747FOCAL; one aircraft widely known to measure higher than its certified EPNLs on approach is the RR powered 747-400. The GE and PW variants appear fine by all accounts. By that reckoning, are you implying that RR aircraft routinely use auto throttle but GE and PW powered -400s do not.
Care to elaborate?
My understanding is that auto throttle simply causes frequent variations in power setting, thus causing transient noise, which is sometimes cited as more annoying than a steady state level.