AKUSTIČKI METAMATERIJALI: PREGLED VIBRACIONIH KARAKTERISTIKA

In the paper the theoretical consideration of the acoustic metamaterials is given. Metamaterials, which are usually composite, are artificial materials whose properties differ from those observed in nature or in the constituent materials. Metamaterials which are suitable for acoustic wave absorption are presented. Acoustic absorber is a beam made of solid material connected with spring-mass subunits. The purpose of the subunits is to give a band gap where some frequencies of acoustic wave are stopped. Mathematical models for various types of connection of subunits in the metamaterial and absorber are discussed. Based on the analogy between electromagnetic and acoustic waves the concept of negative effective mass is introduced as a basic principle for modeling. Acoustic metamaterial beams based on one, two or multi-frequency vibration absorbers are discussed. Depending on connection of absorbers in the beam, the structure may absorb wave in one-direction (for example the longitudinal one) or waves in two directions (transversal and longitudinal). In the paper an overview of mathematical models and suggestions for further investigation are given.