This paper describes the new method of acoustic resonance reduction using a plate, a piezoelectric element, and an LR circuit. The acoustic resonance generated in an enclosed space induces the resonance of the plate. Further, the resonance of the plate induces the electrical resonance between the inductance and capacitance in the piezoelectric element. The electrical resonance equivalently gives damping effect to the plate, and the vibration of the plate suppresses the acoustic resonance in the relatively broad frequency range. The governing equations were theoretically derived, and the optimum values of the plate and electrical system were approximately formulated on the basis of the two fixed points method. The formulations and effectiveness of the proposed method were verified through simulations and experiments.