When my audiologist was adjusting my Oticon OPN 1s BTE hearing aids using real-ear measurements, at some point he found (and I noticed) that the aids weren’t “taking” the adjustments (i.e. the adjustments weren’t reflected in what the in-ear microphone was picking up). I found this a bit odd and pressed him for an explanation, which he gave:
Your question really gets at that “black box” concept I was telling you about last appointment. Many times the manufacturer does not want parameters adjusted beyond a certain point. They employ limiters behind-the-scenes. The most common reason they do this is to increase acceptance. When I make adjustments in the manufacturer software and the Real Ear Measurement does not reflect a change, it is likely that the software input data (the audiogram) has triggered some sort of limiter. Because your right and left audiograms are slightly different, it is possible that there are different limiters are employed for each ear. Again - these are proprietary things which we cannot access. But remember - we are trying to compare apples to oranges.
My question is: does this explanation make sense?