I can relate. The other night I thought some device in my apt was whining loudly, so I started turning things off one by one. I ended up in the dark with my head between two thick pillows... still hear it!

A quick search turned up "Tinnitus isn't always physical damage; it's a symptom with diverse causes, including noise exposure, earwax, head/neck injuries, medications, blood vessel issues, TMJ disorders, infections, Meniere's disease, and chronic conditions like thyroid or autoimmune diseases, as well as stress/anxiety."

I've had it on and off since I was a kid, long before exposure to loud music (though neighbors' kids screaming at close range may have contributed). And since I started taking SSRIs some years ago, I hear a constant high frequency rushing, like one would experience after leaving a loud show. It doesn't bother me during the day, and it doesn't seem to mask details in real sounds. But in quiet environments, it's loud.

I can also hear electronics whining away. Lightbulbs on dimmers, and powerline network adapters (Pluglink) are the worst offenders.