One form of language problems in children and adults is called aphasia. This is where the child understands what you're saying and understands what his response is supposed to be, but has difficulty in verbalizing. We see this in people who have had strokes. Such a person is angry because they can't tell you what they want to say. If you have a child with this problem seek out a good speech therapist who can evaluate the child.
Some children have very hypersensitive hearing.
I used to take my son to church. He was fine until the organ music began, then he would scream, and I would have to leave. He acted like the noise was painful. He told the radiators to be quiet, because he heard these things. A person who is distracted by this super-sensitivity to noise will tune out the world around him when he is trying to focus.