The slider vents are meant to be opened only when the main area of the camper has to be cooled down rapidly, e.g. when you first arrive at the campground after driving for 8 hours in 95 deg.F weather.
Other than that they should be closed and you would find that the noise goes down significantly as the air is then forced through the ductwork.
As I type this to you I am sitting at the dinette with the TV on and can talk to my wife who is by the stove. All at normal levels. Of course it is quieter with the AC off but even with it on it is a heck of a lot quieter than my non-ducted 13.5k BTU unit in my previous small hybrid. This RV has a 15k BTU unit if that makes a difference in the noise level (I am not sure but thought I'd mention it).