Don - that's really interesting. A few places I've looked, I've found a technique called "residual inhibition". I've tried it (what I could conjure up) and found it has really helped me.
When you're exposed to short sound pulses similar in pitch to the tinnitus sound (frequency, amplitude), the pulses can reduce the tinnitus for a short time. And if the pulses are further optimised and repeated, so they sound like little clicks or puffs, the tinnitus can be gradually eliminated, or at least greatly reduced.
Seems the way to do it is to have a *good* aural examination to determine exactly which frequency(s) you're hearing as "background". Have those frequencies made into sound files, and play them *just* loud enough to cover up the tinnitus you have. I do this about an hour a day (or twice a day). Definitely reduces what I hear as tinnitus.
Eventually (haven't reached that point yet), you listen to the sounds in "pulses", which (according to research) "inhibits" the sensation from making it to your brain.
No guarantees, and I'm certainly no doctor. And there are various forms of tinnitus. But I'm sure making progress.
Tom