Duramax Sound Deadening-19 dB

[masterp2]

I finished my 3 week project, entire interior removal.

 

Did the complete sound system overhaul, TNR, and sound reduction treatment, trying to leave no stone unturned. My results overall, using the radio shack SPL meter, C weighted:

 

Idle Before: 77 dB

Idle after: 58 dB (this is 4-5 dB quieter than my wife's Expedition)

19 dB reduction

 

Average road noise reduction is 14-20 dB

 

Call guiness.

 

I used approx:

 

150 sf of Dynamat Extreme

60 sf of peel and Seal

15 sf of HTM (mcmaster)

6 cans of PU expansion foam

200 cubic feet of yellow fiberglass batting (compressed it is like 10-20 cubic ft)

25 sf of 1/2" sound barrier decouple foam ( 1 lb/sf barrier sandwiched between 2 layers of foam).

 

total cost was about $500, about 60 hours (a nightmare). Added weight is about 100 lbs.

 

Now on to the performance exhaust with 2 mufflers.

[Halen5150]

Wow man! That's f'n awesome! Sounds like you did a good job. I wish I had dynamatted my cab when I installed my amp/subs/comps. Did you apply a layer of each material over the entire cab?

[masterp2]

No, I used various materials where I thought they would perform best, including some external treatment.

 

Opening day today, took my son to the game, Cubs killed us. Anyway, he cracked the door on the highway, I thought, what happened to my quiet truck? That thing is sealed up!. My ears pop when I close the door.

 

I also spent some time making the air fan quieter using some fiberglass and foam to deaden that immediate area. Used to swooooosh much more. It is easy to "never stop".

[100R1]

What is "peel & seal" & how does it differ from dynamat ?

 

What it the thickness (single layer) of the peel & seal ?

 

Do you have Link to a website for more info & availability?

 

Do you have a Mcmaster part # for the HTM ?

 

How many layers of the above did you install ?

 

 

I am planning a sound system upgrade and 1st step is to include a sound insulation barrier.

 

I have ample supply of PSA backed neoprene sheet rubber 1/16" & 1/8" thick and PSA backed closed cell foam rubber I was thinking about using. I can get both in long rolls and 36" & 48" widths.

 

I have heard that you can use roofing underlayment (ICE dam) bitumen based.

 

Im looking for lower cost than Dynamat

[masterp2]

Closed cell is fairly worthless for sound absorbing, and at those thicknesses, a worthless effort. It may, however, be a resonant dampener, if it is heavy!! Not trying to be condescending, just keep you from wasting your effort.

 

It was a long project, for my money, here is what I concluded. Dynamat, bought off ebay for $3 psf is hard to beat. There are competitors, but I found out how much I love the stuff when i did some testing. It is more visco-elastic than anything else.

 

What I liked was how inexpensive plain ol fiberglass batting was, and when compressed 3x, it absorbed better than anything else I tried included a foam-vinyl-foam composite at $10 psf. The niche for the composite was the floors, since, at less than 1/2", it is, hands down, the best 1/2" treatment for sound blockage there is. You would need 2-3" of compressed fiberglass to equal it. Ever see those compressed fiberglass cieling tiles for noise deadening? Same concept.

 

P & S is a construction material used in flashing I think, is thinner than dynamat extreme (.070), about .040 thick, and if I did this over, I would not buy it, it is ok, but does not adhere nearly as well as dynamat. My hunch is that it doesn't dampen nearly as well. But if you want it, many lowes or HD's carry it, and there is one mail order place I will get if needed. Still, at $1.50 psf I don't feel it was a value.

 

HTM is the worse for adhering (so only use it with a heat gun, roller and in flat areas, like the roof.) but it wll stay put if you don't use it in complex 3D areas. And it is an extremely good dampener.

 

In my truck, almost every sq in of area got covered. The interior sat in my garage for 2 weeks (and it apears some crawled up into one of my seat and died, cant find the source of the decomposing smell!). The most resonant areas, to cover twice would be each floor pan where the feet go, these 4 places seem very unreinforced and resonant. The back wall is huge, pay a lot of attention there. On each door I did both door skins, trying to seal up any holes on the interior skin for audio performance. Do not attempt to remove the headliner from the truck, but you can drop it pretty easy. Do this area, it is very, very resonant. I used about 2-3" of fiberglass adhered to the top of the liner before replacing it. Make sure you have 2-3 helpers when you put it back up.

 

I stuffed fiberglass in every ineterior hollow opening I could access. I used alot. I would also use it (or a good PU acoustic absorbing foam) on every door panel, use 3m spray adhesive to attach it to the interior panel before putting it back on, huge acoustic performance benefits also.

 

I obtained a 2dB interior improvement by adjusting my hood latch believe it or not (diesel thing)

 

i will go find the mcmaster part # for the HTM.

 

I took a ton of pics.

[willieboy]

You did not plug up your door drains did you? If so, you will want to unplug them, or within two years you will have BIG rusty holes in the bottom of your doors. During rain storms, melting snow and ice, car wahses, etc... some water does get into the door, and those drains allow it to drain off instead of collecting. With all the stuff you shoved in there, you will never here the water sloshing around to let you know you have a problem.

[masterp2]

Nope, wouldn't do that. Had some rain while doing the project, and water does come in. Also makes its way into the kick panel areas, that's not right! Haven't quite figured out where it is coming in from.

 

That is a good point about water in the doors. Don't use anything in there that will mold. Open cell foam at 2 lb/ft^3 seems to be the ideal weight for absorbtion. But as we know open cell is like a sponge with water. Some people discard the plastic liner. I preserved the plastic liner and put it back, highly recommend this if attacjhing foam or fiberglass to the door panel.

[Synster]

Could you go into more detail of what you did with the roof/headliner. I understand that removal and replacement is a PITA. One small area at a time? Did you use regular R-22 and stuff it in or use adhesive? What's the process? What about Dynamat on the roof? Thanks.

[masterp2]

I dropped the headliner in the vehicle, after the entire interior was removed. Don't try to pull it out. Will ruin it.

 

From the doorways of the vehicle, I put patches of HTM on the roof skin, then roll solid covering of Dyn Xtreme over that, sections at a time. I used a spray adhesive to tack the fiberglass batting to the headliner. Anywhere from 2-5 inches depending on the "hollow space" that exists above the headliner.

 

When removing, then replacing headliner, get 2-3 helpers.