Y. J. Kang
J. S. Bolton
1077 Ray W. Herrick Labs., School of Mech. Eng., Purdue Univ., W. Lafayette, IN 47907-1077
Although elastic porous materials such as foams are widely used for passive control of aircraft and automobile interior noise treatments, numerical models of these materials have only recently became available [Y. J. Kang and J. S. Bolton, J. Acoust. Soc. Am. (1995)]. In the work described here the procedures of optimal design were combined with elastic porous material finite elements to optimize the shape of the foam liners. Specially, the surface contour of the foam lining was adjusted to minimize the sound transmission through a foam-lined double panel structure system in a waveguide. This model is a simple representation of an aircraft fuselage segment. The foam finite element was based on a complete elastic porous material theory that accounts for the three wave types known to be significant in foams. The procedures for coupling the foam finite element with adjacent acoustical and structural elements will also be presented. In the example problems, a plane wave is assumed to impinge on the incident surface of the double panel structure. The shape and material parameters of the foam liners were used as design variables, and the performance measure was the frequency-averaged sound transmission loss in the frequency bands of interest, e.g., the speech interference range.