Sound wave absorption structure, sound transmission device, device and preparation method

Abstract

The invention relates to a sound wave absorption structure, a sound transmission device, a device and a preparation method. The sound wave absorbing structure comprises a plurality of sound wave absorbing materials which are arranged at intervals along a preset axis; in the extension direction of the preset axis, the distance between every two adjacent sound wave absorbing materials meets a preset condition; each sound wave absorbing material has a first inclination angle relative to a preset axis, sound waves incident to each sound wave absorbing material have a second inclination angle relative to the preset axis, and when the first inclination angle and the second inclination angle are symmetrical about the preset axis, the first inclination angle is an absorbing inclination angle of the sound wave absorbing material; at least part of the sound wave absorbing material is configured to be obliquely arranged relative to the preset axis within the range that the absorbing inclination angle of the sound wave absorbing material is plus or minus the preset angle. The sound wave absorption structure can achieve sound absorption and noise reduction in the target direction.

Description

Technical Field

[0001] The present invention relates to the technical field of sound wave absorption, and in particular to a sound wave absorption structure, a sound transmission device, a component and a preparation method thereof. Background Art

[0002] Most existing sound-absorbing metamaterials have symmetrical sound-absorbing properties, which may not be applicable in some scenarios. For example, sometimes it is necessary to directional interfere with the sound in a certain direction without affecting the sound wave transmission in other directions.

[0003] In addition, since traditional metastructure sound-absorbing materials are usually prepared based on resonance, they often have the problem of narrow bandwidth. In order to expand the operating frequency range, some measures have been taken, such as using coupled folded Fabry-Pérot channels or Helmholtz resonant cavities. However, these designs usually require coupling multiple resonant cavities and complex structural designs, which increases the difficulty of preparation. In addition, these sound-absorbing structures usually have symmetrical sound absorption characteristics and it is difficult to achieve asymmetric sound absorption characteristics. Summary of the invention

[0004] In order to solve at least one of the above problems, the present invention aims to provide an improved sound wave absorbing structure, sound transmitting device, component and preparation method to effectively shield the sound waves in the target direction.

[0005] In a first aspect, the present application provides a sound wave absorbing structure, comprising:

[0006] A plurality of sound wave absorbing materials are arranged at intervals along a predetermined axis;

[0007] Furthermore, along the extension direction of the preset axis, the spacing ω between two adjacent sound wave absorbing materials satisfies: t<ω<λ, wherein t represents the thickness of the sound wave absorbing material, and λ represents the wavelength of the incident sound wave;

[0008] Furthermore, each of the sound wave absorbing materials has a first inclination angle relative to the preset axis, and the sound wave incident on each of the sound wave absorbing materials has a second inclination angle relative to the preset axis, and when the first inclination angle and the second inclination angle are symmetrical about the preset axis, the first inclination angle is the absorption inclination angle of the sound wave absorbing material;

[0009] Wherein, at least part of the sound wave absorbing material is configured to be inclined relative to the preset axis within a range of its absorption inclination angle plus or minus a preset angle.

[0010] The above-mentioned sound wave absorbing structure can absorb sound waves in a target direction based on the reciprocity law by making at least part of the sound wave absorbing material tilted relative to a preset axis within the range of its absorption tilt angle plus or minus a preset angle, thereby achieving sound absorption and noise reduction in the target direction; at the same time, the above-mentioned sound wave absorbing structure can also make sound waves propagating along the tilt direction of the sound wave absorbing material (a direction symmetrical to the perpendicular line of the target direction about the preset axis) pass through the sound wave absorbing structure, thereby achieving an asymmetric sound absorption effect.

[0011] In one embodiment, each of the sound wave absorbing materials is configured to be tilted relative to the preset axis within a range of its absorption inclination angle plus or minus a preset angle.

[0012] In one embodiment, the absorption tilt angle is greater than 0° and less than 90°.

[0013] In one embodiment, the absorption tilt angle is greater than or equal to 20° and less than 90°.

[0014] In one embodiment, the preset angle is less than or equal to 15°.

[0015] In one embodiment, t≤ω / 5.

[0016] In one embodiment, the working frequency f of the sound wave absorbing structure is w It is negatively correlated with the distance ω between two adjacent sound wave absorbing materials.

[0017] In one embodiment, the sound wave absorbing material includes at least one of a micro-perforated plate, a textile sound absorbing material, and a foam metal.

[0018] In one embodiment, the sound wave absorbing material includes a first end close to the sound wave incident side and a second end close to the sound wave exit side, and the sound wave absorbing structure also includes a first rigid boundary arranged close to the second end, and at least a portion of the first rigid boundary extends in a direction parallel to the preset axis.

[0019] In one embodiment, at least a portion of the second end of the sound wave absorbing material is disposed in contact with the first rigid boundary.

[0020] In one embodiment, the sound wave absorbing structure further includes a second rigid boundary intersecting the first rigid boundary or an extension line of the first rigid boundary, and at least a portion of the second rigid boundary is located on a side of the first rigid boundary close to the sound wave absorbing material.

[0021] In one embodiment, a plurality of the second rigid boundaries are arranged along the circumference of the first rigid boundary, and the plurality of the second rigid boundaries and the first rigid boundary together enclose a cavity opening toward the sound wave incident side for accommodating the plurality of sound wave absorbing materials.

[0022] In one embodiment, the length of the multiple sound wave absorbing materials in the direction perpendicular to the preset axis is greater than or equal to a response length, and the response length is determined based on at least the bulk modulus of air, the effective bulk modulus of the multiple sound wave absorbing materials under the static limit, and the wavelength of the incident sound wave in the air.

[0023] In one of the embodiments, it further includes: a first adjustment mechanism coupled to the plurality of sound wave absorbing materials for adjusting the first inclination angle; and / or a second adjustment mechanism coupled to the plurality of sound wave absorbing materials for adjusting the spacing.

[0024] In a second aspect, the present application also provides a method for preparing a sound wave absorbing structure, comprising: obtaining a plurality of sound wave absorbing materials spaced apart along a preset axis; wherein, along the preset axis, the spacing ω between two adjacent sound wave absorbing materials satisfies: t<ω<λ, t represents the thickness of the sound wave absorbing material, and λ represents the wavelength of the incident sound wave; obtaining the absorption inclination of the sound wave absorbing material; wherein each of the sound wave absorbing materials has a first inclination relative to the preset axis, and the sound wave incident to each of the sound wave absorbing materials has a second inclination relative to the preset axis, and when the first inclination and the second inclination are symmetrical about the preset axis, the first inclination is the absorption inclination of the sound wave absorbing material; and at least part of the sound wave absorbing material is tilted relative to the preset axis within the range of its absorption inclination plus or minus a preset angle.

