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Re: reverse engineering of acoustic sources

Hi Neil and all,

I think the upshot of the inversion problem is that if you have a
reasonably good acoustic model to begin with, you can fill in the
"blanks" (the parameter values) which will yield sounds that match
the corresponding original sounds. (I've heard Neil's bells and they
really do sound good.) But the trick is to find a plausible  model
for an arbitrary sound, and I don't think an algorithm exists that
will pull that out of the hat.

A hypothetical question is: Can different musical instruments mimic
one another?

Jim Beauchamp

Neil McLachlan wrote:
>Hi all,
>I have tackled this inversion as a 3D design problem to generate the
>geometry for bells with harmonic overtones and other tunings.
>We used gradient projection shape optimization methods to iteratively
>alter a finite element model toward the desired overtone frequencies. As
>you would expect from the earlier conversations there were multiple
>solutions to the geometry of many of the bell tunings.
>The optimisation package 'Reshape' we were using is limited to linear
>FEM problems, although I believe that the optimisation algorithms in
>Ansys could be used for non-linear FEM problems. However optimisation in
>Ansys lacks the spatial resolution possible in Reshape.
>You can see and hear the bells at www.ausbell.com and see my article in
>JASA 114(1), 505-511
>-Neil McLachlan