You make several interesting points media, bow away....
I too am delighted with your sliding scale ramping analogies.
The propagation by pressure is cute too, but I always thought waves were propagated by the see sawing between two complimentary out of phase energies. e.g. ElectroMagnetic.
I have a big problem at the moment trying to imagine exactly where the pressure highs are for tangential modes. The usual bounce diagrams suggest the bounce point (HP ZeroV) is mid wall, but the pressure graphs show HP in the corners and elsewhere.
More interestingly (for me).
But if you use an air gap, it needs to be sealed, like enclosing the absorber and air gap in an airtight frame.
Intuitively this strikes me as correct, but that would mean RealTraps, GIK and all of use who recommend using airgaps with individual panels are wasting everyones time and effort. If that indeed is the case, I would love to see some test evidence. Perhaps that 'needs' is a tad overstatement.
I think it much more likely that your ramping analogy applies here to.
e.g. One panel on it's own, is not going to benefit much from an airgap without sealing (which would also have that old drum head side effect).
While many panels with only small gaps between, tends towards being a contiguous boundary.
But aren't we forgetting angles of incidence. And what happens to sound that hits the thin sides and the surface facing the boundary. All of this would be blocked by the frame.
But then the frame has a diffractive benefit....
Swings, roundabouts, and ramps, methinks. But if you do have some data, links, tests, I really would love to see them.