i have known amnesia for 1 year ans i have been studing about it for a very long time so i am telling you guys some useful hints:
if u hear the grunt music fading and the normal music kickes in that means that the enamy has de-spawned
in number 19 (morgue) dont be scared of when the door breaks down and u hear the brute whining that is nothing behind that door they put a trigger at it to make it seem that the brute is there but if u open the door there will be nothing there (i found that pretty funny)
in number 20 (sewer) when you see a brute walk past dont worry he is according to the game data it is an halusination so if u walk up to it ital disappear