I think two circles in an overdesign.
I for one like the idea ...
But i think it would need same mechanic as sight have ... you know, Light > Partial Shadow > Deep Shadow
So ... from the far one HUGE ring where we would make easy stealth checks ... at mid range one conciderably smaller ring, where we would make conciderably harder stealth checks ... and on personal distance VERY hard stealth checks.
If everyone got smaller "detection" circle range would anything of substance was lost?
Yes.
If you check the screenshot, there is no way you can stealth around Crusher without stealth check ... and that is the point here, isnt it?
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I would say if the question is, how often would it make sense in general ...
I mean, there is a waterfall on that screenshot ... have you ever ben this close to waterfall?
![laugh laugh](/images/graemlins/default_dark/laugh.gif)
Do you really think you would hear someone walking?
![laugh laugh](/images/graemlins/default_dark/laugh.gif)