On 7/25/06 5:34 AM, in article daKdnVInGYMnklvZnZ2dnUVZ8qGdnZ2d@casema.nl,

I really don't know how many persons can sit and listen to a sound, any
sound, for more than 5 minutes. We are a nation of channel surfers and used
to going from one 3 minute attention to another. I question how many persons
can sit and "do nothing" while they listen to a sound?
For my patients its better to have an  I pod with a musical or sound in the
room - like a broadway show and be diverted. For T I recommend having the
shopping channel on,.
This is why the "nerve enhancement" where you put the T sound into the good
ear and reduce the volume and allow the affected ear to match that reduced
volume can work, because you are "doing something" actively.

Murray Grossan, MD
Www.earaid.info

Hi Martin,

Right. The question is "which effect is achieving this... is it  residual
inhibition ... or phase cancellation ?"

With residual inhibition, the tuning for such a device is not critical (I've
tried it). When the interfering tone is in the general vicinity of the
tinnitus frequency it has the greatest effect.

(a) But if phase cancellation is at work, we would expect to hear a
'warbling' (beat) effect as we approached the tinnitus frequency.  This
'warble' would become slower and slower and eventually stop when we exactly
matched the tinnitus frequency.
I did look for, and found no evidence for this warble/beat effect when
trying a sound generator with my own tinnitus. And this should not be
surprising; see (b) below...

It's worth remembering too that many peoples' tinnitus is not a single tone
but a compound tone (further complicated by the interaural pitch difference,
when present). Effective phase cancellation would then become a very complex
matter.

(b) It's true our ear/brain system can indeed distinguish between incoming
_stereo_ sounds which are in phase or in antiphase. However sounds entering
the ear/brain system in antiphase do _not_ cancel out to silence, they just
sound 'different' (hard to describe unless you've heard it but useful to
know when you're phasing up loudspeakers!).  This would indicate that the
effect of trying to cancel tinnitus with another antiphased tone might not
be so straightforward either.

Of course actual sound waves out in the outside world _can_ cancel out to
silence when in they meet in antiphase. But we are considering here what the
ear/brain system makes of antiphased signals, not what happens according to
physics in the outside world.

So, my view:

1) At least for stereo sounds, antiphasing just doesn't produce silence in
the ear/brain. Instead things sound 'strange'.

2) I know of no evidence of any 'beat' effect against tinnitus produced
internally by the ear/brain. Such an effect would be observed first if true
phase cancellation to silence were possible.   Even if it were, it would
then be incredibly hard to maintain this phase relationship with the high
(and often multiple) tinnitus frequencies.

Steve

Hi Martin,

This would be true if the brain had a sense of phase, but I sincerely
doubt if such a sense is there. There is a sense of frequency and time,
but that's not enough to do any canceling. The brain's not fast enough
for that, IMO.

cheers,

Enno