Reading the comments, it seems pretty obvious that there are multiple causes. To add my own anecdote (because I don't see it mentioned otherwise): I have very

Reading the comments, it seems pretty obvious that there are multiple causes. To add my own anecdote (because I don't see it mentioned otherwise): I have very specific hearing loss (40dB) in one frequency range frequency (4khz). That is also the frequency of my tinnitus. The cause is almost certainly bored neurons making stuff up: there is never input at that frequency, so they produce their own. Maybe fixing the auditory nerve will help some people. Other folk will need a different cure...