Three simple 1-DOF mass-spring oscillators have natural frequencies (from left to right) of f1=1.6, f2=1.0, f3=0.63. At time t=0 the base starts moving with sinusoidal displacement s(t) = S0sin(t) where the driving frequency is f=1.001. The damping rate for all three oscillators is 0.1 so that the initial transient motion decays and a steady-state is obtained.
The animation at left shows the motion of the base and the resulting motion of all three oscillators together. The masses are color coded to match the frequencies above and the plots below. The horizontal lines indicate the maximum displacement of the base.