Plugging your ears with your fingers has several effects: it reduces the canal volume, changes the canal resonance and impedance. If you want a visual example of this, imagine the difference in the air pressure variation in a sea cave full of water with an opening to the outside and one where there is no opening with the same wave action. That analogy a step further, the relative difference in dome is going to be like a further constriction to the flow, albeit one that stops the wave going out rather than in.
Noise-tracker has multiple trade off’s for noise vs speech, the more aggressively it is set, the more the aid tries to eliminate noise: if it is set too high, speech can start to sound clipped.
The Directional mix is the balance between the ‘focus ear’ and the omni ear, it’s basically deciding how much forward bias is directed to either side. This technology is a bit wooly IMHO.
DFS Ultra is the feedback manager - for somebody in your boat (an experienced wearer), if you’re having difficulty with entrainment (overhang) from certain sounds, you might be better to use a more closed dome/custom tip and turn it off.
Expansion is a technique that literally ‘expands’ the speech element of the signal, relative to the rest of the sound using a bit of weird compression maths that kicks in over certain levels. Setting this too high will make the speech sound very artificial.
Input? Try a new Widex Clear for comparison. It’s a bit of a chalk and cheese difference.
I’ve fitted several Alera 5-7-9 to a few customers, the extras are excellent, they have great user acceptance for some people, not so great for others.