Method for processing acoustic black hole with acoustic wave

Abstract

The application provides a sound wave acoustic black hole machining method, belonging to the technical field of pipeline acoustic black hole machining, comprising the following steps: manufacturing two semicylindrical outer pipe bodies, the inner part of the outer pipe body is provided with a plurality of annular grooves, the axial distance from the annular groove to the front end of the outer pipe body is x; manufacturing a plurality of built-in rings, the inner diameter r of all the built-in rings is a negative linear function of x; manufacturing a circular baffle; selecting part of the built-in rings, mounting the selected built-in rings in one outer pipe body, embedding each selected built-in ring into the annular groove with the corresponding axial distance, mounting the circular baffle at the rear end of the outer pipe body, and then assembling the two outer pipe bodies into a cylinder. The application has the beneficial effects that: the machining procedure is simplified by machining only simple parts, and the machining process is more convenient; the once-machined parts can be flexibly assembled to construct a plurality of SBH sample pieces with different structural sizes by reassembling the machined parts, and the application is suitable for the test research of different structural sizes of SBH.

Description

Technical Field

[0001] This invention relates to the field of acoustic black hole fabrication technology, and in particular to a method for fabricating acoustic black holes by manipulating sound waves. Background Technology

[0002] Sonic black holes (SBHs) are used to manipulate sound waves propagating in the air. They are designed as perfect sound-capturing structures by periodically embedding a large number of rings with gradually decreasing inner radii within a circular acoustic conduit. When sound waves enter the SBH, their propagation speed gradually decreases, resulting in wavelength compression. This wavelength compression continues until the wave speed drops to zero, preventing the incident wave from propagating to the end of the structure. Once inside the SBH, the sound waves are trapped and completely absorbed without any reflection. However, in practical applications, discrete SBH structures with a finite number of embedded rings cannot achieve perfect sound absorption. Nevertheless, the superior sound absorption characteristics of practical SBHs have been verified in research, providing new possibilities for various applications in low-frequency broadband noise control engineering. However, in the research of SBH, there are some problems in the processing and manufacturing of its experimental prototypes: traditional SBH prototypes are mostly 3D printed and manufactured in one piece, which is complicated and costly; more importantly, the number, spacing and length of the internal rings in a single processed prototype are fixed, which can only be used for experimental measurement under a single working condition. This makes it inconvenient to carry out systematic experimental research on the SBH structure, which is not conducive to further exploring the sound absorption characteristics of actual discrete SBH structures, the influence law of structural parameters on sound absorption performance and optimization schemes, thus hindering its application in actual noise control. Summary of the Invention

[0003] In view of this, in order to solve the problem that the current SBH prototype integrated manufacturing can only be used for testing and measurement under a single working condition, the embodiments of the present invention provide a method for processing acoustic black holes by sound wave manipulation.

[0004] Embodiments of the present invention provide a method for fabricating acoustic black holes by manipulating sound waves, comprising the following steps:

[0005] Two semi-cylindrical outer tubes are made. Each outer tube has multiple annular grooves inside. The axial distance from the annular grooves to the front end of the outer tube is x.

[0006] Multiple built-in rings are fabricated, and the outer diameter of all built-in rings is the same as the inner diameter of the annular groove. The inner diameter r of all built-in rings is a negatively correlated linear function with x.

[0007] Make a circular baffle;

[0008] Select a portion of the built-in rings, install each selected built-in ring into one of the outer tubes, so that each selected built-in ring is embedded in the annular groove at its corresponding axial distance, and install the circular baffle at the rear end of the outer tube, and then assemble the two outer tubes into a cylinder.

[0009] Furthermore, it also includes studying the sound absorption effect of sound waves manipulating acoustic black holes by adjusting structural parameters. The structural parameters include one or more of the following: the number of selected built-in rings, the arrangement length of the selected built-in rings, the spacing between the selected built-in rings, and the inner diameter of the selected built-in rings. The optimal structural parameters corresponding to the desired sound absorption effect are determined, built-in rings are selected according to the optimal structural parameters, and the installation positions of the selected built-in rings and the circular baffle are determined.

[0010] Furthermore, the negative linear correlation function between the outer and inner diameters r of all built-in annexes and x is: Where R is the inner diameter of the outer tube and L is the length of the outer tube.

[0011] Furthermore, the outer tube has a length L of 202mm, an inner diameter R of 30mm, and a wall thickness of 6mm; the selected number of inner rings is 19, and the thickness of both the inner rings and the circular baffle is 2mm.

