Sound wave transmission reduction through a plate using piezoelectric synchronized switch damping technique

Wave control and development of anechoic systems in air are of major interest to improve acoustic comfort. Currently, passive control techniques, which consist in using absorbing materials are effective at high frequency, but the principal limitation of this approach is mass and volume, particularly in the low-frequency range. Active control techniques (like the use of antinoise, which uses interference of sound waves) have been successfully applied to reduce the noise level, but their main drawback is the complexity of the global system and global power requirements. Another approach is to reduce the noise transmission by a proper control of transmitting structure oscillations. The aim of this study is to develop a technique of noise reduction by using piezoelectric elements. The device considered is a large clamped plate, equipped with piezoelements. Sound transmission through this plate is strongly related to the various resonances. Vibration damping devices implemented on this plate results in the reduction of the plate resonances and therefore of the correlated transmitted sound. The synchronized switch damping technique (SSD) is implemented. In this semi-passive approach, the piezoelements are continuously switched from the open circuit state to a specific electric network synchronously with the strain. Owing to this switching mechanism, a phase shift appears between the strain induced by an incident acoustic wave and the resulting voltage, thus creating energy dissipation. As many techniques using piezoelements, in this non-linear process, damping performances directly depend on the electromechanical coupling coefficient of the system. An analytical model and a finite element model are proposed in this study to obtain optimal size and location of piezoelectric inserts. Using this design, an attenuation of 19 dB on the plate oscillations and 15 dB on the transmitted wave pressure can be obtained.