Design of Passive Acoustic Wave Shaping Devices and Their Experimental Validation
We discuss a topology optimization based approach for designing passive acoustic wave shaping devices and demonstrate its application to; directional sound emission [1] sound focusing and wave splitting. Optimized devices, numerical and experimental results are presented and benchmarked against other designs proposed in the literature. We focus on design problems where the size of the device is on the order of the wavelength, a problematic region for traditional design methods, such as ray tracing. The acoustic optimization problem is formulated in the frequency domain and modeled by the Helmholtz equation. An exterior 2D model domain is used and an array of point sources is considered as sound emitters. The optimization goal is to identify a distribution of solid material in a design sub domain which produces a desired spatial sound field pattern across a frequency band of interest in a target sub domain. The objective is the integral of the deviation in pressure magnitude, between a prescribed sound field and the solution to the model problem for a given design realization over the target sub domain. Filtering is used for regularization and to allow for meaningful optimization for geometric robustness [2] The Globally Convergent Method of Moving Asymptotes is used to perform the optimization [3] References [1] Christiansen, R. E. and Efren Fernandez Grande, Design of passive directional acoustic devices using Topology Optimization from method to experimental validation. J. Acoust. Soc. Am. 140, p. 3862 3873, 2016. [2] Rasmus E. Christiansen and Boyan S. Lazarov and Jakob S. Jensen and Ole Sigmund, Creating geometrically robust designs for highly sensitive problems using topology optimization Acoustic Cavity Design. Struct Multidisc Optim 52, p. 737 754, 2015. [3] Svanberg Krister, A class of globally convergent optimization methods based on conservative convex seperable approximations. SIAM Journal of Optimization 12, p. 555 573, 2002. E mail: raelch@mek.dtu.dk Address: Nils Koppels Alle 404, DK 2800 Kgs. Lyngby, Denmark