If anyone wants the Submission I was asked to prepare by DOR(Sea) in 1998, just ask. It was intended to be topped and tailed into an Air Staff Requirement, and specifically mentions both fixed and rotary, in all Services. Also, groundcrew. At the time, legal advice was 'the clock runs on litigation from now', as a fully integrated Helmet ANR system had been deployed (i.e. powered from, and part of, the intercom), and the Digital ANR was under development to bring the noise dose below the mooted 75dB(A). Other in-ear devices that have become popular were rejected by the Services at the time - ANR was the agreed solution. OR did not proceed. It was left to whoever had the gumption to do it on any given aircraft. Some of the above comments are true - few gave a toss and I'm glad the court has taken a dim view.
I'd say the date could be pushed back a few years, as the RAF had run a programme for Harrier in the 80s, but run up against the problem of miniaturising it to fit in a Mk10 (?) helmet. However, they gave up instead of committing more to the Applied Research Package. Sea King AEW & HC4 picked it up again in 1994, and it entered service in 1998.