Acoustic superstructure cell with adjustable absorption frequency band and sound absorption structure

Abstract

The invention discloses an acoustic superstructure cell with an adjustable absorption frequency band and a sound absorption structure, and relates to the technical field of sound absorption. Based on the influence of neck structure parameters of a resonant cavity on the noise absorption performance of equipment, the hole diameter and the hole length of a neck hole are adjusted and controlled through an adjustment selecting structure, so that the neck characteristics of the resonant cavity are changed, and the noise absorption performance of the equipment is improved. And meanwhile, parameter adjustment of different resonant cavities in the sound absorption structure is mutually independent and does not influence each other, regulation and control are convenient, and operation is easy. The acoustic superstructure cell comprises a hollow cavity structure and an adjusting structure, N + 1 neck holes communicating the inside and the outside of a cavity of the hollow cavity structure are formed in the hollow cavity structure, the hole diameter and the hole length of each neck hole are different, N is a positive integer, and the adjusting structure is rotationally arranged on the hollow cavity structure and seals the N neck holes of the hollow cavity structure, the rest neck hole in the communicating state and the hollow cavity structure form a resonant cavity, and the neck hole forming the resonant cavity is selected by rotating the selecting and adjusting structure.

Description

Technical Field

[0001] The present application relates to the technical field of sound absorption, and in particular to an acoustic superstructure cell and a sound absorption structure with adjustable absorption frequency band. Background Art

[0002] Equipment noise can be divided into three categories according to the noise source: pneumatic noise, mechanical vibration noise and radiation noise. Among them, mechanical vibration is the main source of noise during the operation of equipment. During the operation of various mechanical systems of equipment, the friction, impact and collision between parts and components generate vibrations and spread outward in the form of sound waves, generating mechanical noise. There are generally two ways to control noise: one is to suppress the generation of noise from the source, mainly by optimizing the processing and assembly process of the mechanical structure; the other is to start from the propagation of noise, install sound-absorbing and insulating materials on the propagation path, and absorb the noise to achieve the control effect. The development of mechanical structure and its processing and assembly technology has been relatively mature at this stage, and the potential and space for further optimization are small and the difficulty coefficient is high. The spatial processing of the noise propagation path uses sound-absorbing and insulating materials to absorb and cut off the noise that has been generated, which is highly operational.

[0003] At present, the materials used for equipment noise control are mainly traditional acoustic materials (such as micro-perforated plates and porous materials) and acoustic superstructures. Traditional acoustic materials have poor sound absorption effect in the low-frequency area. Acoustic superstructures have advantages in absorbing low-frequency sound waves of deep sub-wavelength size, and have become one of the research hotspots of low-frequency noise control in recent years. In the field of sound absorption, sound waves enter the interior of the acoustic superstructure. Due to the local resonance phenomenon, the sound wave energy dissipates when resonating with the air and structure, achieving sound absorption efficiency. Although it can effectively absorb low-frequency noise at deep sub-wavelength size, the sound absorption frequency band is narrow. Summary of the invention

[0004] The present application provides an acoustic superstructure cell and a sound-absorbing structure with adjustable absorption frequency band, which can effectively broaden the low-frequency sound absorption bandwidth of the acoustic superstructure.

[0005] The specific technical solutions are as follows:

[0006] In a first aspect, an embodiment of the present application provides an acoustic superstructure cell with adjustable absorption frequency band, comprising:

[0007] A hollow cavity structure, wherein the hollow cavity structure is provided with N+1 neck holes connecting the inside and outside of the cavity of the hollow cavity structure, and the hole diameter and hole length of each neck hole are different, and N is a positive integer,

[0008] A selection structure is rotatably disposed on the hollow cavity structure to seal the N neck holes of the hollow cavity structure. The remaining neck hole in a connected state forms a resonance cavity with the hollow cavity structure. The neck hole that forms the resonance cavity is selected by rotating the selection structure.

[0009] In some embodiments of the present application, the hollow cavity structure includes a cavity portion and an end cover portion, the cavity portion is a cavity structure with one end open, the end cover portion is arranged at the open end of the cavity portion to seal the open end of the cavity portion, N+1 neck holes are arranged on the end cover portion, and the selection structure is rotatably arranged on the end cover portion to seal the N neck holes of the end cover portion.

[0010] In some embodiments of the present application, a through hole is provided in the middle portion of the end cover portion, and a circular array of N+1 neck holes is distributed on the outside of the through hole. The adjustment structure includes a knob, a positioning pin, a tension spring and a bayonet. The knob includes a sealing plate and a rotating shaft passing through both sides of the sealing plate. The sealing plate is a circular plate with a fan ring notch. The rotating shaft is arranged at the center of the sealing plate, and the central angle of the fan ring notch is 360° / (N+1). The sealing plate is arranged on the end surface of the end cover portion away from the cavity portion, the rotating shaft located on the side of the sealing plate close to the end cover portion is penetrated in the through hole, and the positioning pin is arranged on the rotating shaft located on the side of the sealing plate close to the end cover portion, and the bayonet is arranged at one end of the through hole away from the sealing plate, and the two ends of the tension spring are fixed by the positioning pin and the bayonet respectively. Under the elastic force of the tension spring, the sealing plate seals the N neck holes of the end cover portion.

