阅读说明：本技术 一种用于低频噪声控制的亚波长宽带超材料吸收体 (Sub-wavelength broadband metamaterial absorber for controlling low-frequency noise ) 是由 龙厚友 冯奇 万庆冕 程营 陶建成 刘晓峻 邵雪飞 于 2018-09-13 设计创作，主要内容包括：本发明公开了一种用于低频噪声控制的亚波长宽带超材料吸收体。该吸收体包括多个吸声体胞元,吸声体胞元包括超材料共振器和声学吸声海绵薄层,超材料共振器集成了多个亥姆霍兹共振器,亥姆霍兹共振器为扇形,扇形的外圆周部分设置为迷宫通道,扇形的圆心部分设置为实心体,迷宫通道与实心体之间形成扇形环形腔体；声学吸声海绵薄层包覆在超材料共振器的外面。本发明的吸收体能近完美地吸收波长远远大于其尺寸的宽带声能,对宽频的低频噪声具有良好的抑制作用。(The invention discloses a sub-wavelength broadband metamaterial absorber for controlling low-frequency noise. The absorber comprises a plurality of absorber cells, the absorber cells comprise a metamaterial resonator and an acoustic sound absorption sponge thin layer, the metamaterial resonator is integrated with a plurality of Helmholtz resonators, the Helmholtz resonators are fan-shaped, the outer circumference part of the fan-shaped resonator is provided with a labyrinth channel, the circle center part of the fan-shaped resonator is provided with a solid body, and a fan-shaped annular cavity is formed between the labyrinth channel and the solid body; and the thin acoustic sound absorption sponge layer is coated outside the metamaterial resonator. The absorber can perfectly absorb broadband sound energy with the wavelength far greater than the size of the absorber, and has a good inhibiting effect on broadband low-frequency noise.)

1. The sub-wavelength broadband metamaterial absorber for controlling low-frequency noise comprises a plurality of absorber cells, wherein the absorber cells comprise a metamaterial resonator and an acoustic sound absorption sponge thin layer, the metamaterial resonator is integrated with a plurality of Helmholtz resonators, the Helmholtz resonators are fan-shaped, the outer circumferential part of the fan-shaped resonator is arranged into a labyrinth channel, the circle center part of the fan-shaped resonator is arranged into a solid body, and a fan-shaped annular cavity is formed between the labyrinth channel and the solid body; the sound absorption sponge thin layer is coated outside the metamaterial resonator.

2. The sub-wavelength broadband metamaterial absorber for low frequency noise control of claim 1, wherein the metamaterial resonator is 3D printed with epoxy or injection molded with nylon; the sound absorption sponge thin layer is made of polyurethane foam.

3. The sub-wavelength broadband metamaterial absorber for low frequency noise control as claimed in claim 1, wherein the fan-shaped Helmholtz resonators have an outer radius of 60mm and a wall thickness of 1.4 mm.

4. The sub-wavelength broadband metamaterial absorber for low frequency noise control of claim 1, wherein the thin layer of acoustic absorption sponge is a cylindrical ring with a thickness of 4 mm.

5. The sub-wavelength broadband metamaterial absorber for low-frequency noise control of claim 1, wherein the number of Helmholtz resonators is 4 or 6.

6. The sub-wavelength broadband metamaterial absorber for low frequency noise control of claim 1, wherein the absorber is placed in front of a hard boundary wall; the hard boundary wall body is made of a material with acoustic impedance far greater than that of air.

Technical Field

The invention belongs to the technical field of acoustic noise reduction, and relates to a broadband absorber of low-frequency sound waves, in particular to a sub-wavelength broadband near-perfect absorbing material based on coupling of a labyrinth metamaterial resonator and an acoustic porous material.

Background

Noise pollution has become the fifth pollution source in the 21 st century, noise control has become an important issue in the acoustic field, and absorption of acoustic energy is a very important method for suppressing noise. Traditional acoustic materials, such as porous sound absorption sponges, mainly rely on air friction loss among gaps, and because dissipation coefficients follow a linear response theory, the porous materials absorb high-frequency sound waves well, and absorb low-frequency sound waves very weakly. Therefore, to appreciably absorb the low frequency sound waves, a large thickness of material is required to achieve this, which results in increased cost and increased space occupation.

