A family member is always complaining that her hearing aids are crap, noisy, harsh and yet, not allowing her to actually hear very well.. Shes had them readjusted multiple times with no improvement.

I tried putting some Beyer-dynamics 990 Pro 80 Ohm on her, and then plugging that into the line-out of a hand-held zoom recorder with the sensitivity turned up. She heard _EVERYTHING_ and she told that the sound was pleasant too..

This leaves me with the impression that hearing aids are way behind off-the-shelf consumer parts.. Maybe too much sound quality (you had ONE job!) is being sacrificed for size ?