of the 500 surviving Stradivari violins remain in top conditions fit for concert violinists, but we do not know the quality of instruments entering these stud-ies. Secondly, short-term memory for timbre quality only lasts for seconds, but it takes min-utes for the players to change violins. By the time the next instrument is played, the mem-ory for the previous instrument has severely decayed. Thirdly, the loudness has to be strictly matched to carry out timbre comparisons, but this is not feasible in a listening test with live performances. Louder violins often give the initial impression of sounding better in blind tests, masking timbre dif-ferences[5]. Therefore, it is not surprising that blind tests carried out by Fritz et al. were inconclusive."

Since you mention that the quality differences are apparent using recording, doing blind tests using recordings should address the last two issues and the first is solvable as well.

 

As the saying goes the burden of proof rests on those making extraordinary claims. The problem is nobody in the industry really wants to dispel these myths since it goes against their financial interests of those that have bought into it. Even makers benefit as collectors keep many good instruments out of the hands of musicians.

 

 

" If I have seen further, it is by standing on the shoulders of giants"

Isaac Newton 1675, quoting Bernard de Clairvaux 1140 (Normans again) quoting some ancient Roman geezer.

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6 hours ago, David Burgess said:

Would wood newly cut from the center of large old beam exhibit similar opacity to a much thinner fiddle of similar age? I don't know.

I DO know.  Melvin Goldsmith sent me some samples of Italian spruce cut from 300 year old beams.  It was not opaque, but seemed much more like wood aged perhaps a few decades.  EMC was no different from modern wood.  Full thread was a few years ago, here: 

 

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Thanks for posting the article, Bruce.

After reading most of the responses, I think there is some misunderstanding about the article in this forum. If I am not mistaken the article is more addressed to an interested general public rather than scientific peers. At least that is my interpretation of the lack of sophisticated scientific language in the article. With some minor objections I think it summarizes major points pretty well.
 

If I am taking the article from the conclusion, I am not sure if material treatment is the last missing piece in the puzzle. But regardless, until a few years ago no one had looked at this aspect and there is certainly more to discover. I can only confirm from my workshop practice that using steam treated wood, makes a difference for the sound and I would say it makes more difference than looking for magic varnish recipes. (And I have done that too)
 

No matter how well contemporary instruments of top luthiers are perceived, we have to keep in mind that the effect of ‘spacious sound’ or ‘carrying power’ has been first noticed on classic Italian instruments and without we wouldn’t  have a clue what to look for. At present, there are certainly only a limited number of classic Cremonese instruments around who display this characteristic. Bruce is NOT trying to generalize it like ‘All Strads are unbeatable in the carrying power.’
 

The question is if the equation

wood treatment reducing hemicellulouse = superior carrying power 

is correct. I can only see in the article that Bruce looks on the minefield of factors to come to an irrefutable conclusion. 
 

As a sidenote from my own experiments and thoughts on classical violin making I would say that making instruments with carrying power requires the combination of two major steps: 1. Material optimization in terms of material selection succeeded by additional wood treatment.
2. A  sound calibration process is absolutely necessary. Roughly speaking how to make a functioning arch-membrane and calibrate the rest of the body to it. 
(For this I can only quote from memory Stefan Peter Greiner who said: ‘Tuning the sound of an instrument takes almost as long as making it.’) 

The summary on the varnish looks good, I only wished that scientists finally  would look if there was a difference in the ground for the spruce top made and the rest of the instrument made of maple. I cannot help thinking that some contradiction in interpreting recipes for the ground comes from one scientist looking at a maple section and another scientist looking at a spruce section. So mineral fillers would be on the top and linseed oil based ground for the rest. (My personal guess)

So maybe the article is a disappointing result for informed people on this forum. But I got tired of scientists blasting out a new ‘found-the-secret!’ theory. In the end: one thing will never change ‘sound’ is a matter of personal taste. So everything related to it is based on a personal bias. 

 

 

 

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I'm always depressed when I see articles like this. The reason being that some misguided scientist comes up with fancy ways of analysing Strads to show how some varnish component or other contributes to their "unique" material and compositional properties. 

Well that's as maybe. But if you want to approach this issue scientifically, the absolute first task is to demonstrate objectively that Strads and del Gesus do indeed possess unique acoustic properties, otherwise your analyses are meaningless. As far as I'm aware, a this has never been done in a well-controlled, double-blind test with sufficient numbers of violins of Strads etc versus well made instruments across time, to provide a significant sample. This issue has been discussed many times here and I don't wish to re-open the topic but just to point out that these sorts of papers, while interesting, are a bit pointless from a scientific perspective.

