Cassandra A. Gentry
Chris R. Fuller
Vib. and Acoust. Lab., Dept. of Mech. Eng., Virginia Polytech. Inst. and State Univ., Blacksburg, VA 24061-0238
Acoustic foams possess inherent high-frequency sound absorbing capabilities for radiation and reflection control of structures. Comparatively, active noise control systems generally do not perform well at high frequencies due to the increasing complexity of the physical model and the necessary high speed digital signal processing. The ``smart foam'' concept and design originates from the combination of these two control strategies formulating a passive/active noise suppression device that can efficiently operate over a broad range of frequencies. In this research, the experimental device is comprised of a layer of piezoelectric material embedded in a partially reticulated polyeurethane foam. Depending on the specific application, the distributed actuator alters the surface impedance of the passive absorber such that an incident acoustic wave is totally reflected or absorbed. Error sensor configurations include microphones or piezoelectric sensors integrated directly into the noise suppression device creating a compact passive/active system. Experimental results are presented for piston radiation control. An analytical model of smart foam is described and simulations are presented to illustrate the potential of the device and the interaction between the passive and active components.