We have the coleman 15000 ac unit and when on quick cool it makes a lot of noise on low or high fan settings, but once you close them and let it push through the duct work it get's a lot quieter, I noticed a difference between fan speeds, but I always run on high fan so I really don't know the noise level difference.
DW, 2 Dalmatians and me
2011 Jayco Eagle 330rlts
Parked permanently in 20 acres of woods
Used every weekend