SPICE simulation of a piezoelectric resonator with the air round-up. This circuit uses a model of the acoustic medium adapted to an electric transmission line. In analogy to the equivalent circuit of a transmission line, the model proposed represents the piezoelectric thickness vibrator by lumped elements, i.e., capacitor, inductor, and current-controlled current source. In order to unify electric and acoustic theory, an impedance type analogy is chosen where mechanical force is represented by voltage and particle velocity is represented by current. This configuration implements a Resonator with the Air round-up.