What is spiritual speech?

When spirits converse with each other, do they produce sounds by the use of vocal organs?

Oh, yes—we can speak as you speak, but our speech is quite of a different character—certainly much more refined—spiritual—so much so indeed that we cannot use it on earth. 

Again, we can read the thoughts of spirits and under certain conditions the thoughts of spirits in the body—

We know indeed what a spirit is about to say. But for all that, do not imagine we are silent here. 

We are no mummies. We have tongues and I tell you we know how to use them. We speak to each other as mortal speaks to mortal.

—Hafed, Prince of Persia