[0011] In some embodiments of the present application, end surfaces of the N+1 neck holes close to the sealing plate are all arranged in the same horizontal plane, and end surfaces of the N+1 neck holes away from the sealing plate are not arranged in the same horizontal plane.

[0012] In some embodiments of the present application, the cavity portion and the end cover portion are both made of photosensitive resin, the knob is made of polylactic acid (PLA) resin, and the end cover portion is bonded and fixed to the cavity portion.

[0013] In some embodiments of the present application, the cavity portion and the cavity of the cavity portion are both in a cube shape, and the end cover portion is a square plate with the same size as the cavity portion.

[0014] In a second aspect, an embodiment of the present application provides a sound-absorbing structure with an adjustable absorption frequency band, comprising a base structure and a plurality of acoustic superstructure cells with an adjustable absorption frequency band as described in the first aspect, wherein the plurality of acoustic superstructure cells are arranged on the base structure in a predetermined arrangement.

[0015] In some embodiments of the present application, the number of the acoustic superstructure cells is M 2 , M is a positive integer, the base structure includes a rear cylindrical part and a front circular plate part with the same diameter, M 2 The cavity parts of the acoustic superstructure cells are arranged in a square array on the rear cylindrical part, 2 The end cover parts of the acoustic superstructure cells are arranged in a square array on the front circular plate part, and each of the end cover parts corresponds to the cavity part one by one.

[0016] In some embodiments of the present application, a plurality of positioning posts are arranged on the end surface of the rear cylindrical portion close to the front circular plate portion, a plurality of positioning holes are arranged on the end surface of the front circular plate portion close to the rear cylindrical portion, each of the positioning holes corresponds to the positioning posts one by one, the positioning posts are passed through the positioning holes, the rear cylindrical portion and the front circular plate portion are bonded and fixed, so that the end cover portion of each acoustic superstructure and the corresponding cavity portion are sealed and fixed to each other, forming an M 2 independent resonant cavities.

[0017] In some embodiments of the present application, the diameters of the rear cylindrical portion and the front circular plate portion are 100 mm, the cavity side length of each cavity portion is 20 mm, and the total thickness of the rear cylindrical portion and the front circular plate portion is 30 mm.

[0018] The innovative features of the embodiments of the present application include but are not limited to the following:

[0019] 1. A resonance cavity is configured with multiple neck holes with different neck characteristics, and the diameter and length of the neck hole are selected and adjusted by a knob to achieve an adjustable function.

[0020] 2. Taking the Helmholtz resonator as the basic unit, an acoustic superstructure with multiple resonance cavities in parallel is designed. By controlling the structural parameters of the resonance cavity and adjusting the absorption peak frequency, multiple groups of absorption peaks are superimposed to broaden the sound absorption bandwidth.

[0021] 3. In order to solve the problem that the height of the cavities in the parallel Helmholtz cavity acoustic superstructure is inconsistent, resulting in the overall structure occupying a large space, this application designs nine square parallel Helmholtz resonant cavity acoustic superstructures based on the phase and peak modulation mechanism of the acoustic waveguide. Six cavities with different neck cross-sections and lengths are arranged in the square, and the appropriate absorption neck hole is adjusted by a knob, which greatly reduces the space occupied.

[0022] The beneficial effects of the embodiments of the present application are as follows:

[0023] Based on the influence of the neck structure parameters of the resonance cavity on the noise absorption performance of the equipment, the hole diameter and hole length of the neck hole are adjusted by using the selection structure, thereby changing the neck characteristics of the resonance cavity and realizing the control of bandwidth noise at different frequency stages. At the same time, the parameter adjustments of different resonance cavities in the sound absorption structure are independent of each other and do not affect each other. They are also convenient to adjust and easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 A cross-sectional schematic diagram of an acoustic superstructure cell with adjustable absorption frequency band provided in an embodiment of the present application;

[0026] Figure 2 A schematic diagram of the structure of an end cap portion in an acoustic superstructure cell with adjustable absorption frequency band provided in an embodiment of the present application, wherein (A) shows the end face of the end cap portion close to the cavity portion, and (B) shows the end face of the end cap portion away from the cavity portion;

[0027] Figure 3 A schematic top view of an acoustic superstructure cell with adjustable absorption frequency band provided in an embodiment of the present application;

[0028] Figure 4 A schematic diagram of the structure of a sound-absorbing structure with adjustable absorption frequency band provided in an embodiment of the present application;

[0029] Figure 5 A schematic diagram of the structure of the front circular plate portion in a sound-absorbing structure with adjustable absorption frequency band provided in an embodiment of the present application Figure 1 ;

