Erik Kostson
Ansys Employee

As you say, it will be difficult and perhaps impossible (depending how large the structure is) to model a large perforated structure, so use the Delany-Bazley (DB) perforated material model (defined in engineering data) for a rigid/steel perforated disc , and the mineral wool. So you need to measure or get from the manufacturer the fluid resistivity of the perforated plating and the mineral wool, and enter that in the engineering data for the DB material. This model (DB) works to a certain extent of course and it can not cover all applications, but is worth a try here. It does work OK and has been used for mineral wool, but not sure how accurate and what the limitations are for perforated plates.
You need to model the 1 mm steel plate (solid elastic - structural physics region in harmonic acoustics). So you will have a fully coupled vibro-acoustic analysis.
If you put a mass source excitation on a vertex at the centre, it will give you a spherical acoustic wave.

Finally once you are done with that, you can transfer the outside structural velocities of the 1 mm steel plate to an acoustic exterior domain surrounding the structure, and conduct the exterior acoustics (so calculate spl outside the box).
This is what we call a one way coupled acoustic analysis, that is when structural velocities are transferred to a pure acoustic model, then they are mapped on to the the acoustic mesh and we can calculate the sound generation due to these structural velocities.

All the best of luck