The reason why the Acoustic Surface Velocity has a ? is because your Analysis Settings show the Solution Method is Mode Superposition, but you don't have a Modal Acoustics system feeding the Harmonic Analysis. Either add a Modal Acoustics system and feed that solution into this setup, or change the Analysis Settings Solution Method to Full. While you are there, you also need to set your Analysis Data Management, Save MAPDL db to Yes.

I looked at your settings for the Acoustic Surface Velocity and they look inappropriate.

You used the speed of sound as a surface velocity for a harmonic analysis. This input results in a Mach 1 shock wave sent into the air. The Acoustics solver cannot solve such a model and I doubt that is what you wanted, but correct me if I am wrong.

What sound pressure level did you want coming out of that speaker? Let's assume you want 80 dB.

The above is a Mass Source.

An equivalent to the mass source is the normal velocity:

# I am also concerned about your mesh.

But you have a Mesh Face sizing of 95 mm, which exceeds the maximum calculated above.

Also, it's not just the faces that need element size control, it is the size of the elements in the entire body of air.

Below is a slice through your current mesh. There are elements up to 250 mm edge lengths

Here is the same slice with a uniform element size of no greater than 50 mm.

To save time, changed the analysis settings to output only two frequencies, 500 Hz and 1000 Hz.

You don't need the speaker body to be there, just the walls, which are in the source body. Three bodies are included in the Acoustic body. I expect you want to set some particular conditions on the face of the partition, but for this model, it's all just air. but the solver runs!

The result is close to the 80 dB that was desired above, it is 73 dB due to the resonances in this chamber.

If I create a straight impedance tube with a Mass Source at one end and a Radiation Boundary at the other end, I get a SPL of exactly 80 dB.