Yeah! I have had this as far back as I can remember, and recently found out that (I think) it's tinnitus.

Interestingly enough, it doesn't really bother me unless I'm seeking it out, so I wonder if my young brain just adapted to it.

Another weird fact about me is that I can hear things (I'm 35) that lots of people can't. I can definitely hear switching power supplies in everything (well, almost everything - really high quality electronics mostly seem to be exempt). I also know when bats are around, because I can hear a "clicking" noise from whatever their echolocation-producing organ is. I don't think I can hear the echolocation itself, but there is a very distinctive clicking that they make in the process.