I have had this constantly for 3 - 4 months now and am finally on some strong antibiotics at my request in case it's infected inner passage ways and sinuses because I do suffer allergies and blocked ear passageways.
Anyway, if you are a closet hypochondriac in the making like me, you occasionally GOOGLE things to see what's wrong with you and find references to horrendous things, which make you worry you're going to die, or start dissolving from inside out.
One such site about ringing in the ears is telling me I have some connection to the spirit realm which I can hear as a ringing in the ears. If you don't believe me, GOOGLE ringing in the ears metaphysics, and you will find it is spiritual data downloading, my heightened spiritual awareness, a choir of angels singing or the noise of the spirit realm which I haven't been able to hear until now.
I'm not sure just why there are so many theories, but when I followed some advice, and sat back in my chair and focused on the noise, it is as they tell me, a kind of vibrational thing, and a kind of relaxation can befall you.
I'm not saying I believe any of this, just saying, I can see where the theories stem from. I wonder if there are many metaphysical theories about other diseases or ailments, or just this one?