阅读说明：本技术 一种超薄多吸收峰低频吸声器 (Ultra-thin many absorption peak low frequency sound absorber ) 是由 刘盛春 孔德强 李勇 刘博韬 曹国昕 麻宇祥 吕航 于 2019-10-30 设计创作，主要内容包括：一种超薄多吸收峰低频吸声器,解决了低频吸声器的每个腔体只能引起一个准完美吸收频率峰的问题,属于声波处理技术领域。本发明包括穿孔盖板、内嵌圆孔、螺旋分隔板、无孔挡板、底板和一个或多个穿孔挡板；穿孔位于穿孔盖板的正中心；螺旋分隔板包括筒状壳体和螺旋结构,螺旋结构放在筒状壳体内,螺旋结构的尾部与筒状壳体内壁相连接,形成螺旋通道；螺旋分隔板放置在穿孔盖板与底板之间,在内部形成吸声腔；无孔挡板插入到螺旋结构最外圈与圆筒壁之间,无孔挡板用于隔开宽度不相同的通道,在穿孔盖板的穿孔正下方和穿孔挡板的穿孔上分别加装多个不同尺寸的内嵌圆孔,形成不同波长的吸声体,实现多吸收峰低频吸声器。(An ultrathin low-frequency sound absorber with multiple absorption peaks solves the problem that each cavity of the low-frequency sound absorber can only cause one quasi-perfect absorption frequency peak, and belongs to the technical field of sound wave processing. The invention comprises a perforated cover plate, an embedded round hole, a spiral partition plate, a non-perforated baffle, a bottom plate and one or more perforated baffles; the through hole is positioned at the right center of the through hole cover plate; the spiral partition plate comprises a cylindrical shell and a spiral structure, the spiral structure is placed in the cylindrical shell, and the tail part of the spiral structure is connected with the inner wall of the cylindrical shell to form a spiral channel; the spiral separation plate is arranged between the perforated cover plate and the bottom plate, and a sound absorption cavity is formed inside the spiral separation plate; the nonporous baffle is inserted between the outermost ring of the spiral structure and the cylinder wall, the nonporous baffle is used for separating channels with different widths, a plurality of embedded round holes with different sizes are respectively additionally arranged under the perforation of the perforated cover plate and on the perforation of the perforated baffle, sound absorbers with different wavelengths are formed, and the multi-absorption-peak low-frequency sound absorber is realized.)

1. An ultrathin low-frequency sound absorber with multiple absorption peaks is characterized by comprising a perforated cover plate (1), embedded round holes (2), a spiral partition plate (4), a non-perforated baffle (6), a bottom plate (7) and one or more perforated baffles (3);

the perforated cover plate (1) and the bottom plate (7) are the same in size and shape, and the perforated holes are positioned in the center of the perforated cover plate (1); the spiral partition plate (4) comprises a cylindrical shell and a spiral structure, the spiral structure is placed in the cylindrical shell, and the tail part of the spiral structure is connected with the inner wall of the cylindrical shell to form a spiral channel; the spiral partition plate (4) is placed between the perforated cover plate (1) and the bottom plate (7), is tightly attached to the perforated cover plate (1) and the bottom plate (7), and forms a sound absorption cavity (5) inside; the non-porous baffle (6) is inserted between the outermost ring of the spiral structure and the cylinder wall, the non-porous baffle (6) is used for separating channels with different widths, one or more perforated baffles (3) are inserted into the spiral structure, and embedded round holes (2) with different sizes are respectively additionally arranged under the perforations of the perforated cover plate (1) and on the perforations of the perforated baffles (3).

2. An ultra thin multiple absorption peak low frequency sound absorber according to claim 1, characterized in that the larger the number of said embedded circular holes (2), the larger the number of absorption peaks.

3. The ultra-thin multiple absorption peak low frequency sound absorber of claim 1, characterized in that the absorption peaks of different frequencies are obtained by adjusting the axial distance from the perforated baffle (3) to the spiral baffle (4), the size of the embedded circular hole (2) and the height of the spiral partition plate (4).

4. Ultra-thin multi-absorption peak low frequency sound absorber according to claim 1, characterized in that the perforated cover plate (1) and the base plate (7) are of a lamellar plate-like structure, and the shape of the sound absorber is cylindrical or polygonal.

5. An ultra-thin multi-absorption peak low frequency sound absorber as claimed in claim 1, wherein the spiral structure has a section of a round angle spiral, an obtuse angle spiral, a right angle spiral or an acute angle spiral, and the shape of the contact surface of the spiral separation plate (4) with the perforated cover plate (1) is identical to the shape of the contact surface with the bottom plate (7).

