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Re: Best Overall Thermal, Moisture, and Noise Insulators
tuner4life #668786 August 18th 2014 3:00 am
Joined: Mar 2007
Posts: 4,463
Likes: 12
pooh-bah
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pooh-bah
Joined: Mar 2007
Posts: 4,463
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I 2nd the Secondskin Audio damping products. I've used a lot of what they sell, from the old Damplifier (equivalent to what you'd get at the showdown website) to Damplifier Pro to Alpha Damp to Spectrum/Spectrum Sludge. I also used a lot of 3M's 4274 NVH damping compound caulk.

It's all good stuff, but despite rosy marketing, each behaves differently and each works at its best under certain circumstances which they don't spell out. It *is* also possible to make things worse, typically by covering too much area, although if you don't go overboard you'll have a significant improvement with any of their products, even without performing any acoustic tests.

A piece of sound advice for you - if you use the "sexy" looking black Damplifier Pro, cover the black surface with Aluminum foil when you're done, or the black surface will act like a window and radiate heat into your vehicle in summer and allow the heat out in winter! I measured this and it's for real! They won't tell you *that* on their website!!

I'd also recommend going over the painted surface of your panels with some Acetone or something similar, before applying the damping, using cloth which doesn't leave fibers. You *don't* want any surface contaminants, or the damping material may fall off! I went so far as to spray fresh paint so I had no chance of contaminant issues.

The thing to keep in mind at all times is that as you add damping the resonant frequency will drop, so even as you reduce the amplitude of a nasty peak, you may move it down on top of another lower frequency peak! Don't just slap this stuff on at random; keep listening to the results as you go. As you complete adjacent panels, go back and test what you already did; it *will* have changed!

I took thousands of precision acoustical measurements in my van as I modified it, and tailored the application of each material to do the most good. I'm still working on the front end and driver area.

Please note that I applied more damping than absolutely necessary in many areas; the modal test technique I used, while well established for aircraft, was experimental on a van, and it's far harder to remove this stuff than to keep going! ;0)

In most cases, I'd recommend someone without test equipment or much patience just apply diagonal strips of damping material across the most obnoxious areas of each panel; all you really need to do is break up the worst resonances by redistributing the vibrational energy across the panel.

Honestly, based on my results, the most bang for your buck would be to add additional bow and strainer braces to break up the resonance of the largest unsupported panels. Then far less damping need be applied. Position the additional braces with uneven spacing, to reduce the odds of having multiple panels resonating at the same frequency, creating a peak.

You're in luck; just tonight I uploaded about 300 pictures to my Photobucket account! Here's a few pictures of some of what I've done inside my van, in case it might give you some useful ideas:

I custom installed damping materials, up to 3 layers thick, in every single major and minor panel:
[Linked Image]

I added a bunch of extra bows; the only practical way to deal with the genuinely obnoxious resonances of the roof. The very worst resonances were perversely enough directly over the driver and passenger's heads!!
[Linked Image]

Then I installed custom trimmed pieces of thin foam insulation between each bow. This was a lot of work; the Dodge bows aren't a uniform thickness end to end, so the number of layers varies. There were quite a few layers, to get up to flush with the bow surfaces...
[Linked Image]

A final uniform layer of foam:
[Linked Image]

An example of some of my custom damping on a wall panel; there are three types of material in use here:
[Linked Image]

I added numerous additional strainers and covered all the damping with a layer of Aluminum foil to block heat radiation:
[Linked Image]

This is poly-bagged fiberglass insulation. I sealed the bags with an impulse heat sealer to keep the fibers permanently confined:
[Linked Image]

This is how the damping on the floor looks. It's unnecessary to apply damping materials over the cross braces. The area over the exhaust and end of the transmission were perversely transparent to noise... it required a lot of attention to deal with them, including treating the noisy heat shields!
[Linked Image]

[Linked Image]

I put a layer of Reflectix over the floor damping
[Linked Image]

Then a sandwich of plywood and EDPM rubber, then more plywood went in. I learned this noise reduction technique from our own Vanner Pex, who works at a commercial bus factory in Europe. They use mass loaded Vinyl, on the order of 1/4" thick, which would be prohibitively heavy for a van. EDPM rubber works nearly as well.
[Linked Image]

The EDPM rubber actually extends up the walls 6-8". I could make a swimming pool! No need to worry about spills getting under the floor.
[Linked Image]

The area where the seats bolt down is the only area where the floor is pinned down to the van's floor pan; it floats everywhere else; a really cool trick I learned from our own Vanner Doc 2%. This helps absorb and dissipate quite a bit of vibrational energy.
[Linked Image]

It's *much* quieter inside now; and is quite temperature stable. I do love my A/C!! :0)


Here's a little info on the sort of acoustic testing I do. It's got it's heritage in aircraft noise reduction. I have copies of many of the original research papers.
[Linked Image]

[Linked Image]

A good test hammer for this purpose could make use of a piece of Sorbothane like from a gel shoe insert, taped over the end of a small hammer. Mine uses about a 3/8" thick gel I obtained from McMaster Carr. You wouldn't want anything much firmer or you could damage your paint or warp a panel!

Here is a 24 band per octave test plot of one single point on a large panel on my van before damping:
[Linked Image]

And after the application of my test-driven damping:
[Linked Image]

I did pretty well didn't I? ;)

Another before and after:
[Linked Image]



-It's been such a LONG TIME... BlueShift>> 1981 Dodge Ram B250 Custom Sportsman Maxi Van


[Linked Image]

It's what you learn after you know it all, that counts...

Are you living to work, or working to live?

[Linked Image]

Learning from my own mistakes is good, learning from yours would be much better! [Linked Image]
Re: Best Overall Thermal, Moisture, and Noise Insulators
tuner4life #668797 August 18th 2014 9:16 am
Joined: Sep 2013
Posts: 1,015
Likes: 19
old hand
OP Offline
old hand
Joined: Sep 2013
Posts: 1,015
Likes: 19
Dear God man!! Wow!

I do love overkill...

bow


[Linked Image]
Re: Best Overall Thermal, Moisture, and Noise Insulators
tuner4life #668835 August 18th 2014 3:24 pm
Joined: Mar 2007
Posts: 4,463
Likes: 12
pooh-bah
Offline
pooh-bah
Joined: Mar 2007
Posts: 4,463
Likes: 12
It should make a substantial improvement in the sound quality of my stereo too! smile


-It's been such a LONG TIME... BlueShift>> 1981 Dodge Ram B250 Custom Sportsman Maxi Van


[Linked Image]

It's what you learn after you know it all, that counts...

Are you living to work, or working to live?

[Linked Image]

Learning from my own mistakes is good, learning from yours would be much better! [Linked Image]
Re: Best Overall Thermal, Moisture, and Noise Insulators
tuner4life #668859 August 18th 2014 7:36 pm
Joined: May 2006
Posts: 3,113
Likes: 2
pooh-bah
Offline
pooh-bah
Joined: May 2006
Posts: 3,113
Likes: 2
thats insane! i love it.

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