the A380 is so quiet that it's spooky. I've been on it twice, both Singapore (SIN -> LHR) and Qantas (The Nancy Bird Walton that blew the engine infact!! LAX -> MEL)
On takeoffs you know that your getting faster, if you can see out the window. But it's so quiet that you wonder if it will make enough noise to get off the ground! Next thing you know your in the air and the engines are barely making any more noise than when the plane was taxiing around the airport.
On my SIN -> LHR A380 flight when we were coming in for landing and they cut the engines back I couldn't hear them at all. All that I could hear was the wind going past the fuselage, very very spooky and I was sitting over the wing on the main deck.