The studying results show that the classical elastic wave equation of spherical wave is only true for fixed amplitude phase and described only kinematic equation of phase velocity.

To deal with filter value calculation instability, people put forward and carry out lots of methods in practice such as self-adaptive filter, fixed amplitude filter and square root filter, etc.

For fixed damping and fixed excited frequency the motion of the beam under small amplitude of force is periodic, but becomes chaotic through period doubling bifurcation with increase of the force.