[0025] The method for preparing the above-mentioned sound wave absorbing structure can calculate the absorption inclination angle of the sound wave absorbing material based on the second inclination angle of the incident sound wave relative to the preset axis, and then set the first inclination angle of the sound wave absorbing material relative to the preset axis based on the absorption inclination angle to obtain the above-mentioned sound wave absorbing structure. The above-mentioned preparation method can prepare a sound absorbing structure designed based on the propagation direction of the incident sound wave, thereby realizing directional sound absorption.

[0026] In one embodiment, the method further includes: obtaining the working frequency f of the sound wave absorbing structure w According to the operating frequency f w Adjust the distance ω between two adjacent sound wave absorbing materials; wherein, f w Negatively correlated with ω.

[0027] In one embodiment, the sound wave absorbing material includes a first end close to the sound wave incident side and a second end close to the sound wave exit side, and the preparation method further includes: setting a first rigid boundary close to the second end; wherein at least a portion of the first rigid boundary extends in a direction parallel to the preset axis.

[0028] In one embodiment, the method further includes: setting a second rigid boundary intersecting with the first rigid boundary or an extension line of the first rigid boundary; wherein at least a portion of the second rigid boundary is located on a side of the first rigid boundary close to the sound wave absorbing material.

[0029] In a third aspect, the present application also provides a sound transmitting device, comprising: a sound wave incident surface and a sound wave exit surface arranged opposite to each other; and a sound wave absorbing structure as described above, arranged between the sound wave incident surface and the sound wave exit surface; the sound transmitting device is suitable for transmitting sound waves incident along a first direction and shielding sound waves incident along a second direction, wherein the first direction is parallel to the inclination direction of the sound wave absorbing material, and the first direction and the second direction are symmetrical about a perpendicular line to the preset axis.

[0030] The above-mentioned sound transmission device can realize the transmission of sound waves in a first direction and shield the sound waves in a second direction through the above-mentioned sound wave absorbing structure, thereby realizing an asymmetric sound transmission effect.

[0031] In a fourth aspect, the present application further provides a device, comprising: a containing cavity; a target sound source, disposed in the containing cavity; and a sound wave absorbing structure as described above, for absorbing sound waves emitted by the target sound source.

[0032] The above-mentioned device can absorb and reduce the noise source inside it through the above-mentioned sound wave absorption structure, thereby improving the noise control performance of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the implementation methods of this specification or the technical solutions in the prior art, the drawings required for use in the implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some implementation methods recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0034] Figure 1 (a) is a schematic diagram of the structure of a sound-absorbing metamaterial using a Fabry-Pérot channel;

[0035] Figure 1 (b) is a schematic diagram of the structure of a sound-absorbing metamaterial using a Helmholtz resonance cavity;

[0036] Figure 2 This is a schematic structural diagram of a sound wave absorbing structure according to an embodiment of the present application;

[0037] Figure 3 This is a schematic diagram of sound absorption based on the reciprocity principle according to an embodiment of the present application;

[0038] Figure 4 The curve showing the change of reflectivity, transmittance and absorptivity of the sound wave absorbing material according to one embodiment of the present application under vertical incidence of sound waves as a function of frequency is shown;

[0039] Figure 5 Figure (a) is a function diagram of the absorption rate of the sound wave absorption structure of one embodiment of the present application as a function of the sound wave incident angle and the complementary angle α of the first inclination angle;

[0040] Figure 5 FIG. (b) is a graph showing the reflectivity of the sound wave absorbing structure according to an embodiment of the present application as a function of the sound wave incident angle and frequency;

[0041] Figure 5 Figure (c) is a graph showing the absorption rate of the sound wave absorption structure according to an embodiment of the present application as a function of the sound wave incident angle and frequency;

[0042] Figure 6 Figure (a) is a simulated sound field distribution diagram of the sound wave absorbing structure of one embodiment of the present application when the sound wave is incident at ±45°;

[0043] Figure 6 Figure (b) is a simulated sound field distribution diagram of the sound wave absorbing structure of one embodiment of the present application under a point sound source;

[0044] Figure 7 This is a schematic diagram of the effect of an embodiment of the present application when used as a super structure blind;

[0045] Figure 8 (a) is a schematic diagram of the Gaussian beam experimental structure of a superstructure shutter sample;

[0046] Figure 8 Figure (b) shows the curves of reflectivity, transmittance, and absorptivity changing with frequency when the sound wave is incident on the metastructure shutter sample at ±45°;

[0047] Figure 8 Figure (c) is a schematic diagram of the transmitted sound field distribution when sound waves of different frequencies are incident on the metastructure shutter sample at 45°;

[0048] Figure 8 Figure (d) is a schematic diagram of the reflected sound field distribution when sound waves of different frequencies are incident on the metastructure shutter sample at -45°;

[0049] Fig. 9(a) is a schematic diagram of a point sound source experimental structure of a super structure blinds sample;

[0050] Fig. 9 Figure (b) is a schematic diagram of the transmitted sound field distribution of a point sound source when the super-structured shutter sample is not set (upper) and the super-structured shutter sample is set (lower);

[0051] Fig.10 Figure (a) is a schematic diagram of the structure of Case 1 (setting the first rigid boundary) of this application;

[0052] Fig.10 Figure (b) is a graph showing the absorption rate of Case 1 of the present application as a function of the incident angle and the operating frequency;

[0053] Fig.11 Figure (a) is a schematic diagram of the structure of Case 2 of the present application (setting a first rigid boundary and a second rigid boundary);

[0054] Fig.11 Figure (b) shows the curves of the absorption rate of the micro-perforated plate under vertical incidence of sound waves as a function of frequency for Case 1, Case 2, and the micro-perforated plate;

[0055] Fig.11 (c) shows the normalized intensity (color) and velocity fields (white arrows) simulated at 330 Hz for Case 1 and Case 2;

[0056] Fig.12 Figure (a) is a schematic diagram of the structure of a three-dimensional omnidirectional sound absorber proposed in this application based on Case 2;

[0057] Fig.12 Figure (b) is a graph showing the absorption rate of the three-dimensional omnidirectional sound absorber as a function of the incident angle and the operating frequency when the sound wave is incident in the xz plane;

[0058] Fig.12 Figure (c) is a graph showing the absorption rate of the three-dimensional omnidirectional sound absorber as a function of the incident angle and the operating frequency when the sound wave is incident in the yz plane;

[0059] Fig.13 (a) is a schematic diagram of an impedance tube experimental structure of a three-dimensional omnidirectional sound absorber;

[0060] Fig.13 Figure (b) is a physical schematic diagram of sample 1 and sample 2 of the three-dimensional omnidirectional sound absorber;

[0061] Fig.13 Figure (c) is a schematic diagram of the structure of sample 2;

[0062] Fig.13Figure (d) shows the curves of the absorption rate of sample 1 under experiment and simulation as a function of frequency, and the curves of the absorption rate of sample 2 under experiment and simulation as a function of frequency.

