Low-frequency perfect sound absorption achieved by a modulus-near-zero metamaterial

Abstract

We have analytically proposed a mechanism for achieving a perfect absorber by a modulus-near-zero (MNZ) metamaterial with a properly decorated imaginary part, in which the perfect absorption (PA) is derived from the proved destructive interference. Based on the analysis, an ultrathin acoustic metamaterial supporting monopolar resonance at 157 Hz (with a wavelength about 28 times of the metamaterial thickness) has been devised to construct an absorber for low-frequency sound. The imaginary part of its effective modulus can be easily tuned by attentively controlling the dissipative loss to achieve PA. Moreover, we have also conducted the experimental measurement in impedance tube, and the result is of great consistency with that of analytical and simulated ones. Our work provides a feasible approach to realize PA (>99%) at low frequency with a deep-wavelength dimension which may promote acoustic metamaterials to practical engineering applications in noise control.

Magnetic and Tunable Sound Absorption Properties of an In-Situ Prepared Magnetorheological Foam

“…Consequently, active noise control materials have been developed to enhance noise reduction at low-frequency levels (20–200 Hz) [ 3 , 17 , 18 ]. Nevertheless, from the middle- to high-frequency range (from 200 Hz to 6 kHz), active noise control materials are difficult to implement due to the difference in the phenomenon of sound propagation [ 6 ].…”

SiC Nanowire Mesh in High-Porosity Silicon Foam for Enhanced Electromagnetic Wave Absorption

“…With the rapid development of wireless communication technologies, resolving electromagnetic interference is particularly important in communication, military, and civilian fields. − To solve this serious and ever-growing problem, researchers put great efforts into the investigation of electromagnetic (EM)-absorbing materials, especially in the broadband frequency range. − For an EM absorption material to be practical, a proper balance of low cost, wide absorption bandwidths, intense absorption, low density, and low thickness is necessary. − However, the performance of traditional absorption materials, such as high density, lack of function at high temperature, oxidation, and narrow reflection loss (RL), hinders their wide application as microwave absorbers. − Therefore, electromagnetic absorption materials with adjustable electromagnetic characteristics are becoming more and more favored by researchers. SiC materials, including SiC particles and SiCNWs, are well-known for being important wide band gap semiconductors. − They have been proven to be a candidate for EM absorption materials because of their low density, thermo-chemical stability, superior mechanical strength, and appropriate microwave absorption performance. − However, the impedance matching and conductivity of pure SiC particles are still relatively weak, impeding the widespread application of SiC EM absorbers .…”

A Helmholtz Resonator-Based Acoustic Metamaterial for Power Transformer Noise Control

“…A multi-coiled acoustic metamaterial was proposed which provided perfect absorption at 50 Hz while the structure thickness was about 13 mm, 1/527 the corresponding wavelength [14]. Based on the double channel Mie resonator, the critical coupling concept was utilised to reach perfect absorption at 157 Hz noise with thickness about 1/28 of the corresponding wavelength [15].…”