The Influence of the Percolation Transition on the Electric Conductive and Optical Properties of Ultrathin Metallic Films

Physics of the Solid State - The results of the study of the peculiarities of changes in the electrophysical, optical, and plasmonic properties of ultrathin metallic films during the percolation...     

Laboratory Experimental Facility for Studying Metamaterial Sound-absorbing Duct Linings with Grazing Sound Propagation and How the Type of Source Influences their Efficiency

Acoustical Physics - The article describes an experimental facility for studying and testing sound-absorbing linings made of acoustic metamaterials designed to reduce the noise generated by a...     

Theoretical Model and Experimental Study of an Efficient Resonance-Type Sound Absorber for the Middle Frequency Region

A model of an efficient sound absorber with an internal structure consisting of several compact resonators with different parameters is considered. Maximum efficiency is achieved by matching the impedance characteristics of the sound absorber and the acoustic environment. Experimental results on determining the maximum absorption coefficient in the 100–1000 Hz frequency range for test samples made with 3D printing technology are reported.     

An Optimum Absorber of Vibrational Energy

Analytical expressions for the impedance characteristics inherent to an optimum absorber are derived. The results of the laboratory experiment in which the simplest optimum absorber is constructed and investigated are presented, and the validity of the analytical relations obtained is confirmed.     

Energy approach to solving the noise reduction problem

A new approach to solving the problem of reducing the noise produced by vibrating elastic structures is proposed. It is based on minimizing the flow of acoustic energy between subsystems by means of local structural changes. The author describes the theoretical grounding of this approach and presents the results from experiments that prove its relatively high efficiency (12–15 dB). The approach is useful in cases that require noise reduction without increasing the mass of a structure.     

A discrete model of damped acoustic metamaterials

For damped acoustic metamaterials, a discrete model is proposed in the form of a periodic structure with cells of the simplest type. The effective parameters of the model are determined by criteria based on the equality of dispersion of waves. The general properties of the model are studied. An example of one negative type of metamaterials is presented. The model is useful for analyzing wave properties and creating metamaterials with given acoustic properties.