Fog of war, sound, npc movement

ankheg

I've always found interesting that you can hear the sounds in explored areas even if your characters are not there. For example in nashkel your party standing in the corner and you can hear all the guards walking, the noise of the river etc. if you are scrolling there. It isn't logical for me, but what really annoys me is how these things (especially npc movements) affects the smoothnes of scrollings. Everytime I scroll there it become "jumpy". (also the actions of my own characters do that which is annoying too)
Of course I don't want the non-visible npcs to stop. Just find a way to make the calculations more effective or something.