Seems to me the van is fairly quiet (keep in mind that I'm pretty deaf) till I get up to Seattle on I-5, which has suffered a lot of erosion from their inclement weather.  I've also noticed noise from expansion joints on concrete roads.  

Where do indeed to add sound deadening (and what type/brand) material to limit the noise transmitted to the body by the suspension?  Is the entire body simply acting as a sounding board?

Karl Wolz
Sent from my electronic umbilicus