Every material has a set of resonant frequencies (mode spectrum). I believe you may be referring to the boundary conditions that apply to the problem and this is why I qualified my comment with the phrase "All other things being equal, . . . ." The example of a partially buried telephone pole shows how boundary conditions affect resonance - one end of the pole is clamped, which shortens the effective length of the pole and raises the resonant frequency.
Layers of adhesive or semi-adhesive polymers like Sorbothane also have resonant behavior; the natural frequency depends on the size and shape of the layer. The product web site has data and a nice downloadable calculator to compute resonant frequencies for various applications. On looking into this, I was interested to learn that it's pretty difficult to get the material's resonant frequency much below 5 Hz in any real-world application, especially for thin layers covering large areas.
I'd also like to point out that the Minus-k products contain no servos; they are completely passive. The principle behind these products is to use a coupled spring-flexure system in which some of the springs are near their buckling points. This can create a negative-stiffness situation, hence "minus-k."
Layers of adhesive or semi-adhesive polymers like Sorbothane also have resonant behavior; the natural frequency depends on the size and shape of the layer. The product web site has data and a nice downloadable calculator to compute resonant frequencies for various applications. On looking into this, I was interested to learn that it's pretty difficult to get the material's resonant frequency much below 5 Hz in any real-world application, especially for thin layers covering large areas.
I'd also like to point out that the Minus-k products contain no servos; they are completely passive. The principle behind these products is to use a coupled spring-flexure system in which some of the springs are near their buckling points. This can create a negative-stiffness situation, hence "minus-k."