ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

2pPAb7. Modeling sound propagation in a high porosity fibrous material.

Christopher L. Morfey

Bradley P. Semeniuk

Maurice Petyt

Inst. of Sound and Vib. Res., Univ. of Southampton, Southampton SO17 1BJ, UK

Sound propagation in an air-filled, high porosity fibrous material involves the elastic response of the fiber skeleton as well as thermal and viscous effects at the fiber--fluid boundaries. A theoretical model of wave propagation in such a medium has been constructed based on the idea of an equivalent fluid, which occupies the entire space and whose properties approximate the locally averaged properties of the actual fluid. Once the elastic properties of the skeleton are known---e.g., from in vacuo experiments---the model yields phase speeds, attenuation rates, and complex characteristic impedances for both fast and slow waves in the composite medium. Typical results are presented for fiberglass blankets of the type used as thermal insulation in aircraft fuselages. [BRAIN project supported by the European Commission.]