Viscoelastic materials like Sorbothane convert vibration to heat ONLY if they are constrained. That’s why they call it contained layer damping. Sometimes there is a thin layer of aluminum On top of the viscoelastic material that constrains it. The vibration in the one direction, e.g., vertical direction, produces shear forces in the orthogonal (e.g., horizontal) direction in the soft constrained layer. So it would not actually make sense to attach Sorbothane to anything without constraining it, since the shear forces are due to the fact that the Sorbothane is being constrained. It does make some sense that Sorbothane used as footers (or as insoles of running shoes) since the component or speaker or person’s mass will act as the constraining mechanism. I gave up on Sorbothane myself a long time ago. As I opined recently there are much better materials to use as the constrained layer. But more power to anyone who gets good results with it.