Acoustic transmission structure, device and apparatus

Abstract

The present application relates to a kind of acoustic transmission structure, device and apparatus.The acoustic transmission structure has acoustic wave entrance face and acoustic wave exit face, comprising: multiple acoustic transmission components, each acoustic transmission component extends from acoustic wave entrance face to the acoustic wave exit face, and at least part acoustic transmission component has bending portion at preset position;Wherein, each acoustic transmission component has preset impedance matching parameter, preset impedance matching parameter is configured to make acoustic wave be transmitted in acoustic transmission component with non-resonant base mode in preset frequency band, and make the acoustic wave transmittance of acoustic transmission component greater than or equal to first preset value;And, each acoustic transmission component has preset acoustic path parameter, preset acoustic path parameter is configured to make the absolute value of acoustic path difference in any two acoustic transmission components less than or equal to second preset value in preset frequency band.The above-mentioned acoustic transmission structure can weaken or eliminate the acoustic scattering of object in wide frequency range.

Description

Technical Field

[0001] This invention relates to the field of acoustic wave transmission technology, and in particular to an acoustic transmission structure, device, and apparatus. Background Technology

[0002] Sound scattering refers to the phenomenon where, when a sound wave encounters an obstacle during propagation, some of the sound wave deviates from its original propagation path and spreads outwards from the obstacle. When a sound wave is incident on an obstacle, the obstacle is excited by the incident sound and becomes a secondary sound source, converting some of the incident sound energy into scattered sound energy and radiating it outwards. The portion of the sound wave that spreads outwards from the obstacle is called the scattered sound wave.

[0003] like Figure 1 As shown in Figure (a), many disordered obstacles are distributed in space. When sound waves are incident on these obstacles, due to the extreme impedance mismatch between the obstacles and the background medium (such as air), scattered waves will inevitably be generated, ultimately causing the entire sound field to become chaotic. Therefore, the presence of obstacles greatly affects the propagation of sound waves.

[0004] In many fields, eliminating or reducing sound scattering is an urgent need, and furthermore, the need for frequency bandwidth is also very important. Summary of the Invention

[0005] To address at least one of the aforementioned problems, the present invention aims to provide an improved acoustic transmission structure.

[0006] In a first aspect, this application provides a sound transmission structure. The sound transmission structure has a sound wave incident surface and a sound wave exit surface, comprising:

[0007] A plurality of sound transmission components, each of the sound transmission components extending from the sound wave incident surface to the sound wave emitting surface, and at least a portion of the sound transmission components having a bent portion at a predetermined position;

[0008] Each of the acoustic transmission components has a preset impedance matching parameter, which is configured to allow acoustic waves to be transmitted in the acoustic transmission component in a non-resonant fundamental mode within a preset frequency band, and to make the acoustic wave transmittance of the acoustic transmission component greater than or equal to a first preset value.

[0009] and,

[0010] Each of the sound transmission components has a preset sound path parameter, which is configured such that the absolute value of the sound path difference between any two of the sound transmission components is less than or equal to a second preset value within the preset frequency band.

[0011] The aforementioned sound transmission structure comprises multiple sound transmission components, at least some of which have bends at preset positions, and each component has a preset impedance matching parameter. This allows almost all sound waves to be transmitted into the sound transmission components and propagate forward along the extension direction of the components, bypassing the object. Furthermore, each component has a preset path length parameter, ensuring that the path difference between any two components is almost zero. This makes the wavefronts of the sound waves at the incident and exit surfaces nearly identical, thereby achieving acoustic cloaking of the object and reducing or eliminating sound scattering during the process. In addition, since the sound waves are transmitted in the sound transmission components using a non-resonant fundamental mode, this facilitates a wideband acoustic cloaking effect. In other words, it is beneficial to achieve better sound scattering reduction or elimination effects over a wide frequency range.

[0012] Optionally, the bandwidth of the preset frequency band is greater than or equal to 10kHz.

[0013] Optionally, the preset frequency band includes 1kHz to 16kHz.

[0014] Optionally, the first preset value is one of 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, and 1.

[0015] Optionally, the second preset value is one of 0, 0.05a, 0.1a, 0.15a, 0.2a, and 0.25a, ​​where a represents the vertical distance from the sound wave incident surface to the sound wave exiting surface.

[0016] Optionally, the sound transmission component includes: a conduit extending from the sound wave incident surface to the sound wave emitting surface; a protrusion disposed on the wall of the conduit and extending inward; the impedance matching parameter includes at least one of the wall thickness of the conduit, the cross-sectional diameter of the conduit, the extension length of the protrusion, and the spacing between the protrusions; the sound path parameter includes at least one of the extension length of the conduit, the inner diameter of the conduit, the extension length of the protrusion, and the spacing between adjacent protrusions along the axial direction of the conduit.

[0017] Optionally, among any two sound transmission components with different extension lengths, the sound path adjustment factor of the sound transmission component with the larger extension length is smaller than that of the sound transmission component with the smaller extension length, wherein the sound path adjustment factor represents the ratio of the length of the protrusion in the direction perpendicular to the pipe axis to the inner diameter of the pipe.

[0018] Optionally, the sound transmission member includes at least a pair of protrusions extending in opposite directions, and the sound path adjustment factor ranges from 0.05 to 0.22.

[0019] Optionally, the inner diameter of the pipe is less than or equal to the wavelength of the incident sound wave in a vacuum.

