Candy, that sometimes happens to me, too. It's usually a song I like and had listened to recently or the sound of my phone ringing.
I once heard my favorite song played so vividly I thought my neighbors were listening to it but that would be too wierd because it's not their genre of music and hardly anybody knows this group or song. Plus, it just kept playing and playing and didn't seem to end.
The sound is not inside your head either, right? It really feels like the music/sound is coming into your ears.
The phone ringing was strange for me, too. My phone rings so many times and then the answering machine picks up. I was in my bedroom with the door closed and then I heard the phone ringing from downstairs-I waited for it to stop after the pick up but it didn't, it just kept ringing and ringing. So I thought well, maybe I'm hearing the neighbors phone. But it just kept ringing and ringing and ringing to the point I know my neighbor would have answered it because I knew she was home. So, I got up to investigate but the ringing sound disappeared. It was really strange.
I'm a walkman kid also. My hearing is good, though.
I don't know why I'm hearing phantom sounds but now that I know they're phantom I don't worry about it but the phantom ringing phone can be annoying.