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19 minutes ago, Andreas Preuss said:

 I cannot help thinking that some contradiction in interpreting recipes for the ground comes from one scientist looking at a maple section and another scientist looking at a spruce section. So mineral fillers would be on the top and linseed oil based ground for the rest. (My personal guess)

Why? Based on what? Oilgroundaphobia?

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6 hours ago, Argon55 said:

But if you want to approach this issue scientifically, the absolute first task is to demonstrate objectively that Strads and del Gesus do indeed possess unique acoustic properties, otherwise your analyses are meaningless. As far as I'm aware, a this has never been done in a well-controlled, double-blind test with sufficient numbers of violins of Strads etc versus well made instruments across time, to provide a significant sample. This issue has been discussed many times here and I don't wish to re-open the topic but just to point out that these sorts of papers, while interesting, are a bit pointless from a scientific perspective.

It's extremely difficult to do ANY scientific studies of tone where humans are providing the judgements. 

Almost 30 years ago, Dunnwald published a study in the CAS journal showing fairly clear evidence that there is a difference in the spectral response of old violins vs. modern ones.  Anders Buen has published similar results, and my tests have also followed those trends.  Joseph Curtin's data that I have seen also shows the same characteristics, and (when I cornered him) he admitted to the pattern, although he had his own ideas about what was causing it.  I don't have a cause that I fully believe in.  Yet.  But logically there HAS to be one; it's somewhere in the structure mode shapes/frequencies and damping, it ain't magic.

So I think it's pretty clear that, on average, there is a difference in the sound spectrum.  The never-ending debate comes in when you try to get into player an listener preferences, projection, beauty of tone, clarity, singer formants, and all that squishy non-objective stuff.  I kinda think it's worth trying, though, if you can weather the fire and brimstone from various factions with strong beliefs and preferences.  But if anyone can prove the source of the spectral difference, I think that would be far more interesting to makers like me.

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This for me is what we should be discussing.

I don't need to proselytise about this. Just listen to Jean-Philippe Échard explain.

Why this important tonally is for players to describe as much as listeners.

 

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7 hours ago, sospiri said:

Why? Based on what? Oilgroundaphobia?

As a maker I am trying to be pragmatic. So I have neither a oil phobia nor mineral phobia. The rest is a matter of how to make things work, because no scientific finding provides a recipe. So linseed oil diluted to 1% in turpentine oil might look just like pure undiluted linseed oil in the analysis result. (Don’t take that as a scientific statement)

On the other hand when reading about medieval know how stuff, it is quite apparent that craftsmen back then were very well aware of different wood properties from different trees. On this background it looks not logic to me to treat the top of a violin just exactly the same as the maple parts. 
 

 

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1 hour ago, Don Noon said:

But if anyone can prove the source of the spectral difference, I think that would be far more interesting to makers like me.

It seems that this is hidden in the jungle of high frequencies. Though averages in octaves (or whatever band width you are using) might help to understand that, we need to come up with a better analyzing method. 
 

Maybe we get a better clue when looking at selected single notes and compare the sound level of overtones.
 

The other thing i would try to look at is how a bowed note ‘kicks in’. Those first milliseconds seem to be a crucial sound judgement point for high performance players. 

 

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3 hours ago, Andreas Preuss said:

The other thing i would try to look at is how a bowed note ‘kicks in’. Those first milliseconds seem to be a crucial sound judgement point for high performance players. 

 

The attack phase of a note is of course very critical. No one has a good idea on how to analyze that. It depends so much on the bowing. So scientists choose to analyze the steady-state signal. While we analyze sustained notes played by a human, others prefer to use mechanical bowing devices or mechanical excitation to the bridge.  

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On 4/17/2021 at 10:25 AM, Anders Buen said:

A floor mic has an interesting property. It does not color the recorded sound. The signal becomes a little louder. However, it is probably a little suseptible to "floor noise".
In Hardanger fiddle music, or many other folk fiddle traditions, foot percussion is a part of the experience. 

When you say floor mic, are you talking about a pressure zone mic / boundary mic?

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I always think it is worthwhile to compare violin studies with other instruments.

I first came across guqin from the work of John Thompson: http://www.silkqin.com/

He discusses changes in guqin setup connected to the switch from using silk strings to using metal-nylon composite strings - soundpost position changes or removal, possibly re-graduation. He includes questions about whether the denser higher tension synthetic strings cause more damage or degradation to the structure of the wood than the traditional organic strings.

