Perception Checks

[Legioned]

I have some questions about things I was sure I had read, but now I'm not so sure in re-reading.

When one makes a perception check it usually has a DC of one of two things:
1. An opponents stealth check (modified by all their modifiers).
2. The perception check base plus modifiers.

In a situation where one cannot see such as:
a. Invisibility
b. 50% Concealment such as Obscuring Mist
c. One is blinded by blindess, darkness without darkvision, or the like

Are you permitted to target an exact square? Are you restricted to the direction of the noise? If I use stealth moving close to someone and they beat my stealth check can they target the exact square? What if I am far away, using stealth, and inside Obscuring Mist? Are there any references to these?

[Blymurkla]

Stealth, Perception and Invisibility is an absolute mess.

Invisibility wrote:

A creature can generally notice the presence of an active invisible creature within 30 feet with a DC 20 Perception check. The observer gains a hunch that “something's there” but can't see it or target it accurately with an attack. It's practically impossible (+20 DC) to pinpoint an invisible creature's location with a Perception check. Even once a character has pinpointed the square that contains an invisible creature, the creature still benefits from total concealment (50% miss chance). There are a number of modifiers that can be applied to this DC if the invisible creature is moving or engaged in a noisy activity.

This covers your 'a' scenario. It's probably covered in one single Perception check. If you succeed with the DC 20 you get a hunch and a direction, if that same roll instead brought you to DC 40 you know the exact square. This is regardless of distance and other factors, though you'd still apply all relevant modifiers to Perception.

How total concealment from Obscuring Mist, being blinded or in darkness without darkvision is handled isn't handled by the rules in detail, as far as I know. But as all these situation makes you effectively invisible for your opponent, I'd run it the same way.