[0030] Figure 6 A schematic diagram of the structure of the front circular plate portion in a sound-absorbing structure with adjustable absorption frequency band provided in an embodiment of the present application Figure 2 ;

[0031] Figure 7 A schematic diagram of the grouping of modeling chambers of a sound-absorbing structure with adjustable absorption frequency band provided in an embodiment of the present application;

[0032] Figure 8 A schematic diagram of a finite element simulation model of a sound-absorbing structure with adjustable absorption frequency band provided in an embodiment of the present application;

[0033] Fig. 9 A sound absorption coefficient curve diagram of a first group of parameters of a finite element simulation analysis of a sound absorption structure with adjustable absorption frequency band provided in an embodiment of the present application, wherein the abscissa is the sound absorption frequency and the ordinate is the corresponding sound absorption coefficient;

[0034] Fig.10 A sound absorption coefficient curve diagram of a second group of parameters of a finite element simulation analysis of a sound absorption structure with adjustable absorption frequency band provided in an embodiment of the present application, wherein the abscissa is the sound absorption frequency and the ordinate is the corresponding sound absorption coefficient;

[0035] Fig.11 A sound absorption coefficient curve diagram of the third group of parameters of a finite element simulation analysis of a sound absorption structure with adjustable absorption frequency band provided in an embodiment of the present application, wherein the abscissa is the sound absorption frequency and the ordinate is the corresponding sound absorption coefficient;

[0036] Fig.12 A sound absorption coefficient curve diagram of the fourth group of parameters of a finite element simulation analysis of a sound absorption structure with adjustable absorption frequency band provided in an embodiment of the present application, wherein the abscissa is the sound absorption frequency and the ordinate is the corresponding sound absorption coefficient;

[0037] Fig.13 A sound absorption coefficient curve diagram of the fifth group of parameters of a finite element simulation analysis of a sound absorption structure with adjustable absorption frequency band provided in an embodiment of the present application, wherein the abscissa is the sound absorption frequency and the ordinate is the corresponding sound absorption coefficient;

[0038] Fig.14 A sound absorption coefficient curve diagram of the sixth group of parameters of a finite element simulation analysis of a sound absorption structure with adjustable absorption frequency band provided in an embodiment of the present application, wherein the abscissa is the sound absorption frequency and the ordinate is the corresponding sound absorption coefficient;

[0039] Fig.15 The experimental test data of a sound-absorbing structure with adjustable absorption frequency band provided in the embodiment of the present application is as follows: Figure 1 ;

[0040] Fig.16 The experimental test data of a sound-absorbing structure with adjustable absorption frequency band provided in the embodiment of the present application is as follows: Figure 2 ;

[0041] Fig.17A comparison curve diagram of sound absorption coefficients of a sound absorption structure with adjustable absorption frequency band provided in an embodiment of the present application;

[0042] Fig.18 A comparison curve diagram of simulation results and experimental values ​​of a sound-absorbing structure with adjustable absorption frequency band provided in an embodiment of the present application. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0044] It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The terms "including" and "having" in the embodiments of the present application and the accompanying drawings and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device comprising a series of steps or units is not limited to the listed steps or units, but optionally also includes steps or units that are not listed, or optionally also includes other steps or units inherent to these processes, methods, products or devices.

[0045] The present application discloses an acoustic superstructure cell with adjustable absorption frequency band, which can realize the control of bandwidth noise at different frequency stages by changing the neck characteristics of the resonance cavity. Detailed descriptions are given below.

[0046] The calculation formula of the resonant frequency f0 of the Helmholtz resonant cavity is:

[0047]

[0048] Wherein, c0 is the speed of sound of air; π is the pi; S is the cross-sectional area of ​​the neck of the Helmholtz resonant cavity; V0 is the cavity volume of the Helmholtz resonant cavity; l is the length of the neck of the Helmholtz resonant cavity; Δl is the correction value of the neck length l, which is generally taken as 0.8 times the diameter of the neck.

[0049] It can be seen from the above calculation formula that the resonant frequency of the Helmholtz resonant cavity depends on the cavity volume, neck length and neck cross-sectional area. The sound absorption frequency can be reduced by increasing the cavity volume, extending the neck length and reducing the neck cross-sectional area. However, under normal circumstances, it is difficult to change the cavity volume of the Helmholtz resonant cavity in the actual application of equipment noise control. The embodiment of the present application widens the low-frequency sound absorption bandwidth by changing the neck length and neck cross-sectional area of ​​the Helmholtz resonant cavity.

