Ironically I lived with a husband who had this so severely as to deafen him. He can't hear anything that is the same level or pitch as the ringing. I found a web site called T-gone.
And then I noticed there were three hubs on the subject from two years ago! Guess what, one of the hubs would also take you to the web site I found.
The hubs are all linked together at the bottom. Good Luck!