Does the voice feel like an internal voice (like a memory or you're own inner self talk) or a seperate person than you voice? Like someone is in your head? That's the key question here.

Music is good to drown out voices once you identify them. Distractions are good. When I get that feeling that people are coming up behind me, I sit with my back to the wall, and have a light on. It's silly but it's helpful.