Can most audiologists properly do an initial fitting and ongoing adjustment of Oticon OPN S HA's?

@fred9 said:

my HL is 55 db (75-20), so the HA’s will help me regain less than 50% of my HL.

I found a page which talks all around the “half-gain rule”.

Lybarger 1944 observed that HA users tended to choose gain about half their HL. The NAL formula 1976 gives the number 0.46. Data from the 1980s relates HL to average UCL and MCL (Upper and Most Comfort Levels). When graphed we see that UCL does not change as much as threshold(HL), and that MCL tends to sit mid-way between UCL and HL. Third-gain has also been mentioned. These are meant as starter-goals, and in days of linear aid the user would turn the dial up/down from there to find an optimum. Wide-range automatic gain systems are not so simple. But very often we wind up with half-HL or a little more gain for soft sounds where you need gain, less for loud sounds where you don’t need much gain, and the change of gain with level (compression ratio) is “2:1” (1.6:1 to 2.3:1 for fine tuning). Which for middle loudnesses does indeed come near the old “half HL rule”.

The “about half HL” rule happens to work good for many many people. When HL is over 60 the UCL may rise or drop and other goals may be better. Very steep HL curves are hard to match and some compromise must be found.

This book is older and there has been much refinement in prescription, now mostly built into the HA fitting software. But a half-gain first-fit is still a good start and a significant improvement in hearing.

1/3 gain is a common formula available in fitting software today. I believe it is mainly used for those who are trying to transition from old analog hearing aids. This is what a 1/3 gain correction for your loss would look like. Note that there is only one curve as 1/3 gain (and most older analogs) were not capable of compression.

This is NAL-NL2 which uses lots of compression. Soft sounds get more gain, and loud ones less.

@Sierra said:

1/3 gain is a common formula available in fitting software today. I believe it is mainly used for those who are trying to transition from old analog hearing aids.

And history shows that when “half-gain” was proposed, most HAs had truly ratty response, frequency response not smooth, so gain was an uncertain thing. “Half” may have raised the dips in the curves, the missing tones where speech sounds were weak; the excess gain on peaks was tolerated for better intelligibility in the dips.

Also a good flat high-output HA in loud sounds could be intolerably loud. The older HAs usually clipped too-loud sounds. Nasty but didn’t blow your eardrums away.

Sure, 1/3rd-HL is probably a much better plan today. Anyway it it less annoying to new users and leaves room to turn-it-up as the ear acclimates to sounds it has forgotten. (Though I see you have turned a “acclimatization” knob full-up.)