Dynamic Absorber has different amplitude-rate on the anti-resonance frequency by damping coefficients. A semi-active control was proposed, which switched the damping coefficient by frequency elements of the vibration structure's displacement. Band pass filter (BPF) was introduced to divide the frequency band on whether the amplitude-rate was smaller or not. However, there are another possibility to divide the frequency band by BPF, acceleration of earthquake, displacement of earthquake, structure's velocity and so on. In this paper, the effective switching index is considered by comparing with those candidates and experiments.
