Acoustic cloaking design by means of topology optimization

Abstract

Acoustic cloaking is a term for describing structures capable of deviate sound waves around a particular object, so that the acoustic field behind this object is similar to the acoustic field produced without its presence. A practical example is to make soundproof internal walls in houses, or columns in concert halls, theaters and cinemas, avoiding the reflection of sound waves. However, the design of such structure is not trivial and it is necessary to develop a robust and systematic design method that can be used to design for different applications. The main purpose of this research project is to use the Topology Optimization Method together with waveguide concept in the design of acoustic cloaking structures, by means of two different analysis techniques. The first one is the Multiresolution Topology Optimization (MTOP), where the design variables are decoupled from the finite element mesh (FEM). Thus, it is possible to obtain a higher resolution without increasing the computational cost. The second approach is a new technique called Isogeometric Analysis (IA), which integrates the classical FEM with CAD tools, based on NURBS. One of the main merits of this technique is a complete integration of modeling, analysis and design optimization. Since the same CAD data is used for numerical analysis and design optimization, additional post-processing efforts for converting optimal results into CAD models are not necessary. This advantage is even greater when designing dynamic structures, because they are very sensitive to interpretations of the design variables in the post-processing step. The results obtained with these two methods are compared, in order to verify their efficiencies. The verification of the proposed methodology will be made by characterizing manufactured prototypes. The experimental characterization will be performed by using ultrasound techniques.