Anders Buen

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About Anders Buen

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  • Birthday 06/03/1970

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

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  1. There has been a small group of cello makers at the VSA acoustics workshop each year. I haven´t been there in some years now, however. There is an article about the Double Bass in the Springer book on Stringed musical instruments written by Askenfeldt, who also is an amateur DB player. He has retired from the university now. There is also a chapter on Cellos there, written by Bynum and Rossing. There are also at least one article on FEA on cello bridges by the late jet engine engineer Oliver Rodgers in the CASJ. (CAtgut Acoustical Society Journal). Also Cloin Gough have been modeling the cello bridge in FEA. I think the community on celloes are a bit more reluctant to sharing their findings open than some of the violin researchers are. Attending the VSA acoustics workshop is a good way to get a grasp on what goes on behind and opn the scene of instrument acoustics and -making research. There might be opportunities in Europe as well now, possibly related to the french IRCAM.
  2. Goughs Vuillaume has a fine ringing e-string, by the way.
  3. An article draft for prediction of signature modes in violins based on J. A. Morals work. In 2006 I was one of the lecturers at the violin acoustics workshop, because Pickering was not able to attend. And I was active on a discussion board on this material at that time. One of the talks there was based on this article draft. I think the basic properties of it is correct, but that the frequencies for thin or very thick plates are a bit exaggerated. That is: what happens to the signature modes of the violin if the plates are thinned? There area also predictions on how material properties influences the modes. The material data are a little on the stiff side, based on Haynes measurements and articles. I do have some input from a researcher I wrote with some 14 years ago, which can be used to refine the article draft. It may be spit in two. There are work in progress now, I understand, on the same subject as Morals work, "the Bilbao project". They are working with very small perturbations for the thicknesses I can see in their material at the project webpage. So I will be surprised to see any usable results from that. Prof Anders Askenfeldt once told me that "You really need to make large changes to the violin in order to get any significant results". He was Erik Janssons collegue, and Moral made his PhD work at his institute.
  4. I think some information on correlation between free plate data and assembled violins has beed shared by me, here and on another similar discussion board bafore Colin came with his calculations. Both Colin and Geoprge have seen this lecture. It was shared here In a thread discussion i refer in one of the slides below. J. A. Morals work in the 80ties showed correlations too. So the idea is not new. My slides above show that there are clear correlations also in Schleskes original work where he claims that there are no correlations. But he was probaly only looking a the mode 5.
  5. Gough is a very nice and interesting person to listen to. Ive met him several times both in Oblerlin and in conferences in England and other places. In Cambridge he is sort of an host, with the history and present time knowledge generously shared. A good and spirited lecturer as well. Many former professors and teachers are good at that. I particularly liked his lecture on the bow and its physics. I also like his and Stoppanis idea about the breathing and bending component of the B1+ mode. I know Colin have the model for the A0 and other modes lined out. I saw him working on it once. I just cant find it in any of the 5 JASA articles i think he has. Having said that, there are a lot in these articles that simply isnt relevant for violin making or the violin acoustics. There are a little too much colorful FEA maps with rather questionable usefulness. - Vibration porn.
  6. Most readers are likely to have problems getting anything useful out of it, I´m afraid.
  7. Hi Marty, Good ideas, as usual. A good platform would be the frame of an good old american car with the floor, wheels and suspension intact. :-) The first historical Greek lifter is said to have trained with a calf. It grew and he kept lifting it, even until it became a grown bull - and probably stopped cooperating. Then he had to run from it, and marathon was invented. :-) Filling air in the tires would be sort of warming up.
  8. Yes, this sounds familiar to me. The last ten years or so it has become common with water supplied heat in the floors in condos. The water pipes are usually laid out on 25-40mm of elasticiced EPS with a 35-40mm cement or gypsum screed on top. These floors appear to be boomy. Even if the impact noise requirements are met, still many find these floors noisy. Especially if the owners move from separate housing into a condo with neighbours over them. This is a more widespread problem I think than the gym noise and flooring for that. My concerns here with special very soft mounted floors is a very very small branch for extreme nerds. :-)