6. The ultra-thin multiple absorption peak low frequency sound absorber of claim 1, wherein the perforated cover plate (1), the embedded circular hole (2), the perforated baffle (3), the spiral partition plate (4), the imperforate baffle (6) and the bottom plate (7) are made of the same material, the characteristic impedance of which is much larger than that of air.

7. The ultra-thin multiple absorption peak low frequency sound absorber of claim 6, wherein said material is metal, rigid plastic, ceramic or resin.

8. The ultra-thin multiple absorption peak low frequency sound absorber of claim 1, wherein the perforated cover plate (1), the embedded circular hole (2), the perforated baffle (3), the spiral partition plate (4), the imperforate baffle (6) and the base plate (7) can be formed by 3D printing, mold injection, lathe machining or laser cutting.

Technical Field

The invention particularly relates to an ultrathin quasi-perfect low-frequency sound absorber with multiple absorption peaks, and belongs to the technical field of sound wave processing.

Background

Low frequency sound absorption and noise reduction has been a challenging issue for decades because of the weak interaction between the thin sound absorbing material or structure and the air medium due to the large wavelength of the low frequency (<1000Hz) sound waves, resulting in inefficient dissipation of sound energy. The traditional sound absorption materials such as porous materials, micro-perforated plates, sound absorption wedges and the like have poor absorption performance on low-frequency sound. For this, different approaches have been proposed, such as gradient porous materials, multilayer structures or material microstructure optimization. With these methods, sound absorption performance can be improved to some extent, but many difficulties are still encountered in downsizing the sample.

In recent years, the development of acoustic metamaterials brings about a plurality of unusual acoustic phenomena, realizes a plurality of functions and applications, and particularly provides a solution for the problem of ultrathin low-frequency sound absorption.

At present, two types of metamaterials with better low-frequency broadband sound absorption effects are mainly used, one type is a thin-film metamaterial which can block low-frequency sound through reflection of a negative mass effect. By utilizing the coupling of the film and the cavity under the resonant frequency, the film metamaterial can consume a large amount of sound energy, and perfect sound absorption is realized. A series of films with different design frequencies are arranged on one cavity, so that the target broadband sound absorption can be realized. Although very thin in this way, the tension of the film is required to be uniform and controllable, which presents manufacturing challenges. Furthermore, since the dissipated acoustic energy is essentially the kinetic energy converted into the film, the film is prone to fatigue leading to durability problems.

Another approach is a convoluted resonant structure, essentially rolling the cavity in a plane perpendicular to the incident wave. Such a metamaterial, whose absorption properties are determined by the structure-induced phase delay (acoustic reactance), typically requires a length of a quarter wavelength to achieve a resonant frequency. To achieve perfect absorption, a proper cross-sectional area is required, so that the loss of the cavity can meet the impedance matching with the background medium. In addition to achieving the desired loss for a particular cross-sectional area, this can be achieved by introducing a porous medium or by adding a neck (similar to the neck of a helmholtz resonator). In addition, the embedded hole is introduced or the channel with the non-uniform gradient section is used, so that the impedance control capability of the structure can be improved, and the length of the channel can be effectively reduced. A certain number of Fabry-Perot cavities with different design frequencies are regularly arranged on a plane perpendicular to an incident wave, and broadband sound absorption can be realized.

The quasi-perfect low-frequency sound absorber with a single cavity and multiple absorption peaks is designed for the purpose that each cavity can only cause one quasi-perfect absorption frequency peak (in the case of fundamental frequency).

Disclosure of Invention

Aiming at the problem that each cavity of the low-frequency sound absorber in the prior art can only cause one quasi-perfect absorption frequency peak under a thinner condition, the invention provides an ultrathin low-frequency sound absorber with multiple absorption peaks.

The invention relates to an ultrathin multi-absorption-peak low-frequency sound absorber which comprises a perforated cover plate 1, an embedded round hole 2, a spiral partition plate 4, a non-perforated baffle 6, a bottom plate 7 and one or more perforated baffles 3, wherein the perforated cover plate is provided with a plurality of through holes;

the perforated cover plate 1 and the bottom plate 7 are the same in size and shape, and the perforated holes are positioned in the center of the perforated cover plate 1; the spiral partition plate 4 comprises a cylindrical shell and a spiral structure, the spiral structure is placed in the cylindrical shell, and the tail part of the spiral structure is connected with the inner wall of the cylindrical shell to form a spiral channel; the spiral separation plate 4 is arranged between the perforated cover plate 1 and the bottom plate 7, is tightly attached to the perforated cover plate 1 and the bottom plate 7, and forms a sound absorption cavity 5 inside; the imperforate baffle 6 is inserted between the outermost ring of the spiral structure and the cylinder wall, the imperforate baffle 6 is used for separating channels with different widths, one or more perforated baffles 3 are inserted into the spiral structure, and embedded round holes 2 with different sizes are respectively and additionally arranged under the perforations of the perforated cover plate 1 and on the perforations of the perforated baffles 3.

