Anders Buen

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About Anders Buen

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  • Birthday 06/03/1970

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    Oslo, Norway
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    Violin-, Hardanger- fiddle-, room- and architectural acoustics.

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  1. Thanks back Don, I follow your updates and appreciate your comments and input very much.
  2. Statistically R^2 = 1 would mean that all variation in the frequency of B1- (?) could be explained by the variation in the M5 top plate frequency. We know that e.g. adding a chinrest in general will move the B1 frequencies a bit, sometimes quite a lot. Now, the variation in the top plate can´t explain that and 100% prediction from the top plate M5 frequency is not possible. We can dig up other examples too. From my large dataset about 30% of the variation maybe is reasonable. One need to do multiple regression or maybe some other type of statistics mining technique to figure out this. The input data need to be of high quality. Patrick Kreits book claim very high prediction power like that, but by looking at the data proivided there, and having experience with violin acoustic datasets, one can tell that they are likely to be model predictions and are not real measured data. I think I have explained where I think the fault is in that model too, somewhere here on MN. The problem with Dons and Bissingers datasets is that they are not large enough. And sets with data from before and after regraduation are probably better. Using models from statistics, like this, probably also works better for predicting the perturbations, the expected changes, from regraduation than for a new build of a given model.
  3. Regarding Dünnwalds Sound parameters I have done a few years research in trying to figure out what influences these. The level of the A0 in relation to the mid frequency response is called the L parameter. Lower top plate weights and low Mode 1 frequencies go with stronger L-values. This affects the stiffness of the box. Lower stiffness gives a stronger A0 response. We have also seen some traits of weakening the midfrequency response from adding mass close to or at the f-hole upper wings. A typical patch and repair position. Furthermore higher arching and thinner border region of the back plates seem to go with higher values of the ACD-B (see Figure). The most difficult part is the higher frequencies. DE-F, bass, bridge and setup may be crucial. I have also seen that high values of Dünnwalds parameters does correlate with a lower overall SPL. A «Dünnwaldian» violin may have a certain sound characeristics but may not carry as well. D´Addarios old Naepolitan violin is an example of that, sweet sound but not particularly powerful. (If you attend the VSA Oberlin Violin Acoustics Workshop you will probaly hear or even play it). However some violins have both Have high scores of DW parameters and high SPL. An example is the de Diable del Gesu on the Miracle makers, at least it is like that in the recording. Later research have shown that the nomenclature used by DW for «nasailty» etc was not well founded. Also the frequency regions for different classifications are disputed. But to be honest, I have not been able to understand the contant of this, not from reading it nor from hearing the presentations. I am not going to do the work over. I do think that good violins can have a strong mid frequency response, e.g. Boosting the fundamentals of one or some notes on the E-string. The winner of the VSA 2016 competition was one such instrument. Strong E string instruments are fun to play. How do we measure «fun factor»? Or just let it be?
  4. Many makers do make great violins, every now and then. When somebody does a PhD and spend a lot of time doing measurements and interpretitions of those they need to come up with some results within the budget time they have available. In my opinion Dünnwald did a fundamental error in throwing away the overall SPL in his data. Loudness comes up as the most important factor in percepted acoustic analysis. It is a descriptor of power and distance, fundamental in perception to any animals, I think. E.g. Singing birds must have a loudness war as they are so loud for their tiny size. Dünnwald continued his measurements after the thesis was delivered. It may have been in collaboration with makers, for access to fine instruments, like Greiner. At that time, mid 1980, personal computers and an acoustic measurement system was something very few had access to. Possibly he put some $ and time into this. A system like that can tell if the acoustic properties of a violin is in the ballpark or not. Playing it will too, given enough experience with good instruments and playing capabilities. Light top plates will statistically tend to give instruments with higher L-parameter values. All impact frequency spectra i have analyzed of modern US makers do have L >= 18 dB and most over 20 dB. Factory violins (anno 1985) in general have heavy tops and thus the L is low.
  5. My five cents on the matter, shared many times before. https://www.researchgate.net/publication/336473862_Free_plates_and_signature_modes_of_violins_are_there_any_correlations
  6. One of problems with extracting information and data from violin plates and instruments is that they all are dependant on the MC of the wood, which vary with the climate daily and over the year. I think that controlling the shop humidity is an important factor for consistency in making. Having a good mid range shop RH also is good if instruments are to be shipped worldwide to any climate. Wooden density, youngs moduluses, loss factors (damping), size and shape all are dependent on the MC. The sound too. The idea of plate tuning is an attempt at reducing the complex problem of making decent to good violins to a few parameters. Some probably are a little more important than others, but the complete set is needed to make a violin. Correlations can be found, even in literature claiming there is none. But should these explain more than 50%? The parameters should share the 100% in a good working model. Players and makers do probably not agree on what is good and not. Maybe some grouping can happen. Some do agree on something. This makes a clear unified decision difficult. And do we measure the instrument quality or the test persons preferences? This theme is impossible to solve. I think most makers can line up the important factors for making a good violin. It is definitively more information than three to four numbers with units gram, and Hz. If one stick to the same model and wood: maybe the answer is a little easier? The % variance from these factors are smaller and the remaining variance is explained by the rest, hidden variables or not.
  7. If these data were unimportant, maybe the makers would have shared them more openly?
  8. I think he later said that removing the wide stiffer upper and lower block region parts of the plates to the sides of the blocks made the modern plate behave similar to the older ones for mode 2. This was originlly my intuition. I call these the «Sacconi plateus» but none working in his tradition has approved this name. They are there in Hutchins illustrations of plates, and I think some fine makers prefer to keep these for crack prevention, and for the stability and possibly for the sound.
  9. The bowed string is nonlinear. A linear translation becomes something periodic, eventually. That is nonlinear.
  10. Thanks Marty, good to know. Maybe the most important effect then.
  11. Thanks for the referene. I may write him. He has a nice website on his current activites.
  12. That was a brilliant estimation! Redistributing the numbers into displacement makes them even smaller. 0,02mm @ 25 Hz for the ship at 3mm/s. And about 1 micro m for the violin also at about 3 mm/s, equivalent to 1 g if the math is sound.
  13. Thanks for sharing your experience and thoughts, David! I know you have long experience as a restorer of fine violins as well as deep knowledge on humidity and wood issues. (Maybe even using this in the making, I guess, with those shaped maple backs). :-) Basically I think the museum representatives and their supporting experts do share your and Dons opinion on this. The humidity variations, shape changes and stress gradient variations are much more important than vibrations for degradation of the ships. For the most brittle alum treated "hard bread" like objects maybe the story is more complex? They do run research on this, but mainly on humidity and chemical changes I believe, indicating the same as above. Personally I am a bit surprised by our opinions on the effect of vibration. I thought it did play a role in crack formation in violins, especially around the wings and holes. But this is also a region where the wood will dry out faster or moist up faster and form tension and humidity gradients. The wings are also easily bent under tension, maybe inside cases while closing them, or similar. Just a misplaced thumb while lifting the instrument. I had the idea to count repairs like eyebrows and wing cleats in violins as repairs of vibration caused cracks, but I guess that is not the case.
  14. If we think about bending the wood until it cracks, I would believe the amplitude has to be pretty large before it happens. We hear the cracks form. Maybe a thinner sample can take more bending than a thicker? A violin plate can be bent quite a lot. A cm or even more. But with not perfectly squared samples the cracks may come at lower bending amplitudes. Brittle wood with cracks in them already may take less bending. I guess the humidity content might have an influence too. Drier samples probably crack easier. Letting the wood stay outdoor a couple days making it softer and more moist make it easier to cut with a knife or V-shaped tool.