Abstract
In this paper, we propose a topology optimisation method of sound-absorbing material in two-dimensional acoustics. The sound-absorbing material is modelled with a viscoelastic material, i.e., sound absorption is expressed by the attenuation of the elastic wave (which is excited by the sound wave) due to the viscosity of the viscoelastic material. When dealing with such a model, it is necessary to consider a acoustic-elastic coupled wave problem. Since the problem is categorised in a wave problem in an unbounded domain, the finite element method which is typically utilised in the community of topology optimisation is not the best choice for such a problem, and the boundary element method is employed in this study. In this paper, the optimum design problem of the sound-absorbing material is formulated as to maximise the energy flux on the surface of the sound absorber. After rigorously deriving the topological derivative for the energy flux, we show an example of topology optimisation of a sound-absorbing material. We show that the obtained optimal design has better performance than other con- figurations of equivalent volume with the optimal one, from which we confirm the effectiveness of the proposed method.
