If exposure to Mako is a reason, then a lot more people would hear it. I guess there's nothing that says nobody else hears it, either...
But wouldn't there be extremely high levels of Mako in/around Mako reactors, as well?
I'm reading the game script, and from that it seems like it's just as simple as Bugenhagen taught them about it, and told them what it is, that's why they can hear it.
I guess everyone just skipped over Cetra's official explanation.
Aerith is not some goddess with a magical connection to everyone one beyond the fucking grave, come on people.
Two years after returning to the planet, Aerith still lives on in the hearts of her friends who saved the planet. And in particular to Cloud, as a symbol of his failure to having being unable protect those dear to him, she was a major factor in causing him to close himself off. For Cloud, and the world once again faced with danger, she reaches out and offers her aid. In that sense she is like a mother watching over the entire planet, and it gives the feeling that she lives in every part of the world.
Just being near Aerith is not going to give them the same capabilities as her, that's dumb.
You're dumb. ;( Fine, I don't KNOW why they can communicate with the planet. THEY JUST CAN. Happy? >=(