Preferably, the larger the number of the embedded circular holes 2, the larger the number of absorption peaks.

Preferably, absorption peaks of different frequencies are obtained by adjusting the axial distance from the perforated baffle 3 to the spiral baffle 4, the size of the embedded circular hole 2 and the height of the spiral partition plate 4.

Preferably, the perforated cover plate 1 and the bottom plate 7 are of a thin plate structure, the thickness of the perforated cover plate is in the range of 0.7mm-2mm, and the sound absorber is cylindrical or polygonal.

Preferably, the thickness of the spiral separation plate 4 ranges from 0.7mm to 2 mm; the section of the spiral structure is a round angle spiral, an obtuse angle spiral, a right angle spiral or an acute angle spiral, and the shape of the contact surface of the spiral separation plate 4 and the perforated cover plate 1 is completely the same as the shape of the contact surface of the spiral separation plate and the bottom plate 7.

Preferably, the perforated cover plate 1, the embedded circular hole 2, the perforated baffle plate 3, the spiral partition plate 4, the imperforate baffle plate 6 and the bottom plate 7 are made of the same material, and the characteristic impedance of the material is far greater than that of air.

Preferably, the material is metal, rigid plastic, ceramic, resin or other material having a significant difference in acoustic impedance from air.

Preferably, the perforated cover plate 1, the embedded circular hole 2, the perforated baffle plate 3, the spiral partition plate 4, the imperforate baffle plate 6 and the bottom plate 7 can be formed by 3D printing, mold injection, lathe machining or laser cutting.

The sound absorber has a strong absorption effect on low-frequency noise, can be used for designing structural parameters in a customized manner according to required frequency, and is small in thickness, simple in structure and low in manufacturing cost. The sound absorber of the invention not only has the absorption peak of the original channel with the same size, but also has an additional absorption peak at the position of relative high frequency, and the number of the absorption peaks (fundamental frequency) is consistent with that of the embedded round holes; when broadband coupling sound absorption is realized, the space can be more effectively utilized.

Drawings

FIG. 1 is a schematic view of an expanded structure of a sound absorber according to an embodiment of the present invention;

FIG. 2 is a structural line drawing of the intermediate layer of the sound absorber of FIG. 1;

FIG. 3 is an impedance equivalent model of the acoustic absorber shown in FIG. 1;

FIG. 4 is a schematic view showing the expanded structure of the double absorption peak sound absorber described in example 1;

FIG. 5 is a top view of the expanded configuration shown in FIG. 4;

FIG. 6 is an absorption coefficient of a dual absorption peak sound absorber;

FIG. 7 is a graph of the absorption coefficient of a three absorption peak sound absorber;

figure 8 absorption coefficient of a four absorption peak absorber.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The invention is further described with reference to the following drawings and specific examples, which are not intended to be limiting.

The ultrathin multi-absorption-peak low-frequency sound absorber comprises a perforated cover plate 1, an embedded round hole 2, a spiral partition plate 4, a non-perforated baffle 6, a bottom plate 7 and one or more perforated baffles 3;

the perforated cover plate 1 of the present embodiment is the same as the bottom plate 7 in size and shape, and the perforation is located at the center of the perforated cover plate 1; the spiral partition plate 4 comprises a cylindrical shell and a spiral structure, the spiral structure is placed in the cylindrical shell, and the tail part of the spiral structure is connected with the inner wall of the cylindrical shell to form a spiral channel; the spiral separation plate 4 is arranged between the perforated cover plate 1 and the bottom plate 7 and is tightly attached to the perforated cover plate 1 and the bottom plate 7 to form a sound absorption cavity 5; nonporous baffle 6 inserts between helical structure outer lane and the drum wall, separates the non-rectangular chamber, and sound absorption chamber 5 during the sound absorption is the rectangular chamber, promptly: the width of the channels forming the sound absorption chamber 5 is the same; the imperforate baffle 6 is used for separating channels with different widths, one or more perforated baffles 3 are inserted into the spiral structure, and embedded round holes 2 with different sizes are respectively and additionally arranged under the perforations of the perforated cover plate 1 and on the perforations of the perforated baffles 3. The sound absorption chamber 5 of the present embodiment, i.e., the sound absorber, has a spiral structure with sound waveguides wound therein and having the same width as the sound channel. The larger the number of the embedded circular holes 2 of the present embodiment, the larger the number of absorption peaks. The length of the embedded round hole 2 is far less than the wavelength of sound waves when the sound absorber absorbs sound.