These would all have implications for the kind of questions being studied here.

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4 hours ago, Bill Yacey said:

When you say floor mic, are you talking about a pressure zone mic / boundary mic?

I haven’t seen it, acually. But we sometimes see table mics in AV systems. It is pretty flat.

Every now and then we do measurements of noise outdoor, or indoor. The only positions where you can be sure that the complete spectrum is present is at the facade. We use omni mics. This is a physical phenomenon and not related to the mic technology. 

Indoor we also have resonances to deal with and everything becomes more complex. Still there are some similarities. The sound pressure level is highest at the borders of the room, and corners in particular where also the modes are maximized and active.

A floor or wall mounted mic would remove the comb filtering from the floor or wall reflection. Still there are other reflections in a room even in hard damped studios. 

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12 hours ago, Andreas Preuss said:

As a maker I am trying to be pragmatic. So I have neither a oil phobia nor mineral phobia. The rest is a matter of how to make things work, because no scientific finding provides a recipe. So linseed oil diluted to 1% in turpentine oil might look just like pure undiluted linseed oil in the analysis result. (Don’t take that as a scientific statement)

On the other hand when reading about medieval know how stuff, it is quite apparent that craftsmen back then were very well aware of different wood properties from different trees. On this background it looks not logic to me to treat the top of a violin just exactly the same as the maple parts. 
 

 

Échard discusses some very important points. For example the first layer on the spruce could be just linseed oil or linseed oil and turpentine. Or you can do a layer of oil and then 50/50 oil/turpentine for the next layer. I have many comments I would like to make about the issues he addresses in that very long video. 

11 hours ago, Andreas Preuss said:

The other thing i would try to look at is how a bowed note ‘kicks in’. Those first milliseconds seem to be a crucial sound judgement point for high performance players.

Absolutely,and that is why I swear by this method. It allows superior bow control. 

8 hours ago, Bruce Tai said:

The attack phase of a note is of course very critical. No one has a good idea on how to analyze that. It depends so much on the bowing. So scientists choose to analyze the steady-state signal. While we analyze sustained notes played by a human, others prefer to use mechanical bowing devices or mechanical excitation to the bridge.  

I'm suret the best way to test it is to ask the players. Bow technique is so finely nuanced and individual that no scientific analysis can match what the player feels, regardless of what the listener hears or thinks they hear, it is the player who has to be satisfied first.

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14 hours ago, Don Noon said:

It's extremely difficult to do ANY scientific studies of tone where humans are providing the judgements. 

Almost 30 years ago, Dunnwald published a study in the CAS journal showing fairly clear evidence that there is a difference in the spectral response of old violins vs. modern ones.  Anders Buen has published similar results, and my tests have also followed those trends.  Joseph Curtin's data that I have seen also shows the same characteristics, and (when I cornered him) he admitted to the pattern, although he had his own ideas about what was causing it.  I don't have a cause that I fully believe in.  Yet.  But logically there HAS to be one; it's somewhere in the structure mode shapes/frequencies and damping, it ain't magic.

So I think it's pretty clear that, on average, there is a difference in the sound spectrum.  The never-ending debate comes in when you try to get into player an listener preferences, projection, beauty of tone, clarity, singer formants, and all that squishy non-objective stuff.  I kinda think it's worth trying, though, if you can weather the fire and brimstone from various factions with strong beliefs and preferences.  But if anyone can prove the source of the spectral difference, I think that would be far more interesting to makers like me.

You may well be right about that. But if it's so difficult, it rather undermines the idea that Strads etc are acoustically unique and generally believed by players, many in the trade and many contributors to this forum, to be acoustically superior to other violins (though they may well be superior in other ways).

I wonder whether it is similar to wine tasting, where, when using blind tasting, experts struggle to identify superior wines better than a rate equivalent to mere chance. The hypothesis being that wines are so complex in composition and therefore taste, that it is beyond the human palate to consistently recognise and identify them. As with wine tasting, perhaps with violin sound. This is an interesting article:

https://www.theguardian.com/lifeandstyle/2013/jun/23/wine-tasting-junk-science-analysis

 

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13 hours ago, Andreas Preuss said:

>

>

The other thing i would try to look at is how a bowed note ‘kicks in’. Those first milliseconds seem to be a crucial sound judgement point for high performance players. 

 

Is this the "clicking" sound at the beginning of a note that good players like to have?

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