A simple test you could do would be to mount the rear hub(s) in a truing stand and then mount a disc–wood,metal, or something else–with a cut-out shaped so that it would fit onto any freehub, so perhaps a cut-out with the radial profile of one of Edco’s new hubs with the universal freehub. A spacer and the proper lock ring could hold it all tight. Sure the disc wouldn’t have the same properties of any given wheel, but it would at least allow the sound of each hub to be compared.
This could be done by machining out the center of a flywheel or the like. It doesn’t have to be a big disc at all, just one with a moment of inertia large enough to allow it to spin for the requisite amount of time. Also, doing the tests outside would likely give a result that give riders a better idea what to expect.
As punishment to shop workers, you could make a shop droog who’s gone afoul of his co-workers ride behind a bike with Spinergy hubs. Man those things sound horrible and would provide a cruel punishment.