Sound wave absorption structure, sound transmission apparatus, device and manufacturing method

Abstract

The present invention relates to a sound wave absorption structure, a sound transmission apparatus, a device and a manufacturing method. The acoustic wave absorption structure comprises a plurality of acoustic wave absorption materials arranged at intervals along a preset axis. The distance between every two adjacent acoustic wave absorption materials in the direction of extension of the preset axis meets a preset condition. Each acoustic wave absorption material has a first inclination angle relative to the preset axis, an acoustic wave incident to each acoustic wave absorption 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 acoustic wave absorption material. At least some of the acoustic wave absorption materials are configured to be inclinedly arranged relative to the preset axis within a range where the absorption inclination angle of the at least some of the acoustic wave absorption materials is increased / decreased by a preset angle. The acoustic wave absorption structure can achieve sound absorption and noise reduction in a target direction.

Description

Sound wave absorbing structure, sound transmission device, component and preparation method 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 absorption properties, which may not be applicable in some scenarios. For example, sometimes it is necessary to directional interfere with sound in a certain direction without affecting the transmission of sound waves in other directions.

[0003] Furthermore, because traditional metastructured sound-absorbing materials are typically fabricated based on resonance, they often suffer from a narrow bandwidth. To expand the operating frequency range, several approaches have been explored, such as utilizing coupled, folded Fabry-Pérot channels or Helmholtz resonators. However, these designs typically require coupling multiple resonators and complex structural designs, increasing the difficulty of fabrication. Furthermore, these sound-absorbing structures typically exhibit symmetrical absorption characteristics, making it difficult to achieve asymmetric absorption.

[0004] Summary of the Invention

[0005] According to various embodiments of the present application, a sound wave absorbing structure, a sound transmitting device, a component and a preparation method are provided.

[0006] According to one aspect of the present application, a sound wave absorbing structure is provided, comprising: a plurality of sound wave absorbing materials spaced apart along a preset axis; wherein, along the extension direction of the preset axis, the spacing ω between two adjacent sound wave absorbing materials satisfies the following: t<ω<λ, wherein t represents the thickness of the sound wave absorbing material, and λ represents the wavelength of the incident sound wave; 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; wherein at least some of the sound wave absorbing materials are configured to be tilted relative to the preset axis within a range of their absorption inclination angle plus or minus a preset angle.

[0007] According to another aspect of the present application, a method for preparing a sound wave absorbing structure is provided, 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, where 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; and tilting at least some of the sound wave absorbing materials relative to the preset axis within a range of their absorption inclination angles plus or minus a preset angle.

[0008] According to another aspect of the present application, a sound transmitting device is provided, 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.

[0009] According to another aspect of the present application, a device is provided, 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.

[0010] The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to better describe and illustrate the embodiments or examples of the inventions disclosed herein, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the drawings should not be considered to limit the scope of the disclosed inventions, the embodiments or examples currently described, and any of the best modes currently understood for these inventions.

[0012] FIG1 (a) is a schematic structural diagram of a sound-absorbing metamaterial utilizing a Fabry-Pérot channel;

[0013] FIG1( b ) is a schematic structural diagram of a sound-absorbing metamaterial utilizing a Helmholtz resonant cavity;

[0014] FIG2 is a schematic structural diagram of a sound wave absorbing structure according to an embodiment of the present application;

[0015] FIG3 is a schematic diagram of sound absorption based on the reciprocity principle according to an embodiment of the present application;

[0016] FIG4 shows a curve showing changes in reflectivity, transmittance, and absorptivity of the sound wave absorbing material according to an embodiment of the present application under vertical incidence of sound waves as a function of frequency;

[0017] FIG5(a) is a graph showing the absorption rate of the sound wave absorbing structure according to an embodiment of the present application as a function of the incident angle of the sound wave and the complementary angle α of the first inclination angle;

[0018] FIG5( 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 incident angle and frequency of the sound wave;

[0019] FIG5( c ) is a graph showing the absorption rate of the sound wave absorbing structure according to an embodiment of the present application as a function of the incident angle and frequency of the sound wave;

