There is no soundproofing a pocket door. The pocket acts like an echo chamber and the door never seals like a solid door. Are you asking about soft close Doors? If you’re trying for reducing noise transmission, you need to build two full 2 x 4 stud walls with insulation in the walls and then a pocket between them. Something tells me if you’re doing a pocket door, though you don’t have the room to spare.

Pocket doors are the very opposite of something soundproof. They are sound amplifiers. Avoid them if privacy is a concern.