ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

5aPAa1. A numerical approach of the transmission of a polyurethane foam sphere in an impulse regime.

Abdelkader Sfaoui

Laboratoire d'Acoustique, U.F.R. de Physique, P5, Villeneuve d'Ascq 59655, France

Among the phenomena envolved in the propagation of an acoustic wave in a diphasic medium such as a polyurethane foam, there is the air/structure interaction. According to the Biot theory the latter is characterized by two parameters: (rho)[inf a] the inertial coupling and b the resistivity of the fluid flow. When the material porosity, the Young's modulus, and the Poisson's ratio are determined [G. Deprez, J. Phys. Suppl. C2, 43--52 (1990) and A. Sfaoui, J. Acoust. Soc. Am. 97, 1046--1052 (1995)], it is sufficient to adjust these parameters to describe the acoustic propagation. In this aim, an experimental technique has been elaborated. It consists in studying the transmission of a broadband impulse by a foam sphere. The transmission coefficient is obtained after time filtering and fast Fourier transform calculation of two signals: the incident signal and the transmitted signal at the center of the sphere. By selecting the curve to fit the Young's modulus data [A. Sfaoui, J. Acoust. Soc. Am. 97, 1046--1052 (1995)] by means of a regression program, the transmission coefficient is numerically analyzed in the range of 0--20 kHz. It follows that the transmitted signal is the superimposition of the Biot fast and slow waves.