What to do about unprovoked bites?

My pup is only 11weeks old and always bites clothes, legs and hands when we are just either sitting on the floor or standing outside in the garden. Why does he do this? It's completely unprovoked and whilst he's doing it he looks and sounds aggressive like growling and barks lots after it. High pitched sounds and firm no's don't work, just scruffing him and laying him on the floor till he's calm and even then he tries to bite. How long shall I keep him on the floor? And if I always correct him is this the type of thing they grow out of?