[0020] Optionally, the pipe and the protrusion are integrally formed from a hard boundary material.

[0021] Optionally, the hard boundary material includes at least one of glass, plastic, resin, metal, steel reinforcement, and concrete.

[0022] Secondly, this application also provides a device including the acoustic transmission structure as described above, and the device having at least one slot or cavity for accommodating an object, the slot or cavity being located between the acoustic wave incident surface and the acoustic wave exit surface of the acoustic transmission structure.

[0023] The aforementioned device has a slot or cavity for accommodating an object, so that when sound waves propagate to the vicinity of the object, the sound scattering of the object can be reduced or eliminated over a wide frequency range through the sound transmission structure described above, thereby achieving a better sound stealth effect.

[0024] Thirdly, this application also provides an apparatus including a housing; and an acoustic transmission structure as described above disposed around the housing.

[0025] The aforementioned device, through the sound transmission structure described above, can reduce or eliminate its own sound scattering of sound waves over a wide frequency range, thereby achieving a better sound stealth effect. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 Figure (a) is a schematic diagram of sound waves being scattered when they encounter an obstacle;

[0028] Figure 1 Figure (b) is a schematic diagram of the acoustic transmission structure of this application achieving acoustic cloaking of an object;

[0029] Figure 2 Figure (a) is a schematic diagram of the structure of an acoustic transmission component according to an embodiment of this application;

[0030] Figure 2 Figure (b) shows the sound pressure distribution of the sound wave during transmission in the embodiment shown in Figure (a) under different sound path control factors;

[0031] Figure 2Figure (c) is a schematic diagram showing the changes in transmissivity and phase delay of a sound wave as a function of the acoustic path modulation factor during transmission in the embodiment shown in Figure (a).

[0032] Figure 2 Figure (d) shows the variation of the equivalent refractive index of the embodiment shown in Figure (a) under different path length control factors and different frequencies;

[0033] Figure 3 Figures (a) and (d) are respectively a schematic diagram of an experimental test and a test environment diagram of an embodiment of the acoustic transmission structure of this application;

[0034] Figure 3 Figure (b) is a schematic diagram of the arrangement of some of the sound transmission components in the embodiment shown in Figure (a);

[0035] Figure 3 Figure (c) shows the sound path modulation factor values ​​of some of the sound transmission components in the embodiment shown in Figure (a);

[0036] Figure 4 Figures (a), (c), and (e) respectively show Figure 3 Simulation results and experimental test results of sound pressure distribution when medium sound waves are scattered by obstacles;

[0037] Figure 4 Figures (b), (d), and (f) respectively show Figure 3 The simulation results and experimental test results of the sound pressure distribution when the obstacle is acoustically cloaked, as shown in the embodiment;

[0038] Figure 4 The (g) diagram shows Figure 3 When medium sound waves encounter obstacles, they scatter and Figure 3 The illustrated embodiment shows the curve of the scattering intensity of the transmitted field as a function of frequency when achieving acoustic cloaking of an obstacle.

[0039] Figure 4 The (h) diagram shows Figure 3 When medium sound waves encounter obstacles, they scatter and Figure 3 The illustrated embodiment shows the variation curve of the scattering intensity of the reflected field with frequency when achieving acoustic cloaking against obstacles;

[0040] Figure 5 Figure (a) is a schematic diagram of the acoustic transmission structure according to another embodiment of this application;

[0041] Figure 5 Figure (b) shows the sound path modulation factor values ​​of each sound transmission component in the embodiment shown in Figure (a);

[0042] Figure 5Figures (c) to (e) show the sound pressure distribution results at 4860Hz, 6860Hz, and 8860Hz when the sound waves in Figure (a) are scattered by obstacles and when the embodiment shown in Figure (a) achieves acoustic cloaking of obstacles.

[0043] Figure 5 Figure (f) shows the scattering intensity of the transmitted field as a function of frequency when the sound wave is scattered by an obstacle in Figure (a) and when the embodiment shown in Figure (a) achieves acoustic cloaking of the obstacle.

[0044] Figure 5 Figure (g) shows the scattering intensity of the reflected field as a function of frequency when the sound wave is scattered by an obstacle in Figure (a) and when the embodiment shown in Figure (a) achieves acoustic cloaking of the obstacle.

[0045] Component labels in the diagram:

[0046] 10. Sound transmission structure; 100. Sound transmission component; 110. Pipe; 120. Protrusion;

[0047] P1, sound wave injection surface; P2, sound wave emission surface; P10, sound wave injection surface in the pipe; P20, sound wave emission surface in the pipe. Detailed Implementation

[0048] To make the technical solution and beneficial effects of the present invention more apparent and understandable, a detailed description is provided below by listing specific embodiments. The accompanying drawings are not necessarily drawn to scale, and local features may be enlarged or reduced to more clearly show the details of the local features; unless otherwise defined, the technical and scientific terms used herein have the same meanings as those in the technical field to which this application pertains.

