Optimisation and testing of dead-end pore structure for sub-wavelength sound absorption

The design of periodic structures as a strategy to overcome the sound absorption problems in the lower frequency range has been developed in the last years. The main difficulty with these designs is that they need exact and fixed dimensions to act in a certain frequency region, thus needing optimisation. In this work we used a differential evolution algorithm to optimise a design already available in literature. Two samples were optimised, 3D-printed and tested in an impedance tube. For the first sample a unit absorption coefficient was found in 562 Hz with a thickness of more than 13 times the wavelength. The second sample was optimised for 1000 Hz and the experimental results were compared to COMSOL simulations. Results show good agreement between theory, experiment and simulation, showing that the differential evolution approach can be useful when it comes to periodic structures for acoustic applications.​status: publishe