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Dynamat Sound Deadening Testing Before and After - Worth it?
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presslab
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PostPosted: Thu Nov 29, 2012 6:54 pm    Post subject: Reply with quote

denwood wrote:
A db meter alone is of limited use..as all it measuring is peak.


What makes you think that? I guess that explains why you were always doing an FFT... My old Radio Shack meter does a continuous average. The new version can do average or maximum. It doesn't just take the highest "peak" from your FFT and display that. It's in the time domain, not the frequency domain...

Think of the dBA measurement as the average sound amplitude (time weighted) over a certain frequency range and weighting... FFT is okay if you are curious about the frequency, but it's no use to tell you how loud something is. That's why muffler laws and such don't specify the frequency as it's unneeded information. I mean, if something is loud at 200 hz, something at 1 kHz at the same dBA will be just as loud.
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Jake de Villiers
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PostPosted: Thu Nov 29, 2012 7:59 pm    Post subject: Reply with quote

denwood wrote:

Jake, the tar thing makes sense, however in theses climes, the rust situation dictates anything under the van is viscous, self healing and applied every year or two. Anything that can trap water between itself and the body is likely a safer bet where winter salt is not an issue.


I smeared glass fibre reinforced asphaltic compound directly to the metal, so I don't see how anything's going to get in there to cause rust - not water and not air.

I guess you'd want to be sure that the substrate was rust-free to start with...

Biggest bang for me was the roofing compound, followed by damping the front doors, followed by the plywood Vortex Eliminator for the luggage rack. Damping down in the D pillars was very effective, too. Doing the slider and hatch was noticeable and I still need to do the nose and the driver's side wall of the van - it still rings there.

Plugging the bottom of the A pillars took some low frequency wind noise right out of the picture. It all adds up. Wink
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presslab
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PostPosted: Thu Nov 29, 2012 8:26 pm    Post subject: Reply with quote

Jake de Villiers wrote:
Plugging the bottom of the A pillars took some low frequency wind noise right out of the picture. It all adds up. Wink


This is next on my list. What did you plug it with?
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denwood
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PostPosted: Thu Nov 29, 2012 9:19 pm    Post subject: Reply with quote

Jake, what was the plywood vortex dealio story?

Press, the RTA tests i did do provide both an "average" db rating ( top center) and the frequency breakdown. My thoughts on the frequency data are pretty simple. For one thing the RTA does not require selecting a range, like many of the meters I've seen. The other is that a peak average Db rating of 70, where the frequency weight is below 150 hz will sound a lot different than the same 70 db peak average biased in the 1 kHz range. If you are comparing sound treatment before/after, results that show max drop in the ranges that our ears are more sensitive too, would be better buzz for your buck.

Obviously I'm still learning as I go here, but I believe RTA and FTA tell us a lot more than just a straight up db level comparison. For example, the RTA rear seat average db numbers show a 3-5 db drop in the averages post dynamat. This sounds good until you look at the frequency data and see that the difference is biased below 150hz..making the difference barely detectable to most ears.

One thing I will do now is pull the floor instead of just over coating it... Based on 2Ply's post above.
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ragnarhairybreeks
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PostPosted: Thu Nov 29, 2012 9:20 pm    Post subject: Reply with quote

Jake is right about the A -pillars. VW put foam plugs in them. Here is some badly (google) translated info from http://www.t3-infos.de/

"From approval-technical reasons (in Germany in 1990, the noise worse), VW must revise the T3 again, while the diesel some missed to sound, which looked something like this (may be that I have forgotten in the list or what it is not amending the 1990 one):
Tin roof inside (slight felt mats)
Engine room: longitudinal beams and motor bucket inside passenger side rear interior including maintenance hatch
D-pillar in the lower section and the front outer wall (approx. 40 cm), on the left base foam wedge under the air intake hose / bow
Exhaust system: shielding with aluminum-coated insulation mat around the muffler and the exhaust pipe side
Wind noise package at the front doors (only Caravelle, Multivan etc.) including foam plugs A-pillar down"

some pics of A-pillar plugs and where they go:

Image may have been reduced in size. Click image to view fullscreen.


Image may have been reduced in size. Click image to view fullscreen.


