John,
they were very successful ! I hosted a university team who had been tasked to investigate db and frequencies inside the a/c. The report made interesting reading but nothing was ever done. When i was with the HEART, we asked MOD about noise levels in the forthcoming 'J'. They eventually admitted that it would probably be even higher than the 'K' ! Thankfully I had retired by the time the much delayed 'J' entered service.