If you don’t encounter this “distortion” with the Resound and Phonak aids, but encountered it across the board with pretty much ALL Oticon aids so far, one possibility is that perhaps there’s something about the Oticon VAC+ proprietary fitting rationale used for the default P1 program is not suitable for your hearing loss for some reason. Have you tried to have the HCP give you a few more programs using the standard fitting rationales like NAL-NL1 or NAL-NL2 or DSL v5a Adult? There are up to 4 programs you can have on the Oticon aids, so you can have all 4 fitting rationales (the Oticon VAC+ and the other 3 standard ones) programmed into your trial aid so you can do A/B/C/D comparison between them all.
That is the one common denominator between all the Oticon models (the VAC+ Oticon rationale) that would be different from whatever is used on the Resound and the Phonak. I would try this first before trying to mess with anything else.
The OPN only has the traditional feedback manager, while the More and Real and Zircon all have the new proprietary feedback manager. If you also hear that exact same “chirping”/“distortion” sound you hear on the Real (and the Zircon) when you trialed the OPN as well, then it can’t be due to the new Oticon feedback manager (they call it the Optimizer) because the OPN doesn’t have the Optimizer technology in it.
I assume that you don’t use the Speech Rescue frequency lowering technology at all because you don’t have the normal ski slope loss, but more of a linearly flat declining loss as you go up in frequency. But if you do for some reason, make sure you turn it off because 1) you don’t need it because it’s not going to be helpful for your type of loss, and 2) at least you will have eliminated another variable that may (or may not) contribute to this “chirp/distortion” you hear.
As for the Transient Noise Management, it’s in the OPN and the Zircon and More, but the Real no longer has it, as it’s now replaced by the Real’s new Sudden Sound Stabilizer. Anyway, either of those technologies are supposed to suppress the sudden sounds, so if anything, it should be a more muted experience rather than a spike of some sort that would result in a distortion/chirping sound, unless that feature was turned off completely. So it’s unlikely that the TNM is the culprit, but again, for the Real, you could have tried to turn that Sudden Sound Stabilizer feature ON and/or OFF to eliminate it as a variable. With the Zircon, it would be the Transient Noise Management. With the distortion only noticeable at sudden loud speech/sounds, you would thing that it would be the very FIRST thing your HCP(s) in those trials would have reached out and turn ON/OFF to see if it solves the problem for you or not.
You never said what your HCP(s) did when you trialed the OPN, then the Real, then the Zircon now, to try to get rid of that distortion. Surely they must have tried something and you must have recorded down (or at least remember) what they tried. Those things like turning off Speech Rescue, Transient Noise Management, Sudden Sound Stabilizer, Feedback Manager, etc, would have been obvious things that your HCP(s) should have/could have tried. Another obvious thing is whether your HCP(s) installed the Music program on the OPN (or MyMusic on the Real or Zircon) to see if the distortion went away? Usually the Music/MyMusic program are designed to have many of the signal processing features disabled, so it would have been a very obvious thing to try to establish a baseline in terms of eliminating contributing factors that could have caused that distortion you hear.
