Hot and Hi
Not sure where that came from. I attended the final trials in 2000 for the upgraded, progammable system that rendered the analog system obsolescent. As the programme manager in MoD (UK), for both analog and digital systems, I signed off on them, thus initiating the production phase. MoD was, by definition, the lead, as it owns the Intellectual Property Rights to the latter. The aim of that upgrade was to meet the new legal limit of 75dB(A). Analog had reached its practical limit of about 83dB(A), against the old legal requirement of 85dB(A).
There are many ways of expressing noise exposure and effects. Reams of decibel notation doesn't work. To acquire the funding for the upgrade, I simply pointed out that (in the lead aircraft at the time) aircrew were limited to 59 flying hours per year, before damage set in. The threat of litigation is powerful. The operational requirement was 600. It so happened that, if we achieved 75dB(A), this permitted 600+ hours. That was a happy coincidence.
I cannot say what aircrew here fly in or what their noise dose is. But what is simple fact is that, to design a 75dB(A) system you need to measure the noise in each aircraft type and design the ANR to attack the damaging frequencies without masking audio cues. Separately, a pilot may assess his dose/usage and decide if he needs a system. For example (again, MoD UK), a Sea King ANR happens to work perfectly well in a Harrier, despite the noise sources being different (epicyclic gears vs engine). But it is almost entirely useless, in fact quite dangerous, in a Lynx, because the pilot can no longer hear certain critical audio cues. My point was, very few "commercial" ANRs are truly transferable between types. They must be a compromise. In analog days that meant multi-type pilots had a range of helmets. With digital systems, you plug into a work station and blow an EPROM, depending on type to be flown that day. I do of course concede technology may have moved on since then, but passive attenuation hasn't.