Radial power transfer efficiency drops off proportional to r^2, as does omni-directional sound. Unless there is some sort of directional beam established to focus the energy transfer, I imagine these power losses will indeed occur. Note that room effects may well be non-negligible - reflections may mean more power arrives at the receiver than the naive estimate.

So I would imagine the ceiling mounted charging station would be a fairly heavy duty outfit with a multi-kW rating if it is to be able to service a large room.