I have a 2006/2005 chassis
Chevy Based Tioga and never had any problem with road noise,in fact it is very quiet inside. I also have a battery compartment under the entry steps,it is made of a heavy plastic or composite type of material and the lid/top step has a rubber seal that seals it when fastened down.
You might check underneath,my exhaust/muffler runs just behind it and there is a heat shield attached to the frame there, although my RV is on a Chevy Workhorse Chassis, I have found that ones of the same vintage on non Workhorse Chassis don't have a lot of upgrades that mine has.
