周期構造を利用した機能性モード形の設計

抄録

Design space of vehicle acoustic performance is restricted by strong demand for weight reduction of a car body. This paper focuses our effort on the improvement of vehicle interior acoustic performance with the least increase in weight, by adding periodic structures to the panels. It is generally known that a sound pressure level at an evaluation point is dominated by the correlation between structural panel mode shapes and acoustic cavity mode shapes. As structural vibration modes are a superimposition of waves, the functional mode shapes, which has a function to reduce interior noise, may be designed by passive wave control using periodic structures. In this paper, a part of a panel is structurally modified with periodic structures to obtain functional mode shapes. By the periodic structures, the waves in a specific frequency band cannot propagate in the modified part of the panel. This enables us to design intended functional modes by virtually changing panel configuration to the simple panel, such as a rectangular panel, by filling up a part of the panel by the periodic structures. The advantage of this method is that the eigenpair of rectangular panels is readily designed by hand calculation.