Hi Mark, list,
Even though not being an expert in tinnitus myself (but recently got
attracted to it), I think I could add two pieces of information here:
- There is this (pretty fantastic) paper:
Kujawa, S. G., and Liberman, M. C. (2009). “Adding insult to injury:
cochlear nerve degeneration after
temporary noise-induced hearing loss,” J. Neurosci. 29, 14077–14085.
that shows that there might be a connection between noise trauma, (not
easily detectable) hearing loss and tinnitus. Some of these
implications will probably also apply once the damage is more severe.
Based on this paper we did a study that indicates also implications for
supra-threshold hearing (Epp et al., J. Acoust. Soc. Am. 132 (3), EL196
). You might also want to check out the references...they might aim at
what you are looking for.
- You idea about the dip in the audiogram: Depending on the level you
see in the audiogram, this might indeed be an "artifact" of the poor
frequency resolution of audiograms, neglecting fine structure effects
when assessed with pure tones. SOAEs are also (always) associated with
a region of high sensitivity (i.e. up in the audiogram) - but they are
most likely not a source of tinnitus. If you mean by "dip" a poor
sensitivity, then there might be what is being discussed as
"deafferentiation" going on (see above) - with implications still to be
clarified.
The distinction between a hearing loss and masking by you tinnitus as
the source of the dip in the audiogram is hard to define: The audiogram
defines your ability to detect a tone - testing the whole auditory
pathway rather than just parts of it. So by definition it is some kind
of hearing loss if you can't detect a tone close to your tinnitus...no
matter what the reason is.
These just as some additional thoughts
All the best
Bastian
On 09/09/12 11:09, Mark Fletcher wrote:
Hello everyone,
I've noticed that
tinnitus researchers often talk about the
frequency of tinnitus being at a dip in the audiogram (in some people).
It's
then said that tinnitus, therefore, occurs at the frequency of a
hearing loss. Even
if I could be said to have an area of expertise, tinnitus research
wouldn't be
it, but it's certainly an area of interest for me and I am someone with
tinnitus who has done several audiograms. On my audiogram there is a
dip around
the frequency of my tinnitus, but I suspect this dip is due to masking
of the
tone or warble used rather than necessarily being indicative of a
hearing loss.
I'd be very interested to know how people make the distinction between
masking
by tinnitus and a hearing loss.
Many thanks,
Mark Fletcher
Institute
of Hearing
Research, Nottingham
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