A new method to compute sound transmission loss by acoustic FEM

Abstract

In this paper, a new method to evaluate performance of sound insulating plates in closed medium is investigated by using acoustic finite element method (FEM) under such two conditions that plates are having free ends and that plates are simply supported. The proposed method is able to compute sound transmission loss by using sound pressures at the small numbers of properly selected nodes considering acoustical symmetry of modal shapes in the closed medium, which is equivalent to the theoretical transmission loss without using all nodes existing in the medium. By the proposed method, the computed transmission loss does not depend on sizes or shapes of the medium; it is the unique transmission loss of the sound insulating plate itself. As sound insulating plates, the following three models are constructed; a single plate, double-leaf plates and the high-rigid sandwich panel called “trusscore panel”. It is also shown that sandwich trusscore panel works effectively at low frequency range since it is sufficiently rigid and that computed sound transmission loss of the trusscore panel has tendency as observed on a single plate having the equivalent weight and stiffness to the trusscore panel. Trusscore panels can be applied widely in industrial fields in the future such as walls or floors in a car, train or building to reduce interior noise.