[0063] Component number description:

[0064] 100. Sound wave absorbing structure, 101-102. Sound wave absorbing material;

[0065] 200, first type omnidirectional sound wave absorbing structure, 300, second type omnidirectional sound wave absorbing structure;

[0066] AX, preset axis, θ i , the sound wave incident angle, β, the first inclination angle, α, the complementary angle of the first inclination angle, γ, the second inclination angle. DETAILED DESCRIPTION

[0067] In order to make the technical solutions and beneficial effects of the present invention more obvious and easy to understand, the following is a detailed description by listing specific embodiments. The 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 in this application have the same meanings as those in the technical field to which this application belongs.

[0068] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0069] Sound absorption has long been a fundamental field in acoustic research and is widely used in indoor acoustics and noise control engineering. Traditional porous materials, such as plastic foam, glass fiber, and mineral wool, rely on the dissipation of wave energy during propagation to achieve absorption. However, these materials need to be thick enough to match the maximum operating wavelength. Some studies have also proposed that the thickness can be reduced through local resonant structures, such as micro-perforated plate (MPP) resonators, which use the resonance principle to achieve impedance matching within certain frequency ranges. However, the inherent strong dispersion of these structures limits the bandwidth of impedance modulation.

[0070] On the other hand, acoustic metamaterials have demonstrated impressive capabilities to manipulate sound in unprecedented ways and have led to many interesting applications. In particular, acoustic metamaterials have overcome the limitations of traditional materials and opened up new avenues for designing sound absorbers. Several metamaterial-based sound absorbers have been proposed, including decorative films, bubbles in rubber, spiral space structures, and Helmholtz resonant cavities. However, these approaches are limited in their operating frequency range due to their resonant mechanism. In order to achieve broadband sound absorption, the following two methods are usually used in traditional sound-absorbing metamaterials:

[0071] (1) Coupled folded Fabry-Pérot channel

[0072] like Figure 1 As shown in Figure (a), when sound waves enter the Fabry-Pérot channel, they will propagate repeatedly in the channel, forming reflections and interference. Due to the effects of folding and coupling, sound waves of different frequencies will interfere at different positions and depths, thus achieving broadband sound absorption.

[0073] (2) Coupled Helmholtz Resonant Cavity

[0074] like Figure 1 As shown in Figure (b), when a sound wave enters the Helmholtz resonant cavity, it will be repeatedly reflected in the cavity and form a standing wave. By designing resonant cavities of different sizes and shapes, it is possible to absorb sound waves of different frequencies. By reasonably coupling resonant cavities of different sizes and shapes, good sound absorption performance can be achieved in a wide frequency range.

[0075] However, these designs usually require coupling multiple resonant cavities and complex geometries, which increases the difficulty of fabrication. In addition, these sound-absorbing structures usually have symmetrical absorption characteristics, while it is difficult to achieve asymmetric absorption characteristics.

[0076] To solve the above problems, the present application uses a non-resonance method and considers various physical properties such as dispersion and effective parameters of the prepared material to provide a sound wave absorption structure designed based on the reciprocity principle. The sound wave absorption structure of the present application has an asymmetric sound absorption characteristic (or directional sound absorption characteristic) with almost zero reflection, and also has the characteristics of a wide working frequency band and thin thickness.

[0077] In one embodiment, if Figure 2As shown, the sound wave absorbing structure 100 includes a plurality of sound wave absorbing materials arranged at intervals along a preset axis AX; and, along the extension direction of the preset axis AX, the spacing ω between two adjacent sound wave absorbing materials (such as the sound wave absorbing material 101 and the sound wave absorbing material 102) satisfies: t<ω<λ, wherein t represents the thickness of the sound wave absorbing material, and λ represents the wavelength of the incident sound wave. Moreover, each sound wave absorbing material has a first inclination angle β relative to the preset axis AX, and the sound wave incident to each sound wave absorbing material has a second inclination angle γ relative to the preset axis AX, and when the first inclination angle β and the second inclination angle γ are symmetrical about the preset axis AX, the first inclination angle β is the absorption inclination angle of the sound wave absorbing material; wherein, at least part of the sound wave absorbing material is configured to be arranged tilted relative to the preset axis AX within the range of its absorption inclination angle plus or minus the preset angle.

[0078] Based on the reciprocity principle, Figure 3 As shown in the figure, when the sound wave is incident on the sound wave absorbing structure 100 in a direction parallel to the surface of the sound wave incident material, the sound wave can be transmitted from the other side of the sound wave absorbing structure 100 without reflection. At this time, the sound wave incident angle θ i It can be recorded as α1; and when the sound wave is incident at an incident angle symmetrical to α1 about the normal (recorded as -α1), the sound wave will also be incident into the sound wave absorbing structure 100 without reflection, and then absorbed by the sound wave absorbing material in the sound wave absorbing structure 100, where R represents reflectivity, T represents transmittance, and H represents the thickness of the sound wave absorbing structure 100. At this time, the sound wave absorbing structure 100 matches the air impedance, α1 and the first tilt angle β are complementary, -α1 and the second tilt angle γ are complementary, so that the first tilt angle β and the second tilt angle γ are symmetrical about the preset axis AX, and the first tilt angle β is the absorption tilt angle of the sound wave absorbing material. When at least part of the sound wave absorbing material is tilted relative to the preset axis AX within the range of its absorption inclination plus or minus the preset angle, the part of the sound wave absorbing material can achieve better absorption of sound waves incident at a certain angle (such as -α1). In other words, the sound wave absorbing structure 100 can have asymmetric sound absorption characteristics for sound waves incident at angles α1 and -α1. If the sound dissipation provided by the sound wave absorbing material is large enough, it is conducive to obtaining a perfect sound absorption effect. Exemplarily, the upper limit of the preset angle can be 15°, and exemplary, the preset angle can be 3°, 5°, 8°, 10°, 15°. On the other hand, by controlling the spacing between two adjacent sound wave absorbing materials to be less than the wavelength of the incident sound wave and greater than the thickness of the sound wave absorbing material, it is conducive to further ensuring that there is basically no diffraction during sound wave transmission, thereby ensuring the sound absorption effect of the sound wave absorbing structure 100.

[0079] Exemplarily, the sound wave absorbing structure 100 may further include a substrate, and each sound wave absorbing material is fixedly disposed on the substrate. Optionally, the first inclination angle of each sound wave absorbing material relative to the substrate is adjustable, thereby facilitating achieving a better sound absorption effect for sound waves incident at different angles.

[0080] Exemplarily, the sound wave absorbing material includes at least one of a micro-perforated plate, a textile sound absorbing material, and a foam metal.

