Ive just bought new ones for the kids bedrooms as the old ones were sooooo noisy. My youngest couldn't sleep with the a/c on so nearly overheated by morning.
I specifically asked for the quietest brand/model when I bought the new ones
we went with panasonic remote controlled - you can set the desired temp instead of just dials with high, med, low etc
they are great. Really quiet. My youngest doesn't even seem to notice that it's on.