Loudness decay (fwd)

Eric Smith erc at cinenet.net
Sun Dec 10 19:29:00 EST 1995


In article <199512080614.AAA03993 at curly.cc.utexas.edu>,
Jeffrey G. Sirianni <sirianni at UTS.CC.UTEXAS.EDU> wrote:
>Greater decay in the high frequencies indicates a cochlear lesion and not a
>retrocochlear lesion

The decay also happened in a promontory stimulation test which was part
of an evaluation to see if a cochlear implant would be indicated.
Therefore, the cochlea itself is not the cause of the strange
symptoms.  It's either the auditory nerve or the brain.

I wonder if it could somehow be caused by adapting to tinnitus.  Since
tinnitus tends to sound like a steady tone or other steady sound, could
it be that the auditory nerve and/or auditory processing in the brain
has learned to filter out all steady tones and other steady sounds that
last more than a couple of minutes?  The fact that the sound comes back
to full loudness instantly if it's interrupted for even a fraction of a
second seems to support this.

An MRI is now scheduled, as you suggested.  But so is a cochlear
implant, a few weeks later, if the MRI doesn't show anything.  With the
cochlear implant, it might be easier to analyze the strange symptoms,
assuming they continue then.  In particular, it will be easy to say for
sure that none of them are caused by hair cells.  But in any case,
since the problem only happens with steady tones, and not when the tone
is interrupted, nor with any kind of modulated sound, it's really just
of academic interest, because in real life there are very few
situations where anyone wants to listen to a steady tone for more than
a minute.

I'm not sure if I mentioned this, but an OAE and brainstem test (BSER)
showed no response at all.  The BSER used clicks which tested from
2000-8000 Hz.  I probably didn't mention these tests because they were
only done recently, and my last posting on this subject was probably
before that.




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