I have a 2005 35GS with two 13,500BTU ACs. The front is ducted and the rear is not. On high fan the front ducted unit is loud enough that I have to turn up the tv. Alot of times, if watching a movie, I'll crank up the non-ducted unit in the bedroom so as not to had to deal with the noise. There is a noticeable difference in the sound of both units on high and low fan.... however, I changed out my ducted unit AC with a heatpump and used the low fan wire for the heating function and it no longer has a low fan setting.