Gus Calabrese wrote:

> You would be wrong about that.  My thought is that if you got any kind
> of results with trying phase reversal (using a free running
> oscillator), it would be worth proceeding to the next step.  Which
> would be trying to locate some kind of nervous system signal you could
> lock onto and phase reverse.  I am talking about basic research that
> may never yield any useful results.

  OK, you're serious.  Problem is, there *IS* no sound source, so you
can't detect, amplify or phase shift a signal that doesn't exist in the
first place.

  "Blocking" by an external signal works entirely differently.  It is an
attempt to generate a signal which closely replicates the non-existent
noise, but has different characteristics which the brain will choose to
ignore.

  IOW, there is no noise, but a higher processing level than simply
sensation, is receiving interference which it *interprets* as a signal
but can't properly figure its characteristics (naturally, since it's
not real).  It's probably the very inability to characterise it (because
it's randomly noisy) which you find so annoying.

  Your job in masking, is to provide a *real* signal which it *can*
properly determine, so that it is "happy" with the real signal,
proceeds to ignore it, and regards the false signal as a trivial
aberration to the real signal, ignoring it in the process.

  But it's most likely not at the sensory level, and whichever level it
is at is physically inaccessible.  (Very occasional sufferers have had
ablation of the auditory nerve; preferring deafness!)  While the
tinnitus is annoying, even in a quiet environment it is unlikely (IMO)
to represent a detectable component of the datastream in the acoustic
nerve.

  If you were exceptionally lucky, it might show up as a regular
"relaxation oscillator" stream with some coherency on autocorrelation,
but most averaging (correlation) techniques require the repetitive
input to synchronise and here again you just have no input!

  In general, the best you have is a really wide loop consisting of your
masking source, the ear, brain, conscious evaluation of the perception
of the noise and manual adjustment of the masker parameters by the
sufferer.
--
  Cheers,
        Paul B.