I've had it for as long as I can remember, I suspect it's been there since birth. As a small child, I thought it was normal and that it was what the Simon & Garfunkel song "The Sound of Silence" was talking about. Anyway, I think I may be lucky in that I've never experienced not having it, so it doesn't bother me at all. It's just there.
Same here. The sound's always been there and it's the only thing I can control my attention towards perfectly. Kind of like how you can't not think about pink elephants but through a lifetime of practice I can do it with this one specific thing.