In the embodiment, absorption peaks with different frequencies are obtained by adjusting the axial distance from the perforated baffle 3 to the spiral baffle 4, the size of the embedded round hole 2 and the height of the spiral partition plate 4. The perforated cover plate 1 and the base plate 7 of the present embodiment are thin plate-shaped structures having a thickness ranging from 0.7mm to 2mm, and the sound absorber has a cylindrical or polygonal shape (e.g., hexagonal, square, and triangular shapes). The thickness range of the spiral partition plate 4 of the present embodiment is 0.7mm to 2 mm; the section of the spiral structure is a round angle spiral, an obtuse angle spiral, a right angle spiral or an acute angle spiral, and the shape of the contact surface of the spiral separation plate 4 and the perforated cover plate 1 is completely the same as the shape of the contact surface of the spiral separation plate and the bottom plate 7. In order to ensure the sound absorption effect, the perforated cover plate 1, the embedded circular hole 2, the perforated baffle plate 3, the spiral partition plate 4, the imperforate baffle plate 6 and the bottom plate 7 of the present embodiment are made of the same material, which forms a huge impedance mismatch with air. The material is one of metal, hard plastic, ceramic and resin. The perforated cover plate 1, the embedded circular hole 2, the perforated baffle plate 3, the spiral partition plate 4, the imperforate baffle plate 6 and the bottom plate 7 of the present embodiment can be formed by 3D printing, mold injection, lathe machining or laser cutting.

To achieve sound absorption, the sound absorption coefficient of such a structure needs to be known, and the sound absorption coefficient of the metamaterial can be determined by its (normal) acoustic impedance, in the relationship:

the sound absorption coefficient of the sound absorber can be calculated from the impedance according to equation (1). When the linear degree of the channel is far less than the wavelength, the coiled channel is straightened, and the absorption is not changed. Thus, when calculating the impedance of the structure shown in fig. 1, it can be equated to fig. 3.

Since the straight channel, which is equivalent to the coiled channel, is divided into several small channels, one of the channels (i-th from the left) is considered first. For a terminal impedance (right) of Z_i-1According to an impedance transfer formula, which transfers an impedance (left) Z_viComprises the following steps:

where Li is the length of the ith channel, where k_c、ρ_c、c_cThe complex wave number, the complex density and the complex sound velocity in the cavity. For an infinite length of diameter d_iThe impedance per unit length can be written as:

Z_ai＝-jρωJ₀(κd_i/2)/J₂(κd_i/2) (3)

in the formula J_nIs a first class of nth order bessel functions. Wherein κ²In addition, the ends of the acoustic mass modify the acoustic radiation from the aperture into free space, and the effective length on both sides of the aperture increases by δ_i'＝2×(4/3π)d_i. Further, the aperture is supported at both ends by the coiled channel and a further end correction delta should be applied_i＝2×(1-1.25ε)×(4/3π)d_iWhere e ═ d/min (w, h0) is the ratio of the pore diameter to the narrower side of the coiled channel, w is the width of the channel, and h0 is the height of the channel. At the same time, the end correction of the acoustic resistance caused by the friction loss gives an additional part of the acoustic resistance

Therefore, the acoustic impedance of the embedding aperture to the rectangular cavity can be calculated by the method

In the formula₁＝A₁/A₂A1 anda2 is the cross-sectional areas of the inset hole and the rectangular cavity, respectively. Note that for the last channel (Nth), the end of the embedded hole is modified to δ since it radiates to free space at one end and is supported by the channel at the other end_N＝[1+(1-1.25ε)]×(4/3π)d_N. In the equivalent acoustic path, the holes are in series with the channels, so that the impedance of the i-th cavity is

According to the literature, the acoustic impedance of a rectangular pipe with rigid termination is: z_v1＝-jρ_cc_ccot(k_cL₁) Whereby the impedance Z of the Nth channel can be determined by an iterative method_NThe input impedance of the hypersurface can be estimated as Z ═ Z_N/φ₂Here phi₂＝A₂/A₃And a3 is the surface area of the super-surface, i.e. the incidence area.