The Hamlet Project

Why do these gentlemen need to swear over the location of the ghost’s voice?
Is it so the ghost will hear?
He seems to hear them fine.
Is one spot of ground more sacred than another?
Are the ley lines better suited for swearing wherever the ghost
leads them with his voice?
What is the value of shifting ground over and over for this swearing?
Why tunnel underground to call up above?
What does the ghost get out of it?
Besides maybe the pleasure of messing with a group of people.