Sound Insulation Analysis for High Performance Double Walls for Automobile included Thin-Film Cells by Filling Gas

Abstract

We report effects of acoustic transmission loss of double-walled structure including thin-film cells by filling gasses. Our past experiment and computation showed that this double wall structure with filled air has higher sound insulation performance than the hollow double wall. This was because of diffraction originated from high inplane acoustic resistance of thin-film cells. Sound transmission loss of the double wall structures with different filling gasses (CO2 and He) were calculated by numerical analysis using finite element method (FEM) and transfer matrix method (TMM). Influences of low sound speed for CO2, and high sound speed for He were clarified on sound insulation properties when these gasses were filled in the thin-film cells in consideration of diffraction and total reflection.