[0081] The sound wave absorbing structure 100 of the present embodiment is configured such that at least part of the sound wave absorbing material is tilted relative to the preset axis AX within the range of the absorption tilt angle plus or minus the preset angle, so that the sound wave absorbing structure 100 can absorb sound waves in the target direction based on the reciprocity law, thereby achieving sound absorption and noise reduction in the target direction; at the same time, the sound wave absorbing structure 100 can also allow sound waves propagating along the tilt direction of the sound wave absorbing material (a direction symmetrical to the perpendicular line of the target direction about the preset axis) to pass through the sound wave absorbing structure, thereby achieving an asymmetric sound absorption effect.

[0082] In some embodiments, continue to refer to Figure 2 Each sound wave absorbing material is configured to be tilted relative to the preset axis AX within the range of its absorption inclination angle plus or minus a preset angle. In this way, when sound waves in a target direction are incident on different parts of the sound wave absorbing structure 100, better sound absorption effects can be achieved, thereby helping to improve the overall sound absorption characteristics of the sound wave absorbing structure 100.

[0083] In some embodiments, the absorption angle is greater than 0° and less than 90°, for example, the absorption angle can be 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°. If the absorption angle is 0°, the sound wave absorbing material is arranged parallel to the sound wave incident surface of the sound wave absorbing structure 100, and it is difficult to achieve sound absorption and noise reduction in the target direction through the reciprocity principle. At this time, even if the vertical incidence method is adopted, it is difficult to achieve a better sound absorption effect, such as Figure 4 As shown, when a micro-perforated plate is used as the sound wave absorbing material, the transmittance of the micro-perforated plate under vertical incidence is still basically around 0.3; similarly, if the absorption angle is 90°, the sound wave absorbing material is arranged perpendicular to the sound wave incident surface of the sound wave absorbing structure 100. At this time, the incident sound wave can pass directly through the sound wave absorbing structure 100 under vertical incidence, making it difficult to achieve sound absorption and noise reduction. Furthermore, the absorption angle is greater than or equal to 20° and less than 90°. By controlling the absorption angle to meet the above range, it is beneficial to ensure the sound absorption performance of the sound wave absorbing structure 100 in actual application, and it is also beneficial to improve the structural strength of the sound wave absorbing structure 100. Figure 5 As shown in Figure (a), α represents the angle complementary to the first tilt angle β. It can be seen that the incident angle θ with high absorption iIt will increase with the increase of α until α is about 70°, so it can be seen that the limit value of the absorption angle is about 20°.

[0084] During the preparation of the sound wave absorbing structure 100, once the absorption inclination angle is determined, the first inclination angle β of the sound wave absorbing material can be set within the range of the absorption inclination angle plus or minus a preset angle, thereby achieving sound absorption and noise reduction of the sound wave absorbing structure 100 in a target direction.

[0085] In some embodiments, the thickness t of the sound wave absorbing material satisfies t≤ω / 5. In this way, the thickness of the sound wave absorbing material can be much smaller than the spacing, so that when the sound wave is incident in a direction parallel to the surface of the sound wave absorbing material, each sound wave absorbing material has almost no effect on the sound wave, and based on the reciprocity principle, the sound absorption effect of the sound wave absorbing structure 100 can be further guaranteed.

[0086] In some embodiments, the operating frequency f of the sound wave absorbing structure 100 is w is negatively correlated with the distance ω between two adjacent sound wave absorbing materials. That is, the smaller the distance ω between two adjacent sound wave absorbing materials, the higher the working frequency f of the sound wave absorbing structure 100. w The higher the value, the smaller the ω can be for the required operating frequency f w Make adjustments.

[0087] The following will refer to Figures 4 to 9 Specific embodiments that can reflect the inventive concepts of this application are further described.

[0088] In this specific embodiment, a micro-perforated plate (MPP) with a high absorption rate is used as the sound wave absorbing material, wherein the distance between two adjacent micro-perforated plates is greater than the thickness of the micro-perforated plates and less than the wavelength of the incident sound wave in the air, the perforation diameter of the MPP is 0.1 mm, the plate thickness is 1 mm, and the porosity is 10%.

[0089] Figure 4 The curves of the reflectivity, transmittance, and absorptivity of the MPP of this embodiment under vertical incidence of sound waves as a function of frequency are shown, wherein the relationship between the reflectivity, transmittance, and absorptivity can be expressed as the sum of the three approaches 1. It can be seen that the absorptivity of the MPP is about 45%. However, Figure 5 and Figure 6 It can be seen that when the MPPs are tilted at a certain angle to form an array, that is, to form a sound wave absorbing structure 100, its absorption performance will be greatly improved, wherein the thickness H of the sound wave absorbing structure 100 is 7 cm, and the distance between two adjacent MPPs is 3 cm.

[0090] like Figure 5As shown in Figure (a), with a sound wave incident at a frequency of 4000 Hz, when the incident angle of the sound wave is the complementary angle of the first inclination angle (that is, the sound wave is incident in a direction parallel to the MPP surface), the absorption rate A is almost 0 (shown by the white dotted line), which means that almost all the sound wave energy will pass through the sound wave absorption structure 100; on the other hand, when the incident angle of the sound wave is antisymmetric to the complementary angle of the first inclination angle (that is, the second inclination angle of the sound wave is symmetric with the first inclination angle about the preset axis), the absorption rate A is quite high (basically greater than or equal to 0.9, shown by the black solid line). Figure 5 As shown in Figure (b), a sound wave with a frequency of 1000Hz to 6000Hz is used as the incident wave, the first inclination angle of the MPP is 45°, and the distance between two adjacent MPPs is controlled to be smaller than the wavelength of the incident sound wave. It can be seen that within the range of the incident angle less than or equal to 70°, the reflection is symmetrical relative to the incident angle and is quite low (basically less than or equal to 0.1, shown by the white solid line). In addition, when the incident angle is 45°, zero reflection may occur. Figure 5 As shown in Figure (c), using the same setting as Figure (b), the absorption of the sound wave absorption structure 100 when the incident angle is ±45° is antisymmetric, that is, within a wide frequency range, when the sound wave incident angle is 45°, there is basically no absorption, but when the sound wave incident angle is -45°, complete absorption greater than or equal to 0.9 can occur, indicating that the sound wave absorption structure 100 has asymmetric sound absorption characteristics and can achieve sound absorption and noise reduction in the target direction.

[0091] Figure 6 Figure (a) shows the simulated acoustic field distribution diagram of the acoustic wave absorbing structure 100 with a first inclination angle of 45° when the acoustic wave is incident at ±45°. It can be seen that the reflection phenomenon is eliminated in both cases, and when the acoustic wave is incident at -45°, a nearly perfect absorption phenomenon can be observed. Figure 6 FIG. (b) shows a simulated acoustic field distribution diagram of the acoustic wave absorbing structure 100 under a point sound source. It can be seen that the reflection is still quite low at this time, while the transmission shows obvious angular asymmetry. Based on this characteristic, this specific embodiment can be used for example Figure 7 The preparation of the super-structured blinds shown in the figure can provide a quiet area only on one side and achieve normal sound transmission on the other side, which has important application value in some specific scenarios.