  9. I do not know. But the effect of the mats physically is that the stop length goes up, smearing out the impulse in time, thus reducing the trnsferred noise. However, the mat or cushioning on the plates, or both, act as a sort of low pass filter. The thicker and softer the mat the lower the cutoff frequency. I think that some mat technologies for gyms or even more for climbing crash mats, do use similar materials and tecnholigies as the bed mattresses. We are interested in what the technical limits are How much damping can be achieved. The best solutions consist both of thick mats, and floating floors. The mats need to he stable enough for standing and lifting on them, but still soft enough to give optimal demping and filtering. However there are a practical limit there for the mats. The noise they do not damp or filter must be delat with by the flaoting floor, with most possible mass, and as soft as possible support. The softer support, the lower the cutoff frequency. And we hear bassy sounds ever less well the lower the frequency. Spring supported floors have very low frequencies like 5 Hz ish, but if its not vented, the resonance may be much higher due to the air stiffness maybe 20 Hz or 25 Hz. Simple calculations of the A0 for such a floating floor 4x5m 100mm thick and with 20cm slit along the walls, would have a resonance around 60 Hz ish. That is a A0 above the main floor resonance at 5 Hz or 10 Hz ish. 100mm floating concrete floors on 50-100mm minerla wool have reosnance frequencies around 35 Hz. They too have a perimeter of 10-20mm minerrla wool against the walls to prevent short cirquiting. These are very noisy, and I wonder if an A0 may play a role for them too. The company I work in and collegues in other companies recommend these spring supported floors, and we do not know how well they perform. Other techonoloiges have data up to insertion losses of about 50 dB (the difference between the impact noise from a weight drop on the bare floor and on the test floating floor and mats). But they are tested on muckup floors with vented perimeters. They have thick mats, 50-100mm concrete tiles plyvwood on 25-50mm PUR foam pads. But they probaly perform worse than that in a closed floor volume. Maybe the spring supported floors are better, but I would like to know. Not anticipate and recommend something that might not work. How common is it with gyms in the same building as appartments in the US?
  10. The only situation I have heard about phase locking in violin acoustics is for the bowed string.
  11. I am trying to reverse engineer and understand the behavior of the supposedly best floating floors out there: casted concrete floors supported on steel springs. Jackup floors. The suppliers does not provide information on the performance of these floors. I think there is no well functioning models for them, and I believe with the knowledge from violin acoustics that the AO may play a role for the performance of such floors, The air stiffness also may play an important role. The most noisy gym goers I know of are young guys in the free weight area, probably a culture thing. Strongman guys are not allowed in regular gyms here. They will be asked for an urine test, or to leave if they refuse. A 40 kg hand 12mm ish urethane covered hand manual dropped from a bench on a concrete floor give about 75 kN force and some 97dBA structural noise. That is three times the force the heaviest impact hammer from PCB can measure, essentially a sledge hammer with a softish tip. If we dropped a kettlebell from the same height straight on the concrete it would be even higher forces and noise levels. Such rather simple weights are immensely strong noise sources. Interesting to model. In a sort of larger scale this is hammering a building structure, similar to hammering a violin with a miniature hammer. But the physics might still carry over from one to the other. Vibrations are another issue. It is interesting physics, and it is not much studied. I try to understand these floors better using scale models in 1:10 or so.
  12. I just found an old excel file with some mass, spring dashpot models for the three first violin modes, A0, B1- and B1+. It calculates the admittance of each of these modes based on a given frequency and effective mass. Then they are summed up. I moved the A0 up to 500Hz and compare the summed admittance curves for the typical case A0 = 277Hz, B1- = 430 Hz and the B1+ = 550 Hz. The response around the A0 becomes much weaker when it is moved up almost an octave. I am not sure if the phase relations beteeen the resonances are modelled correctly, but I think we pretty much see what will happen in a simple manner.
  13. I've seen a movie of a guy rolling off large concrete rings, pobably tube elements, from a truck on a pile of tires. The tires took the energy from the falling ring and it rolled gently from the flattened pile aftwerwards. - Very impressing! I am not making any platform. But are interested in the subject. DIY solutions are interesting, though. Many lifters do it in their garage and do not want to disturb their family, sleeping babies etc. Tires on the side would probaly work fine with a plate on it., maybe with a rubber granulate mat on top. Many of the mats in gyms are rebound shredded tires, by the way. Some bumper plates too. I think it would work nicely.