ResoNix Sound Deadening Materials

What is a Constrained Layer Damper Sound Deadener? How does it work?

       Constrained Layer Damper sound deadening material, such as our ResoNix CLD Squares, ResoNix Heavy Duty CLD Squares, and ResoNix Lite CLD Rectangles, which many technical hobbyists will refer to as “CLD,” and the general hobbyists and many ill-informed installers and salesmen refer to as “sound deadener,” is the most common product used to sound treat a vehicle. A CLD features two layers; a visco-elastic (fluid to a degree yet stretchy/snappy like elastic) butyl rubber layer and an aluminum constraining layer on top. Typical CLD’s use a backing paper and are peel-and-stick for their application. 

       How a Constrained Layer Damper sound deadening material works is for the most part, pretty simple. When the panel it is adhered to bends and flexes, and subsequently, so does the CLD. The aluminum constraining layer provides a stiff reference across the top surface of the visco-elastic butyl. The differences between the panel the CLD is adhered to and the top aluminum constraining layer causes the butyl to stretch, resist, and want to snap back into position. The shear forces generated by the viscoelastic butyl is what “Constrains” the panel to prevent flexing. This process converts the mechanical energy of the panel into minuscule amounts of heat. This conversation of energy is the reduction of resonance that we are looking for.

       The stiffer the aluminum constraining layer, the more of a “hold” it has on the butyl. The better the butyl formula, the better it constrains the panel against the aluminum constraining layer. The goal when installing this product onto a panel is it will ideally go from sounding like a hollow drum when knocking on it to sounding something like a wooden table top.

       Again, the point of a CLD is to lower the resonance of the panel or surface it is adhered to. It does this by using the natural shear resistance of the visco-elastic butyl stretching and wanting to snap back into place. Note how I said it “lowers resonance”, not “lowers the panels resonant frequency”. They are two different things, and a proper Constrained Layer Damper works by damping the resonance, not by lowering its resonance frequency, although the latter is usually a side effect of the added mass of the CLD on the panel.