I worked on this a couple of years ago. I insulated the cold air return and it helped some overall (on the inside) but its just as loud on the outside. I did a write up on this if you want to do a search (I will see if I can find it and post it hear later).
I also stuffed insluation under every cabenet / drawers to absorb sound (perhap keeps a little more heat in or out of the RV depending on the season?)
IMO all of these furnuces are loud so most likey yours in operating fine. It wakes me up at night so I will heat up the RV some before I go to bed then turn it down to like 60 at night so it minimizes the amount it come one. I also will use a ceramic heater if its really cold when im plugged into shore power. But I dont do much winter camping so its not an issue for me.
Try insulating the cold air return and see how you like it. Let us know how it turns out. 
__________________
2017 Axis / 25.4: Big Foot Levelers, Aims 1200 Watt inverter, Ceramic Window Tint, Full River AGM 6V batteries, Front Hellwig Sway bar / Rear Track Arm, Safe T Plus Steering Stabilizer, PD 4655 converter, Hard Wired Surge Guard, WEboost + WiFi Ranger, LED Headlights/Driving lights, TPMS, Surge tank, Tornado flush, Viair Compressor
|
Thor Forums