[0049] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0050] Acoustic metamaterials, using subwavelength microstructures as their basic units, can achieve unique properties not found in natural materials, including negative mass density, negative elastic modulus, and anisotropic parameters. Acoustic metamaterials can freely manipulate sound waves to achieve remarkable phenomena and applications, such as negative refraction, cloaking, and super-resolution imaging. Acoustic cloaking devices include transmissive and reflective cloaking devices. Transmissive cloaking involves encasing the object to be cloaked; when sound waves are incident on the object, they are bent and bypass the object, continuing their propagation and ultimately achieving a "disappearing space" cloaking effect (the space occupied by the device and object). Reflective cloaking simulates mirror reflection; the cloaking device covers the object, and when sound waves are incident on the object, they are not affected by the non-uniform surface caused by the object but are reflected back by the cloaking device, ultimately achieving the cloaking effect.

[0051] Acoustic stealth devices can effectively eliminate the scattering of sound waves caused by obstacles during propagation. However, traditional transmissive acoustic stealth devices typically employ resonance to increase the transmissivity of sound waves and reduce or even eliminate scattering in order to ensure that sound waves propagate as losslessly as possible. But this limits the operating frequency of the device to the resonant frequency, resulting in a narrow operating frequency band. Furthermore, traditional acoustic stealth devices have relatively complex structures and high manufacturing costs. For example, [1] Research.2019,8345683(2019), this paper proposes an air-transmitting acoustic stealth structure based on PT symmetry theory, but the acoustic stealth effect can only be achieved at a single frequency; for another example, [2] Phys.Rev.Lett.106,024301(2011), [3] Phys.Rev.B.95,180104(2017), both of these papers disclose underwater transmission-type stealth structures, but the structures of these two papers are relatively complex, and although the working frequency band is widened to several kHz, the acoustic stealth effect is not very good.

[0052] To achieve a wider frequency band and better acoustic stealth effect, such as Figure 1 As shown in Figure (b), the acoustic stealth device needs to meet the following conditions as much as possible:

[0053] A. Sound waves cannot cause backscattering when they are incident on an obstacle;

[0054] B. Acoustic stealth devices can guide sound waves around obstacles without damage;

[0055] C. The wavefront on the sound wave emitting surface of the acoustic stealth device should be kept as consistent as possible with the wavefront on its sound wave emitting surface.

[0056] The wavefront, in this context, represents the surface formed by particles that have just begun to displace as a wave propagates through a medium. It signifies the spatial location where the wave energy arrives at a given moment; in other words, the wavefront is in motion. Based on the shape of the wavefront, waves can generally be classified into spherical waves, plane waves, cylindrical waves, etc.

[0057] Meeting the above three conditions is very demanding, but this application has successfully overcome these difficulties and designed an acoustic transmission structure 10 that can achieve acoustic stealth effect over a wide frequency range. Furthermore, the structure of the acoustic transmission structure 10 is relatively simple, which helps to reduce manufacturing costs and increase the possibility of industrialization.

[0058] Please refer to Figure 1 As shown in Figure (b), the acoustic transmission structure 10 of this application is disposed around an object (such as an obstacle) and has an acoustic wave incident surface P1 and an acoustic wave exit surface P2. The incident acoustic wave can bypass the object during its transmission from the acoustic wave incident surface P1 to the acoustic wave exit surface P2, and can continue to propagate forward without changing the wavefront when exiting from the acoustic wave exit surface P2.

[0059] Specifically, the sound transmission structure 10 includes a plurality of sound transmission members 100, each extending from the sound wave incident surface P1 to the sound wave exit surface P2, and at least a portion of the sound transmission members 100 has a bent portion at a predetermined position to allow the sound wave to bypass the object. For example... Figure 4 Figures (b), (d), and (f) show the effect of multiple sound transmission members 100 with bent portions at the same location causing sound waves to bypass an object. In this example, the degree of bending of the bent portions of different sound transmission members 100 can be different. Figure 5 Figures (c), (d), and (e) illustrate the effect of sound waves bypassing an object by multiple sound transmission components 100 with bent portions at different locations. In this example, the degree of bending of the bent portions of different sound transmission components 100 can be different, and the degree of bending of different bent portions of the same sound transmission component 100 can also be different. Optionally, the coordinates of the preset positions (or the bending positions of the sound transmission components 100) can be obtained based on the size and outline of the object combined with transformation acoustics theory. By setting bends at these coordinate positions of the sound transmission components 100, it is more beneficial to guide sound waves around the object. Optionally, the size of the object can be arbitrary, and the outline of the object can be a regular square, circle, rhombus, triangle, etc., or other irregular shapes.

[0060] Optionally, the sound transmission component 100 may be made of a hard boundary material, which refers to a material with a very high acoustic impedance compared to air. When a sound wave is incident on this material, the sound wave undergoes total internal reflection. Thus, the sound wave can be transmitted forward in the sound transmission component 100 made of hard boundary material by total internal reflection. In other words, a bent pipe made of hard boundary material can be used to guide the sound wave around the object. Optionally, the hard boundary material includes at least one of glass, plastic, resin, metal, steel reinforcement, and concrete.

[0061] Each acoustic transmission component 100 has a preset impedance matching parameter, which is configured to ensure that the acoustic wave propagates in the acoustic transmission component 100 in a non-resonant fundamental mode within a preset frequency band, and that the acoustic wave transmittance of the acoustic transmission component 100 is greater than or equal to a first preset value. The acoustic impedance represents the complex ratio of the pressure of the transmission medium per unit area on the wavefront to the volume velocity passing through that unit area. It reflects the damping characteristics of a particle caused by a mechanical disturbance at a certain location in the medium. The larger the acoustic impedance, the easier it is for the acoustic wave to scatter upon incidence. The fundamental mode represents the basic mode of the acoustic wave propagating in the acoustic transmission component 100; for example, a plane wave is a fundamental mode. The preset frequency band can represent the operating frequency band of the acoustic transmission component 100, such as 500Hz~11kHz, 1kHz~12kHz, 2kHz~13kHz, 3kHz~16kHz, 4kHz~17kHz, etc.

