I have wondered the same thing. I hear things, but I do not hear them clearly enough to understand what is being said. What I hear is more like a TV or radio is on a few rooms down the hall. I can hear it well enough to tell if it is music or talking. I can tell if it is male or female. The cadence is usually consistent with a talk show and not actual conversation.

Doing the reality check thing, there are no radios on TVs on within the range of my hearing. I have had this experience scores of time over a period of decades. I have never told anyone about it, because what is there to tell really? I can not understand wha is being said, so it really does not effect me, other than being a bit unnerving.