[0050] Figure 1 – Figure 3 FIG. 1 shows an acoustic superstructure cell with adjustable absorption frequency band provided according to an embodiment of the present application. Figure 1 As shown, the acoustic superstructure cell includes: a hollow cavity structure 1 and a selection structure 2, wherein the hollow cavity structure 1 is provided with N+1 neck holes 121 connecting the inside and outside of the cavity 111 of the hollow cavity structure 1, and the hole diameter and hole length of each neck hole 121 are different, which can be pre-designed according to the needs, and the selection structure 2 is rotatably arranged on the hollow cavity structure 1 to seal the N neck holes 121 of the hollow cavity structure 1, and the remaining neck hole 121 in a connected state forms a Helmholtz resonance cavity with the hollow cavity structure 1. In the acoustic superstructure cell, any one of the N+1 different neck holes 121 can be selected to be in a connected state by rotating the selection structure 2. Since the hole diameter and hole length of each neck hole 121 are different, the neck characteristics of the formed Helmholtz resonance cavity, that is, the neck mouth length and the neck mouth cross-sectional area, can be changed by changing the neck hole 121 in a connected state, thereby realizing the regulation of the resonance frequency of the Helmholtz resonance cavity. Wherein, N is a positive integer. It should be noted that the neck hole 121 in the present application is equivalent to the neck of the Helmholtz resonance cavity when forming a Helmholtz resonance cavity together with the hollow cavity structure 1 .

[0051] In some embodiments, Figure 1As shown, the hollow cavity structure 1 includes a cavity portion 11 and an end cover portion 12. The cavity portion 11 is a cavity structure with one end open, and the end cover portion 12 is arranged at the open end of the cavity portion 11 to seal the open end of the cavity portion 11. N+1 neck holes 121 are centrally arranged on the end cover portion 12. The adjustment structure 2 is rotatably arranged on the end cover portion 12, and seals the end of the N neck holes 121 of the end cover portion 12 away from the cavity portion 11. With such a design, on the one hand, the hollow cavity structure 1 adopts a split structure, which is easier to process and provides a setting position for multiple neck holes 121. On the other hand, multiple neck holes 121 are centrally arranged at the end cover portion 12. On the cover portion 12, it is more convenient for the selection and control of the multiple neck holes 121 by the selection structure 2, so that by controlling the position of the selection structure 2 on the end cover portion 12, one of the N+1 neck holes 121 can be selected to remain in a connected state (that is, the cavity is connected to the outside air), and the remaining N neck holes 121 are in a closed state (that is, the cavity is not connected to the outside air). The neck hole 121 in the connected state forms a Helmholtz resonance cavity with the hollow cavity structure 1, and then the selection of the noise frequency is achieved by adjusting the hole cross-section and hole length of the selected neck hole 121.

[0052] Further, such as Figure 2 As shown, a through hole 122 is provided in the middle of the end cover 12 to provide a mounting hole for the adjustment structure 2 on the end cover 12, and N+1 neck holes 121 are distributed in a circular array on the outside of the through hole 122. Figure 1 As shown, the adjustment structure 2 includes a knob 21, a positioning pin 22, a tension spring 23 and a latch 24, wherein the knob 21 includes a sealing plate 211 and a rotating shaft 212 penetrating both sides of the sealing plate 211, the sealing plate 211 is a circular plate with a fan ring notch 213, the rotating shaft 212 is arranged at the center of the sealing plate 211, the central angle of the fan ring notch 213 is 360° / (N+1), the sealing plate 211 is arranged on the end surface of the end cover portion 12 away from the cavity portion 11, the rotating shaft 212 located on the side of the sealing plate 211 close to the end cover portion 12 is penetrated in the through hole 122, and a positioning spring 23 is arranged on the rotating shaft 212 located on the side of the sealing plate 211 close to the end cover portion 12 The pin 22 and the bayonet pin 24 are arranged at one end of the through hole 122 away from the sealing plate 211. The two ends of the tension spring 23 are fixed by the positioning pin 22 and the bayonet pin 24 respectively. Under the elastic force of the tension spring 23, the sealing plate 211 of the knob 21 is tightly attached to the end face of the end cover 12 away from the cavity 11. Through the design of the 360° / (N+1) central angle fan ring notch 213, the sealing plate 211 can only seal the N neck holes 121 on the end cover 12, and keep one neck hole 121 in a connected state, so that the sealing plate 211 of the knob 21 can be rotated by the rotating shaft 212 of the knob 21, and the neck hole 121 in a connected state on the end cover 12 can be selected. In the specific implementation process, combined with Figure 1 – Figure 3As shown, the end surfaces of the N+1 neck holes 121 close to the sealing plate 211 are all arranged in the same horizontal plane, and the end surfaces of the N+1 neck holes 121 away from the sealing plate 211 are not arranged in the same horizontal plane, so as to realize the setting of different hole lengths of the neck holes 121, and the bayonet 24 is fixedly set at the end of the through hole 122 away from the sealing plate 211, and is used to fix one end of the tension spring 23, and the other end of the tension spring 23 is connected to the rotating shaft 212 of the knob 21 through the positioning pin 22, so that the sealing plate 211 can be rotated relative to the end cover part 12, and the sealing plate 211 can be pressed against the end surface of the end cover part 12 away from the cavity part 11 through the pre-tightening force of the tension spring 23, so as to seal the N neck holes 121 on the end cover part 12 with good sealing performance.