[0092] The following will refer to Figure 8 and Fig. 9 To carry out relevant experimental verification on the above-mentioned super-structure blinds.

[0093] exist Figure 8 and Fig. 9 In the experiments, steel MPPs with periodically arranged triangular conical holes were used. Under vertical incidence, the absorption rate at the working frequency was about 30%.

[0094] The experimental setup of the Gaussian beam is composed of Figure 8 Figure (a) shows two measurement areas on the xy plane, the reflection side and the transmission side, respectively. They are presented in the form of gray rectangular areas, and the size of each area is 32*30cm 2 , 3cm away from the sample, the inset shows a photo of the real sample, the inclination angle of the MPP (i.e., the first inclination angle β) is 45°, and the spacing ω is 3cm. In order to generate a quasi-Gaussian sound beam, a speaker array with a parabolic mirror was also constructed, and then the microphone was mounted on a mobile stage to scan the sound field distribution with a step size of 10mm. The experiment was carried out in an anechoic chamber to minimize reflections and noise.

[0095] Figure 8 Figure (b) shows the curves of reflectivity, transmittance, and absorptivity as a function of frequency when the sound wave is incident on the metastructure blinds sample at ±45°. It can be seen that the reflectivity is quite low when the sound wave is incident at ±45°, while the transmittance and absorptivity show an asymmetric phenomenon. Specifically, when the sound wave is incident at 45°, the transmittance is quite high, with basically no absorption; while when the sound wave is incident at -45°, the absorption of the MPP causes the transmittance to decrease, and the absorptivity is about 60%. Optionally, an MPP with a higher absorptivity can be used or the thickness of the sound wave absorption structure can be increased to further improve the absorptivity. It can be understood that when the thickness of the sound wave absorption structure increases, the distance that the sound wave is transmitted in the sound wave absorption structure is longer, so that the sound wave energy can be more fully dissipated by the MPP. In addition, some experimental errors may be caused by inaccuracies in sample preparation and defects in Gaussian beams.

[0096] Figure 8 Figure (c) shows the transmission sound field distribution when sound waves of different frequencies are incident on the metastructure shutter sample at 45°. Figure 8 Figure (d) shows the reflected sound field distribution when sound waves of different frequencies are incident on the metastructure blinds sample at -45°. It can be seen that at 3000Hz, 4000Hz, and 5000Hz, when the sound waves are incident at 45°, the sound waves are almost completely transmitted, and the reflection of the sound waves is almost zero, indicating that the sound wave absorption structure has an ultra-wideband zero reflection characteristic protected by the reciprocity principle; and when the sound waves are incident at -45°, the sound wave absorption structure shows better sound absorption effect at different frequencies.

[0097] The experimental framework of the point sound source is composed of Fig. 9 As shown in Figure (a), the measurement area is marked by a black frame in the figure, and its size is 40*20cm 2 , the distance between the measurement area and the sound wave absorbing structure is 2 cm, and the distance between the loudspeaker and the sound wave absorbing structure is 2 cm. Fig. 9Figure (b) shows the transmitted sound field distribution of the point sound source when the super structure louver sample is not set (above) and the super structure louver sample is set (below). It can be seen that the left half of the transmitted sound field shows greater absorption, while the right half of the transmitted sound field shows greater transmission.

[0098] In summary, the above-mentioned meta-structure blinds exhibit asymmetric sound absorption characteristics (i.e., have obvious angular asymmetry) under the incidence of sound waves from different sound sources. In other words, the above-mentioned meta-structure blinds can absorb sound waves in the target direction, and at the same time transmit sound waves in a direction symmetrical to the target direction about the normal.

[0099] In some embodiments, the boundary conditions can be adjusted to introduce the reciprocity principle and the complex resonance principle at the same time, thereby achieving ultra-wideband omnidirectional sound absorption performance. Fig.10 As shown in FIG. (a), the sound wave absorbing material (MPP) includes a first end close to the sound wave incident side and a second end close to the sound wave exit side, and the sound wave absorbing structure also includes a first rigid boundary arranged close to the second end, and at least part of the first rigid boundary extends in a direction parallel to the preset axis. In this way, a first type of omnidirectional sound wave absorbing structure 200 can be formed. Due to the addition of the first rigid boundary, the transmitted sound wave will be reflected back to the sound wave absorbing structure and continue to be dissipated by the sound wave absorbing material, which is conducive to achieving an omnidirectional sound absorption effect.

[0100] In some embodiments, the second end of at least part of the sound wave absorbing material is arranged in contact with the first rigid boundary. By directly contacting the first rigid boundary with the second end, the thickness of the sound wave absorbing structure is reduced, making the sound wave absorbing structure thinner.

[0101] In some embodiments, Fig.11 As shown in Figure (a), the sound wave absorbing structure also includes a second rigid boundary intersecting with the first rigid boundary or the extension line of the first rigid boundary, and at least part of the second rigid boundary is located on the side of the first rigid boundary close to the sound wave absorbing material. In this way, a second type of omnidirectional sound wave absorbing structure 300 can be formed. Due to the addition of the first rigid boundary and the second rigid boundary, complex resonance can be supported, thereby further improving the sound absorption effect of the omnidirectional sound wave absorbing structure. Optionally, there is a gap between the second rigid boundary and the sound wave absorbing material, which is conducive to further enhancing sound dissipation.

[0102] In some embodiments, continue to refer to Fig.11In (a), multiple second rigid boundaries are arranged along the circumference of the first rigid boundary, and the multiple second rigid boundaries and the first rigid boundary together enclose a cavity for accommodating multiple sound wave absorbing materials, which is open toward the sound wave incident side. The above arrangement is conducive to forming a three-dimensional omnidirectional sound wave absorber, so that the sound waves are more fully absorbed by the sound wave absorbing material, thereby further improving the sound absorption performance.

[0103] In some embodiments, the length of the plurality of acoustic wave absorbing materials in a direction perpendicular to the predetermined axis is greater than or equal to a response length, and the response length is determined based on at least the bulk modulus of air, the effective bulk modulus of the plurality of acoustic wave absorbing materials in a static limit, and the wavelength of the incident acoustic wave in air. Specifically, the material response function of the incident acoustic wave must satisfy the principle of causality, which leads to an inequality that relates a given absorption spectrum to the sample thickness d:

[0104]

[0105] Among them, λ and A(λ) represent the wavelength and absorption coefficient of sound waves in air respectively. The absorption coefficient is a function of wavelength. B0 is the bulk modulus of air. eff represents the effective bulk modulus of multiple sound wave absorbing materials in the static limit, and the response length is Through the above relationship, the thickness of the sound wave absorbing structure can be reduced as much as possible while satisfying the causal law. In other words, the thickness of the sound wave absorbing structure can be made consistent with the response length, thereby achieving a lightweight and thin sound wave absorbing structure while satisfying the causal law.

