Hi,
Yes more information might help. But likely you can not change the A/C and find one that is significantly more quiet.
If you have ducted air, then the air flows out of vents in the ceiling, several feet from the air intake with the air filter in it.
If you do not have ducted air, then the air intake will be in the center of a larger grill, and have all the air blowing out of that grill cooled off. Many times a non-ducted air will also have all the controls mounted to the grill.
I had a 1985 RV with non-ducted air, and bought one with ducted air to make it easier to sleep with the A/C on. Still both are noisy, the ducted is 'much' quietier, but not as silent as the one in my house.
So ducted air is something to look for in the next RV. You can not change a RV that was built without air ducts to a ducted air system. The air ducts must be installed at the factory. If the RV was built before about 1990, it will not have air ducts in the ceiling.
Good luck!
Fred.