If the unstated question is: "why do porous absorbers work well when placed at areas of high mode pressure?", I think part of the answer is that the pressure max is not that far from the velocity max and porous traps require significant volume to provide adequate absorption, so they overlap into the high velocity zone due to simple geometry.
+1. Absolutely. What is near? One wonders if the transition from one zone to another is gradual, linear, or logarithmic? How thin is this zone of highest pressure and how soon does velocity become significant?
1/10 lambda springs to mind.
Plus- corner effects (prime LF locations) are not often lab measured or included in predictions.
Plus- surface area has something to say here.
One trap, a quarter wavelength from a boundary will hardly do much....
Context and perspective will turn any of these seemingly contradictory views into reality. In other words, two 4x2 foot panels are best placed in tricorners. But a full wall of fibre say 200cm thick will very likely function brilliantly at a particular frequency if placed at a velocity peak spaced away from the boundary. Obviously a 1-2 Metre fibre wall even at the boundary will absorb a lot.
Pedantically it may of course be ultimately correct to suggest that there may be velocity zones at viable locations for absorptive trapping. Nobody has suggested how to find them. Or even predict them.
EDIT exactly as Icecube said....
Then, yes, my "unstated" question is how do you decide?
I think we can leave that one aside until we have commonly available velocity meters. (I have had my eye on Intensity Probes for some time now, waiting for a serious price drop).
To be frank, corners and the difference between LF hard or soft boundaries are blatantly visible to the eye.
I have suggested Sine Waves for two reasons. They will help chose trap locations from the viable options. e.g. Chose between the Front and Back corners. But more importantly the experience of walking through that null and into those high pressure zones is extremely useful when one is encouraging clients to go for it.