I have been using occlusion in its dictionary meaning (cf. the related verb occlude), which is entirely an objective physical one of obstruction or closure without regard to any resulting subjective feeling. However, the only instance of the term I’m aware of in Target is the “Occlusion Compensation” control on the Fitting::Global Tuning page, where it has the effect you describe and therefore implies the subjective-feeling meaning.
If Power Domes are not tolerable for me, I can go to custom molds. The one I’m wearing now is completely tolerable: I’m not aware of it.
My primary interest, expressed in the title of this thread, is speech intelligibility and I’ve been assuming that the most relevant range for that is above 4 kHz, i.e., the consonants on the right side of the “speech banana.” And I was particularly concerned about the region above 6 kHz, because that’s where I see the biggest gaps between gain and target gain. But now I see that the consonants, even the /s/ and /sh/ sounds, are all below 5 kHz. Regardless, with my Feedback and real ear test, the divergence starts at about 3 kHz on the right, and 4-5+ kHz on the left:
I think my hypothesis is still viable. It is, a bit more broadly stated than in the thread title, that for speech intelligibility occlusion (per dictionary) should be maximized or venting should minimized. To that end I’m going to try to get my KS9 dispensation fitting done with power domes. But even if she demurs, I have some power domes and I’m feeling more confident with Target…