2Ply - I like the video and what you did. Also like the use of the oscillating multi-tool to cut the stall mat.

alistair
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denwood
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PostPosted: Thu Nov 29, 2012 9:28 pm    Post subject: Reply with quote

Alistair, so the 90's have these mods? I need to check my a pillars... Never noticed a void there. Will look. For sure zero in my D pillars, but the engine hatch and rear firewall are fully treated with foam in my 90 Westy.
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ragnarhairybreeks
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PostPosted: Thu Nov 29, 2012 9:42 pm    Post subject: Reply with quote

denwood,

I did not notice them on a '91 syncro westie (simonslp's) when I went looking for them. Maybe they fell out or maybe it was a German only mod?

alistair
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ZanaEvyPapa
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PostPosted: Thu Nov 29, 2012 9:59 pm    Post subject: Reply with quote

I totally stalked Jake's profile for the "plywood dynamix luggage rack humma humma"
Found it: https://www.thesamba.com/vw/gallery/pix/852200.jpg
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Otmar
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PostPosted: Thu Nov 29, 2012 11:13 pm    Post subject: Reply with quote

denwood wrote:
Alistair, so the 90's have these mods? I need to check my a pillars... Never noticed a void there. Will look. For sure zero in my D pillars, but the engine hatch and rear firewall are fully treated with foam in my 90 Westy.


My 90 DOKA is up on the lift, it's from Germany, looks like a base model and does not have plugs in the A pillars.
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randywebb
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PostPosted: Fri Nov 30, 2012 12:01 am    Post subject: Reply with quote

ragnarhairybreeks wrote:
J


Image may have been reduced in size. Click image to view fullscreen.




not sure what I'm looking at here -- is this lying on the ground with the camera looking up, or what?
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Jake de Villiers
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PostPosted: Fri Nov 30, 2012 12:16 am    Post subject: Reply with quote

Yup, you're looking up past the frame to the bottom of the A pillar. I shoved a couple of pieces of pool noodle (it was lying around - we don't have a pool...) up in there and jammed it up tight but expanding foam insulation would probably be better.

I think I got the idea from Al's earlier post - thanks, Al!

ZEP found the photo - its merely old plywood on pool noodles with bungees holding it down but it makes a difference to the wind roar and your gas mileage. Wink
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BetaVan
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PostPosted: Fri Nov 30, 2012 12:33 am    Post subject: Reply with quote

Prepping to do a pretty major interior overhaul, and I will be spraying down a few layers of Quietcoat - http://www.quietrock.com/soundproof-products/quietcoat.html - as they are located with 20 minutes of my house, and I can get it without paying shipping Smile I am going to try and get away with 3 gallons. My main areas of concern are inside the door panels, the firewall, and the underside of the wheel wells. I also plan on buying some luxury liner pro (LLP) - http://store.secondskinaudio.com/luxury-liner-pro/ - to cut down on the engine drone. With the Vanistan + WBXaust, there is a decent hum from the magnaflow that I would like to tone down a bit. Don't get me wrong, I love making car alarms chirp as I go by, but I wouldn't mind getting the cabin noise down a tad. I've been driving around without the back cushion in and recently replaced it, and man what a difference that makes!

My plan is to completely cover the firewall with LLP, and maybe some/all of the back under the cushion, although that may be too pricey. I am thinking of installing small squares of it within each door panel as well, although I'm not sure how effective that will be.

Anyway, maybe if I get off my arse I can take some readings of driving around with things at stock, and then do a comparison with my upgrades? I know there's been a lot of debate on which instruments (iPhone app) to use for measuring, what to measure, etc, but I'd love to help/add to the knowledge base. Most of the technical stuff goes whhhheeeerrrrrrppppp, over my head, but if someone wants to guide me in the right direction, I am game.
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denwood
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PostPosted: Fri Nov 30, 2012 7:57 am    Post subject: Reply with quote

On my conversion I originally used one magnaflow...too loud as it is a straight thru design. I added a second with a different volume. Much better now. Exhaust noise drone at highway speeds is pretty much gone.
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2PLY
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PostPosted: Fri Nov 30, 2012 9:13 am    Post subject: Reply with quote

All great information guys. I'm mostly winging it from here on out. The floor thing was mostly to end up with a more camping compatible floor that would carry all the way under the cabinets, give me a surface that didn't need a carpet but would help keep stuff on the floor from sliding around.

I ride Trials Dirt Bikes when I camp so any carpet gets hammered quickly so I wanted something that could be wiped clean and dry easily that wasn't as cold and slick as the stock westy floor with no carpet.. And then if it could help quiet things down, that was just a side benefit.

I'll be looking to improve the other places you guys are pointing out.. Thanks!

Also, the videos are mostly for my own record of what I did and the thoughts I had for doing things as I go. I'm not trying to make a good production, just something that I can look back over to see what I did and why and then if I can put something together to help others through the same process, then that's just a side benefit. So pardon any sloppy editing or poor camera techniques... These are just video logs as I go. I'll have many more later when I can stop working.... "On a Van down by the River" Wink
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denwood
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PostPosted: Fri Nov 30, 2012 11:01 am    Post subject: Reply with quote

Beta, read the first page of this post. The iPhone is perfect for this type of testing, particularly for comparison as many folks have an iPad or iPhone available to them. The testing is very simple and takes only 5-10 minutes.

