Depends where you sit really - for sure towards the rear of the A/C is going to be a bit noisier, but that's were the empty seats are going to be on a less than full flight. (I usually choose rear seats on the 777 instead of those further forward). Combine this with an airline which provides good IFE and supplement it with a decent noise cancelling headset which is my most important piece of passenger comfort equipment. End result? It doesn't make any difference how noisy the plane is.