This always annoyed me, especially when it's done through walls or even within the same room, where there are more NPCs with their backs turned. How do any of them just magically know it's not any of their allies walking about? They immediately go on alert, like hearing footsteps could only automatically mean: ME! (I mean it DOES, yes, but they shouldn't know that!). How can developers (definitely not expecting Bethesda here) make this be more dependent on, say, line of sight, for confirmation, when you're moving along a corridor, passing between rooms, so they won't get alerted until they see you and realize it's not one of them. OR, when it's all in one room, one of the enemies pottering about won't automatically switch to search and destroy mode, if they hear some feet shuffle anywhere behind them, because it just might very well be the other person in the room with them (I mean it's NOT, but they shouldn't know that!) Maybe they ought to give NPCs an attribute called "nerves" or something, that, depending on their level and particular skills, would determine their calmness, so they may or may not be jittery. They'd either be generally more relaxed and wouldn't immediately investigate or even care to turn around when they'd hear footsteps that could be from their allies (when they have them - conditional) or they might jump at a flea farting.