Structural–acoustic optimum design of shell structures in open/closed space based on a free-form optimization method

Noise reduction by structural geometry optimization has attracted much attention among designers. In the present work, we propose a free-form optimization method for the structural–acoustic design optimization of shell structures to reduce the noise of a targeted frequency or frequency range in an open or closed space. The objective of the design optimization is to minimize the average structural vibration-induced sound pressure at the evaluation points in the acoustic field under a volume constraint. For the shape design optimization, we carry out structural–acoustic coupling analysis and adjoint analysis to calculate the shape gradient functions. Then, we use the shape gradient functions in velocity analysis to update the shape of shell structures. We repeat this process until convergence is confirmed to obtain the optimum shape of the shell structures in a structural–acoustic coupling system. The numerical results for the considered examples showed that the proposed design optimization process can significantly reduce the noise in both open and closed spaces.