# Can I use FEniCSx to calculate resonance modes of an object?

Hi, I’m new to FEM and I’m investigating if FEniCSx can be used for my new project.
For this project I want to calculate the resonance frequencies (modes) of some kind of objects. This to be able to synthesize the sound they would make when hitting the object at some position.
So can FEniCSx be used to calculate the modes/frequencies?
And if so, can you give some hints how to tackle this?

Maybe some of @bay_swiss work is of use to you: https://undaproject.com/

Your question is fairly general, and as DOLFINx is a general purpose Finite Element solver I am quite confident that it is possible.

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Thanks,
but Undaproject (or Undabit) is a commercial company with acoustics related calculation services. Not what I was looking for.
I would like to know if and how FEniCSx can be used by myself to calculate the resonance modes.
I’m willing to learn. But I do not know where to start for this.

While Undabit is a buisness, we are active in open trainings and open-source code sharing.

In the following video:
I explain how to setup a SLEPc solver for a modal analysis.
You can easily adapt the code both to structural and acoustic domain by changing the stiffness and mass matrices accordingly.

For more complicated analyses, you will find a complete script to simulate external radiation with a ready-to-use automatic PML that I built one year ago, here:
https://github.com/bayswiss/autogen_LC_PML

At the link that @dokken shared, you also will find my blog, where I shared scripts for many type of applications.

Have fun!

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That is really interesting!
But if I understand correctly this is for simulating the acoustics inside some cavity like the interior of a car.
But I want to do calculations on resonating objects to simulate things like a drum-pad, cymbal or xylophone.
Or is that somehow equivalent?

It is enough to rewrite the stiffness and mass matrices according to the structural equation weak form (from linear elastodynamics). The rest of the code will be basically the same.

As I said, I’m new to this FEM stuff. So I will need to learn a lot before I will understand what you are saying. And I’m eager to learn!
Where should I start to learn the stuff needed to do this modal analysis?
I did check the FEniCSx book. From the parts that I do understand I do not see how to do these modal analysis.

Consider The FEniCSx tutorial — FEniCSx tutorial for FEniCS usage, and Tom Hughes’ book for theory.