[0053] In some specific embodiments, Figure 1 – Figure 3 As shown, the cavity portion 11 and the cavity of the cavity portion 11 are both in a cube shape, and the end cover portion 12 is a square plate of the same size as the cavity portion 11. Further, a sealing groove 123 matching the shape and size of the sealing plate 211 is provided on the end surface of the end cover portion 12 away from the cavity portion 11, and the sealing plate 211 is placed in the sealing groove 123, which further enhances the sealing performance of the sealing plate 211 to the N neck holes 121, and controls the overall size of the acoustic superstructure cell, so that the knob 21 does not occupy additional space, greatly improving the compactness and practicality of the structure. In addition, a circular groove 124 with the same shape and size as the sealing groove 123 is arranged on the end face of the end cover portion 12 close to the cavity portion 11, and the through hole 122 is located at one end of the circular groove 124 and is in the shape of a hollow cylinder. Each neck hole 121 is respectively arranged on a sector ring with a central angle of 360° / (N+1), and the hole length of the neck hole 121 is set by setting the height of each sector ring end face relative to the end face of the hollow cylinder.

[0054] In other specific embodiments, the cavity portion 11 and the end cover portion 12 are both made of photosensitive resin, and the knob 21 is made of PLA resin, which can effectively save natural energy. The end cover portion 12 and the cavity portion 11 are bonded and fixed, for example, by glue.

[0055] The present application also discloses a sound absorbing structure with adjustable absorption frequency band, such as Figure 1 – Figure 6As shown, the sound absorbing structure with adjustable absorption frequency band includes a base structure 3 and a plurality of acoustic superstructure cells with adjustable absorption frequency band, the acoustic superstructure cells are the acoustic superstructure cells with adjustable absorption frequency band provided in the above embodiment, and the plurality of acoustic superstructure cells are arranged on the base structure 3 in a predetermined arrangement. It should be noted that the structure and principle of the acoustic superstructure cells with adjustable absorption frequency band in this embodiment are the same as those in the above embodiment, and for the sake of brief description, for the parts not mentioned in the embodiment of the sound absorbing structure with adjustable absorption frequency band, reference may be made to the corresponding contents in the above embodiment of the acoustic superstructure cells with adjustable absorption frequency band.

[0056] In some embodiments, the number of acoustic superstructure cells is M 2 , M is a positive integer, such as Figure 4 As shown, the base structure 3 includes a rear cylindrical portion 31 and a front circular plate portion 32 with the same diameter. 2 The cavity parts of the acoustic superstructure cells are arranged in a square array on the rear cylindrical part 31. Similarly, M 2 The end caps 12 of the acoustic superstructure cells are arranged in a square array on the front circular plate portion 32, each end cap 12 of the front circular plate portion 32 corresponds to the cavity portion of the rear cylindrical portion 31, and each end cap 12 is provided with a tuning structure 2, and the corresponding cavity portion, end cap 12 and the tuning structure 2 thereon constitute an acoustic superstructure cell, forming M 2 There are parallel Helmholtz resonance cavities, and each Helmholtz resonance cavity is independent of each other and does not affect each other. The neck holes 121 with different hole diameters and hole lengths can be selected by adjusting the structure 2, and then the respective resonance frequencies can be adjusted, thereby realizing multiple sound absorbers with different sound absorption performances.

[0057] Further, such as Figure 6 As shown, a plurality of positioning holes 321 are provided on the end surface of the front circular plate portion 32 close to the rear cylindrical portion, and correspondingly, a plurality of positioning posts (not shown in the figure) are provided on the end surface of the rear cylindrical portion close to the front circular plate portion 32, and each positioning hole 321 corresponds to a positioning post one by one, and the rear cylindrical portion and the front circular plate portion 32 are positioned by penetrating the positioning holes 321 with the positioning posts, so as to facilitate the subsequent bonding and fixing between the rear cylindrical portion 31 and the front circular plate portion 32, so that the end cover portion 12 of each acoustic superstructure and its corresponding cavity portion 11 are sealed and fixed to each other, forming an M 2 In a specific implementation, the number of the positioning holes 321 and the number of the positioning posts are 4. Figure 6 As shown, the four positioning holes 321 are respectively arranged at the arc-shaped middle part of the outer side of each side of the largest outer square.

[0058] In some specific embodiments, the front circular plate portion 32 is prepared by a Form3 light-curing 3D printer, made of photosensitive resin, and has a diameter of 100 mm. Figure 5 and Figure 6 As shown, 3×3 end caps 12 are provided thereon, and 6 neck holes 121 are respectively provided on each end cap 12. Similarly, the rear cylindrical portion 31 is also prepared by the Form3 light-curing 3D printer, made of photosensitive resin, with a diameter of 100mm, and 3×3 cavities 111 of the cavity portion 11 are provided thereon, corresponding one to one with the 9 end caps 12 of the front circular plate portion 32. Further, the cavity side length of each cavity portion 11 is 20mm, and the total thickness of the rear cylindrical portion 31 and the front circular plate portion 32 is 30mm. In addition, the knob 21 can be prepared by the Raise3D Pro2 fused filament manufacturing 3D printer, made of PLA resin, based on a thin disc with a thickness of 5mm, and a fan ring with a central angle of 60 degrees is cut off, so that only one neck hole 121 in each end cap portion 12 can connect the cavity 111 of the cavity portion 11 with the outside air, and the remaining 5 neck holes are closed. Thus, nine square parallel Helmholtz resonant cavity acoustic superstructures are formed, which can realize 69 sound absorbers with different sound absorption properties.

