I love this story today in the aviation newsletter AVweb.com saying that the superjumbo A380 aircraft are so quiet in long-haul flight that off-duty Emirates pilots trying to sleep in the compartment near the flight deck are being kept awake. They're having a hard time sleeping because without the "white noise" effect of typical aircraft engines, they "can hear all the crying babies and flushing toilets" in the passenger cabins.
Last year, when I flew a Lufthansa-operated A380 on a shakeout flight with a full passenger load from Frankfurt to New York, the first thing I noticed on board was how quiet it was. So as someone who sometimes depends on noise-canceling earphones in flight and a portable white-noise machine for hotels on the road, I feel their pain.
[Correction: Please note the excellent comment below. On the Emirates A380, the crew rest compartment is poorly located (from the crew's perspective) aft, not forward by the cockpit.]