Driver fatigue due to environmental noise can be the difference between getting to your next destination or stopping over to rest. What I found though is that passenger fatigue due to environmental noise is the bigger stressor on a road trip. The driver has driving to preoccupy them, and this does reduce some of the effects of a loud rig, bouncing suspension, etc... But, the passenger typically feels all of it. In a vehicle there are 4 different categories of noise as I see it: Engine Noise. Tire Hum. Exterior Environment. Interior Environment.
Engine Noise- Big time with a diesel, but typically only an issue around town and under acceleration. Check your doghouse fitment. Use my patented
"hit the footman loop with a hammer" method to tighten the seal back up. Just make sure they bend toward the firewall. This will suck the doghouse down and forward. Adding insulation under the stock stuff inside the doghouse will help, but the OEM job around the firewall is where the van is really lacking on sound deadening material. I lump exhaust noise in with engine noise. If you are running stock exhaust, then it really isn't an issue. Aftermarket exhausts can drone badly, so a resonator may be required.
Tire Hum- Mud tires hum more distinctly, but all tires have a frequency that can be heard inside the cab. The stock E-rated tires that ran 70-80 psi had a really high pitched hum that bothered me more than the Toyo MT's. Heavy sound control products like DynaPad or mass loaded vinyl are where it's at to address this. Expensive and heavy. I can attest to the impressive nature of the DynaPad, but I think it's cost prohibitive to do an entire floor of a van. I think that a layer of Raammat, Dynamat, FatMat, etc, followed by doubled up Ensolite, DynaLiner, etc, in the foot well and rear wheel well areas would be sufficient.
Exterior Environment- Wind noise, traffic noise, weather, conversations, etc... Door seals are notorious for whistling. Noise is going to come through window glass no matter what. Dynamat, Raammat, and the like area designed to reduce the resonation inherent in sheet metal and plastics. Vans have a ton of sheet metal and therefore, will need more control in the resonation department. If you rap you knuckles against your back doors, you'll see what I mean. Try doing that to VANdiana or Optima's SEMA van and all you'll hear is a dull thud and the sound of your knuckle bone. Rain on an untreated metal van roof will sound like the Steel Drums of Jamaica. The other big noise offenders are carried by airborne sound waves. Harley exhaust, semi-trucks, voices, music, etc... These need to be either blocked or diffused with a barrier material. These are typically the DynaPad, mass loaded vinyl products. Again, they are heavy and expensive and hard to affix to walls and roofs. That's why I think DynaLiner, Ensolite are a good option. They are super light, self adhesive, and do a pretty decent job diffusing sound.
Interior Environment- Think of the van as one big subwoofer box. It has a tune that it hums all on its own. It's way down in the frequency range and can really be felt when the van is emptied out of all seats. The most obvious offender though is rattles from interior plastic panels and squeaks from the metal clips that hold them on. They can be a pain to track down by yourself, so have a passenger sit in back with a roll of blue tape to mark the areas that make noise. The fuzzy side of Velcro can be really useful to place in areas where metel clips or plastic panels rub together. Interior noise really becomes apparent after you have addressed the above areas.
Hope that helps. BTW, if you ever make it up the the Seattle area, I have a 5-gallon bucket of a liquid sound-deadener that I will happily donate to your build. This would be a great option for painting on the interior side of your roof.
Brad