[0062] When the acoustic wave transmittance of the acoustic transmission member 100 is greater than or equal to a first preset value, it can be considered that the acoustic wave transmittance of the acoustic transmission member 100 is sufficiently large to possess impedance matching characteristics with the background medium (such as air or water), thereby allowing almost all sound waves to be incident into the acoustic transmission structure 10. Optionally, the first preset value can be one of 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or 1. The larger the first preset value, the higher the impedance matching degree between the acoustic transmission member 100 and the background medium. Optionally, the impedance matching parameters of the acoustic transmission member 100 may include the wall thickness of the acoustic transmission member 100, the area of ​​the portion of the acoustic transmission member 100 that blocks sound wave transmission at the sound wave transmission cross section, etc.

[0063] Furthermore, each sound transmission component 100 has a preset sound path parameter, which is configured such that the absolute value of the sound path difference between any two sound transmission components 100 is less than or equal to a second preset value within a preset frequency band. Here, sound path represents the distance a sound wave travels in one direction. Numerically, sound path can be expressed as the product nl of the refractive index n of the medium and the path l of the sound wave in that medium. For example, if a sound wave travels 1m in one direction in air (refractive index 1), then the sound path of that sound wave is 1m. By ensuring that the absolute value of the sound path difference between any two sound transmission components 100 is less than or equal to the second preset value within a preset frequency band using the preset sound path parameter, when the sound wave exits from the sound wave exit surface P2, the wavefront of the sound wave at the sound wave exit surface P2 is almost identical to the wavefront of the sound wave at the sound wave entry surface P1, thus almost eliminating scattering throughout the process.

[0064] Optionally, the preset sound path parameters may include the extension length of the sound transmission member 100, and structural parameters that affect its equivalent refractive index, such as the inner diameter of the sound transmission member 100 or related parameters of its internal structure specifically used to adjust the sound path. Optionally, the second preset value may be one of 0, 0.05a, 0.1a, 0.15a, 0.2a, and 0.25a, ​​where a represents the vertical distance from the sound wave incident surface P1 to the sound wave exiting surface P2. The smaller the second preset value, the more consistent the sound path of the sound wave is in different sound transmission members 100, which helps to make the wavefront of the sound wave at the sound wave exiting surface P2 almost consistent with the wavefront of the sound wave at the sound wave incident surface P1, thereby ensuring the reduction or elimination of sound scattering.

[0065] The aforementioned sound transmission structure includes multiple sound transmission components 100, at least some of which have a bent portion at a preset position. Each sound transmission component 100 has a preset impedance matching parameter, allowing almost all sound waves to be transmitted into the sound transmission component 100 and bypass the object to continue propagating forward. Furthermore, each sound transmission component 100 has a preset sound path parameter, ensuring that the wavefront of the sound wave at the sound wave incident surface P1 and the wavefront of the sound wave exiting surface P2 are almost identical, thereby achieving acoustic cloaking of the object and reducing or eliminating sound scattering during the process. In addition, since the sound wave is transmitted in the sound transmission component 100 in a non-resonant fundamental mode, it is beneficial to achieve a wideband acoustic cloaking effect. In other words, it is beneficial to achieve a better sound scattering reduction or elimination effect over a wide frequency range.

[0066] In some implementations, the bandwidth of the preset frequency band is greater than or equal to 10kHz. In other words, the bandwidth of the preset frequency band can be 10kHz, 11kHz, 12kHz, 13kHz, 14kHz, 15kHz, 16kHz, or 18kHz. A larger bandwidth means that the reduction or elimination of sound scattering can be achieved over a wider frequency range. However, as the frequency increases further, the wavelength of the sound wave also becomes shorter. When the wavelength of the sound wave is smaller than the cross-sectional size of the sound transmission member 100, the modulation effect of the sound transmission member 100 on the sound wave will weaken, and the performance of improving sound scattering will disappear. Therefore, the bandwidth should not be too large.

[0067] Optionally, the preset frequency band includes 1kHz to 16kHz. The operating frequency band of the sound transmission structure 10 is within this preset frequency band, which ensures the bandwidth for reducing or eliminating sound scattering from obstacles and can be applied to most scenarios requiring the reduction or elimination of sound scattering from obstacles. If the operating frequency exceeds 16kHz, the wavelength of the sound wave is too small, which is not conducive to the modulation effect of the sound transmission component 100 on the sound wave. Even if the size of the sound transmission component 100 is made smaller to meet the application requirements of high frequency, the excessively small size is prone to causing greater loss of the sound wave, which is not conducive to the transmission of the sound wave. If the operating frequency is below 1kHz, the wavelength of the sound wave is too large, which may be much larger than the obstacle. In this case, the sound wave can bypass the obstacle, and the scattering itself is not obvious, so the significance of scattering elimination is not great.

