nYour model looks good. nRegarding the modal solver you should be using the undamped solver. Your current Harmonic Response does not have any damping applied therefore this will be consistent between the two. If you are to apply damping, and want to use MSUP, then damping can still be applied at the harmonic response stage. The damped modal solver is technically challenging to say the least. An advantage of doing an MSUP is that damping can then be input in the Harmonic Response as a percentage of critical damping.nTypical damping values exist around 0.01 to 0.1, percent of critical damping, for many structures. But for a MEMs device this may not hold true. To really know the correct damping you should seek out some literature or perform experiments.nAlso make sure that if you are using MSUP, you are creating another Modal analysis environment that is pre-stressed by the existing Static Structural environment.nYour command snippet also looks fine.nI saw in another post you were looking at performing FSI. Are you happy with the current Harmonic Acoustic analysis? or is there still a need for fluid coupling? My interpretation from your earlier posts is that you are primarily looking for energy loss, which Harmonic Acoustic is a suitable analysis for. I don't see the need for FSI in this analysis.n