sub·vo·cal·ize 
(sŭb-vōkə-līz′)
(sŭb-vōkə-līz′)tr. & intr.v. sub·vo·cal·ized, sub·vo·cal·iz·ing, sub·vo·cal·iz·es
To articulate or engage in articulation by moving the lips or other speech organs without making audible sounds, as in reading to oneself.
sub·vo′cal·i·zation (-kə-lĭ-zāshən) n.
sub·vocal·iz′er n.