[0059] In the specific implementation process, the hole diameter of each group of neck holes 121 (i.e., the six neck holes 121 of each end cover portion 12) in the nine square parallel Helmholtz resonant cavity acoustic superstructure is selected according to the perforation rate. The perforation rate should generally be controlled between 0.2% and 1.2%, and the optimal perforation rate is 0.7%. Therefore, in the nine square parallel Helmholtz resonant cavity acoustic superstructure, when the hole diameters of the two neck holes d1 and d2 are the same and the perforation rates are selected as 0.7%, 0.6%, 0.5%, 0.35% and 0.25% respectively, the hole diameters can be calculated to be 5.92mm, 5.48mm, 5.00mm, 4.18mm and 3.54mm; the hole diameters of the three neck holes d3, d4 and d5 are the same, and the perforation rates are selected as 0.7%, 0.6% and 0.7% respectively. , 0.5%, 0.4% and 0.3%, the hole diameters can be calculated to be 4.83mm, 4.47mm, 4.08mm, 3.65mm and 3.16mm; the hole diameters of the four neck holes d6, d7, d8 and d9 are the same, and when the perforation rates are selected as 0.7%, 0.6%, 0.5%, 0.4% and 0.3% respectively, the hole diameters can be calculated to be 4.18mm, 3.87mm, 3.54mm, 3.16mm and 2.74mm. Based on the consideration of the strength of the acoustic superstructure material and the accuracy of 3D printing, the thickness t of the side wall of the rear cylindrical part 31 and the bottom of the cavity 111 is 2 mm, and the hole length li of the neck hole 121 (equal to the thickness of the corresponding fan ring plate) and the depth Ti of the cavity 111 of the cavity part 11 are corresponding, so that the total size of the designed nine square parallel Helmholtz resonant cavity acoustic superstructure sound absorber is fixed to 30 mm (li+Ti+t=30 mm). Specifically, the hole diameter, hole length and cavity 111 depth parameters of each group of neck holes 121 (i.e., 6 neck holes 121 of each end cover part 12) in the nine square parallel Helmholtz resonant cavity acoustic superstructure are selected as shown in Table 1 below:

[0060] Table 1 Summary of geometric parameters of nine parallel square Helmholtz resonant cavity acoustic superstructure

[0061]

[0062]

[0063] In order to further verify the noise reduction performance of the nine square parallel Helmholtz resonant cavity acoustic superstructure in the embodiment of the present application, simulation tests and experimental tests are performed on it.

[0064] This embodiment uses a finite element simulation analysis software developed by Swedish COMSOL, namely COMSOL Multiphysics multi-physics field simulation software for finite element simulation analysis. This software is separated from Matlab's finite element toolbox and is rooted in mathematical physics theory. It converts the physical problem to be solved into a mathematical model. It has a strong advantage in solving mathematical models and simulates real physical phenomena by solving differential equations. Sound absorption is the attenuation and dissipation phenomenon of sound waves during propagation in a medium. Its absorption mechanism is mainly viscous dissipation and heat conduction dissipation. COMSOL is used to model the acoustic superstructure of nine square parallel Helmholtz resonant cavities. The grid model is as follows: Figure 8 According to the parameters in Table 1 above, the nine square parallel Helmholtz resonant cavity acoustic superstructures are numbered from R1 to R9, as shown in Figure 7 shown.

[0065] Through the above modeling, the finite element simulation analysis of the nine square parallel Helmholtz resonant cavity acoustic superstructures was obtained to obtain the boost distribution at each frequency point. The first absorption peak corresponds to the resonance frequency of 552 Hz, the peak sound absorption coefficient is 0.8115, which is mainly achieved by chambers R1 and R2; the second absorption peak corresponds to the resonance frequency of 562 Hz, the peak sound absorption coefficient is 0.8309, which is mainly achieved by chamber R3; the third absorption peak corresponds to the resonance frequency of 576 Hz, the peak sound absorption coefficient is 0.8239, which is mainly achieved by chamber R4; the fourth absorption peak corresponds to the resonance frequency of 606H z, the peak sound absorption coefficient is 0.8287, which is mainly achieved by chamber R5; the fifth absorption peak corresponds to the resonance frequency of 632Hz, and the peak sound absorption coefficient is 0.9006, which is mainly achieved by chambers R6 and R7; the sixth absorption peak corresponds to the resonance frequency of 650Hz, and the peak sound absorption coefficient is 0.9191, which is mainly achieved by chamber R7; the seventh absorption peak corresponds to the resonance frequency of 682Hz, and the peak sound absorption coefficient is 0.8948, which is mainly achieved by chamber R8; the eighth absorption peak corresponds to the resonance frequency of 732Hz, and the peak sound absorption coefficient is 0.9751, which is mainly achieved by chamber R9.

