I've read that some folks habituate to tinnitus at different rates,
that most do after a period lasting from a few months to a few years.
And yet there are some that do not habituate -- that is, their tinnitus
continues to bother them even after many years.

I wonder if this might be related to differences between tinnitus that
stems from damage of some kind to the inner ear and tinnitus that might
be caused by some kind of damage to the auditory cortex.

I have read that Jastreboff and Hazell have proposed that the tinnitus
signal originates as a weak signal in the inner ear and that there are
multiple sub-cortical filters that can be brought into play through
tinnitus retraining therapy (TRT) to cause the cortex to cease paying
attention to it.

But what if the tinnitus signal orignates in the auditory cortex
itself, upstream from all of the neurological machinary that TRT is
supposed to train to ignore it.  Could that account for those cases
where people cannot seem to habituate, even though their tinnitus, when
evaluated using matching techniques, does not seem materially different
in pitch or loudness to cases where people do habituate?

If there is tinnitus that does not originate in the inner ear or
auditory nerve, but in the brain, then it is very unlike any real sound
in that all of the neurological subsystems that (according to TRT) can
gate out real noise are unavailable.

In any case, it seems to me that TRT's success rate is not that much
better (over the recommended 18 month period) than natural habituation
that occurs without any kind of treatment.

Perhaps the people who fail at natural habituation and (in some cases)
fail even with other types of therapy (including TRT), are suffering
from a centrally-generated form of tinnitus that cannot be habituated
to in the way one can adjust to peripherally-generated tinnitus, which
comes into consciousness in the same way real sounds do.

Just a thought; I'm certainly still just learning about T (having had
it for about two months).