Imagine a situation when I'm standing with another person. The person hears something and responds back. In fact, I had not spoken anything. It is because of his faulty ears. So, what can I comment on his ears? I'm an Indian. In India, we say tere kaan baj rhe hain (Indian language), which literally means this in English: Your ears are striking/ringing. How do we say this in English when we want to say something about the ears of person which heard something which has not been spoken by anyone?
I think the general phrase in this situation would be:
Are you hearing things?" (AmE)
things is used as a general term, because you don't really know what the other person heard (unless they tell you).
But you have to be careful, because in some situations it could be considered critical or rude:
No that is not what I said. Are you hearing things?"
which implies someone acts like you said something other than what you said, for various reasons.
Google Translate says that the Hindi phrase
tere kaan baj rhe hain translates to
your ears are ringing
However, in English we use "ears are ringing" to describe a certain sound in one 's ears, that does not come from outside, but is caused by some defect in hearing. (See tinnitus).This condition is likely to cause someone to NOT hear what you did say, rather than to "hear" something you did NOT say.
If they "heard" words not spoken, you could say they were - hearing voices
This is technically called an auditory hallucination.
Some schizophrenics report "hearing voices in their head". Some killers have even reported that the voice(s) in their head told them to kill.
So asking someone if they hear voices in their head suggests that you think they are mentally ill. Make sure they know you are kidding.