1) Communication disorder 2) Not making sounds 3) Silence 4) Uncommunicativeness 1) Silence 2) Taciturnity 
Muteness or mutism ({ety|la|mutus|silent}) is an inability to speak caused by a speech disorder. ==Causes== Those who are physically mute may have problems with the parts of the human body required for human speech (the throat, vocal cords, lungs, mouth, or tongue, etc.). Being mute is often associated with deafness as people who have been unable ...
• (n.) The quality or state of being mute; speechlessness.
Mute'ness noun The quality or state of being mute; speechlessness. 
[n] - a refusal to speak when expected
muteness A reference to people who are unable to speak; being mute or deaf-mute.
noun a refusal to speak when expected; `his silence about my contribution was surprising`