Ultrathin Ashoka Chakra like acoustic metastructure as a sound absorber

Absorption of undesirable sound is a fundamental issue with broad applications in a variety of situations, such as in a conference room, cinema hall, aircraft cabin noise, etc. A variety of sound absorbers, e.g., micro-slit, concrete walls, porous media, etc., are used for noise control but are required to have a thickness comparable to the working wavelength. Here, we report a novel ultrathin “Ashoka Chakra” like acoustic metastructure that can be utilized as a sound absorber. The developed acoustic metastructure demonstrates broad bandwidth and high absorption characteristics. Each unit cell contains 24 hollow spokes through which acoustic wavefront can move freely. Despite its simplicity, this approach provides tunability of the metastructure functionality such as operating frequency range by altering the structure dimensions. Finite element based simulations were carried out in order to optimize the metastructure’s dimensions to achieve maximum absorption. The efficacy of the metastructure is validated through excellent agreement between simulation and experimental measurements. Realization of the proposed acoustic metastructure can show promising applications in the field of sound absorption.