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Jeffrey Sirianni sirianni at uts.cc.utexas.edu
Fri Jun 9 08:51:08 EST 1995

In article <3r89ub$km8 at newsbf02.news.aol.com>, youngluz at aol.com (YoungLuz) says:
>I recently read where the formulas in
>the programmer are not much different with Audiogram Plus vs. Audiogram +
>LGOB. Most of our staff Audiologist don't use the LGOB and have had very
>satisfactory results.

I just attended a ReSound training seminar yesterday in Dallas and found
it very helpful.  The concepts were finally solidified...

I was once under the impression that the LGOB was not necessary, but my
mind has been drastically changed.  Here is why.... Without LGOB
measurements, the algorithm has no way of setting minimal and maximum
gain for the user.  I ONCE thought that the MCL and UCL values were
used in the algorithm or fitting.  That is NOT true, they are not used
in anything, except for record keeping.  If no LGOB values are used, the
fitting is based on normative data.

Here is what I believe to be the logic behind the LGOB and its relation
to fitting.  In the LGOB process, the patient's thresholds (at 500, 1k, 2k,
and 4k) are essentially determined.  They are estimated at 10 dB above the
highest level at which the patient responds "Can't Hear".  Frequency specific
UCLs are determined to be the level at which the pateint responds "Too Loud".
The algorithm then determines the amount of gain required to make a 80 dB
input tolarable.  Then the amount of gain required to make soft sounds audible
is determined by using the estimated threshold values from the LGOB.  From this
point, gain is reduced as input increases, based on the loudness growth function
obtained from the LGOB. Since ReSound uses linear compression, the reduction in
gain, as a sound increases from 50 dB to 80 dB, will be determined by the
subject's reported rise in loudness.

By using Audiogram Plus only, the UCLs are estimated from normative data, but
should approximate the user's actual UCLs.  The LGOB is one way of assuring
enough, but not too much gain, at loud input levels.

Jeff Sirianni     @(((<{
University of Texas at Austin
Communication Sciences and Disorders
CMA, 2nd Floor Clinic
Austin, TX  78712-1089
sirianni at uts.cc.utexas.edu
jgsaudio at aol.com

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