I have completed a fairly involved project in quieting the cab of my 2001 Cummins powered truck. I learned a lot of general soundproofing from the competition stereo guys, and I learned a TON from Greg the “Noise Nazi” from this forum.
If you are looking into really reducing the sound level in the cab of your truck, additional soundproofing will make a significant noise reduction. On my truck, I pulled the complete interior – less dash, and put down a “Dyna-mat” type material on the floor and rear wall (“Brown Bread” is the best product of its kind on the market right now, and is what I will use on my next project). I covered the “Dyna-mat” on the floor with a layer of 2 ½ pound per square foot lead sheet. I got the lead sheet from a metals house that supplies roofers. I glued CSI sound stop foam on the rear wall of the cab. I removed the door panels and glued 1” CSI foam on the inside of the door skins – all four (quad cab). I also covered the complete firewall on the engine side with 1” CSI foam. I removed the headliner and glued foil faced “Jute” to the roof of the cab. I had tried using “Dyna-mat” above the headliner of another vehicle, and had problems with it getting too hot and either falling or “liquifying” when the car (black) was parked in the sun during a hot California day. The foil faced jute works as both sound and temperature insulation, I used “Weldwood” contact adhesive to bond it to the inside of the roof. It has been holding fine for three years now. I insulated the “cowl” –the box in the engine compartment that the windshield wiper motor sits in with “Dyna-mat” and foam.
I wish that I had purchased a Db meter prior to starting this project. I did purchase a Db meter about half way through the project, and it really helped quantify some of the changes. Lead sheeting on the floor and CSI foam on the back wall were a couple of the best “return on investments” – from a time and cost of material standpoint. Covering the complete firewall with the CSI foam was difficult and time consuming, but I really liked the result.
In January of 2001 I purchased a “full Set” of blankets covers from ATP for the: Oil pan, Valve cover, Exhaust manifold, Turbocharger, Downpipe, and Hood liner. I had done some serious research into what was available, and was tremendously impressed with the quality of the ATP products. The quality of their products is Aerospace / Military. In 2 ½ years of use, and over 50,000 miles, the ATP products on my truck are “like new” no problems or issues what so ever. These are expensive components, and they really work well. I am not sure they reduced my trucks sound level by 24 Db’s, but they did provide a very noticeable sound reduction. Reducing noise at the sources – oil pan, valve cover, turbo, exhaust pipe (the sound that resonates from the pipe itself) The oil pan is a huge source of noise, for my truck, stock at idle, 95 DbC, after covering it, 92 DbC. A difference of three Db is a reduction in sound energy of ½! At first, I was concerned about over-insulating the engine, and causing heat related problems with the oil etc. . This has not been the case at all, marine and generator versions of our engines see far more insulation and work much harder that our trucks without any airflow over the block.
Now when my wife and I travel, we now talk at a normal voice level. We feel much less fatigue after a long day on the road. The stereo system seems to sound better now that we don’t have it turned up as loud. We have also noticed that much less heat gets transferred into the cab, from the floor, firewall, and roof.
I know this was long, I hope it helps.
Geoff