In order to solve the problem, perfect sound absorbers based on acoustic metamaterials are produced. In order to provide the absorber with sub-wavelength characteristics, a local resonance type material, such as an acoustic Helmholtz resonator, an acoustic metasurface, an acoustic membrane material, a curved space, and the like, is typically selected to construct the sub-wavelength or deep sub-wavelength scale absorber. These absorbers highly localize acoustic energy by resonance, and are dissipated by converting the acoustic energy into thermal energy by frictional losses. Compared with the traditional absorption material, the novel absorption body has the advantages of small size and high efficiency. However, since these absorbers are based on a single resonance structure, they generally act at a single frequency, which greatly limits the application of acoustic absorbers.

Recently, an optimized acoustic absorber generation (mater. horiz.,2017,4, 673-.

Disclosure of Invention

The invention aims to solve the technical problem that the existing sub-wavelength low-frequency sound absorber only works at a single frequency, and provides a sub-wavelength broadband near-perfect (> 98%) absorber designed by utilizing a metamaterial resonator coupled with a porous sound absorption sponge, and the absorber can efficiently inhibit the low-frequency noise of the broadband.

The technical scheme adopted by the invention is as follows:

a sub-wavelength broadband metamaterial absorber for controlling low-frequency noise comprises a plurality of absorber cells, wherein the absorber cells comprise a metamaterial resonator and an acoustic sound absorption sponge thin layer, the metamaterial resonator is integrated with a plurality of Helmholtz resonators, the Helmholtz resonators are fan-shaped, the outer circumferential part of each fan-shaped resonator is a labyrinth channel, the circle center part of each fan-shaped resonator is a solid body, and a fan-shaped annular cavity is formed between each labyrinth channel and the solid body; the sound absorption sponge thin layer is coated outside the metamaterial resonator.

Further, the metamaterial resonator is formed by 3D printing of epoxy resin or nylon injection molding; the sound absorption sponge thin layer is made of polyurethane foam.

Preferably, the fan-shaped Helmholtz resonator has an outer radius of 60mm and a wall thickness of 1.4 mm.

Preferably, the thin layer of acoustic sound absorption sponge is a cylindrical ring with the thickness of 4 mm.

Preferably, the number of helmholtz resonators is 4 or 6.

Further, the sound absorber is placed in front of the hard boundary wall body; the hard boundary wall body is made of a material with acoustic impedance far greater than that of air.

The absorber provided by the invention has the characteristics of sub-wavelength, broadband and high absorption efficiency, can perfectly absorb broadband sound energy with the wavelength far greater than the size of the absorber, has a good inhibition effect on broadband low-frequency noise, and provides a feasible solution for noise control.

Drawings

Fig. 1 is a three-dimensional view of a metamaterial resonator integrated with 6 helmholtz resonators according to the present invention, wherein 1 is a labyrinth-type pipe of the resonator, 2 is a sector-ring-shaped cavity of the resonator, and 3 is a solid body.

Fig. 2 is a two-dimensional sectional view of the metamaterial broadband sound absorber of the present invention, and 4 is a sound absorbing sponge.

Fig. 3 shows how the metamaterial absorber cells of the present invention are installed, and 5 is a hard boundary.

Fig. 4 is a two-dimensional cross-sectional view of a metamaterial sound absorber integrating 4 helmholtz resonators of the present invention.

Fig. 5 shows the sound absorption coefficient of a 6 helmholtz resonator integrated metamaterial absorber with the parameters Ro-64 mm, t-1.4 mm and w-3.5 mm.

Fig. 6 shows the sound absorption coefficient of a metamaterial absorber integrated with 4 helmholtz resonators, where the parameters Ro-64 mm, t-1.4 mm, and w-4.7 mm.

Detailed Description

The metamaterial resonator in the sub-wavelength broadband near-perfect sound absorber can be obtained by using an epoxy resin material through a 3D printing technology or using a nylon material for injection molding. As shown in fig. 1, a plurality of helmholtz resonators are integrated together, each of which includes an labyrinth type pipe 1, a fan-shaped annular cavity 2, and a solid body 3, and the resonance frequency can be adjusted by adjusting the inner radius of the fan-shaped annular cavity 2. In order to eliminate the valleys between the formants, the resonator is covered with a layer of sound absorbing sponge 4.

In this example, the outer diameter of the resonator was 60mm, the wall thickness was 1.4mm, the channel width w was 3.5mm or w was 4.7mm, the cavity inner diameter was as shown in table 1, and the sound absorption sponge 4 had a thickness of 4mm, so R was R_o64 mm. The sponge material is polyurethane foam.

TABLE 1 metamaterial resonator absorber parameters (unit: mm)

The present invention is further illustrated by the following examples.