
The following info is hard coded behind the scenes stuff no one ever sees :
Passive (default) mode
Trap detection radius: 5ft
Trap detection rate: 6 seconds (every round)
Trap detection roll: d20 + half skill (possible bug after 1.68 giving full skill)
Spot/Listen roll: d10 + half skill
Active (Detect) mode
Trap detection radius: 10ft
Trap detection rate: 3 seconds (twice per round)
Trap detection roll: d20 + full skill
Spot/Listen roll: d20 + full skill
Stealth checks
Player detects stealth: 5 times per second
Player rolls for hide/move silently/spot/listen: 6 seconds
NPC detects stealth: 4 seconds
NPC rolls for hide/move silently/spot/listen: 6 seconds
Now here comes the interesting stuff lacking in the game docs -
Listen/Move Silently:
* Automatically cannot detect silenced creatures
* Can only detect invisible (or when you're blind) creatures within the max attack range.
* Cannot hear sanctuaried creatures
* If there is something between you and the target (including creatures) there's a modifier of +5 DC for every 40cm of thickness in outdoor areas
* In indoor areas, if the LOS is blocked and the target is within 4 tiles (dfs search) there's a modifier of +2 DC
* Area listen check modifiers
* +10 DC if you are in combat
* +5 DC if the target is standing still
* -5 DC if you are standing still
* +1 DC for every 3 meters of distance to the target
* Relative size modifiers (Tiny: +8, Small: +4, Medium: 0, Large: -4, Huge: -8)
* Favoured enemy bonuses
Spot/Hide In Shadows:
* Automatically cannot detect invisible creatures
* Automatically cannot detect anything while blinded
* Area spot check modifiers
* During Night, if you do not have a light on you (including weapon lights and darkvision) there is a +5 DC modifier
* During Night, if the target has a light on them, there is a -10 DC modifier
* For stealthed players only, there is a +5 DC if they are in the back arc
* +10 DC if you are in combat
* +5 DC if the target is standing still
* -5 DC if you are standing still
* Relative size modifiers (Tiny: +8, Small: +4, Medium: 0, Large: -4, Huge: -8)
* Favoured enemy bonuses
Listen Check DCs to Detect Invisible Creatures
Invisible Creature Is . . . DC
In combat or speaking 0
Moving at half speed Move silently check result
Moving at full speed Move silently check result –4
Running or charging Move silently check result –20
Some distance away +1 per 10 feet
Behind an obstacle (door) +5
Behind an obstacle (stone wall) +15