Hapy Noises - Part 1

Today, I share my thinking around how to reduce the din when driving Hapy. He's a 50 year old bus. He runs a turbo-diesel engine. How quiet do we want to be? Or should I say how quietly do you want to spend? Or, maybe, how quiet do I really think this can get? I am actually taking this on, slowly, over the course of the winter and spring with hopes of a more comfortable drive experience when camping season really open up. For now, I will just put my think into words because what's a car person to do when s/he can't work on their cars? Thinks about them. Like so many posts, this got really long. So, I split this up. Today's post will cover controlling the resonation effect with constrained layered dampener material.

Before I begin, Hapy Groundhogs Day. Regardless of what the critter in PA does, it will always be 6 more weeks before the Spring Equinox. Here in the Pacific NW, it will rain until then. With expectations set, let's go.

Constrained Layered what?

Other places do a better job of explaining this. For our purposes, a Constrained Layered Dampener (CLD) reduces vibration by transferring that vibration into heat, which then dissipates. These materials have 3 basic components: the adhere layer, the butyl layer and a foil layer. The adhere layer is obvious: it is the super-sticky that gets the CLD to stick to the metal that vibrates. The foil layer is also sort of obvious: this is the top layer that you see when it's done. The butyl layer is the key: this is the science part that accepts the vibration from the adhere side and the vibration-resistance from the foil side. The butyl does the work of trying to get the vibration to stay put by equalizing between the two layers. The better the quality of the butyl layer, the more effective it will be per square inch. Again, there are better explanations out there, but that is a basic high-level summary.

Noico / FatMat / Hushmat / Kilmat

When I did the work on Oliver (1978 MGB), I used the Noico noise deadener stuff sold via Azn. I had read around the web that it was pretty good stuff, but when you are reading about what amateurs did on forums, it quickly becomes an echo chamber. Many forums dedicated to home-wrenching have posts that ask about one or more of the products listed above. Since most folks only ever use one on that one car, and aren't doing it professionally, the general consensus on Noico is "it's good". For the most part, the testing I have seen put all of these (Noico, FatMat, Hushmat, Kilmat, etc) in the same mediocre category. They sorta work, but you need a lot of it for it to get anything out of it.

Slamming Amazon side-bar.... Azn is excellent at hyping a mediocre product; this happened with Noico. We, as consumers, are led to believe that the marketplace will decide, and if people give positive reviews of something, it's probably fairly good. This works for products or services with which we all are somewhat familiar. Want advice on a TV or a phone? The market will weed out the garbage eventually. The issue is created when someone buys an inferior product about which they know little in a product market about which they also know little. Their experience goes from sucky before it arrived to perceived slightly-less-sucky. So, they think the product is fantastic, because they think life got better. What they may not realize is that they really did not make their life that much better, if at all, for the money they spent. They invested a small amount of money (like $2 per square foot for Noico) and a bunch of time, and when the noise in their car seemed reduced, they figured it was the product. Maybe it was. Maybe it was simply from removing the panels, cleaning a bunch and putting them back on. Most likely, the reduction was not as great as it could have been had they used a genuinely good product. The misperception is then influenced by the amplification of the echo chamber and the desire to not be taken advantage of, so a belief that the product was good is formed. And, the feedback loop continues.

In the convertible, I didn't know any better and, frankly, it doesn't really matter. It is a convertible running a carburetor and an aftermarket header; it will be loud when driving around. That's actually part of the fun: put your foot in it and it goes "waaah!". I put the Noico in the doors and now they have a nice "chunk" noise when they close. Same goes for the trunk. I think the overall din from the drive train is lessened because of the full-floor (both cabin and trunk) install I did plus the liquid rubber liner, the insulation and thick carpet. Exactly how much the Noico helped is unclear. For Hapy, I have way more noise control opportunity. It is not a convertible, and there may be 4 times as much steel panel to resonate-control. I had put something on some of the panels years ago (like the old brown bread, delivered in a roll, smelled bad), so it is not completely bare. I don't think that stuff was terribly effective, but it was what was available 15 years ago.

DynaMat, Second Skin and ResoNix

For learning about quality, viable noise control, I hit the car audio forums. I figured that if they were using something that helped them win car stereo competitions, it would probably do a good enough job lowering the noise in Hapy from incredible racket to tolerable. At least, they would know which lower-price options were actually worth using. In my research, I also engaged with Second Skin audio, and will use their stuff above the CLD (constrained layered dampener), which I will detail in another post. For vibration noise control, though, I am using ResoNix CLD. This stuff is super expensive, compared to Noico, but only a few cents per square foot more than the Second Skin stuff. DynaMat usually appears at the bottom of this higher-quality group, by the way. Based on the testing evidence on the ResoNix site and in the audio forums, the ResoNix stuff is really next-level. In the end, I will need to apply far less material than Noico, which means less work and less weight, while enjoying better vibration noise containment.

