tsuresuregusa

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  1. From the experiments we've seen, the "bridge hill" is always there, but Strad has it a bit before the rest.
  2. just to be clear, we are not ignoring the cross grain elastic modulus in our simulations. We vary it as well as the longitudinal stiffness but its effect is negligible. This is a result we obtain from the simulations and not an assumption. Maybe the range of variation in natural materials is way larger for the cross grain than for the longitudinal in which case our simulations would not be representative. We don't have data on this so we went for what it seemed a reasonable guess. It may be the case for a rectangular plate but not for the violin plates we simulated, and I trust more our
  3. those results are bridge admittance measurements so they are normalised by the impact force of the hammer on the bridge, therefore we cannot compute absolute values of power. Maybe with the simulations is easier to do: that's some different examples for top plates with clamped boundary conditions. Don't ask me why we stopped at 2000hz, it was just a test run and we wanted to have an idea of how many points we would need. We need to re-run the sims and then I can maybe say something about to what variables the onset of the raising is related to. Will take a few days, it takes a
  4. yes. The Strad is from a rather famous professional player, and according to him the copy also sounds quite good. Of the Cremonese makers, they were part of the last Mondo Musica so maybe the recordings are online. I'm not sure I can de-anonymise the data though.
  5. Thanks for the data, if you could share the actual numbers instead of a picture it would be lovely. Is that an acoustic measurement or a bridge admittance? We have another paper (submitted not yet online) where we study ways to quantify the differences between FRF by extracting "features" from the data (amplitude, frequency, damping), and using them to "sort" violins by the distance between the features. As you well say, the frequencies vary quite a lot but your conclusion is not warranted: maybe is some relation between the frequencies that is important rather than their absolute values
  6. Probably, but for the sake of simplicity we decided to use fixed length violin bodies. It seems to us that this is the common practice nowadays, we can easily re-run the simulations and the analysis if it's not the case (or luthiers would be interested in seeing those results). If you had the data of the really crappy violins which have identical frequencies of great violins we would love to see it. We have yet to find two violins with the same FRF. The sound produced by a loudspeaker is a function of its geometry and their frequency response, in which the damping has indeed a great
  7. One of the limitations of Colin's approach is that he is varying one parameter at the time in ranges that don't make much physical sense. Does it make sense to have a maple top plate? I don't think so. Secondly, this way of studying things "keeping everything else constant" hides any non-linearity between the parameters. And that's why our approach is more complete/realistic. I doubt you can find two pieces of wood that only vary on one parameter, let alone a whole set for doing the kind of experiments Colin does with his simulations. I don't want to boast but I really think it's time to start
  8. One needs to note that the scale of the anisotropy here is for extremely different materials: So his results are coherent with ours. Even if you would find a wood that only changes on the cross grain, the effect would be minor. As I said the before, the most material important parameters are density and longitudinal stiffness, so when changing the wood those are the ones that will dominate, not the cross grain stiffness.
  9. The cross grain stiffness is not really important, the two most important parameters are density and longitudinal stiffness. We are actually varying all the material parameters in the figure above, just didn't write them down. We could do a cross grain only variation but my student is super busy at the moment so would have to wait a bit. Do you have values for the density and longitudinal stiffness for plywood?
  10. Just to illustrate the point. In magenta you can see the starting outline for a material with rho = 400 kg/m^3 and E = 10.8 GPa and in black the optimised shape to reproduce the eigenfrequencies of the initial top with the materials parameters that the figure shows. So unless you are working with extremely stiff balsa wood the optimised outline does look like a violin. Note that these results are only for the optimisation of the outline, when you also include the thickness optimisation my impression is that the outline changes even less. Tomorrow I try to get th
  11. I think that's a bit of a stretch. The results we present show variations of around 5% in the area of the outline for a 10% variation in the sound speed of the wood. Probably the area variation will be way smaller when we consider varying arching. On the other hand, I think we will be able to provide precisely such a tool in the near future. And hopefully with an easy interphase where you input images of the arching and outline, material parameters, and desired frequency output.
  12. Thanks a lot for your feedback Daniel, you are totally correct. Will change the intro/abstract when it comes back from the reviewers. I really appreciate you took the time to go trough the paper and get the big picture. Marty, we actually tried to do something along the "evenness" by optimising the location of the eigenfrequencies so they are equally spaced, ie, equal tempered, but the results were quite bad. Probably a random location of the peaks is easier to obtain. Concerning the amplitude of the peaks in the frequency response function (FRF), this is a function of where you p
  13. Sorry for the slow replies but the moderators need to approve my responses so it's taking far too long to reply one by one the comments... Thanks Davide, I hope we can have another live session soon here in Cremona presenting our last results. Concerning previous research... I do think the A0 B+ B- focus of previous research is a bit, how to put it nicely, ungrounded? I don't have a formation in musical acoustics, my PhD is in Physics, so I didn't approach the problem the way the literature has done before. One particular thing we tried to avoid is the "leave all the other parameter
  14. I need to justify my position for at least 3 more years so cannot answer all the questions in our first paper Agreed, and we are not even thinking of that for the moment. Our question is much more simple and and concerns how to modify the shape of an instrument so it sounds like another one. (Think of making acoustic copies of a given instrument.) We have demonstrated in our second article that you can compensate for material variations with variations of the outline, making two different pieces of wood to vibrate the same under free boundary conditions. Now, the sound pressure i