If you use the same app, you can compare to my 90 Westy before and after.
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PostPosted: Fri Nov 30, 2012 12:41 pm    Post subject: Reply with quote

I know I'll lose face in this august, scientific discussion, but I'm currently doing tests holding different materials over my ears at home'Smile' (listening to stereo-jazz with distinct bass & vocals). The winning materials get to ride in the van while I do the same (a friend will drive).

I've tried different sleeping bags, pillows and cushions, at different degrees of compression ('til my arms got tired-medium compression seemed the quietest) including tempurpedic (no good at all), the rear foam cushion(not very good, relatively), and will continue.

I know its not the same accoustic application context, and won't be still while I'm riding in the van pressing sleeping bags to my ears, but so far there's a clear winner. If there continues to be, and if I can fab up something out of it and save a bunch of $ over the commercial products, I might just try it.

BTW, current obvious winner, with drastic noise reduction, is a pillow filled with Comforel, about 1/2 to 2/3 compressed. Looked up prices just a little. Won't be real cheap. I bet it would work really well, though. Of course, that would be couple of inches thick, for cavities and under seats, maybe. Have to test a thinner sandwich of it to see if it does anything.

I know carpet padding is supposed to be good and economical. It does have a high density (mass). I'll get some.

I'd like to get the wheel well liners and adhere some adsorptive/dampening layer to them that leaves an air space next to the metal fenderwell to avoid rust. I wonder how much clearance there is under them. I know, to be most effective accoustically, this space would need to be closed around the edges, and not have openings, so how would it breathe to keep dry?Maybe a tiny breather hole would be enough and not too loud to ruin the system's possible benefits. Maybe sealing it up is too much of a reach, but it might be worth doing it fully ventilated if it works somewhat anyway.

I'll keep posting. Have to get the van running to do my "before" tests. And replace the dying old iPhone.
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PostPosted: Fri Nov 30, 2012 3:24 pm    Post subject: Reply with quote

denwood wrote:
Beta, read the first page of this post. The iPhone is perfect for this type of testing, particularly for comparison as many folks have an iPad or iPhone available to them. The testing is very simple and takes only 5-10 minutes.

If you use the same app, you can compare to my 90 Westy before and after.


One important factor to consider if you are going to make serious measurements is to be sure to drive the same stretch of road at the same speed and under the same conditions..

For example: I-90 heading East from Seattle. There are sections that are new and the Van is super quiet on those sections, but then most of the way has worn wheel tracks that are deep enough to expose the aggregate in the concrete and asphalt sections to the degree that it sounds and feels like you are on gravel. It annoys me enough that I often crowd the lane lines to get out of the rough spots. The difference in noise and even feel is VERY noticeable.

Also, my tires are not known to be one of the quiet brands, I'm running the Nokian WRC "Cargo" tires at 195/75 R16 that have a weight capacity of over 2,200 pounds per tire at 70 PSI and I run them at close to 50 PSI. And on THIS van, I'm running the stock suspension.... for now..

A lot of variables to consider for a really true scientific measurement. I think I'm just going to have to measure the width of my smile when I'm done to really know the results.. Wink
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BetaVan
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PostPosted: Fri Nov 30, 2012 4:03 pm    Post subject: Reply with quote

Yeah, I've been following this post, and I do have an iPhone, so I guess that's what I'll use to measure things. Same road, same speed, Got it. I've got the Hydroedges, and I think they're a pretty quiet ride. It's going to be a few months before any of this happens, as the new panels won't ship for 3 weeks, and I've got to find the time over a few weekends to get all this done. But...

Gambari-masu!
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denwood
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PostPosted: Sat Dec 01, 2012 9:40 pm    Post subject: Reply with quote

I did the testing at 60 and 100 km/h and did each speed test twice, on the same road surface each time. The road was flat as possible so that we were neither coasting, nor climbing.

Benjamin, testing with material over your ears does make some sense. A gent back a few pages posted about a neoprene half inch sheet material he was using . Cold weather windsurfing, I have worn on many occasions a neoprene hood which has a dramatic effect on noise... so one might predict good results there. Based on what I've seen so far, technical wonder materials tend to be more marketing hype than effective.

I suspect panel dampening with spray on rocker guard and covering with carpet having integrated foam underlay would rival products costing many times more. We'll likely never see this test unless someone posts their sound profile with a van treated this way.
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PostPosted: Sat Dec 01, 2012 9:58 pm    Post subject: Reply with quote

The $70 price on that app is keeping me from contributing to any testing. Are there any lower cost options for good enough performance out there?
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