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Because of the recent influx of people wanting to save money by purchasing roofing products, I decided to write a short article as to why these products are not a valid option.

Disclaimer: The views and opinions expressed herein are those of the author and do not necessarily reflect those of Second Skin Audio or this website.

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The main three.

When it comes to controlling and eliminating vibrations there are typically three categories of products to choose from. Mass loaders, CLDs and FLDs.

Mass loaders are exactly what they sound like, they add mass to lower the resonance frequency of the panel.

Mass loading was a popular technique in years past, but mass loading is extremely ineffective and is considered old technology. Why? To be effective, mass loading requires approximately four times the weight of the panel to be added to reduce the panels resonance just one octave. This in not an efficient way to control vibrations, not to mention the negative impact it'll have on your gas mileage.

Next up you have CLDs (constrained layer dampers). CLDs work by converting the vibrational energy into low level negligible heat. Because of their efficiency at controlling vibrations, these products are typically thinner and lighter then traditional mass loaders while performing two or three times as well. Thinner, lighter, and less product needed to achieve greater results.

And finally you have FLDs (free-layer dampers), or extensional dampers. These type of products include most liquid vibration products and a few self sticking mat products. The way they work is that vibrational energy is dissipated as a result of extension and compression of the damping material, vs. a cld where the energy is lost through shear deformation of the material.

In most cases CLDs have the upper hand over FLDs because of their ability to maintain a higher loss factor across a wider range of frequencies, temperatures, and thicknesses of the substrate. Basically they are more efficient at controlling vibrations. This is especially true when applications require a light weight solution. For instance on a substrate of say 1/8", a cld mat of only 1/16" may be required to control the vibrations. The FLD on the other hand may require three or four times the thickness, so 3/16 to 1/4", to achieve the same loss factor.

Why roofing materials aren't a suitable product for use in vibration control.

People looking for a cheaper alternative to proper sound deadening seem to flock towards the roofing department at their home improvement stores.

Products that are typically found and used are Peel & Seal and other similarly produced roofing membranes. Often these look and feel similar, if not the same, as actual vibration control products so it becomes an obvious choice. Heck there has even been several companies that went as far as rebadging these roofing products as automotive sound deadening and sell them at a premium. Go capitalism! ;)

The reason these roofing products are not an effective or efficient alternative are many. Most roofing products are made from asphalt or a combination of asphalt, bitumen, petroleum distillates, and/or low grade rubber. These in most any combination equate to a low grade adhesive. Because of this, these products are intended for use on low sloping roofs, typically not exceeding 30°, as their their adhesive is the limiting factor. If you were to apply such product to a vertical surface, such as a car door, failure can be imminent.

Another reason these roofing products are not ideal is the fact that they lack a thick enough constraining layer (foil) to do any good. Without this constraining layer the product can't withstand the shear strain of panel flex and the conversion of the vibrational energy into low level heat is lost.

Even as inefficient as mass loading is, these products wouldn't even cut the mustard as a mass loader because they are just too light weight (averaging about .30 pounds per sq. ft.).

At the end of the day, it's your vehicle and your money. Take the info presented here in this article and make an informed decision.

Later,

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