thats the exact same idea I was thinking of! I wouldn't make it a perk though, I mean it's not that good, how often do you need to listen someone whispering. Something like 'better senses' would be awesome for thieves. It would be the combination of what you said, what someone mentioned some time ago about seeing other people area of sight and could be something like 'you hear steps' when someone is approaching and you are stealing/picking/sneaking. That needs much work though. It'd be so awesome if someday fonline would have such situations as you the thief are sneaking inside some peoples base, have to sneak using this type of perks = avoiding other people sights and hiding as they march nearby, and after all this you can go to their weapon stockpile or some safe to steal some intelligence, documents etc.
