Automotive Sound Dampening

Automotive Sound Dampening

Quieting the din, rattle and ruckus in your car's interior

One of the most satisfying achievements for any car or truck owner is the act of finding and silencing the rattles, squeaks, drones and clunks that seem to emanate from the auto around you. They permeate the entirety of your motoring experience. We have a simple trick for you, one that requires minimal time and is capable of not only killing those annoyances (and handing you a satisfying accomplishment), but also deadening road noise, exhaust drone and that general state of in-cabin buzz that can send a driver off the proverbial cliff. What we're talking about is the installation of sound-deadening dampening matting, and it's just one step beyond kindergarten-simple.

What You'll Need

This material is not rocket science, and can be bought at nearly every stereo supply store (automotive or home). Some brand names experiment with varying thicknesses, backing material, foil overlay (heat resistance), expensive composite materials and dampening matrixes (less weight and easier installation), but in the end most of what you're dealing with is a heavy vibration/resonation-stopping sticky mat. Many of the vendors on the market distributing self-adhesive sound dampening material use a tar or butyl-based heavy polymer material as the primary deadening substance, backed with a strong adhesive that keeps the malleable sections of cut material well attached to your interior's base metal surfaces. Total adhesion is key to proper sound cancellation, as much of what you're trying to lose is resonation. This heavy material essentially smothers that high-hertz movement, something like ringing a piece of crystal, then shoving it into a bowl of pudding.

Buying your matting is not complicated: go to a local sound shop; and don't be afraid to invest in a little extra square-footage. They'll likely have small, prepackaged kits in the showroom, for which they'll nick you a pretty penny. Ask for a manager or the shop chief and tell them you'd like to buy several installer-grade sheets, usually stacked up in the installation area in 3x5-foot sections. Installers buy this stuff in bulk. If you offer to take four or five sheets off their hands for the right price, who'd refuse? Just make sure your dollar-per-square-foot ticket is less than what it would have been to buy the sales-floor packages. As for what to use, there's not a lot of technology here. The tin-backed sheets go on more easily and offer some heat shielding, but can cost up to double the non-foil, standard butyl-based sheets. The old-fashioned heavy stuff works fine, in 99 percent of all applications, and costs less (if not a bit of a load to haul).

Tools you'll need for this action are limited: a decent roller, preferably with a rubber/soft plastic wheel; heavy scissors; a sharp knife (X-Acto or box cutters work well); a heat gun (hair dryers usually don't get hot enough or last long enough); the presence of Mother Nature's mother of all heaters, the sun. Prior to engaging the sticky side of your deadening material, degrease the uncovered interior metal and hard surfaces with a light alcohol-based cleaner, strong enough to remove slick stuff and factory-based installation mung, but not so potent it'll damage the surface to which you'll be sticking the sound mat. A pop-fastener puller will make removing factory interior panels a painless, scratch-free affair.

What You'll Do

It's possible that the hardest part of this project is the disassembly and reassembly of your interior in preparation for and following your work. Everything not bare body metal comes out, though in our case we left the factory's [paltry attempt at] sound dampening in place, pasting ours right over it. When using a high-quality dampening material, you're likely to find the adhesive backing more than effective enough to achieve this, sticking to just about anything that's been properly cleaned.

First things first, peel out your OEM interior. We did it to our 2002 Subaru Impreza WRX one compartment at a time. You can break an all-day sucker into a one-hour sundae, and get back to the project when you have the clock necessary. On our list was the easiest section-the trunk. It required us to remove all trunk accouterments and the rear seat backs, uninstalling as many parts as possible because everything that's out of the way leaves more uncovered metal and raw surfaces available for matting. The targeting strategy is not complicated: every dense, hard or stiff body panel that is capable of vibrating, rattling, resonating or shaking at a high rate benefits from an application of sound deadener. If you properly cover the core elements of your car's metal body, everything inside should be isolated from the sound-producing vibrations and thusly quieted.

Once the sheets of sound dampener have been heated in the driveway to a mushy, workable temperature (leave them there too long and they'll be too hot to touch), it's back to kindergarten. Cut and paste. Work with bigger sheets (initially avoiding small pieces; bigger pieces mean better vibration control), and try to avoid having a chunk of matting that bends around a sharp angle. Make those hard edges your cut-point. You'll hear various trains of thought from the "pros" about how and where to install sound sheeting, but the core importance is to cover as many hard metal surfaces as possible. The matting is easier to work with when in big sheets, too, so perhaps the where and how of installing the deadening material can as much be dictated by the facilitation of the use of these overlarge pieces as anything else.

The use of a heat gun (any hardware store, many electronics stores, most hobby stores) is essential for the tar/rubber sound dampening sheets. Heat the sun-warmed material after it's been laid into place to the point of super elasticity, not melting, but too hot to the touch. You want the sheets to change dimension and size to match all the nooks and crannies of the body panel, pliable and moldable without resistance. Roll the dampener into place heavily, not worrying excessively about minor splitting as long as the material is stretching into place easily while showing no tendency to return to its original dimension, and covering all metal contours. This is not difficult; it just involves a little patience and a forearm workout. Don't be unwilling to climb right into your trunk to make sure you've got the necessary leverage.

You'll notice the presence of many leftover chunks of matting after cutting the large pieces to shape. They're perfectly usable, though we may have gone overboard in seeing that none were wasted on our WRX. Two of our 3x5 sheets of installer-sourced industrial-grade sound dampening were used in this installation, so there were a good deal of little snippets available for filling the uncovered spots between larger portions. In the photos with this story, you'll notice several spots where the dampening material was pulling up-a perfect indication that we'd not heated it enough before rolling. Go back with your heat gun and wheel and do it again, thoroughly. One of the charming facets of this material's composition is that the dampener breaks down before the adhesive, so you can heat the sheet until it stays put and know it'll stick around.

It's not hard and, if you don't mind taking the interior apart, you can go to town with six or eight sheets of sound deadening material, quieting the vibration and noise that can otherwise befoul the acoustic loveliness of your motoring experience.

Automotive Sound Dampening
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