Furnace ? on New 2011 21 FBS North Trail

We took our new camper and camp on the side of the house since we werent able to get reservation anywhere to late of notice. When we turn on the furnace work great but made humming noise inside and outside from the holes where the heat comes out not sure if that is normal. On new furnaces couldnt remember from our other campers, if that is normal. Heated the RV very nicely just the humming noise. You could still watch TV and everything just wondering if this is normal. Removed access panel couldnt find anything lose.
 
Top