Does that make it "wrong"? Is any model that misses some detail "wrong"? Or is it a useful tool that can be used to approximate a real device with a mathematical abstraction. Obviously, this is the case.

Over the last couple of decades, a new suite of tools has been evolving, called Finite Element Analysis, or FEA. It is a way of reducing a model into many component pieces and analyzing each one separately. Deformation/stress analysis can be made of complex shapes. Heat flow and magnetic flux are modeled with FEA. Recently, an adaptation called Boundary Element Modeling or BEM has been used for acoustics problems. You can model wave propogation and resonance with it, so better models can be made of oddly shaped acoustic apertures, chambers and devices.

Here are a few links about BEM for acoustics:

• The Sound Field at the Mouth of a Horn, Rick Morgans, Colin Hansen, Anthony Zander, David Murphy
  
• Simulation of the acoustic field produced by cavities using the Boundary Element- Rayleigh Integral method (BERIM) and its application to a horn loudspeaker, S. M. Kirkup and A. Thompson
  
• Boundary-Element-Method.com