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Hi

I have some problems to undrstand what you are looking for, your model has 4 domains with 4 materials, but only 3 are assigned, I suppose the "air " is the last domain not assigned (bottom cylinder) ?

THen you have 2 physics, the air in acoustic, but you impose an acceleration from the first phyiscs on all boundaries, while there is only 1 that is in contact with the PZT, this is not "physical" from my understanding

Then your PZD physics defines the rest, but the structural sub part has no BC defined, your device is "floating" in thin air, you should at least fix one boundary or some combination of elements to block all 6 DoF of a 3D solid

Then you do a frequency domain analysis at 1 frequency (by the way have you checked that the "h" mesh size is much smaller than the wavelength of the pressure wavs you expect to get, and this for all materials ? this will give yu a frequency response, but not any eigenfrequencies, for that you need to perform an eigenfrequency solver run. But you need also to define the "fixed elements". Now an eigenfrequency analysis depends quite a lot on the surroundign, how your part is held, and most of you boundaries are external boundaries for which little or nothing is said in your model this might have some important effectson any true eigenfrequency response

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Good luck
Ivar

Thnks