There are lots of folks out there, especially among the boomers, who are beginning to experience hearing loss and related problems like tinnitus - a constant hissing noise that sounds like escaping steam. The problems are most often caused by damage to the hair cells in the cochlea due to exposure to loud noises (like music on our i-pods) or chemicals. Most Ear, Nose and Throat specialists (ENTs) say there's usually not much to be done about it at present except the use of hearing aids and some kinds of therapy to help with the tinnitus.
Lately, however, a promising line of research has emerged that might afford hope. It turns out that transplanted stem cells have been shown to regenerate and repair these cells to some extent which may restore, at least partially, the lost function and diminish the annoying ringing that often accompanies hearing loss.
Another potentially helpful line of research employs gene therapy to regenerate damaged hair cells.
Despite these breakthroughs it seems as if treatments for humans are still years away. A list of links to reports on this kind of research can be found here.
RLC