[0106] In some embodiments, the sound wave absorbing structure further includes a first adjustment mechanism coupled to a plurality of sound wave absorbing materials for adjusting a first inclination angle; and / or a second adjustment mechanism coupled to a plurality of sound wave absorbing materials for adjusting the distance between two adjacent sound wave absorbing materials. Through the first adjustment mechanism, the first inclination angle of the sound wave absorbing material can be adjusted, which is conducive to adjusting the first inclination angle to the corresponding absorption inclination angle based on the second inclination angle of the incident sound wave, thereby achieving a better sound absorption effect. Through the second adjustment mechanism, the distance between two adjacent sound wave absorbing materials can be adjusted, which is conducive to broadening the range of the operating frequency of the sound wave absorbing structure and meeting the application requirements of higher operating frequencies. Exemplarily, the first adjustment mechanism can achieve the adjustment of the first inclination angle by connecting the sound wave absorbing material through a pivot structure or a motor. Exemplarily, the second adjustment mechanism can achieve the adjustment of the distance by connecting the sound wave absorbing material through a thread, a screw or a motor.

[0107] The following will refer to Figure 10 to Figure 12 Specific embodiments that can reflect the inventive concepts of this application are further described.

[0108] like Fig.10As shown in Figure (a), the bottom of the first type of omnidirectional sound wave absorbing structure 200 (Case 1) changes from an open boundary to a rigid boundary, and the relevant parameters are the complementary angle of the first inclination angle α=60°, so that the first inclination angle β is 30°, the spacing ω between two adjacent sound wave absorbing materials (MPP) is 1cm, the length D of the first rigid boundary is 10cm, the thickness of the first rigid boundary is 2mm, the thickness H of the sound wave absorbing structure is 10cm, and the periodic boundary represents the infinite boundary during simulation. Among them, the parameters of MPP are pore size (diameter) of 0.2mm, plate thickness of 0.1mm, and porosity of 2%. Fig.10 Figure (b) shows the functional relationship between the absorption rate of the first type of omnidirectional sound wave absorbing structure 200 and the incident angle and the operating frequency. It can be seen that the absorption rate of the sound wave is symmetrical about the incident angle and has been significantly improved; in addition, almost |θ i |≤75° incident sound waves can obtain a higher absorption rate (A>0.9) and can cover a wider operating frequency range. For example, in |θ i |≤60°, sound waves from 800Hz to 16800Hz can obtain a higher absorption rate.

[0109] like Fig.11 As shown in Figure (a), the second type of omnidirectional sound wave absorbing structure 300 (Case 2) also sets rigid boundaries (i.e., second rigid boundaries) on the left and right sides of the first type of omnidirectional sound wave absorbing structure 200. At this time, the sound waves can form complex resonances in the sound wave absorbing structure, which is beneficial to further improve the absorption rate; in addition, an opening with a distance of s = 5 mm is also set on the left side of the second type of omnidirectional sound wave absorbing structure 300 to enhance sound dissipation. Fig.11 Figure (b) shows the curves of the absorption rate of Case 1, Case 2, and the micro-perforated plate under vertical incidence of sound waves as a function of frequency, where the back cavity depth of the micro-perforated plate is 9.8 cm (the total thickness is 10 cm). It can be seen that Case 2 has significantly better sound absorption performance than the other two. In order to intuitively illustrate the complex resonance supported by Case 2, Fig.11 Figure (c) shows the normalized sound intensity (|P|) at 330 Hz for Case 1 and Case 2. 2 ) and velocity field (indicated by white arrows). It can be seen that in Case 1 (M), the acoustic intensity accumulates uniformly along the propagation direction, indicating that the dissipation of the microperforated plate itself plays a dominant role here. However, due to the second rigid boundary constraints on both sides, the highest intensity in Case 2 (Q) appears in the lower left corner, showing a complex resonance that contributes to the highest sound absorption. In addition, the curvature of the velocity flow in Case 2 (Q) (indicated by white arrows) shows that the coupling between the microperforated plates is stronger than that in Case 1 (M). It can be understood that with strong coupling, the overall absorption of the sound wave absorption structure is higher and smoother, and with weak coupling, the overall absorption effect of the sound wave absorption structure will also deteriorate.

[0110] Fig.12 Figure (a) is a schematic diagram of the structure of the three-dimensional omnidirectional sound absorber proposed based on Case 2, where: represents the incident angle of the sound wave in the xz plane, represents the incident angle of the sound wave in the yz plane. The relevant parameters of the three-dimensional omnidirectional sound absorber can be referred to in Example 2 and will not be repeated here. Optionally, the bottom surface of the three-dimensional omnidirectional sound absorber is a square. For clarity, the front panel of the three-dimensional omnidirectional sound absorber is rendered transparent to observe the internal details. Fig.12 Figure (b) shows the functional relationship between the absorption rate of the three-dimensional omnidirectional sound absorber and the incident angle and the operating frequency when the sound wave is incident in the xz plane. It can be seen that the three-dimensional omnidirectional sound absorber exhibits omnidirectional and ultra-wideband absorption performance in the xz plane. For example, When the sound wave is 370Hz, the absorption rate reaches 90%, and the average absorption rate in the frequency band of 370Hz to 12000Hz is 92.4%. When the second inclination angle is symmetrical to the first inclination angle about the preset axis, the average value of the absorption rate of the sound wave in the frequency band of 370 Hz to 12000 Hz can reach 97.1%. Fig.12 Figure (c) shows the functional relationship between the absorption rate of the three-dimensional omnidirectional sound absorber and the incident angle and the operating frequency when the sound wave is incident in the yz plane. It can be seen that although the sound absorption effect of the three-dimensional omnidirectional sound absorber is slightly inferior to the sound absorption effect when the sound wave is incident in the xz plane, it also shows omnidirectional and ultra-wideband sound absorption performance. On the other hand, by substituting the parameters of the three-dimensional omnidirectional sound absorber into the above formula (1), the theoretical minimum value d of the thickness of the three-dimensional omnidirectional sound absorber can be obtained. min =9.52 cm, which is also close to the actual thickness of the three-dimensional omnidirectional sound absorber (H=10 cm), indicating that the three-dimensional omnidirectional sound absorber has been made as thin as possible.

[0111] The following will refer to Fig.13 To carry out relevant experimental verification of the above-mentioned three-dimensional omnidirectional sound absorber.

