Dan almost scraped against it. Though his scenario doesn't really furnish you with positive proof - the same sound is made when an opponent is compulsively clicking around on his pieces thinking about using a power (never understood why ppl do this - it betrays your plans). Then what if there are multiple non-stepping ledges.
I left the answer hanging to see what you guys had come up with, but here it is, nothing earth-shattering, but nonetheless helpful at (rare) times:
When your dastardly opponent has two or more invisibles and one is JP. You can distinguish which is moving by the sound alone. If he has multiple JP invisi's of course this tip is hardly useful. I know many here probably already realize this, but I thought it interesting that just having your sound on gives you actual useable information about your opponent, especially if he has only has two invis and one's JP.
But, I think this borders on a gameplay hole (like the disabled ability to double-switch search for an opposing invis).
The solution is to alter the sound of an invis torus moving around. It ought to become a muffled/canned version of the current sound effect, with no special JP moving sound effect, like there is now.