Superman can hear someone from another planet, and hear a bullet and be there before it hit someone...but the sound it self have only sound speed. How Superman can hear that in the instant that happens ?
Anyone ever make some explanation or he just can do that...?
Yep. He even heard GL calling him for help from another solar system. It may've even been another galaxy but I can't remember because it's been so long since I read that story... It doesn't really make sense though considering sound isn't supposed to travel in space. But, it's not like there isn't already a ton of stuff in comics anyway that doesn't make any sense. Things like Zoom punching Superman without breaking every bone in his hand, for example. LOL.
__________________ Darwin's theory of evolution is the great white elephant of contemporary thought. It is large, completely useless, and the object of superstitious awe.-Dr. David Berlinski, Philosophy
Most people believe Evolution not because they themselves are dumb, but cause they trust the "experts" who are feeding them evolutionary fast food, and so they don't bother questioning whether or not it's true.
Superman can hear EM and gravitational radiation, that's how sensitive his ears are. His speech mechanisms are similarly impressive, with the ability to form EM and gravitational radiation into words in the vacuum of space. This way, not only can others hear him, but others can actually talk to each other in space even when the Man o' Steel isn't present.
Shinier than a speeding bullet.