[0012] Furthermore, the axial distance between the last inner ring and the circular baffle is 10mm, and the other inner rings are arranged at equal intervals of 8mm.

[0013] Furthermore, the circular baffle can be installed within one of the annular grooves.

[0014] Furthermore, the diameter and thickness of the circular baffle are the same as the outer diameter and thickness of the inner ring, and the circular baffle is embedded in an annular groove behind the last inner ring.

[0015] Furthermore, the built-in ring is an annular plate.

[0016] Furthermore, the thickness of the built-in ring is equal to the width of the annular groove.

[0017] Furthermore, the outer tube, the inner ring, and the circular baffle are all made of aluminum alloy.

[0018] The beneficial effects of the technical solutions provided by the embodiments of the present invention are as follows:

[0019] This invention discloses a method for fabricating acoustic black holes using acoustic waves. On one hand, it simplifies the fabrication process by processing only simple components, making the originally complex process more convenient. On the other hand, by reassembling some of the fabricated components, multiple SBH (Sound-Based Hole) prototypes with different structural dimensions can be flexibly constructed from components processed in a single step. This method is suitable for experimental research on SBHs under different structural dimensions, such as flexibly changing the number of internal rings, the spacing between rings, the inner diameter of the internal rings, and the overall length of the SBH structure. This fabrication method further enhances the convenience of conducting systematic experimental research on SBH structures, helping to deeply explore the sound absorption characteristics of actual discrete SBH structures, the influence of structural parameters on sound absorption performance, and optimization schemes, thereby promoting its early application in practical noise control. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a pipe acoustic black hole sample made by a method for fabricating acoustic black holes using acoustic waves according to the present invention.

[0021] Figure 2 This is the front view of the outer tube.

[0022] Figure 3 This is a schematic diagram of the built-in circular ring and circular baffle;

[0023] Figure 4 This is an installation diagram of the inner ring, circular baffle, and outer tube.

[0024] Figure 5 The pipe acoustic black hole prototype with 19, 11, and 10 built-in rings was fabricated in this embodiment.

[0025] Figure 6 It is a graph of the sound absorption coefficient of a pipe acoustic black hole sample with 19 built-in rings.

[0026] Figure 7 It is a graph of the sound absorption coefficient of a pipe acoustic black hole specimen with 11 built-in rings;

[0027] Figure 8 This is a graph showing the sound absorption coefficient of a pipe acoustic black hole specimen with 10 built-in rings.

[0028] In the diagram: 1. Outer tube; 101. Annular groove; 2. Inner ring; 3. Circular baffle. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described below with reference to the accompanying drawings. The following description presents a preferred embodiment of the various possible embodiments of the present invention, intended to provide a basic understanding of the invention, but not intended to identify key or decisive elements of the invention or to limit the scope of protection sought.

[0030] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0031] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0032] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures. Also, it should be understood that, for ease of description, the dimensions of the various parts shown in the figures are not drawn to actual scale.

[0033] It should be noted that, unless otherwise explicitly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0034] Please refer to Figure 1-4 The present invention provides a method for fabricating acoustic black holes by manipulating sound waves, used to create acoustic black hole prototypes in pipelines, mainly including the following steps:

[0035] Two semi-cylindrical outer tubes 1 are fabricated, and the two outer tubes 1 can be joined together to form a complete cylindrical tube. Each outer tube 1 has multiple annular grooves 102 inside, which are excavated into the inner wall of the outer tube 1, and all annular grooves 102 have the same depth. The axial distance from the annular grooves 102 to the front end of the outer tube 1 is x, and the front end of the outer tube 1 is the sound inlet end.

[0036] Multiple built-in rings 2 are fabricated. For ease of processing and assembly, the built-in rings 2 can be made of annular plates. The outer diameter of all built-in rings 2 is the same as the inner diameter of the annular groove 102, and the thickness of the built-in rings 2 is equal to the width of the annular groove 102, so that the built-in rings 2 can be precisely embedded in the annular groove 102.

[0037] Furthermore, the inner diameter r of all the built-in rings 2 is negatively correlated with x as a linear function, meaning that the inner diameter of all the built-in rings 2 gradually decreases.

[0038] A circular baffle 3 is fabricated, the diameter of which is approximately the same as the inner diameter of the outer tube 1. This baffle is used to block the rear ends of the two outer tubes 1, i.e., to block the sound outlet. The diameter and thickness of the circular baffle 3 are the same as the outer diameter and thickness of the inner ring 2; therefore, the circular baffle 3 can also be installed in any of the annular grooves 102.

