I remember flying in a fairly new A320 on UA (might've been 319, not sure) from SFO-PDX on E+ (row 6) and it was the quietest plane I've flown in ever! The 2nd quietest one was a 757 from SMF-LAX and I was in E- back then, but it was very comfortable. Speaking of which, is F usually quieter? I flew in F on a 757 but couldn't really notice. On the CR-7 I noticed that the back is much louder than the front due to the engines being in the back.

Loudest must be sitting in Row 43 or something on an LH A340. I'd always fly a 777 over A330-340 if I get to choose. A330 and A340 are just crappy products, I don't even know why airlines would buy it over a 777/767.