Deep Canal Fittings
acampane at postbox.acs.ohio-state.edu
Sat Jul 1 17:00:03 EST 1995
In article <3sp8ne$ct3 at lastactionhero.rs.itd.umich.edu> mstaben at umich.edu (Matthew S. Staben) writes:
>>In a later posting you noted that you have shortened the canals for a
>>matter of comfort. I've found that I can simply narrow the end of the
>>CIC slightly by grinding and buffing. I have solved the discomfort and
>>seemingly had no adverse results such as feedback.
What I have found, in wearing earplugs for noisy environments (small
airplane cockpits, etc.. 90-100 dBA, chiefly low frequency noise) is that
earplug fit, which I am comparing to hearing aid fit, is very variable.
If the plug is too firm, then jaw, chewing and speaking movements
invariably encompass a range where firm plugs will unseat, breaking the
seal, or hurt, adding to fatigue and general disgust in usage. The best
earplugs are quite compliant, allowing for 20-30% in size from one
jaw extreme to another (a subjective estimate on my part). The worst
earplugs are those that are firm and especially cylindrical. I don't
think very many ear canals are circular.. rather they are probably quite
eliptical. Furthermore, I don't think that many canals are straight, but
rather they are arced..
One of the more useless earplugs I have ever had was a pair that was
especially maolded for me by an audiologist. If I sat with my mouth
closed (a rare event!), they would seal. But as soon as I talked or
especially opened my mouth widely, they would unseat. I never used them
in practice. They would bend, but they would not expand or shrink in
crossectional area as is desparately needed to maintain a good sound seal.
Now, considering the above enviroment, (and I have not been following your
dialogue very closely... so forgive me if I have misinterpreted the problem
extant) use of a long and deep cylinder, looking for a firmer interior
base is quite likely to cause discomfort if the full dynamic range of
flesh motion is not accounted for. Your beveling of corners and length
trimming actions seem to properly (to me) address this dynamic problem.
Fortunately, the closeness of fit for hearing aids need not be as tight as
that needed for high attenuation earplugs, so there is good hope that you
can achieve your goal..
I envision a standard itinerary of jaw movements and maybe spoken words that
will allow you to survey the fit.. and - much as a dentist trims the seat of
fillings and caps while asking you to do specific jaw clenching actions -
you will be able to 'home in' on the best dynamic fit .. one that the user
can enjoy far into the future..
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