This proposal addresses acoustic impedance dynamics in porous material. It continues work initiated on an earlier project which investigated the properties of flexible porous frames consisting of very long, very fine, man made fibers. In this project, the effort is broadened to include a wider variety of porous materials, and a wide range of sound intensity levels. Work includes studies both of bulk properties and surface properties. The research falls under three disciplinary headings including (1) a comprehensive study of consolidated porous frame dynamics using a new apparatus of special design, (2) further study of interactions between frame motion and fluid motion in the pores at high intensity levels, and (3) developing a better theoretical model for the frame that can account for a variety of phenomena including internal resonances. The ultimate objective is to improve the understanding of the bulk properties of porous materials in air in order to improve the design of porous materials and configurations for specific purposes such as noise control.
