Bioinspired periodic panels optimized for acoustic insulation

The design of structures that can yield efficient sound insulation performance is a recurring topic in the acoustic engineering field. Special attention is given to panels, which can be designed using several approaches to achieve considerable sound attenuation. In a previous work, we have presented the concept of thickness-varying periodic plates with optimised profiles to inhibit flexural wave energy propagation. In this work, motivated by biological structures that present multiple locally-resonant elements able to cause acoustic cloaking, we extend our shape optimisation approach to design panels that achieve improved acoustic insulation performance using either thickness-varying profiles or locally-resonant attachments. The optimisation is performed using numerical models that combine the Kirchhoff plate theory and the plane wave expansion method. Our results indicate that panels based on locally resonant mechanisms have the advantage of being robust against variation in the incidence angle of acoustic excitation and, therefore, are preferred for single-leaf applications.