[0068] In some implementations, such as Figure 2 As shown in Figure (a), the sound transmission component 100 includes: a conduit 110 extending from the sound wave incident surface P1 to the sound wave exit surface P2; and a protrusion 120 disposed on the wall of the conduit 110 and extending inward. As can be seen from the foregoing, impedance matching parameters may include the wall thickness of the acoustic transmission member 100, the area of ​​the portion of the acoustic transmission member 100 that blocks acoustic wave transmission in the acoustic wave transmission cross section, etc. Therefore, in this embodiment, impedance matching parameters may correspond to at least one of the following: the wall thickness of the pipe 110, the cross-sectional diameter of the pipe 110, the extension length of the protrusion 120, and the spacing between the protrusions 120. Similarly, as can be seen from the foregoing, sound path parameters may include the extension length of the acoustic transmission member 100, and structural parameters that affect its equivalent refractive index, etc. Therefore, in this embodiment, since the inner diameter of the pipe 110 and the arrangement of the protrusions 120 both affect the sound path, the sound path parameters may correspond to at least one of the following: the extension length of the pipe 110, the inner diameter of the pipe 110, the extension length of the protrusions 120, and the spacing between adjacent protrusions 120 along the axial direction of the pipe 110.

[0069] It is understood that, since at least a portion of the sound transmission member 100 has a bent portion, in this embodiment, at least a portion of the conduit 110 also has a bent portion. Further, the conduit 110 includes a conduit sound wave ingress surface P10 and a conduit sound wave egress surface P20, with the conduit sound wave ingress surface P10 located at the sound wave ingress surface P10 and the conduit sound wave ingress surface P20 located at the sound wave egress surface P20. Therefore, the extension length of the sound transmission member 100 can be expressed as the extension length from the conduit sound wave ingress surface P10 to the conduit sound wave egress surface P20.

[0070] Optionally, the material of the conduit 110 can be a hard-boundary material. Optionally, the material of the protrusion 120 can also be a hard-boundary material. Optionally, the conduit 110 and the protrusion 120 can be integrally molded from hard-boundary materials to simplify the manufacturing process and improve integrity. Optionally, the hard-boundary material can be one of the aforementioned materials commonly found in daily life to reduce the manufacturing cost of the sound transmission component 100.

[0071] Optionally, the inner diameter of the pipe 110 is less than or equal to the wavelength of the incident sound wave in a vacuum. For example, the inner diameter of the pipe 110 may be less than or equal to one of 0.1λ0, 0.2λ0, 0.4λ0, 0.5λ0, 0.6λ0, 0.8λ0, or λ0, where λ0 represents the wavelength of the incident sound wave in a vacuum. As can be seen from the foregoing, when the wavelength of the sound wave is smaller than the cross-sectional size of the sound transmission component 100, the modulation effect of the sound transmission component 100 on the sound wave will be weakened. Therefore, if the inner diameter of the pipe 110 is less than or equal to λ0, it can at least ensure the modulation effect of the sound transmission component 100 on the incident sound wave when the background medium is air; if the inner diameter of the pipe 110 is less than or equal to 0.5λ0, it can at least ensure the modulation effect of the sound transmission component 100 on the incident sound wave when the background medium is silicone; and if the inner diameter of the pipe 110 is less than or equal to 0.1λ0, it can at least ensure the modulation effect of the sound transmission component 100 on the incident sound wave when the background medium is water.

[0072] By setting the pipe 110 as the transmission structure for sound waves, it is beneficial to control the transmission direction of sound waves. Furthermore, by using a hard boundary material to prepare the pipe, it is beneficial to enable the sound waves to be transmitted in the pipe 110 by total internal reflection, thereby reducing the loss of sound wave energy during transmission.

[0073] In some embodiments, among any two sound transmission members 100 with different extension lengths, the sound path adjustment factor of the sound transmission member 100 with the larger extension length is smaller than that of the sound path adjustment factor of the sound transmission member 100 with the smaller extension length. The sound path adjustment factor represents the ratio of the length of the protrusion in the direction perpendicular to the axis of the pipe 110 to the inner diameter of the pipe 110. For example... Figure 2As shown in Figure (a), w represents the inner diameter of pipe 110, h represents the extension length of protrusion 120, t represents the width of the protrusion (i.e., the wall thickness of pipe 110), d represents the interval between adjacent protrusions 120 along the pipe axis, and a represents the horizontal length of the pipe (i.e., the vertical distance from the sound wave inlet surface P1 to the sound wave outlet surface P2). Optionally, as can be seen from Figure (a), protrusion 120 extends in a direction perpendicular to the axis of pipe 110; therefore, the sound path adjustment factor can be expressed as h / w. Optionally, the interval between adjacent protrusions 120 can be different according to actual needs.

[0074] See also Figure 2 Figures (b) and (c) show that in this example, the minimum value of w is 1.95 mm, the maximum value of w is 8.95 mm, t is 1 mm, d is 5 mm, a is 20 cm, and the frequency of the incident sound wave is 6860 Hz. Figure (b) shows that the uppermost sound transmission member 100 has no protrusion 120 (h / w = 0), and the sound path in this member is approximately 4 wavelengths. The middle sound transmission member 100 has a shorter protrusion 120 (h / w = 0.23), and the sound path in this member is approximately 4.5 wavelengths. The lowermost sound transmission member 100 has a longer protrusion 120 (h / w = 0.32), and the sound path in this member is approximately 5 wavelengths. Figure (c) shows that as the parameter h / w changes, the transmission phase delay... The amplitude gradually increases, with the parameters marked by the vertical dashed line corresponding to the sound pressure diagram in Figure (b), representing the 0, π, and 2π phase shifts of the sound wave at the sound wave exit surface P2, respectively, and also corresponding to the sound path variation in Figure (b). It can be seen that as h / w increases, the sound path in the sound transmission component 100 will correspondingly lengthen. Therefore, when the horizontal length of the pipe 110 is uniform, the sound path control factor of the sound transmission component 100 with a larger extension length is smaller than that of the sound transmission component 100 with a smaller extension length.