[0112] like Fig.13 As shown in Figure (a), the impedance tube method was used for the experiment. Fig.13 Figure (b) shows a photograph of a real sample (Sample 1) made using steel plate etching technology. A smaller sample (Sample 2) was also made to measure the sound absorption performance at higher frequencies. Fig.13Figure (c) shows the structure of sample 2. The relevant parameters of sample 2 are the complementary angle of the first inclination α=60°, so that the first inclination β is 30°, the spacing ω between two adjacent sound wave absorbing materials (MPP) is 1 cm, the bottom surface of sample 2 is square, wherein the length D of the first rigid boundary is 5 cm, the length D of the second rigid boundary in the direction perpendicular to the preset axis is 5 cm and the spacing s with the sound wave absorbing material is 3 mm, the thickness H of sample 2 is 10 cm, and the parameters of MPP can refer to the MPP parameters in Case 1. The experimental equipment includes two square impedance tubes with side lengths of 10 cm and 5 cm, respectively. Their cross-sectional dimensions indicate cutoff frequencies of approximately 800 Hz and 3300 Hz, respectively. Beyond these frequencies, the measurement results become inaccurate. Fig.13 The large figure of Figure (d) shows the absorption rate curves of Sample 1 and Sample 2 under simulation, where Sample 1 (simulation) is represented by a solid circle and Sample 2 (simulation) is represented by a solid square; and the inset in the large figure shows both the absorption rate curves of Sample 1 and Sample 2 in the gray area in the large figure and the absorption rate curves of Sample 1 and Sample 2 under experimental measurement, where Sample 1 (experiment) is represented by a hollow circle and Sample 2 (experiment) is represented by a hollow square. It can be seen that the experimental measurement results are very close to the simulation results, and Sample 1 and Sample 2 can even achieve high sound absorption in the frequency range of 10000Hz and above under simulation. In addition, as a comparison, the inset also adds the absorption rate curves of the MPP with a back cavity depth of 9.8cm (total thickness 10cm) under simulation and experimental measurement, where MPP (simulation) is represented by a solid triangle and MPP (experiment) is represented by a hollow triangle. Obviously, compared with the traditional MPP, the three-dimensional omnidirectional sound absorber of the present application exhibits excellent sound absorption performance.

[0113] The present application also provides a method for preparing a sound wave absorbing structure.

[0114] In one embodiment, the preparation method comprises the following steps:

[0115] S100, obtaining a plurality of sound wave absorbing materials spaced apart along a preset axis; wherein, along the preset axis, the spacing ω between two adjacent sound wave absorbing materials satisfies: t<ω<λ, t represents the thickness of the sound wave absorbing material, and λ represents the wavelength of the incident sound wave.

[0116] Exemplarily, the sound wave absorbing material includes at least one of a micro-perforated plate, a textile sound absorbing material, and a foam metal.

[0117] S200, obtaining an absorption inclination angle of the sound wave absorbing material; wherein each sound wave absorbing material has a first inclination angle relative to a preset axis, and the sound wave incident on each sound wave absorbing material has a second inclination angle relative to the preset axis, and when the first inclination angle and the second inclination angle are symmetrical about the preset axis, the first inclination angle is the absorption inclination angle of the sound wave absorbing material.

[0118] Exemplarily, when the first inclination angle and the second inclination angle are symmetrical about a preset axis, a broadband impedance matching characteristic can be achieved based on the reciprocity principle.

[0119] S300, tilting at least a portion of the sound wave absorbing material relative to the preset axis within a range of its absorption inclination angle plus or minus a preset angle.

[0120] Exemplarily, the upper limit of the preset angle may be 15°. Exemplarily, the preset angle may be 3°, 5°, 8°, 10°, or 15°.

[0121] The method for preparing the above-mentioned sound wave absorbing structure can calculate the absorption inclination angle of the sound wave absorbing material based on the second inclination angle of the incident sound wave relative to the preset axis, and then set the first inclination angle of the sound wave absorbing material relative to the preset axis based on the absorption inclination angle to obtain the above-mentioned sound wave absorbing structure. The above-mentioned preparation method can prepare a sound absorbing structure designed based on the propagation direction of the incident sound wave, thereby realizing directional sound absorption.

[0122] In some embodiments, the preparation method further comprises:

[0123] S10. Obtaining the working frequency f of the sound wave absorbing structure w ;

[0124] S20, according to the working frequency f w Adjust the distance ω between two adjacent sound wave absorbing materials; where f w Negatively correlated with ω.

[0125] In this way, the distance between two adjacent sound wave absorbing materials can be adjusted according to the frequency of the incident sound wave, so as to meet the customized sound absorption requirements. Optionally, these two steps can be arranged before step S100 or after step S100. This application does not limit this.

[0126] In some embodiments, the sound wave absorbing material includes a first end close to the sound wave incident side and a second end close to the sound wave exit side, and the preparation method further includes:

[0127] S400, setting a first rigid boundary near the second end; wherein at least a portion of the first rigid boundary extends in a direction parallel to the preset axis.

[0128] In this way, the transmitted sound waves will be reflected back to the sound wave absorbing structure by the first rigid boundary and continue to be dissipated by the sound wave absorbing material, which is conducive to achieving an omnidirectional sound absorption effect.

[0129] Furthermore, the preparation method also includes:

[0130] S500, setting a second rigid boundary intersecting with the first rigid boundary or an extension line of the first rigid boundary; wherein at least a portion of the second rigid boundary is located on a side of the first rigid boundary close to the sound wave absorbing material.

[0131] In this way, the transmitted sound waves will be reflected by the first rigid boundary and the second rigid boundary to form a complex resonance in the sound wave absorbing structure, which is beneficial to further enhance the sound absorption effect of the omnidirectional sound wave absorbing structure.

[0132] The present application also provides a sound transmission device.

[0133] In one embodiment, the sound transmitting device includes: a sound wave incident surface and a sound wave exit surface arranged opposite to each other; and a sound wave absorbing structure as described in the previous embodiment arranged between the sound wave incident surface and the sound wave exit surface; the sound transmitting device is suitable for transmitting sound waves incident along a first direction and shielding sound waves incident along a second direction, wherein the first direction is parallel to the inclination direction of the sound wave absorbing material, and the first direction and the second direction are symmetrical about a perpendicular line of a preset axis.

[0134] Exemplarily, the microphone device can be used in directional communication devices and encrypted communication devices.

[0135] The above-mentioned sound transmission device can realize the transmission of sound waves in a first direction and shield the sound waves in a second direction through the sound wave absorbing structure as described in the above-mentioned embodiment, thereby achieving an asymmetric sound transmission effect.

[0136] The present application also provides a device, comprising: a containing cavity; a target sound source, which is arranged in the containing cavity; and a sound wave absorbing structure as described above, which is used to absorb the sound waves emitted by the target sound source.

[0137] Some devices may generate loud noise when working. After locating the noise source, a sound wave absorption structure as described above can be set near the noise source or on the noise transmission path to absorb sound and reduce noise, thereby improving the noise control performance of the device.

