Abstract: The harmonic vibration produced by the gear meshing in the helicopter’s main reducer is one of the main sources of noise in the helicopter cabin. Designing vibration-isolating gearbox struts to suppress vibration transmission to the airframe can effectively reduce cabin noise. The piezoelectric stack actuators periodic strut （PSAPS）， composed of periodically arranged piezoelectric stacks and metallic materials， demonstrates ‘mechanical filtering’ characteristics within specific frequency bands， serving as a passive vibration control method. By adjusting the driving voltage of piezoelectric stacks in PSAPS to achieve variable stiffness characteristics， active vibration control is enabled. In order to study the electromechanical coupling relationship between active vibration control and passive vibration control of PSAPSs， a specialized PSAPS configuration is developed to address helicopter gear meshing noise suppression， and the electromechanical coupling dynamic model of PSAPSs with the form of transfer matrix is established for the mechanical filtering characteristics of periodic structure and elastic wave propagation in piezoelectric stack. In frequency domain， the force and velocity at both ends of the PSAPSs， the driving voltage and current， the geometrical parameters of the strut and the material parameters are coupled in this model. In this paper， the maximum attenuation rate of the PSAPS can be obtained under the limitation of the maximum driving voltage and current of the piezoelectric stack by using this model. The influence of rubber damping loss factor， excitation force， and cell number in PSAPS on the required driving voltage and current for active control is analyzed in this article.