The effect through the ground occurs in a crawlspace, though possibly a slab foundation could do the same thing.
It can really be quite eerie sometimes.
So the size and shape matching the frequency traveling through the ground would be responsible, and nothing to prevent it if it matches up.
Parallel walls create a standing wave effect, which is the buzz you can hear in some empty rooms if you make a noise of the right frequency.
This can be part of the resonance effect from the ground or not.
It never helps though.
There are better ways to kill this in houses with parallel walls, but they don't really apply here.
(I have some suggestions for anyone improving acoustics in the home, esp for music/film, and they don't involve damping.)
Things like carpet can't stop bass, but they can redirect the sound to some extent.
Of course, higher frequency is much easier to kill.
It is all directly related to the physical wavelength of each wave.
The lower the frequency, the longer the wavelength.
This is why bass penetrates solid materials so easily.
Reflection and isolation is always more effective than absorption.
Unfortunately, mass is key, which is kind of antithetical to portable structures.