Control of sound radiation from a plate into an acoustic cavity using active piezoelectric-damping composites

Sound radiation from a plate into an acoustic cavity is controlled using patches of active piezoelectric-damping composites (APDC). The APDC under consideration consists of piezoelectric fibers embedded across the thickness of a visco-elastic matrix in order to control the compressional damping characteristics of the composite. The effectiveness of the APDC treatments in attenuating the sound radiation from thin plates into cavities is demonstrated theoretically and experimentally. A finite element model (FEM) is developed in order to describe the dynamic interaction between the plate, the APDC patches and the acoustic cavity. The FEM is used to predict the dynamics of the plate/acoustic cavity and the sound pressure distribution for different control strategies. The predictions of the FEM are validated experimentally using a square aluminum plate whose sides are 29.8 cm long and have a thickness of 0.04 cm. The plate is mounted on a 29.8 cm x 29.8 cm x 75 cm cavity. The test plate is treated with a single APDC patch placed at the plate center. The patch is 5 cm x 5 cm x 0.03125 cm and is made of 15-25% lead zirconate titanate (PZT) fibers embedded in soft and hard polymeric resin matrices and provided with silver-epoxy electrodes. Vibration and sound pressure level attenuations of about 70% are obtained, at the plate/cavity first mode of vibration, with a maximum control voltage of 330 V using a derivative feedback controller. Such attenuations are attributed to the effectiveness of the APDC treatment in increasing the modal damping ratios by about a factor of four over those of conventional passive constrained layer damping (PCLD) treatments. Comparisons between the theoretical predictions of the FEM and the experimental results indicate close agreement between theory and experiments. The obtained results suggest the potential of the APDC treatments in controlling the sound radiation from plates into acoustic cavities. Such potential can be exploited in many critical applications such as cabins of aircrafts and automobiles to ensure a quiet environment for the occupants.