Eccentric Mass Designs of Membrane-Type Acoustic Metamaterials to Improve Acoustic Performance

Abstract

Membrane-type acoustic metamaterials (MAMs) are engineered to be both extremely compact and lightweight with periodic structure. These materials reveal dramatically better sound insulation especially at lower frequencies than the conventional systems of similar dimensions and weight. It promises for the applications of lightweight construction and vehicular cabin to insulate sound at a specific frequency range. In this experiment, MAMs with eccentric masses were designed, and these prototypes were used for investigating their acoustic performances for seeking the optimised distribution of eccentric masses that can drastically increase the frequency band of sound absorption, which occurs especially in the low frequency range. Through simulations, their acoustic performances were quantified and graphed, and their surface displacement diagrams and transmission loss graphs were generated and analysed. The results showed that the MAMs with optimised eccentric mass distribution are able to drastically widen the frequency band of sound absorption in the low-frequency range, with the effectiveness varying slightly for different designs.