[0066] Using finite element simulation software, the sound absorption coefficient test is carried out according to the six groups of parameters selected in Table 1 above, and the following results can be obtained: Fig. 9 – Fig.14 Six groups of finite element simulation analysis sound absorption coefficient curves of nine square parallel Helmholtz resonant cavity acoustic superstructures are shown, where the abscissa is the sound absorption frequency and the ordinate is the corresponding sound absorption coefficient.

[0067] In this embodiment, the noise reduction performance of the nine square parallel Helmholtz resonant cavity acoustic superstructure with adjustable neck hole cross section and length is tested by the AWA6290T transfer function sound absorption and sound insulation coefficient measurement system. The AWA6290T transfer function sound absorption and sound insulation coefficient measurement system consists of an impedance tube, a power amplifier, a signal generator, a multi-channel noise vibration analyzer, a 1 / 4-inch microphone pair with strict phase matching, and analysis software. The specific test equipment includes a computer with dynamic signal analyzer software, a level 1 sound calibrator, an AWA2022 / AHAI2021 signal acquisition instrument, an impedance tube with a speaker (AHAI2060 / 2061), two 1 / 4-inch microphones and corresponding pre-stages, an AHAI4002 signal generator, an AHAI2043 power amplifier, and multiple wiring. The test process adopts the exchange channel method, and the test frequency range is related to the selected microphone spacing. When the distance between the two microphones is 70 mm, the distance between the front microphone and the experimental sample is 170 mm, the number of sampling lines is 65536, the overlap rate is 50%, the number of repeated measurements of a single frequency point is 200, and the measured frequency range is 200-1600 Hz; when the distance between the two microphones is 140 mm, the distance between the front microphone and the experimental sample is 240 mm, the number of sampling lines is 65536, the overlap rate is 50%, the number of repeated measurements of a single frequency point is 200, and the measured frequency range is 50-1000 Hz.

[0068] The data results obtained during the test are as follows Fig.15 and Fig.16 As shown, it mainly includes frequency, transfer function, reflection factor, sound absorption coefficient, acoustic impedance ratio, and acoustic admittance ratio. In this experiment, the frequency and the corresponding sound absorption coefficient are mainly used. The six groups of parameters are summarized to adjust the sound absorption coefficient of the nine square parallel Helmholtz resonant cavity acoustic superstructures. Fig.17 shown.

[0069] Among them, the fifth group of simulation data was compared with the experimental data obtained by using the AWA6290T transfer function sound absorption and sound insulation coefficient measurement system to obtain the comparison results, such as Fig.18 As shown, the two sets of data are basically consistent, and the superposition of multiple groups of obvious absorption peaks results in a wide absorption band, with the sound absorption coefficient reaching above 0.8 in the range of 560–750 Hz.

[0070] In summary, the "optimal" parameters of the structure were obtained through simulation experiments. In the target frequency range of 500-1200Hz, both the simulation results and the experimental results achieved broadband sound absorption, verifying the feasibility and effectiveness of the design method of the nine square parallel Helmholtz resonant cavity acoustic superstructure. With different geometric parameters, the noise reduction performance of the parallel Helmholtz resonant cavity acoustic superstructure varies significantly. According to different equipment noise reduction requirements and scene noise control requirements, the noise reduction performance of the parallel Helmholtz resonant cavity acoustic superstructure can be flexibly adjusted. It has a simple structure, easy operation, and low cost, which can effectively promote the practical application of the Helmholtz resonant cavity acoustic superstructure in equipment noise control and urban noise pollution prevention and control.

[0071] The present application discloses an acoustic superstructure cell and a sound-absorbing structure with adjustable absorption frequency band. Based on the influence of the neck structural parameters of the resonance cavity on the noise absorption performance of the equipment, the diameter and length of the neck hole are adjusted by using a selection structure to change the neck characteristics of the resonance cavity, thereby achieving control of bandwidth noise at different frequency stages. At the same time, the parameter adjustments of different resonance cavities in the sound-absorbing structure are independent of each other and do not affect each other, and the adjustment is convenient and easy to operate.

[0072] Those skilled in the art will understand that the accompanying drawings are only schematic diagrams of an embodiment, and the modules or processes in the accompanying drawings are not necessarily necessary for implementing the present application. In addition, the modules in the devices in the embodiments may be distributed in the devices in the embodiments according to the description of the embodiments, or may be changed accordingly and located in one or more devices different from the present embodiments. The modules in the above embodiments may be combined into one module, or may be further split into multiple sub-modules.

