Free-free beams excited at the center are commonly used as the specimens of the measurement of damping performance of sheet materials. The antiresonances appearing in the driving point transfer function of the free-free beams are studied, and it is shown that resonance modes of a cantilever beam of a half length is observed at the antiresonances. The damping ratio estimated from the antiresonance trough is compared with the one evaluated from the resonance peak introducing a lumped parameter system. They coincide if the damping is assumed to be hysteretic, which agrees with the experimental results on a composite steel sheet with a viscoelasitc core layer.
