Enhanced Low-Frequency Sound Absorption of a Porous Layer Mosaicked with Perforated Resonator

Abstract

A composite structure composed of a porous-material layer mosaicked with a perforated resonator is proposed to improve the low-frequency sound absorption of the porous layer. This structure is investigated in the form of a porous-material matrix (PM) and a perforated resonator (PR), and the PR is a thin perforated plate filled with porous material in its back cavity. Theoretical and numerical models are established to predict the acoustic impedance and sound absorption coefficient of the proposed structure, and two samples made of polyurethane and melamine, respectively, are tested in an impedance tube. The predicted results are consistent with that of the measured. Compared with a single porous layer with the same thickness, the results show that the designed structure provides an additional sound absorption peak at low frequencies. The proposed structure is compact and has an effective absorption bandwidth of more than two octaves especially below the frequency corresponding to 1/4 wavelength. A comparison is also made between the sound absorption coefficients of the proposed structure and a classical micro-perforated plate (MPP), and the results reveal equivalent acoustic performance, suggesting that it can be used as an alternative to the MPP for low–mid frequency sound absorption. Moreover, the influences of the main parameters on the sound absorption coefficient of PPCS are also analyzed, such as the hole diameter, area ratio, flow resistance, and porous-material thickness in the PR. The mechanism of sound absorption is discussed through the surface acoustic impedance and the distributions of particle velocity and sound pressure at several specific frequencies. This work provides a new idea for the applications of the thin porous layer in low- and medium-frequency sound absorption.

Development of Adjustable Parallel Helmholtz Acoustic Metamaterial for Broad Low-Frequency Sound Absorption Band

“…In order to obtain the desired sound absorption performance, it is essential to adjust structural parameters of the acoustic metamaterial [ 15 , 16 , 17 , 18 , 19 ]. Li et al [ 15 ] had proposed the composite structure composed of porous-material layer mosaicked with a perforated resonator and its structural parameters were optimized to enhance the low-frequency sound absorption of the porous layer.…”

“…In order to obtain the desired sound absorption performance, it is essential to adjust structural parameters of the acoustic metamaterial [ 15 , 16 , 17 , 18 , 19 ]. Li et al [ 15 ] had proposed the composite structure composed of porous-material layer mosaicked with a perforated resonator and its structural parameters were optimized to enhance the low-frequency sound absorption of the porous layer. An optimization methodology was proposed by Lee et al [ 16 ] to develop a more compact local resonant sonic crystals window, and three optimal sets of design parameters on the corresponding interested frequencies of 630 Hz, 800 Hz and 1000 Hz were obtained.…”

Study on the Sound Absorption Properties of Recycled Polyester Nonwovens through Alkaline Treatment and Dimple Processing

“…Porous sound-absorbing materials consist of numerous micropores, converting incident sound wave energy into thermal energy through the frictional resistance of a skeleton and the air within the pores, effectively dissipating it [12,13]. This type of material is particularly effective in reducing noise in the mediumand high-frequency bands with short wavelengths, displaying the ability to absorb and disperse sounds of various frequencies [14][15][16][17][18][19][20]. Resonant sound-absorbing materials, on the other hand, feature a surface structure with multiple small holes, employing the basic principle of the Helmholtz resonator.…”

Preparation and sound insulation of honeycomb composite structures filled with glass fiber

“…Meng et al 20 discovered that unlike conventional honeycomb sandwich panels, panels with holes produced a higher sound absorption coefficient at low frequencies. Given the noise in the low and medium frequency bands, currently, microperforated panels based on resonators have been successfully used in room acoustics, and MPPs filled with porous material perform better than MPPs with only air in the cavity 21 . Although the mechanical properties and sound transmission characteristics of honeycomb sandwich structures have been extensively explored, the acoustic properties of honeycomb‐filled sandwich structures receive much less attention.…”