I can relate to that beep thing! My daughter and I were talking about that a few months ago - like you hear a siren or a beeping or something that goes on for a little while and it's not really loud or it gets softer and softer because it's going further away, and it comes to the point of, "Am I still HEARING it or is it in my head??" We never thought anything about that, just something that happens. Our brains are funny things! When I was a kid and young teen I would lay in bed and think of a band's song, or a commercial jingle, and I'd keep thinking really hard, so hard to the point I actually HEARD the music!! Some nights it wouldn't stop and I couldn't fall asleep! Needless to say I stopped doing that because it would make me uncomfortable. So those things happen, means NOTHING at all regarding your mental health.
I think phantom smells are common too. With me I tend to have a sniffer like a blood hound and I'll smell things no one else does (some things I can verify are real because I'll smell natural gas and NO ONE else will, not even the gas guy when I call him, but he'll do the tests and bingo! He finds a leak!) Then there are smells that I can't get verified by anyone else, so who knows if it's just my doglike nose, or is it phantom.