Sound absorbing system as an application of the active elasticity control technique

Active elasticity control has recently become a promising method used in acoustics to suppress the vibration of mechanical systems or to increase the noise transmission loss. The principle of this technique is based on the simultaneous utilization of both the direct and inverse piezoelectric effects, which is realized by connecting the piezoelectric sample to an external feed back circuit. The action of the feedback circuit results in an essential change of the vibrational response of the system, and a significant change of the resonant frequency in the mechanical system. This leads to the modification of the acoustic properties of the system. For that reason, this technique offers a very general approach to solve vibration and noise problems. To demonstrate this method, the design and theoretical analysis of an experimental realization of a sound absorbing system are presented. The system consists of a curved piezoelectric membrane and a passive sound absorber, which are attached to a rigid backing wall....