An efficient numerical approach to evaluate the sound insulation of acoustic metasurface

Aiming to design building façade with both natural ventilation and noise insulation performance, we propose an acoustic metasurface (AMS) by scaling up structured unit cells in a planar array. Each unit cell is in the shape of a short acoustic duct lined with periodic sub-chamber scatters. Acoustic stop-band exists in the periodic structure mainly due to the accumulated scatter resonance effect. An efficient numerical approach to evaluate the sound insulation performance of the proposed AMS is presented. The standard sound reduction index (SRI) is determined from the averaged sound pressure level (SPL) difference between a diffuse source room and a receiving room. The coupling between the AMS with the acoustic fields is formulated using a sub-structuring approach, and the unit cells are treated as a cluster of acoustic elements, modelled by finite element method. Modal based formulations are applied to the source and receiving rooms to characterize the acoustic excitation and the coupling effect, enabling an efficient calculation in the interested frequency range. The predicted SRI suggests it is possible to achieve high sound attenuation using the proposed metasurface, while maintaining the ability to ventilate naturally.