Theoretical Study of Sound Insulation Simulations (About Attaching Effect of Sound Absorbing Material and Consideration of Sound Insulation Performance by Height of Origami Core)

We have developed a new truss core panel by origami forming to get the higher aspect ratio than that by multi-stage press molding. Our object is to apply the new origami truss core to the train floor. Whether or not this goal can be achieved depends on whether this new origami truss core with a high aspect ratio has excellent sound insulation characteristics. Therefore, as a development of the analysis technology by FEM which accurately estimates the sound insulation characteristics, at first, the relation between the aspect ratio and the sound insulation performance is discussed in the flat plate with one core. So far, sound insulation simulations using FEM did not match with theory of the mass law. However, this can be achieved by setting the end of the transmitted side to be a nonreflective boundary. In this paper, to generalize this method, it is determined theoretically that the sound pressures from the FEM can be separated accurately into the sound pressures of the forward and backward waves from Helmholtz’s equation. Then, the sound insulation characteristics of a flat plate obtained using the proposed theoretical method and the conventional method are compared while assuming that the flat plate is a rigid body. In addition, the validity of the proposed method is confirmed by evaluating the effect of attaching a sound absorbing material to the plate. Furthermore, application of the proposed method to a flat plate with a truss core and an examination of whether a high aspect ratio is advantageous for sound insulation are also presented.