Hi Quest,
We're just back from our stay at GCH last week (3/24 - 3/27).
We stayed in a standard room (4414) just above a construction site. Being on the 4th floor we heard nothing........but I would expect that someone being on the 1st or 2nd floor might very well hear select construction noises if they were really listening for them. I was up at 6 am and saw workers already milling around.
That being said, I do believe that the rooms are very well insulated from sound, because when we opened our sliding glass door, you could really hear outside "park" sounds.......not so with the doors closed.
There was a MAJOR crane situated on the property as well.....but did not bother us. All in all, GCH is a SPECTACULAR hotel . Have a great time.