振動増幅による圧電吸音板の吸音特性の広帯域化

Abstract

This paper describes an improvement method of the sound absorption effect for the piezoelectric sound absorbing panel. The piezoelectric sound absorbing panel has a high sound absorption coefficient at around the natural frequency of the fundamental vibration mode of the panel. However, the effective bandwidth is narrow because the sound absorption coefficient depends on the amplitude of the vibration of the panel. To solve this problem, we propose a resonance amplification method for the panel. The resonance of the panel is amplified by adding force to the panel using another piezoelectric elements in this method. The added force must be proportional to the sound pressure at the left-hand surface of the panel. Because this method requires a large value of an equivalent stiffness ratio of the piezoelectric element that enhances the equivalent stiffness ratio is also used in this method. The governing equations were theoretically derived, and the optimum values of the LR circuit were formulated. The effectiveness of this method was verified through simulations and experiments.