If one had a water-filled balloon containing living auditory sensory cells and placed this in a larger container of water, any vibrations that passed through the larger container would pass right on through the balloon and its contents. The vibrations would undoubtedly shake the cells and if there were nerve fibers connected to them a stimulation would result. If the balloon were brought out of the water so as to be surrounded by air, any vibrations occurring in the air would, mostly, be reflected back from the surface of the balloon. Because of the great difference in the physical properties of air and liquid, only very small vibrations (compared to those in the air) would be produced in the water-filled balloon.
The situation could be complicated even further by encasing this water-filled balloon in some rigid material, such as bone, and covering this with a sound-absorbent material. Under these conditions,
LAWRENCE M. Applied Physiology of Middle Ear Sound Conduction. AMA Arch Otolaryngol. 1960;71(2):133–140. doi:10.1001/archotol.1960.03770020005003