[0075] On the other hand, as can be seen from Figure (c), when h / w is in the range of 0 to 0.2, the transmittance of the sound transmission component 100 (|t) 2 The transmittance remains essentially constant, consistently maintaining an extremely high (greater than 0.95) transmittance. When h / w is in the range of 0.2 to 0.35, the transmittance decreases slightly, but still remains within the range of greater than 0.8. It is evident that h / w can affect the impedance matching characteristics of the acoustic transmission component 100, but the effect is minor, allowing the acoustic transmission component 100 to still possess high acoustic wave transmittance.

[0076] On the other hand, the sound transmission member 100 with the bent portion can be equivalent to a straight pipe with a high refractive index (extension length a), and the equivalent refractive index n of the straight pipe is... r The acoustic path remains essentially unchanged over a wide frequency range; in other words, the acoustic path of the acoustic transmission component 100 can be expressed as L = n. r a. From diagram (d) (equivalent refractive index n) r As can be seen from the contour plot, with the increase of the sound path adjustment factor h / w, the equivalent refractive index n of the equivalent straight pipe... r It also increases accordingly, but for a fixed sound path control factor, n r It remains essentially unchanged within the range of 0.1kHz to 15kHz.

[0077] Optionally, the shape of the bend in the pipe 110 can be arbitrary, which is beneficial for better guiding sound waves around the object. Optionally, the inner diameter of each part of the pipe 110 can be different, but the extension length of the corresponding protrusion can be set according to the different inner diameters of the pipe to ensure that the sound path control factor of the same pipe 100 remains almost unchanged. This is beneficial for using pipes 110 with different inner diameters as the material for the sound transmission component 100, thus broadening the range of material selection.

[0078] Optional, please continue to see Figure 2 Figure (b) shows that the sound transmission member 100 includes at least a pair of opposing protrusions to facilitate path control of the sound waves within the sound transmission member 100. Optionally, in this example, the path control factor ranges from 0.05 to 0.22; in other words, the path control factor h / w of any sound transmission member 100 can be one of 0.05, 0.07, 0.09, 0.11, 0.13, 0.15, 0.17, 0.19, 0.21, or 0.22.

[0079] The following two specific embodiments further illustrate the effect of the acoustic transmission structure 10 of this application on reducing or eliminating acoustic scattering from objects. Specific Implementation Example 1

[0081] Sample setup

[0082] This embodiment designs a realistic sound transmission structure 10 and verifies its effectiveness through simulation and experimentation. Three rhomboid objects serve as obstacles to form sound scattering.

[0083] See Figure 3In Figures (a) and (b), three rhomboid obstacles are arranged along the y-axis, spaced 20 cm apart, with diagonal lengths of 20 cm and 10 cm respectively. The sound wave ingress surface P1 and sound wave egress surface P2 of the sound transmission structure 10 have the same shape, both designed as two planes. The sound transmission structure 10 is formed by three minimum repeating units arranged along the y-axis, each minimum repeating unit corresponding to a rhomboid obstacle. The top view of the minimum repeating unit is a square with a side length a of 20 cm (i.e., the horizontal length of the sound transmission member 100 is 20 cm), containing 20 independent sound transmission members 100. Since the lengths of the pipes 110 in these 20 sound transmission members 100 are different, the sound paths are usually different as well. Therefore, by introducing protrusions 120 with different extension lengths extending perpendicular to the axis of the pipes 110, an almost identical effective sound path can be achieved. In this embodiment, the sound path of the sound transmission component 100 is set to L = 22.5 cm. Furthermore, since the structure formed by the three rhomboid obstacles and their arrangement is mirror symmetric, ten different sound transmission components are provided in each minimum repeating unit, symmetrically arranged on both sides of the rhomboid obstacle. The sound path adjustment factor (h / w) of the 10 sound transmission components 100 in the minimum repeating unit is determined by… Figure 3 Figure (c) shows the figure.

[0084] See Figure 3 In Figures (a) and (d) of this embodiment, the obstacle and the sound transmission component 100 are both fabricated from resin using 3D printing technology. The height of the experimental system is 3 cm. The speaker is positioned 20 cm away from the sample d1 to excite cylindrical waves. A microphone is fixed to a stepper motor to measure the transmitted signal. The motor scanning accuracy is 1 cm, scanning a total of 231 points. The measurement area is a rectangular region, consisting of... Figure 3 The black dashed box in Figure (a) indicates that Δy is 20cm, Δx is 5cm, and the distance from the sample d2 is 5cm. Sound-absorbing sponge is placed vertically around the experimental system to reduce unnecessary reflections and noise.