[0039] Select a portion of the built-in rings 2 and install each selected built-in ring 2 inside one of the outer tubes 1, so that each selected built-in ring 2 is embedded in the annular groove 102 at its corresponding axial distance. Then, install the circular baffle 3 at the rear end of the outer tube 1, and then assemble the two outer tubes 1 into a cylinder. The two outer tubes 1 can be connected by detachable means such as bolts or pins.

[0040] It should be noted that, in order to achieve the desired sound absorption effect when selecting the built-in ring 2, the sound absorption effect of the acoustic black hole manipulated by sound waves can be studied by adjusting the structural parameters. The structural parameters include one or more of the following: the number of selected built-in rings 2, the arrangement length of the selected built-in rings 2, the spacing between the selected built-in rings 2, and the inner diameter of the selected built-in rings 2. The optimal structural parameters corresponding to the desired sound absorption effect are determined, the built-in rings 2 are selected according to the optimal structural parameters, and the installation positions of the selected built-in rings 2 and the circular baffle 3 are determined.

[0041] Specifically, the installation position of the circular baffle 3 can be adjusted by installing the circular baffle 3 into an annular groove 102 on the outer tube 1, so that the circular baffle 3 is embedded in an annular groove 102 behind the last built-in ring 2. Then, the built-in rings 2 are arranged in a portion of all the annular grooves 102 between the circular baffle 3 and the front end of the outer tube 1. In this way, the arrangement length of the selected built-in rings 2 of the pipeline acoustic black hole specimen can be adjusted to study the influence of the length of the pipeline acoustic black hole specimen on its acoustic characteristics. Secondly, the influence of the number of built-in rings 2 on the acoustic characteristics of the pipeline acoustic black hole specimen can be studied by freely increasing or decreasing the number of built-in rings 2. Finally, the influence of the inner diameter and position of the built-in rings 2 on their acoustic characteristics can be studied by adjusting the rings with different inner diameters and arranging the built-in rings 2 in different positions.

[0042] Furthermore, this embodiment also verifies the fabrication of a low-frequency, ultra-wideband sound-absorbing pipe acoustic black hole sample using the aforementioned acoustic wave-manipulated acoustic black hole fabrication method, as detailed below:

[0043] like Figure 5 As shown, in this embodiment, the outer tube 1, the inner ring 2, and the circular baffle 3 are all made of aluminum alloy. The outer tube 1 has a length L of 202mm, an inner diameter R of 30mm, and a wall thickness of 6mm; the selected number of inner rings 2 is 19, and the thickness of both the inner rings 2 and the circular baffle 3 is 2mm.

[0044] The negative linear correlation function between the outer and inner diameters r of all built-in annulus 2 and x is: Where R is the inner diameter of the outer tube 1 and L is the length of the outer tube 1.

[0045] By assembling the two outer tubes 1, the 19 inner rings 2, and the circular baffles 3 in a certain manner, pipe acoustic black hole sample pieces with different structural parameters are formed:

[0046] The pipe acoustic black hole specimen is assembled with 19 built-in rings 2. The axial distance between the last built-in ring 2 and the circular baffle 3 is 10 mm, and the other built-in rings 2 are arranged at equal intervals of 8 mm.

[0047] The pipe acoustic black hole specimen is assembled with 11 built-in rings 2. The axial distance between the last built-in ring 2 and the circular baffle 3 is 4 mm. The other built-in rings 2 are arranged at equal intervals of 16 mm.

[0048] Assemble a pipe acoustic black hole specimen with 10 of the aforementioned built-in rings 2, which is equivalent to a pipe acoustic black hole specimen with 11 of the aforementioned built-in rings 2, minus the rearmost of the aforementioned built-in ring 2 in the pipe acoustic black hole specimen with 11 of the aforementioned built-in rings 2.

[0049] Using a B&K standard standing wave tube to test the perpendicular incidence of sound waves, sound absorption tests were conducted on pipe acoustic black hole specimens with 19, 11, and 10 of the aforementioned built-in circular rings 2. The results showed that:

[0050] from Figure 6 As can be seen, the absorption coefficient of the pipe acoustic black hole specimen with 19 built-in rings 2 first increases sharply to nearly 1 near 200 Hz, then decreases slightly near 250 Hz, after which the absorption coefficient curve oscillates, showing several peaks and troughs. Starting from a very low frequency of about 350 Hz, the absorption coefficient can reach as high as 0.8, and then remains at this value until the highest value with several peaks even reaches almost 1. This demonstrates that the pipe acoustic black hole specimen with 19 built-in rings 2 has excellent low-frequency and broadband sound absorption performance.

