It is not the age nor the engines - it is the ridiculous a/c system;
In this cabin walk-around video you can hear the extreme noice from A/C. It is a parked aircraft! No engine sound, no movement noise from outside just the A/C system. Unbelievable. Only in the front section before doors 2 it seems to be a bit more silent and in the middle of the of Economy cabin. I haved noticed this over and over on my flights with 777Ws and even asked cabin crew if it is only me feeling disturbed. Nobody really admits the problem and hundreds of these planes are sold. Typical airline industry problem. I love the 777 for many aspects but the noise is sometimes unbearable if you want to sleep.