David,
www.starkey.com/ They are computer adjustable and work really well in somehow blocking the feedback circuit of the inner ear ringing. I can remove mine and instantly the ringing increases. I don't know how they work, just that the audiologist told me they would help. I didn't really believe her at the time, but since I was almost deaf at the mid to high freq., that need for aids for hearing was the main reason I got them. The are expensive (@$6000 per pair,) but adjustable by freq, volume and balancing, all from a laptop, with 3 settings for different hearing situations. A couple of the GFMPH guys have them or similar, so they may have some more info in their particular problem. Maybe they will post about
them.