I detest roof air and Onan generators. I use a Honda 2000 and an 8000 btu window ac. I went out and checked around 45 db on low. The db measurement does not measure tone some sounds are much worse than others. Think scratching nails on a chalkboard. I have 3 minis in my house and if I had room for the evaporator in my little Toyota would have put one in there a long time ago!
They duct the cooling air in some RV's, ok good. Then leave a hole in the roof to where the fan and blower motor are, well duh!! Might as well sit the unit on the kitchen table! Very simple fix, duct the return air with baffles.
I am sure some are reading this thinking well whats the big deal? Some are more sensitive to noise than others is the big deal.