How does perception work here? Can he Hear where the enemies are? Can his allies point out where the enemies are standing?
I have a player that is a Oracle with blindness, and he is trying to wiggle his way past the invisibility by having the archer shoot whistling arrows at targets beyond 30ft.
I feel that he is abusing the game by bypassing one of the core flaws of the oracle. What shall i do, and dont say "rocks fall on his head"
You cannot see anything beyond 30 feet
Assuming this means you are considered having the blinded condition vs. creatures past 30 ft.,
The creature cannot see. It takes a –2 penalty to Armor Class, loses its Dexterity bonus to AC (if any), and takes a –4 penalty on most Strength- and Dexterity-based skill checks and on opposed Perception skill checks. All checks and activities that rely on vision (such as reading and Perception checks based on sight) automatically fail. All opponents are considered to have total concealment (50% miss chance) against the blinded character. Blind creatures must make a DC 10 Acrobatics skill check to move faster than half speed. Creatures that fail this check fall prone. Characters who remain blinded for a long time grow accustomed to these drawbacks and can overcome some of them.
then such creatures have total concealment from you.
If you have line of effect to a target but not line of sight, he is considered to have total concealment from you. You can't attack an opponent that has total concealment, though you can attack into a square that you think he occupies. A successful attack into a square occupied by an enemy with total concealment has a 50% miss chance (instead of the normal 20% miss chance for an opponent with concealment).
You'd have to use Perception to locate him (non-visibly, with a -4 penalty if they're stealthing).
Also, note that
Some spells have a target or targets. You cast these spells on creatures or objects, as defined by the spell itself. You must be able to see or touch the target, and you must specifically choose that target. You do not have to select your target until you finish casting the spell.
doesn't apply, since Sleep is an area spell (which would also negate the 50% miss chance, since it's not an attack).