[0085] Simulation and experimental results

[0086] When the frequency of the incident sound wave is 4860Hz, such as Figure 4 In Figure (a), due to the presence of the obstacle, a large number of scattered waves were generated throughout the space, forming a distinct low sound pressure "shadow" in the measurement area. Conversely... Figure 4Figure (b) shows that when the sound transmission structure 10 surrounds an obstacle, the incident cylindrical sound wave can bypass the obstacle, while the transmitted sound wave maintains the waveform (i.e., wavefront) of the cylindrical sound wave almost unchanged. Furthermore, the back reflection and scattering throughout the space are significantly less than in the case with only an obstacle. Simultaneously, from the perspective of the transmitted waveform, the space filled by the device appears to "disappear," meaning the point source seems to have moved from the coordinates (-30cm, 0cm) to the coordinates (-10cm, 0cm). In other words, after the sound transmission structure 10 surrounds the obstacle, the sound pressure distribution in the transmission region is similar to the sound pressure distribution formed by a cylindrical sound source located at (-10cm, 0cm) without an obstacle. This is due to the illusion of the obstacle space disappearing caused by the surround effect of the sound transmission structure 10. Additionally, due to the excessively long sound path caused by the sound transmission member 100, the transmitted sound wave exhibits a phase shift, which corresponds to a time delay.

[0087] To demonstrate wideband performance, Figure 4 Figures (c) and (d) show the effect of acoustic scattering reduction or elimination of the acoustic transmission structure 10 when the incident acoustic wave frequency is 6860 Hz. Figure 4 Figures (e) and (f) illustrate the sound scattering reduction or elimination effect of the sound transmission structure 10 when the incident sound wave frequency is 8860 Hz. It can be seen that this embodiment can effectively reduce or eliminate sound scattering caused by obstacles over a wide frequency range. Furthermore, the use of cylindrical sound wave incidentness in this embodiment also indicates that the sound transmission structure 10 of this application possesses a wide-angle sound scattering reduction or elimination effect.

[0088] Furthermore, we quantitatively demonstrate the effectiveness of this embodiment using normalized scattering intensity curves as a function of frequency. Normalized scattering intensity is defined as γ... t,r =|p s | 2 / p0| 2 , where p s Let p0 be the sound pressure of the scattered field and p0 be the sound pressure of the empty field. The subscripts t and r correspond to the transmission field region and the reflection field region, respectively, located in the regions (x∈(10cm,50cm),y∈(-30cm,30cm)) and (x∈(-50cm,-10cm),y∈(-30cm,30cm)) in the figure. The scattered field sound pressure is obtained by subtracting the empty field sound pressure without a sample from the total field sound pressure when there is an obstacle or the sound transmission structure 10 surrounds the obstacle. The smaller this value, the better the effect of reducing or eliminating sound scattering. The result is obtained by... Figure 4Figure (g) (transmission field region) and figure (h) (reflection field region) are shown. It can be seen that the scattering intensity (i.e., the contrast curve) corresponding to the case containing only obstacles is significantly greater than the scattering intensity (i.e., the scattering cancellation device curve) corresponding to the case where the sound transmission structure 10 surrounds the obstacles. Therefore, it can be concluded that the sound transmission structure 10 of this application can better reduce or eliminate sound scattering caused by obstacles, and has a very good effect in an ultra-wide frequency range (1kHz to 16kHz). Specific Implementation Example 2

[0090] Sample setup

[0091] In this embodiment, another sound transmission structure 10 was designed, and its effectiveness was verified by simulation. In this structure, three rhomboid objects were used as random obstacles to form sound scattering.

[0092] See Figure 5 Figure (a) shows three rhomboid obstacles randomly arranged along the x and y axes, with dimensions identical to those in Specific Embodiment 1. The sound wave ingress surface P1 and sound wave egress surface P2 of the sound transmission structure 10 are both designed as planes. The overall dimensions of the sound transmission structure 10 are 45cm in length and 45cm in width, and it contains 46 independent and distinct sound transmission components 100. Among these 46 sound transmission components 100, due to the different lengths of the pipes 110, the sound paths typically differ. Therefore, by introducing protrusions 120 with different extension lengths extending perpendicular to the axis of the pipes 110, an almost identical effective sound path can be achieved. Furthermore, the horizontal length of each sound transmission component 100 is 2.25a (a = 20cm), and the corresponding sound path adjustment factor (h / w) is determined by… Figure 5 Figure (b) shows the diagram.

[0093] Simulation results

[0094] See Figure 5 Figure (c) shows that when the frequency of the incident sound wave is 4860 Hz, the presence of random obstacles generates a large number of scattered waves throughout the space. However, when the sound transmission structure 10 surrounds these random obstacles, the incident cylindrical sound wave can bypass the obstacles, and the transmitted sound wave maintains the waveform (i.e., wavefront) of the cylindrical sound wave almost unchanged. Furthermore, the back reflection and scattering throughout the space are significantly less than in the case with only obstacles. To demonstrate broadband performance, Figure 5 Figures (d) and (e) illustrate the sound scattering reduction or elimination effect of the sound transmission structure 10 when the incident sound wave frequency is 6860 Hz and 8860 Hz, respectively. It can be seen that this embodiment can effectively reduce or eliminate sound scattering caused by random obstacles over a wide frequency range. Furthermore, the use of cylindrical sound wave incidentness in this embodiment also indicates that the sound transmission structure 10 of this application possesses a wide-angle sound scattering reduction or elimination effect.

