I am trying to do a modal analysis of musical instruments. If I do it by using plates have free boundary conditions, I can get very similar results with experimental results. But when I apply similar test on the whole body includes top and back plate and air cavity (image), results are very different. Because coupling with plates and the air inside is not considered during solving the vibration modes.
for example, guitar top plate has three first mode (T1,1)1, (T1,1)2,(T1,1)3 because of coupling. First one is Helmholtz resonance, second and third one are shown due to top and back plate coupling. and questions; how to get best results which are similar to experimental results by using ANSYS, Where should I start to search this issue? Mechanics ? CFD ?