Constrained Layer Damping
SDS polymers are designed to damp resonance & vibration....
the result of exciting a natural frequency of a system (striking a tuning fork, for example). In automotive applications, energy is typically input continually to produce a forced vibration. Without some way of dissipating the energy of the interaction, noise and vibration will be continually generated.
That's where Sound Dead Steel comes in. Its viscoelastic properties absorb noise-producing energy by converting shear strain to negligible heat. The higher the strain, which is transferred to the polymer, the higher the energy dissipation.
Shear strain is generated by sandwiching a thin layer of viscoelastic polymer between a vibrating surface and a stiff constraining layer of metal. This holds one surface of the polymer in check while the other extends and compresses.
- Unconstrained layer damping where a layer of bitumastic (or similar) high damping material is stuck to the surface
- Constrained layer damping where a laminate is constructed
The following link from a government web site gives further information on Constrained Layer Damping (CLD) and other noise issues