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Sound and Heat Shield Install

By: · August 17, 2009

Everybody appreciates a quiet car and that solid “thunk” you hear when the door slams shut. But there’s more to sound insulation than just personal comfort. High levels of noise can also interfere with your reaction time and driving ability. Also, with good insulation, not only are decibel levels lower, but temperatures are, too. Your air conditioner can operate more efficiently, reducing fuel consumption and the risk of radiator boil-over on a hot day. And your audio system should have better fidelity with extra cabin shielding. Quite often, it’s the stuff you cannot see that makes for a cool and quiet ride.

To see what’s involved in reducing sound and heat in a vehicle, we sought out some expert assistance from Tim Cox of Quiet Ride Solutions. Drawing on Cox’s advice and experience, we’ll address the noise aspect first. Note that sound can emanate from a least two different sources on a car: via a solid material (the frame and body panels) and through the air (such as from the exhaust pipes, and somewhat surprisingly, the air intake as well).
Lowering airborne noise from under the hood might not be possible, but one option for an enclosed car (coupe or sedan) is to check the rubber stripping on the windows. If you spot any big cracks or missing chunks, install new rubber. If the rubber looks dry but is otherwise intact, apply some Vaseline to make it more compliant for a better seal. In addition, inspect the floorboard and firewall for any unnecessary openings (which also might help with an open-top car). Those can be filled with spray-on foam (the type typically used for filling holes and cracks in home-remodeling projects).

As for minimizing vibration-borne noise, the basic approach is similar to placing your hand on the skin of a drum. Flat areas of your vehicle’s sheetmetal produce the most sound, so those need the most attention, but the entire cabin area should be insulated wherever possible. Installing Dynamat, a material composed of rubber and asphalt, is the rough equivalent of placing your hand on the drumming motion of your interior body panels. Quiet Ride Solutions starts an insulation project by laying down intermittent strips of this self-adhesive material.

Why not use just one big sheet? Keeping the cost down is one reason, and Cox says those individual strips work just as well. Why so? Imagine dropping a stone on the surface of the water, which forms ripples. Those waves of water provide a visual analogy to sound waves, and the Dynamat strips act as breakwaters to attenuate the motion. In addition, from an installation standpoint, laying down small strips is easier in tight corners or other hard-to-read areas.

Next goes on a layer of Quality Heat Shield, dense padding bonded to a reinforced layer of aluminum foil. It’s important that the foil be placed on top (instead of against the body panels) for several reasons. It not only serves as a skin to protect the padding, but also creates an air pocket, similar to a double-pane thermal window. It’s that layer of air that provides the insulation (sound travels more easily through solids).

As just one example, Cox recalls a hot-rodded ’64 Chevelle he insulated. Prior to adding the materials, at 60 mph the sound level was 100 db (equivalent to that of an unbridled jackhammer, he says), but afterward it dropped to 80 db. Ditto for the levels at idle (80 and 60 db, before and after). That’s a huge difference, especially when you consider that decibels are measured on a logarithmic scale, so this decrease represents approximately 50 percent reduction in sound!

As for reducing temperature, the foil also helps to reflect back heat emanating from the engine and exhaust system. This material acts a fire retardant, and reflects back 97 percent of infrared energy, Quiet Ride claims, resulting in a temperature drop of as much as 30 degrees. As already noted, this reduction can benefit both the passengers and the engine.

It’s fairly easy to put in the materials, and Quiet Ride offers a wide range of pre-cut kits for cars, trucks, RVs and other projects. A universal package that you can custom fit is available as well. It’s important to make sure the materials form a consistent barrier or envelope that’s sealed with foil tape at the seams, and is glued down securely. That ensures the insulation will be the most effective at blocking out both heat and noise, keeping your ride both cool and quiet.

Quiet Ride Solutions, 6507 Pacific Avenue, Ste. 334, Stockton, CA 95207, (209) 942-4777, www.quietride.com


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