Soundproof enough?

[stesmit]

Is a sound barrier necessary under a sub floor?

I'm planning to install 1/2" plywood on 1/2" polyiso for the rear 7' or so of my 2005 E350 XLT Passenger. No joists or furring strips, just glue to metal. I am on an assumption that the combination of proper glue, insulation, and plywood will deaden and absorb sound. Impacts of an adhesive or spray dampener under the floor would be negligible compared to the floor itself. Any thoughts?

[Orv]

My '90 E-250 is just plywood and a vapor barrier on metal, no other insulation or sound deadening. There's carpet on top of the plywood.


Most of the noise I get is wind noise and engine noise. Tire noise from the back is pretty minimal. I can hear some diff whine but it's not objectionable to me; I mostly notice it below 50 mph. Above that the wind noise drowns it out.



The floor does get cold on cold nights, though.


Do make sure you use long enough bolts or screws when you mount stuff to the floor. I just had to redo the table mount in mine because some of the original screws failed to catch metal. With some of the screws in metal and some only in plywood it got wobbly over time.

[bec_n_em]

Sound deadening the Doghouse was probably our biggest improvement in noise reduction in the cabin. https://photos.app.goo.gl/CTTZKhPdRzbcWczm9

Although our Ford OEM insulation was minimal; some years are better.

Sorry, no experience on the floor of the van.

Also did the cabin floor, and hood. https://photos.app.goo.gl/KtsuUkYqzPW9bPVy5

Hope the thoughts are helpful.

Best,

Em -

[bcrittendon]

I have 1" polyiso, 1/2 plywood subfloor (framed in) and vinyl flooring on top. Its plenty. I don't even hear clicking from the fuel pump for the diesel heater.
Use subfloor it has no voids.

Brian C.
SW MICH
2008 EXT ECONOLINE 2500 CONVERTED

[stesmit]

Thanks for sharing your experiences! I think I’ll skip any additional sound proofing and count on the subfloor design to do the trick

[AndrewJM82]

Originally Posted by bec_n_em

Sound deadening the Doghouse was probably our biggest improvement in noise reduction in the cabin. https://photos.app.goo.gl/CTTZKhPdRzbcWczm9

Although our Ford OEM insulation was minimal; some years are better.

Sorry, no experience on the floor of the van.

Also did the cabin floor, and hood. https://photos.app.goo.gl/KtsuUkYqzPW9bPVy5

Hope the thoughts are helpful.

Best,

Em -

How effective was the sound deadening on the engine? Is it a diesel?

[bec_n_em]

V10, 6 to 8 dB reduction total, I did a poor job understanding the incremental improvements, didn't do measurements untill I finished. Doghouse most noticeable on acceleration and hill downshifts.

[JWA]

For me adding a 3/4" plywood subfloor served two purposes:

1. Acts as a damper against the vibration and road-noise transmission through the drum head-like sheet metal OEM van floor.

2. Provided a completely flat surface across the strengthening ribs the factory rolls into the floor's sheet metal.

I noticed when bringing my 3 plywood sheets home in the van they would be installed a big difference could be heard with them just laying on the floor.

IMHO there's no good reason trying to add more noise reduction under the plywood flooring. As mentioned almost no one leaves bare plywood uncovered with carpet or other coverings.

[Pntyrmvr]

I'll second the plywood as a serious noise reducer.

I removed the 1/2" plywood from my van as the yahoo that installed it used self drilling/tapping screws to install it and punched holes into the top of the gas tank during the process.

I pulled the tank and welded up every hole in the floor. About 80 of them along with a few other openings.

The first test drive with it all buttoned up, but without plywood reinstalled was eye opening for the increased road and drivetrain noise.

I wouldn't bother with the heavy vinyl/butyl sound deadening in the cargo area of a van if one were installing plywood with sheet flooring above. The plywood alone does a great job in sound reduction.

I also believe the inherent stiffening of the floor by way of screwing down the plywood reduces "drum skin" vibrations.

[REF]

I don’t know, I think every bit helps, especially with my 7.3. I put a few strips of Noico (dynamat) in the rib valley’s to help minimize any chance of having any vibration or noise transfer from road or exhaust, I then used Vantred, it’s a polypropylene foam and TPO rubber cutout piece made by Bedrug which is custom cut to each vehicle, fills the rib voids, it’s only 1/2” thick and helps insulate from heat and noise and since it’s precut, easy to fit in place and I was able to use it as a template for the ply floor going on top of it.
Don’t skip insulating and soundproofing the doghouse. I used Dynamat and I taped in a piece of foil backed hood liner material to help with heat transfer, helped a ton.