There are some good Theads on What is called Sound Proofing, and they tons of good info, but they just don't go far enough.
IMHO: Strategically placed materials can make a significant difference in noise absorption/deflection, over covering every sq inch. If you add heat shielding that flips the equation 180 deg.
Each area of a vehicle has it's unique cariostatic properties, so it is important the proper materials for that cariostatic be used.
Example: Inner fender wells, firewalls, doors, and roofs. They all require different methodologies and materials. It has been My experience that no matter what you use or how much of it you use, You will only drop the ambient noise to a given level whatever that level is. Here is where you guess WHY???? Oh and I'm going to make you wait for it also LOL.
Here are some real numbers you can mill around while I explain myself (this will be long winded so you can bail if not interested or think I'm full of it). Noise readings for the day w/stereo off min35dB max 102dB.
Ambient noise parked w/engine off: outside 45dB inside 35dB (each 3dB cuts/adds 50% of the power/noise) Start the engine high 50"s this noise you wana cut. Turn on the stereo @ wife's level low 60's Mine well Rock Concert. this kind of noise you wana reflect! to reduce outside noise put a patch of sound mat (dyna mat ect.) on the inside of the outside skin. to reflect the inside noise cover the inside door skin on the passenger compartment side. One absorbs the noise and the other reflects.
I can hear the questions being fired at Me, what I hear the most is how you know what to use where. Does the area need to absorb vibrations or reflect sound and or heat. If it is absorption needed it would be best to install the shielding on the heat side. If it is reflection needed it would best to install on the sound side, and always follow what the engineers have already done. Like they used a butyl patch just make it larger, or they used felt pads make em thicker an so on. I even go so far as to fill voids with expanding foam . Warning (you don't wana hear what the Saats of CA says here) This procedure is very messy and can create big problems later on if not done carefully (cover fasteners and wires).
I've done cars both ways and Yes if you cover everything you will decrease the noise level in your car, but after a given point you will only know the difference with a sound meter. Why????? Have you really thought about it? OK OK, I hear ya, It's the windows. They are glass and you shouldn't cover then according to DOT regulations, so noise deadening isn't an option.

Missile going off!!!!!! The house is rattling animals howling. I've been watching rocket since a small boy and it never gets old WoHooooo while
Damn I lost my train of thought LOL Any Thoughts?? Mike/EZ
PS: I try to make it entertaining so if you don't get my humor just say so don't be a troll Okey Dokey

 

I took a few pic's today I hope it helps you visualize
I stated one patch in the middle of the outer skin, well in this pic it would probably be better top do 2 patches due to the support bar.

Looks like th PO ripped off the inner oem cover that will have to be replaced for sure

If it seems like I'm jumping around I am LOL. I'm trying to use up what I already have on hand. I started with some expanding foam rember cover everything and if there are any kind of drain don't plug it up. The Expedition uses several drain channels through-out the vehical.



I'm trying something a little different here. instead of covering every sq in, I injected foam in the roof supports, and I'm installing butyl strips in the area between the supports. the thermal layer is going on the outside of the roof. I used to put all 3 layers on the inside, and yes it helps immensely in the hot AZ desert. Yet you can still feel heat from the headliner. I believe it is because the metal roof is in direct sunlight, so it will heat up. It is Ezer to reflect heat than it is to dissipate heat. Example: My Isuzu Rodeo when loaded with Kayaks on the roof was quieter, cooler and more stable at higher speeds jus from kayaks on the roof no other layers. What I' going to try is 1 layer on the outside the other 2 inside. The best option I came up with is: Trk bed coating as a base layer, a safari rack using a lightweight material with a reflective coating as a floor. This should cut noise and heat plus add to storage space. And the last pic is just to show how I got rid of the rattle from the moon roof motor.
Next is going to be the wheel wells, a major source of road noise. Mike EZ
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I started on the front wheel wells today. 1st layer is automotive undercoating.
as you can see I was spraying in the blind and layed it on a bit thick, so a little touch is needed. next layer will go on the inner wheel cover

 

I finished up the front wheel wells. first there is undercoating then the void was stuffed with OEM felt, finally dynaliner in the inner wheel well. I haven't road tested it yet but the knock test went extremely well. I did snap a video noting the difference. here are the stills.

 

I forgot to mention all materials except for the undercoating was recycled material. I found in another vehicle.
So, 15.00 for the front wheel wells

 

The wife and I took a road trip yesterday Good and bad. It was all good with the Expedition With the front wheel well what I consider done the noise level dropped, how much I'm not sure, It was notably quieter but the sound meter was all over the place, and I had to roll the window down to really hear the front wheels. using repurposed materials and the fact all is hidden I went for functionality over pretty (patch work looking) This being a good example of where I started this thread, strategically placed materials can be just as effective as covering everything. I would guess that the undercoating was not needed, but I wanted this area sealed dust ext..
I will need to do something different in the rear and I' not shure what yet.. Different configuration different materials needed and most of the noise is in the rear with AT tires and a howling diff (no metal)
One point I glazed over, I said I wanted the area sealed that is because these materials are not water friendly and being in the wheel area was a concern but we drove in the rain most of the day and all dry when we arrived home. If I could not have closed this area I would have had to use more water friendly, but much more costly materials (buytal on the inner fender well and firewall covering elsewhere. I will be keeping tabs on this and will update if it becomes a issue.
I'm on a flash flood and water spout warning "shelter in place" Here in sunny CA WoW!! So rainy day projects will be the marching orders.... Mike/EZ

 

I do have some good pic's of the sound proofing in My Crown Vic, If you all want to do a show n tell? I covered everything with something even the windows (limo tint) LOL The Gray Ghost came out sweet, yet it was overkill cuz after a givin point I felt I was wasting time and money with little to no decrease in noise level of the car. Mike/EZ

 

This is how all the door panels started. I removed the felt installed dynaliner then put the felt back on

The roof is dynamat then dynaliner last a new head liner

this Stainless Sheet divids the trunk from the passenger compartment the felt has a vapor barrier

the trunk lid with foam and dynamatt

the hood has foam,, dyna matt then a new liner
The floor was so thick I needed longer bolts to put it back together. I covered stuffed and injected foam everywhere, I also spent a gazillion bucks doing it. This time I'm using as much repurposed material I can get my grubby paws on. If there is a next one I would like to use roll on sealer and a 3 layer substrate over that.