[0020] FIG6 (a) is a diagram showing a simulated sound field distribution of the sound wave absorbing structure according to an embodiment of the present application when the sound wave is incident at ±45°;

[0021] FIG6( b ) is a diagram showing a simulated sound field distribution of the sound wave absorbing structure under a point sound source according to an embodiment of the present application;

[0022] FIG7 is a schematic diagram showing the effect of an embodiment of the present application when used as a super structure blind;

[0023] FIG8 (a) is a schematic diagram of a Gaussian acoustic beam experimental structure of a metastructured shutter sample;

[0024] Figure 8 (b) shows the curves of reflectivity, transmittance, and absorptivity as a function of frequency when the sound wave is incident on the meta-louver sample at ±45°;

[0025] Figure 8 (c) is a schematic diagram of the transmitted sound field distribution when sound waves of different frequencies are incident on the meta-louver sample at 45°;

[0026] Figure 8 (d) is a schematic diagram of the reflected sound field distribution when sound waves of different frequencies are incident on the meta-louver sample at -45°;

[0027] FIG9 (a) is a schematic diagram of a point sound source experimental structure of a superstructured blind sample;

[0028] Figure 9(b) is a schematic diagram of the transmitted sound field distribution of a point sound source when the super-structured louver sample is not set (top) and when the super-structured louver sample is set (bottom);

[0029] FIG10( a ) is a schematic structural diagram of Case 1 of the present application (setting a first rigid boundary);

[0030] FIG10( b ) is a schematic diagram showing the absorptivity of Case 1 of the present application as a function of the incident angle and the operating frequency;

[0031] FIG11( a ) is a schematic structural diagram of Case 2 of the present application (setting a first rigid boundary and a second rigid boundary);

[0032] Figure 11(b) shows the curves of the absorptivity 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;

[0033] Figure 11(c) shows the normalized intensity (color) and velocity fields (white arrows) simulated at 330 Hz for Case 1 and Case 2;

[0034] Figure 12 (a) is a schematic structural diagram of the three-dimensional omnidirectional sound absorber proposed based on Case 2;

[0035] FIG12( 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;

[0036] FIG12( 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;

[0037] FIG13( a ) is a schematic diagram of an impedance tube experimental structure of a three-dimensional omnidirectional sound absorber;

[0038] FIG13( b ) is a schematic diagram of samples 1 and 2 of the three-dimensional omnidirectional sound absorber;

[0039] Figure 13 (c) is a schematic structural diagram of sample 2;

[0040] FIG13( d ) shows the curves of the absorption rate of sample 1 changing with frequency under the experiment and simulation, and the curves of the absorption rate of sample 2 changing with frequency under the experiment and simulation.

[0041] Component number description: 100, sound wave absorbing structure, 101-102, sound wave absorbing material; 200, first type omnidirectional sound wave absorbing structure, 300, second type omnidirectional sound wave absorbing structure; AX, preset axis, θ i , the angle of incidence of the sound wave, β, the first inclination angle, α, the complementary angle of the first inclination angle, γ, the second inclination angle. DETAILED DESCRIPTION

[0042] To make the technical solutions and beneficial effects of the present invention more clearly understood, the following detailed description is given by way of specific embodiments. The accompanying drawings are not necessarily drawn to scale, and local features may be enlarged or reduced to more clearly illustrate 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.

[0043] 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 the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0044] 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 by using local resonant structures, such as microperforated plate (MPP) resonators, which use the resonance principle to achieve impedance matching within a certain frequency range. However, the strong dispersion inherent in these structures limits the bandwidth of impedance modulation.

[0045] On the other hand, acoustic metamaterials have demonstrated an impressive ability to manipulate sound in unprecedented ways, giving rise 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 resonators. However, these methods are limited in their operating frequency range due to their resonant mechanism. In order to achieve broadband sound absorption, the following two methods are generally used in traditional sound-absorbing metamaterials:

[0046] (1) Coupled folded Fabry-Pérot channel

[0047] As shown in Figure 1(a), when a sound wave enters a Fabry-Pérot channel, it propagates repeatedly within the channel, causing reflections and interference. Due to the effects of folding and coupling, sound waves of different frequencies interfere at different locations and depths, achieving broadband sound absorption.

