If you 'hear' someone but don't see them, are you supposed to play it like you don't know where they are enough to flat out attack them -directly-?

This isn't really a question based on any specific scenario, but for a long while, when I see people RPing having 'heard' someone but not seen them, they usually look about curiously, trying to pin point the sound. On average they don't pull out a bow and shoot them in the eye with pinpoint accuracy.

So, how are we supposed to treat having heard someone, but not seen them?

Go ahead and shoot 'em, if you've got reason to.

Otherwise, invis would automatically end fights.

-Cross

Crosswind Go ahead and shoot 'em, if you've got reason to.

Otherwise, invis would automatically end fights.

-Cross

Without see invis you can't attack them more than five feet away. Doesn't that just support the idea that unless you see them you can't attack them?

No, it's fair game to swing your big greatsword at what you think you might have heard. The engine even applies miss penalities. If you (or anyone!) do start playing a character that lashes out at every single noise that passes him, please don't be discriminate with who/what you target. You hear "something," it could be a person, a goblin, a dragon, and you'll never know who/what it is exactly unless you have a good reason to suspect something specific.