Acoustic waves propagating in a fluid-filled spherical shell placed in a liquid

Acoustic waves arising in a fluid-filled elastic spherical shell placed in a liquid are considered. It is demonstrated that, in general, none of the four types of waves possible in such a system (subsonic and supersonic antisymmetric Lamb waves, symmetric Lamb waves, and whispering galleries) is realized separately, but an interaction between the waves of different types takes place.