[0095] Further, see Figure 5 In Figures (f) and (g), we also quantitatively demonstrate the effectiveness of this embodiment using normalized scattering intensity curves as a function of frequency. It can be seen that the scattering intensity corresponding to the case containing only random obstacles (i.e., the comparison curve) is significantly greater than the scattering intensity corresponding to the case where the acoustic transmission structure 10 surrounds the random obstacles (i.e., the scattering cancellation device curve). This indicates that the acoustic transmission structure 10 of this application can effectively reduce or eliminate acoustic scattering caused by random obstacles, and has a very good effect over an ultra-wide frequency range (1kHz to 16kHz). This embodiment also further demonstrates the robustness of the invention against arbitrary obstacles.

[0096] This application also provides a device including the acoustic transmission structure 10 as described above, and the device having at least one slot or cavity for accommodating an object, the slot or cavity being located between the acoustic wave incident surface P1 and the acoustic wave exit surface P2 of the acoustic transmission structure.

[0097] The aforementioned device has a slot or cavity for accommodating an object, so that when sound waves propagate to the vicinity of the object, the sound scattering of the object can be reduced or eliminated over a wide frequency range through the sound transmission structure 10 as described above, thereby achieving a better sound stealth effect.

[0098] Optionally, the device can be in the form of a plate, a ball, a column, a cone, or other irregular shapes, and can be used to store objects. The shape of the device can be designed according to actual needs, and this application does not limit it.

[0099] This application also provides a device including a housing; and an acoustic transmission structure 10 as described above disposed around the housing.

[0100] The aforementioned device, through the sound transmission structure 10 described above, can reduce or eliminate its own sound scattering of sound waves over a wide frequency range, thereby achieving a better sound stealth effect.

[0101] Optionally, the device can be a self-moving or controlled-moving tool, such as a vehicle, airplane, aircraft, submarine, ship, etc.

[0102] It should be understood that the above embodiments are exemplary and are not intended to encompass all possible implementations included in the claims. Various modifications and changes can be made to the above embodiments without departing from the scope of this disclosure. Similarly, the various technical features of the above embodiments can be arbitrarily combined to form other embodiments of the present invention that may not be explicitly described. Therefore, the above embodiments only illustrate several implementations of the present invention and do not limit the scope of protection of this patent.

Claims

1. A sound transmission structure having a sound wave incident surface and a sound wave exit surface, characterized in that, The acoustic transmission structure includes: A plurality of sound transmission components, each of the sound transmission components extending from the sound wave incident surface to the sound wave emitting surface, and at least a portion of the sound transmission components having a bent portion at a predetermined position; in, Each of the acoustic transmission components has a preset impedance matching parameter, which is configured to allow acoustic waves to be transmitted in the acoustic transmission component in a non-resonant fundamental mode within a preset frequency band, and to make the acoustic wave transmittance of the acoustic transmission component greater than or equal to a first preset value. and, Each of the sound transmission components has a preset sound path parameter, which is configured such that the absolute value of the sound path difference between any two of the sound transmission components is less than or equal to a second preset value within the preset frequency band. The sound transmission component includes: a conduit extending from the sound wave incident surface to the sound wave emitting surface; a protrusion disposed on the wall of the conduit and extending inward; the impedance matching parameters include at least one of the wall thickness of the conduit, the cross-sectional diameter of the conduit, the extension length of the protrusion, and the spacing between the protrusions; the sound path parameters include at least one of the extension length of the conduit, the inner diameter of the conduit, the extension length of the protrusion, and the spacing between adjacent protrusions along the axial direction of the conduit.

2. The acoustic transmission structure according to claim 1, characterized in that, The bandwidth of the preset frequency band is greater than or equal to 10kHz.

3. The acoustic transmission structure according to claim 2, characterized in that, The preset frequency band includes 1kHz to 16kHz.

4. The acoustic transmission structure according to claim 1, characterized in that, The first preset value is one of 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, and 1.

5. The acoustic transmission structure according to claim 1, characterized in that, The second preset value is one of 0, 0.05a, 0.1a, 0.15a, 0.2a, and 0.25a, ​​where a represents the vertical distance from the sound wave incident surface to the sound wave exiting surface.

6. The acoustic transmission structure according to claim 1, characterized in that, In any two sound transmission components with different extension lengths, the sound path adjustment factor of the sound transmission component with the larger extension length is smaller than that of the sound transmission component with the smaller extension length, wherein the sound path adjustment factor represents the ratio of the length of the protrusion in the direction perpendicular to the pipe axis to the inner diameter of the pipe.

7. The acoustic transmission structure according to claim 6, characterized in that, The sound transmission component includes at least one pair of protrusions extending in opposite directions, and the sound path adjustment factor ranges from 0.05 to 0.

22.

8. The acoustic transmission structure according to claim 1, characterized in that, The inner diameter of the pipe is less than or equal to the wavelength of the incident sound wave in a vacuum.

9. The acoustic transmission structure according to claim 1, characterized in that, The pipe and the protrusion are integrally formed from a hard boundary material.

10. The acoustic transmission structure according to claim 9, characterized in that, The hard boundary material includes at least one of glass, plastic, resin, metal, steel reinforcement, and concrete.

11. A device, characterized in that, The device includes an acoustic transmission structure as described in any one of claims 1-10, wherein the device has at least one slot or cavity for accommodating an object, the slot or cavity being located between the acoustic wave incident surface and the acoustic wave exit surface of the acoustic transmission structure.

12. An apparatus, characterized in that, It includes a housing; and an acoustic transmission structure disposed around the housing as described in any one of claims 1-10.

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