[0138] It should be noted that the numbers representing quantities or properties used to describe and claim certain embodiments of the present application should be understood to be modified by the terms "roughly", "about", "approximately" or "substantially" in some cases. For example, unless otherwise specified, "roughly", "about", "approximately" or "substantially" can indicate a ±20% variation of the value described. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may change according to the required features of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of the present application are approximate values, in specific embodiments, the setting of such numerical values ​​is as accurate as possible within the feasible range.

[0139] It should be understood that the above embodiments are exemplary and are not intended to include all possible implementations included in the claims. Various modifications and changes may be made on the basis of the above embodiments without departing from the scope of the present disclosure. Similarly, the various technical features of the above embodiments may be arbitrarily combined to form other embodiments of the present invention that may not be explicitly described. Therefore, the above embodiments only express several implementations of the present invention and do not limit the scope of protection of the patent of the present invention.

Claims

1. A sound wave absorbing structure, characterized in that: include: A plurality of sound wave absorbing materials are arranged at intervals along a predetermined axis; and, Along the extension direction of the preset axis, the spacing ω between two adjacent sound wave absorbing materials satisfies: t<ω<λ, wherein t represents the thickness of the sound wave absorbing material, and λ represents the wavelength of the incident sound wave; and, Each of the sound wave absorbing materials has a first inclination angle relative to the preset axis, and the sound wave incident on each of the sound wave absorbing materials has a second inclination angle relative to the preset axis. When the first inclination angle and the second inclination angle are symmetrical about the preset axis, the first inclination angle is the absorption inclination angle of the sound wave absorbing material; in, At least part of the sound wave absorbing material is configured to be tilted relative to the preset axis within a range of an absorption inclination angle thereof plus or minus a preset angle.

2. The sound wave absorbing structure according to claim 1, characterized in that: Each of the sound wave absorbing materials is configured to be tilted relative to the preset axis within a range of its absorption inclination angle plus or minus a preset angle.

3. The sound wave absorbing structure according to claim 1, characterized in that: The absorption tilt angle is greater than 0° and less than 90°.

4. The sound wave absorbing structure according to claim 3, characterized in that: The absorption tilt angle is greater than or equal to 20° and less than 90°.

5. The sound wave absorbing structure according to claim 1, characterized in that: The preset angle is less than or equal to 15°.

6. The sound wave absorbing structure according to claim 1, characterized in that: t≤ω / 5.

7. The sound wave absorbing structure according to claim 1, characterized in that: The working frequency f of the sound wave absorbing structure w It is negatively correlated with the distance ω between two adjacent sound wave absorbing materials.

8. The sound wave absorbing structure according to claim 1, characterized in that: The sound wave absorbing material includes at least one of a micro-perforated plate, a textile sound absorbing material, and a foam metal.

9. The sound wave absorbing structure according to claim 1, characterized in that: The sound wave absorbing material includes a first end close to the sound wave incident side and a second end close to the sound wave exit side. The sound wave absorbing structure also includes a first rigid boundary arranged close to the second end, and at least a portion of the first rigid boundary extends in a direction parallel to the preset axis.

10. The sound wave absorbing structure according to claim 9, characterized in that: At least a portion of the second end of the sound wave absorbing material is disposed in contact with the first rigid boundary.

11. The sound wave absorbing structure according to claim 9, characterized in that: The sound wave absorbing structure further includes a second rigid boundary intersecting the first rigid boundary or an extension line of the first rigid boundary, and at least a portion of the second rigid boundary is located on a side of the first rigid boundary close to the sound wave absorbing material.

12. The sound wave absorbing structure according to claim 11, characterized in that: A plurality of the second rigid boundaries are arranged along the circumference of the first rigid boundary, and the plurality of the second rigid boundaries and the first rigid boundary together enclose a cavity which is open toward the sound wave incident side and is used to accommodate the plurality of sound wave absorbing materials.

13. The sound wave absorbing structure according to any one of claims 9 to 12, characterized in that: The lengths of the multiple sound wave absorbing materials in a direction perpendicular to the preset axis are greater than or equal to a response length, and the response length is determined based on at least the bulk modulus of air, the effective bulk modulus of the multiple sound wave absorbing materials under the static limit, and the wavelength of the incident sound wave in the air.

14. The sound wave absorbing structure according to claim 1, characterized in that: Also includes: a first adjustment mechanism coupled to the plurality of sound wave absorbing materials for adjusting the first inclination angle; and / or, A second adjustment mechanism coupled to the plurality of sound wave absorbing materials is used to adjust the spacing.

15. A method for preparing a sound wave absorbing structure, characterized in that: include: Acquire a plurality of sound wave absorbing materials spaced apart along a preset axis; wherein, along the preset axis, the spacing ω between two adjacent sound wave absorbing materials satisfies: t<ω<λ, t represents the thickness of the sound wave absorbing material, and λ represents the wavelength of the incident sound wave; Obtaining an absorption inclination angle of the sound wave absorbing material; wherein each of the sound wave absorbing materials has a first inclination angle relative to the preset axis, and the sound wave incident on each of the sound wave absorbing materials has a second inclination angle relative to the preset axis, and when the first inclination angle and the second inclination angle are symmetrical about the preset axis, the first inclination angle is the absorption inclination angle of the sound wave absorbing material; At least part of the sound wave absorbing material is tilted relative to the preset axis within a range of its absorption inclination angle plus or minus a preset angle.

16. The preparation method according to claim 15, characterized in that: Also includes: Obtain the operating frequency f of the sound wave absorbing structure w ; According to the operating frequency f w Adjust the distance ω between two adjacent sound wave absorbing materials; wherein, f w Negatively correlated with ω.

17. The preparation method according to claim 16, characterized in that: The sound wave absorbing material comprises a first end close to the sound wave incident side and a second end close to the sound wave exit side, and the preparation method further comprises: A first rigid boundary is disposed near the second end; wherein at least a portion of the first rigid boundary extends in a direction parallel to the preset axis.

18. The preparation method according to claim 17, characterized in that: Also includes: A second rigid boundary is provided to intersect the first rigid boundary or an extension line of the first rigid boundary; wherein at least a portion of the second rigid boundary is located on a side of the first rigid boundary close to the sound wave absorbing material.

19. A sound transmission device, characterized in that: include: A sound wave incident surface and a sound wave exit surface arranged opposite to each other; as well as, The sound wave absorbing structure according to any one of claims 1 to 8, disposed between the sound wave incident surface and the sound wave exit surface; The sound transmitting device is suitable for transmitting sound waves incident along a first direction and shielding sound waves incident along a second direction, wherein the first direction is parallel to the tilt direction of the sound wave absorbing material, and the first direction and the second direction are symmetrical about a perpendicular line of the preset axis.

20. A device, characterized in that include: Receiving cavity; a target sound source, disposed in the accommodating cavity; and The sound wave absorbing structure according to any one of claims 1 to 14, for absorbing the sound waves emitted by the target sound source.

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