I like this third paper/link (written by Widex people) that you shared a lot. That’s because it addresses the dynamic range issue specific to the HAs. But it’s interesting to note that they talk about shifting the operating range of their 16-bit A/D converter and not really using the obvious solution of just going to a 24-bit A/D converter. But that’s probably due to their platform/design limitations and they’re stuck with finding workarounds for the 16-bit design. Other HAs like the Oticon OPN has 24-bit processing and is able to get 114 dB SPL on the input side without having to do any kind of workaround like operating range shifting.
But again, I still don’t see any conflict between all 3 papers. This Widex paper focuses the dynamic range advantage to avoid distortion at the INPUT stage of the HAs due to very loud sounds, like at a live music environment. That’s just another angle and another advantage of having 24-bit A/D converter and processing. But that’s a different issue entirely than saying that 16-bit processing is not good enough for music compared to 24-bit and human can tell the difference.
What I’m trying to say is that the headroom issues that a 24-bit system solves (more noise, distortion at high input level, speech in noise due to distortion, etc), while real, does not make 16-bit processed sound have a discernible lower sound quality than 24-bit processed sound that a normal person can tell. For most normal hearing situations, they’ll sound the same, quality wise. If you play music from your sound system or watch TV at a reasonable listening level, I don’t think you can tell the difference between 16-bit and 24-bit HAs.
Now if you go to a concert or listen to live music, then 24-bit HAs will sound better for sure because they can take in the higher dynamic range at the input to handle louder volumes and attacks of the live instruments and don’t get distorted or suffer from input dynamic compression. But even the Widex 16-bit system they talk about in the 3rd paper can manage loud inputs after they shift its operating range. So if you wear that 16-bit Widex HA at a live music concert, you can probably enjoy the live music pretty well, too, even though it’s only 16 bits. It just goes to show that headroom/dynamic range and sound quality, while inter-related, are different attributes and shouldn’t be combined and generalized together in a definitive way.