[0073] It should be noted that similar numbers and letters represent similar items in the following figures, so once an item is defined in one figure, it does not need to be further defined and explained in the subsequent figures. In addition, in the description of the embodiments of the present application, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood in specific circumstances. Moreover, in the description of the present application, it should be noted that the orientation or position relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application.

[0074] Finally, it should be noted that the above-described embodiments are only specific implementation methods of the present application, which are used to illustrate the technical solutions of the present application, rather than to limit them. The protection scope of the present application is not limited thereto. Although the present application is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed in the present application, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. An acoustic superstructure cell with adjustable absorption frequency band, characterized in that: include: A hollow cavity structure, wherein the hollow cavity structure is provided with N+1 neck holes connecting the inside and outside of the cavity of the hollow cavity structure, and the hole diameter and hole length of each neck hole are different, and N is a positive integer, A selection structure is rotatably disposed on the hollow cavity structure to seal the N neck holes of the hollow cavity structure. The remaining neck hole in a connected state forms a resonance cavity with the hollow cavity structure. The neck hole that forms the resonance cavity is selected by rotating the selection structure.

2. The acoustic superstructure cell with adjustable absorption frequency band according to claim 1, characterized in that: The hollow cavity structure includes a cavity portion and an end cover portion, the cavity portion is a cavity structure with one end open, the end cover portion is arranged at the open end of the cavity portion to seal the open end of the cavity portion, N+1 neck holes are arranged on the end cover portion, and the selection structure is rotatably arranged on the end cover portion to seal the N neck holes of the end cover portion.

3. The acoustic superstructure cell with adjustable absorption frequency band according to claim 2, characterized in that: A through hole is provided in the middle of the end cover portion, and a circular array of N+1 neck holes is distributed on the outside of the through hole. The adjustment structure includes a knob, a positioning pin, a tension spring and a bayonet. The knob includes a sealing plate and a rotating shaft passing through both sides of the sealing plate. The sealing plate is a circular plate with a fan ring notch. The rotating shaft is arranged at the center of the sealing plate, and the central angle of the fan ring notch is 360° / (N+1). The sealing plate is arranged on the end surface of the end cover portion away from the cavity portion, and the rotating shaft located on the side of the sealing plate close to the end cover portion is penetrated in the through hole, and the positioning pin is arranged on the rotating shaft located on the side of the sealing plate close to the end cover portion. The bayonet is arranged at one end of the through hole away from the sealing plate, and the two ends of the tension spring are fixed by the positioning pin and the bayonet respectively. Under the elastic force of the tension spring, the sealing plate seals the N neck holes of the end cover portion.

4. The acoustic superstructure cell with adjustable absorption frequency band according to claim 3, characterized in that: The end surfaces of the N+1 neck holes close to the sealing plate are all arranged in the same horizontal plane, and the end surfaces of the N+1 neck holes away from the sealing plate are not arranged in the same horizontal plane.

5. The acoustic superstructure cell with adjustable absorption frequency band according to claim 3, characterized in that: The cavity part and the end cover part are both made of photosensitive resin, the knob is made of PLA resin, and the end cover part is bonded and fixed to the cavity part.

6. The acoustic superstructure cell with adjustable absorption frequency band according to claim 2, characterized in that: The cavity part and the cavity body of the cavity part are both in a cube shape, and the end cover part is a square plate with the same size as the cavity part.

7. A sound-absorbing structure with adjustable absorption frequency band, characterized in that: It comprises a base structure and a plurality of acoustic superstructure cells with adjustable absorption frequency bands as described in any one of claims 1 to 6, wherein the plurality of acoustic superstructure cells are arranged on the base structure in a predetermined arrangement.

8. The sound absorbing structure with adjustable absorption frequency band according to claim 7, characterized in that: The number of the acoustic superstructure cells is M 2 , M is a positive integer, the base structure includes a rear cylindrical part and a front circular plate part with the same diameter, M 2 The cavity parts of the acoustic superstructure cells are arranged in a square array on the rear cylindrical part, 2 The end cover parts of the acoustic superstructure cells are arranged in a square array on the front circular plate part, and each of the end cover parts corresponds to the cavity part one by one.

9. The sound absorbing structure with adjustable absorption frequency band according to claim 8, characterized in that: A plurality of positioning posts are arranged on the end surface of the rear cylindrical part close to the front circular plate part, and a plurality of positioning holes are arranged on the end surface of the front circular plate part close to the rear cylindrical part, each of the positioning holes corresponds to the positioning posts one by one, and the positioning posts are inserted into the positioning holes, and the rear cylindrical part and the front circular plate part are bonded and fixed, so that the end cover part of each acoustic superstructure and the corresponding cavity part are sealed and fixed to each other, forming an M 2 independent resonant cavities.

10. The sound absorbing structure with adjustable absorption frequency band according to claim 8, characterized in that: The diameters of the rear cylindrical portion and the front circular plate portion are 100 mm, the side length of each cavity portion is 20 mm, and the total thickness of the rear cylindrical portion and the front circular plate portion is 30 mm.

Images