Dual-frequency anti-nonlinear sound-absorbing metasurface via multilayer nested microslit resonators

Abstract

We propose a dual-frequency anti-nonlinear sound-absorbing metasurface (DASM) based on multilayer nested microslit resonators. Under the assumption of a linear system, the theoretical acoustic impedance of the DASM is derived by the transfer matrix method. Furthermore, the influence of structural parameters on sound absorption is also explored. The numerical and experimental results show that the proposed DASM can achieve quasi-perfect sound absorption at two low frequencies corresponding to the first two orders of the acoustic cavity mode frequencies of the structural unit, and enjoys strong anti-nonlinear performance and robustness to incident angles.

A parameter optimization method of multi-layer nested slit resonator for the converter transformer noise in high voltage direct current converter station

“…The transmission matrix of sound pressure and volume velocity of the incident sound from the left side (pin,i and uin,i) of the i th air channel to the right side (pout,i and uout,i) are as follow, 13 where, lt,i is the equivalent propagation distance of sound in the i th air passageway, keff2,i and Zeff2,i are the equivalent wave number and equivalent impedance of i th air passageway. Since the air passageway has a rectangular cross section of width w and height H, the equivalent wave number keff2,i and equivalent impedance Zeff2,i can be calculated by analogy with the connecting slit.…”

“…According to the conclusion of the parametric analysis in the previous study, 13 the length and width of connecting slits and the width of the nested air passageways are taken as the optimization parameters (where H is 20 mm and L is 60 mm), and the optimization model is established with the objective of maximizing the sound absorption coefficient at the target frequencies, as shown below,…”

“…Liu et al 12 proposed a dual-band absorber with the series connection of HRs and then constructed a broadband absorber that achieved near-perfect continuous absorption within 380 Hz–3600 Hz. The aforementioned literature only utilizes the first-order acoustic cavity modes of the structures, while the multilayer nested slit resonant previously proposed by the authors utilized the first-two orders of acoustic cavity modes of the structure to achieve dual-frequency quasi-perfect acoustic absorption, 13 showing a good application prospect. However, the two frequencies affect each other, developing an efficient design approach to the structural parameters according to the target frequencies is a worthy research topic.…”

Study on the acoustic performance of bending metasurface with ultra-thin broadband quasi-perfect sound absorption

“…Therefore, the emergence of acoustic metamaterials with small size control large wavelengths brings new directions for low frequency broadband noise control [7][8][9][10]. In 2000, Liu [11] first proposed local resonant acoustic metamaterials and then a large number of acoustic metamaterials with negative mass density, negative bulk modulus and dual negative characteristics have studied [12][13][14][15]. These acoustic metamaterial have a subwavelength characteristic in thickness, which can achieve perfect sound absorption at low frequencies.…”