I have the same system. I have an EB 50 layout and the exhaust is located in front of the rear wheel on the drivers side and inside noise is not all that loud. Can you route the exhaust to a different location? Also my fan vent is below the sink area and also not that loud. Outside is a bit loud for me but I try not to camp right next to tent campers! I use to own an RB 50 with the Suburban heater mounted under the bed and that was loud. Earplugs would be the easiest solution.
We have the 110S layout so our bed sits crosswise at the back of the van (we're short) and converts to a dinette. The entire heating system, fan, vent plumbing etc. is right under one of the dinette seats and under my head when the dinette is made into a bed. If it had been installed more to the front of the van, away from the dinette I imagine I would not be having such issues with the noise. C'est la vie.