[0048] (2) Coupled Helmholtz Resonant Cavity

[0049] As shown in Figure 1(b), when a sound wave enters a Helmholtz resonator, it repeatedly reflects within the cavity, forming standing waves. By designing resonators of different sizes and shapes, sound waves of varying frequencies can be absorbed. By properly coupling resonators of varying sizes and shapes, good sound absorption performance can be achieved across a wide frequency range.

[0050] However, these designs typically require coupling multiple resonant cavities and complex geometries, which increases fabrication difficulty. Furthermore, these sound-absorbing structures typically have symmetrical absorption characteristics, making it difficult to achieve asymmetric absorption properties.

[0051] To address these issues, this application utilizes a non-resonant approach, taking into account various physical properties of the prepared material, such as dispersion and effective parameters, to provide a sound-absorbing structure designed based on the reciprocity principle. This sound-absorbing structure exhibits asymmetric sound absorption properties (also known as directional sound absorption) with near-zero reflection, a wide operating frequency band, and a thin thickness.

[0052] In one embodiment, as shown in FIG2 , a sound wave absorbing structure 100 includes a plurality of sound wave absorbing materials spaced apart along a predetermined axis AX. Furthermore, along the extension direction of the predetermined axis AX, the spacing ω between two adjacent sound wave absorbing materials (e.g., sound wave absorbing material 101 and sound wave absorbing material 102) satisfies the following relationship: t<ω<λ, where t represents the thickness of the sound wave absorbing material and λ represents the wavelength of the incident sound wave. Furthermore, each sound wave absorbing material has a first inclination angle β relative to the predetermined axis AX, and the sound wave incident on each sound wave absorbing material has a second inclination angle γ relative to the predetermined axis AX. When the first inclination angle β and the second inclination angle γ are symmetrical about the predetermined axis AX, the first inclination angle β represents the absorption inclination angle of the sound wave absorbing material. Furthermore, at least some of the sound wave absorbing materials are configured to be tilted relative to the predetermined axis AX within a range of their absorption inclination angles plus or minus a predetermined angle.

[0053] Based on the reciprocity principle, taking FIG3 as an example, when a 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 iIt can be denoted as α1. When a sound wave is incident at an angle of incidence symmetric to α1 about the normal (denoted as -α1), the sound wave will also enter the sound absorbing structure 100 substantially without reflection and be absorbed by the sound absorbing material in the sound absorbing structure 100. Here, R represents reflectivity, T represents transmittance, and H represents the thickness of the sound absorbing structure 100. In this case, the sound absorbing structure 100 is impedance-matched with air, α1 and the first tilt angle β are complementary, and -α1 and the second tilt angle γ are complementary. Therefore, the first tilt angle β and the second tilt angle γ are symmetric about the predetermined axis AX, and the first tilt angle β represents the absorption tilt angle of the sound absorbing material. When at least a portion of the sound absorbing material is tilted relative to the preset axis AX within a range of its absorption inclination angle plus or minus a preset angle, this portion of the sound absorbing material can achieve better absorption of sound waves incident at a certain angle (e.g., -α1). In other words, the sound absorbing structure 100 can exhibit asymmetric sound absorption characteristics for sound waves incident at angles α1 and -α1. If the sound dissipation provided by the sound absorbing material is sufficiently large, this can facilitate achieving a perfect sound absorption effect. Exemplarily, the upper limit of the preset angle can be 15°. Exemplarily, the preset angles can be 3°, 5°, 8°, 10°, or 15°. Furthermore, by controlling the spacing between adjacent sound absorbing materials to be less than the wavelength of the incident sound wave and greater than the thickness of the sound absorbing material, it is further advantageous to ensure that there is essentially no diffraction during sound wave transmission, thereby maintaining the sound absorption effect of the sound absorbing structure 100.

[0054] For example, the sound wave absorbing structure 100 may further include a substrate, with each sound wave absorbing material 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.

