What?!

From: Affio Buss

You scream and you shout,
But no one can hear,
So you begin to fret,
You begin to feel fear.
Is there no one alive,
Is there, really, only you?
That surely can't be,
That's surely untrue.
So what can it be,
The reason you're unheard,
From the depths of the worm,
To the height of the bird?