[0051] like Figure 7 and8 As shown, reducing the number of the embedded rings 2 to 11 and 10 correspondingly decreases the sound absorption coefficient of the pipe acoustic black hole specimen, indicating that reducing the number of embedded rings 2 significantly reduces the sound absorption performance of the pipe acoustic black hole specimen. This demonstrates that...

[0052] The sound absorption characteristics of the pipe acoustic black hole specimen are directly related to the number of the built-in circular rings 2.

[0053] Furthermore, the pipe acoustic black hole specimen with 19 built-in rings 2 exhibits excellent low-frequency ultra-wideband sound absorption. However, when the number of built-in rings 2 is reduced to 11 and 10 rings, its sound absorption effect is significantly reduced. This is consistent with the previous numerical simulation results on the pipe acoustic black hole structure, and further demonstrates the great advantages of the above-mentioned acoustic wave-manipulated acoustic black hole processing method: it simplifies the processing and manufacturing procedure of the pipe acoustic black hole specimen, greatly reduces the experimental cost, and enhances the convenience of its testing. This is more conducive to further research, verification, and optimization of the pipe acoustic black hole structure, enabling the pipe acoustic black hole structure to be better applied to low-frequency broadband noise control.

[0054] In this document, the directional terms such as front, back, top, and bottom are defined based on the position of the components in the accompanying drawings and their relative positions to each other, solely for the purpose of clarity and convenience in expressing the technical solution. It should be understood that these are relative concepts and can vary depending on different methods of use and placement; the use of these directional terms should not limit the scope of protection claimed in this application.

[0055] Where there is no conflict, the embodiments and features described above can be combined with each other. The above descriptions are merely preferred embodiments of the present invention and are not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for fabricating acoustic black holes using acoustic wave manipulation, characterized in that, Includes the following steps: Two semi-cylindrical outer tubes are made. Each outer tube has multiple annular grooves inside. The axial distance from the annular grooves to the front end of the outer tube is x. Multiple inner rings are fabricated, with the outer diameter of all inner rings being the same as the inner diameter of the annular groove. The inner diameter *r* of all inner rings exhibits a negative linear correlation with *x*. The negative linear correlation function between the inner diameter *r* and *x* of all inner rings is: Where R is the inner diameter of the outer tube and L is the length of the outer tube; Make a circular baffle; Select a portion of the built-in rings, install each of the selected built-in rings into one of the outer tubes, so that each selected built-in ring is embedded in the annular groove of its corresponding axial distance, and install the circular baffle at the rear end of the outer tube, and then assemble the two outer tubes into a cylinder. The sound absorption effect of acoustic black holes manipulated by sound waves is studied by adjusting structural parameters. The structural parameters include one or more of the following: the number of selected built-in rings, the arrangement length of the selected built-in rings, the spacing between the selected built-in rings, and the inner diameter of the selected built-in rings. The optimal structural parameters corresponding to the desired sound absorption effect are determined, the built-in rings are selected according to the optimal structural parameters, and the installation positions of the selected built-in rings and the circular baffle are determined.

2. The method for fabricating acoustic black holes by manipulating sound waves as described in claim 1, characterized in that: The outer tube has a length L of 202mm, an inner diameter R of 30mm, and a wall thickness of 6mm; the selected number of inner rings is 19, and the thickness of both the inner rings and the circular baffle is 2mm.

3. The method for fabricating acoustic black holes by manipulating sound waves as described in claim 2, characterized in that: The axial distance between the last inner ring and the circular baffle is 10mm, and the other inner rings are arranged at equal intervals of 8mm.

4. The method for fabricating acoustic black holes by manipulating sound waves as described in claim 1, characterized in that: The circular baffle can be installed in one of the annular grooves.

5. The method for fabricating acoustic black holes by acoustic wave manipulation as described in claim 4, characterized in that: The diameter and thickness of the circular baffle are the same as the outer diameter and thickness of the inner ring, and the circular baffle is embedded in the annular groove behind the last inner ring.

6. The method for fabricating acoustic black holes by acoustic wave manipulation as described in claim 1, characterized in that: The built-in ring is a ring plate.

7. The method for fabricating acoustic black holes by acoustic wave manipulation as described in claim 1, characterized in that: The thickness of the built-in ring is equal to the width of the annular groove.

8. The method for fabricating acoustic black holes by acoustic wave manipulation as described in claim 1, characterized in that: The outer tube, the inner ring, and the circular baffle are all made of aluminum alloy.

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