Mine is most likely from loud sound I’ve been told by ear doc. I played in rock bands in the 60-80s. So it’s possible. I recall coming home after a job, and my ears were ringing like mad.
Lately, I believe I’ve had it nearly all my life. I recall as a kid it’d overwhelm me when I was going to sleep.
Day to day, I think my brain has filtered it, but when I stop to listen it’s there singing away!
I’ve used the noise as a sound when I meditate, so it’s not all bad. Do I wish I didn’t have it? Yes!!! Can it be cured? I don’t think but I’d love to hear remedies.