Install How

Install for any of these products is simple: clean the area to practically food-grade clean, measure and cut to fit with scissors, pull the backing paper and press it in place. Then, with an installation roller, roll around on the foil to get any air bubbles out and to ensure a quality adhere. Don't damage the foil; I can't emphasize that enough. Also, if the surface isn't clean, the product will not adhere as well, defeating the purpose. The amount of CLD you use is directly related to the product you are using, though the larger the uncut piece of CLD you use the better it will work. Meaning, if you use a bunch of small pieces over a section of metal, it will be far less effective as compared to one single piece. The strength of the CLD effectiveness comes from the foil topper preventing the panel from moving. This forces the vibration energy to change shape into heat energy as the Butyl tries to adhere to the metal yet retain it's shape as defined by the foil topper. If the sheets are tiny or if there are tears in it, there is less constraining, so more room for the metal to move, and much less of the vibration is converted to heat energy.

I found 2 different types of rollers on the market. The one in the image below has a completely smooth roller for foil-contact. While it may lose traction on super-smooth foil, it will probably not accidentally tear the foil. I say "may" and "probably" because I bought the other kind that has ridges running across the roller surface. That kind of roller can tear the foil, but it definitely does not slip. Ask me how I know :) Buyer beware, and if you get the same kind I did, mind you don't get too zealous with it or you may apply splits into the foil.

Coverage

Something like Noico will require nearly 100% coverage to get anywhere near the same amount of dampening as 25% of something high end. Under-apply and the vibration noise may just lower in frequency, not the full resonance so the vibration does not actually get resolved. So, you will think it's better, but you just lowered the note. If you watch car shows on Speed/Velocity/MotorTrend, you will see that those guys cover 100% of the interior and trunk (though they never broadcast the application. No sparks = bored producers). If you have the money, and haven't a worry about weight, I imagine doing the entire car, covering every square inch like that, provides maximum vibration reduction. There are diminishing returns though. Some small areas hardly vibrate / amplify car noise at all because they are small or have multiple connection points and can be skipped. The key to maximizing your product application / minimizing cost is to focus on the large flat sections first. Whether material should be multi-layered is a frequent question. The common understanding, demonstrated with some testing, is that layering product is money and cost ineffective without much return. That doesn't stop folks from doing it. Your project, your choice. I would suggest what the high-end manufacturers say: if you are willing to buy multiple layers of less expensive stuff, why not buy the good stuff for the same price and far less work/weight?

When I apply CLD, I can't help but tap on the area with the roller handle before and after I apply it so I can hear the difference. Before, it sounds tinny, after, it has more bass. Is this a reflection of what the vibration effect will be? Oh, heck no; I just can't help doing it. It feels like you're doing something. The only real tell is after you're done and you go for a drive. With Hapy's diesel engine running, we will get a fairly good idea without actually getting out on the road. My hope is that after I have finished, driving Hapy will no longer feel like you're operating a diesel generator inside an old leaky steel shed during a wind storm.... like it does now.

Liquid Deadener

One last thing on deadening: there are liquids that deaden too. These fall under the Liquid Applied Sound Deadener (LASD) umbrella. Second Skin sells "Spectrum" (see here), but there are others, like LizardSkin, dBSkin and QuietCoat. Since these products target the same thing as the CLD does, I thought I would mention it here. Based on the studies and the science of the CLD, I am not convinced the liquid works as well. The product websites don't specifically say how effective they are in decibel reduction terms, but for hard to reach spots where getting a sheet of CLD is not practical -OR- for exterior areas like the under body or wheel wells, this may be better than nothing. Or, this could just be fancy marketing of what amounts to liquid asphalt painted onto your car, reducing noise like a cheaper CLD does simply by being a thick coating. For the coverage, the liquids are much more expensive per square too. Still, I am going to try Lizard Skin in the spots I can't reasonably get to with CLD (wheel wells) because I want to try it out. I may hit between the belly pans and the floor, since I can't get in there with anything other than an undercoating nozzle. If it does little for the noise, but it helps retard the rust, it would still be worth doing, IMHO.

Next time, I get into different materials for subsequent layers, as well as some decibel readings for a "before" image to compare against after I add some of this stuff. Thanks, as always, for following along-