Furnace exhaust wop wop wop noise?

[MojoRisin]

This new to me 2013 Jayco X18D has been used a few times this year since we purchased it and the furnace gets a fair amount of use here in the cold colorado nights. I've noticed lately the outside exhaust is very "wop wop wop" sounding and it can be quite loud - don't notice it as much inside. I don't recall it doing this on our first few trips... Am I just noticing something that is normal sounding? Here is s short video clip of the sound it makes... https://youtu.be/ZJ_klXVg0qU

[RedHorse1]

My guess is the flame is not burning smoothly. Possible that insects have set up housekeeping in the burner tube or the burner may need cleaning. If the exhaust is sooty that’d be another clue that would point to a flame problem. Again, it’s my guess.