[0055] Exemplarily, the sound wave absorbing material includes at least one of a micro-perforated plate, a textile sound absorbing material, and foam metal.

[0056] The sound wave absorbing structure 100 of this embodiment is configured such that at least a portion of the sound wave absorbing material is tilted relative to a preset axis AX within a range of a predetermined absorption inclination angle plus or minus a predetermined angle. This allows the sound wave absorbing structure 100 to absorb sound waves in a target direction based on the reciprocity law, thereby achieving sound absorption and noise reduction in the target direction. Furthermore, the sound wave absorbing structure 100 allows sound waves propagating in the tilted direction of the sound wave absorbing material (a direction symmetrical to the target direction about a perpendicular line to the predetermined axis) to pass through the sound wave absorbing structure, achieving an asymmetric sound absorption effect.

[0057] In some embodiments, referring again to FIG. 2 , each sound absorbing material is configured to be tilted relative to a predetermined axis AX within a range of its absorption inclination angle plus or minus a predetermined angle. This allows for improved sound absorption when sound waves in a target direction strike different locations of the sound absorbing structure 100, thereby enhancing the overall sound absorption properties of the sound absorbing structure 100.

[0058] 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°, or 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, making it difficult to achieve sound absorption and noise reduction in the target direction through the reciprocity principle. In this case, even if vertical incidence is used, it is difficult to achieve a good sound absorption effect. As shown in FIG4 , when a microperforated plate is used as the sound wave absorbing material, the transmittance of the microperforated plate under vertical incidence is still approximately 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. In this case, 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 inclination angle is greater than or equal to 20° and less than 90°. By controlling the absorption inclination 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. Taking Figure 5 (a) as an example, α represents the angle complementary to the first inclination angle β. It can be seen that the incident angle θ with high absorption i It 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°.

[0059] 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.

[0060] In some embodiments, the thickness t of the sound absorbing material satisfies t≤ω / 5. This allows the thickness of the sound absorbing material to be much smaller than the spacing between the materials. Consequently, when a sound wave is incident parallel to the surface of the sound absorbing material, each sound absorbing material has little effect on the sound wave. This further enhances the sound absorption effect of the sound absorbing structure 100 based on the reciprocity principle.

[0061] In some embodiments, the operating frequency f of the sound wave absorbing structure 100 is w It 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. wThe higher the value, the better the ω can be for the required operating frequency f w Make adjustments.

[0062] Specific embodiments that reflect the inventive concept of the present application will be further described below with reference to FIG. 4 to FIG. 9 .

[0063] 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%.

[0064] Figure 4 shows the curves of the reflectivity, transmittance, and absorptivity of the MPPs of this embodiment as a function of frequency under normal acoustic incidence. The relationship between reflectivity, transmittance, and absorptivity can be expressed as their sum approaching 1. The MPP absorptivity is approximately 45%. However, Figures 5 and 6 show that when the MPPs are tilted at a certain angle to form an array, i.e., a sound absorption structure 100, their absorption performance is significantly improved. The thickness H of the sound absorption structure 100 is 7 cm, and the distance between adjacent MPPs is 3 cm.

[0065] As shown in Figure 5 (a), when a sound wave with a frequency of 4000 Hz is incident, 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 symmetrical 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). As shown in FIG5(b), with an incident sound wave of 1000 Hz to 6000 Hz, the first MPP inclination angle is 45°, and the spacing between two adjacent MPPs is controlled to be less than the wavelength of the incident sound wave. It can be seen that within the range of incident angles less than or equal to 70°, the reflection is symmetrical with respect to the incident angle and is very low (essentially less than or equal to 0.1, shown by the white solid line). In addition, when the incident angle is 45°, zero reflection occurs. As shown in FIG5(c), using the same configuration as FIG5(b), the absorption of the sound wave absorbing structure 100 at incident angles of ±45° is antisymmetric. That is, over a wide frequency range, there is essentially no absorption at an incident angle of 45°, but at an incident angle of -45°, complete absorption of greater than or equal to 0.9 occurs. This demonstrates that the sound wave absorbing structure 100 has asymmetric sound absorption characteristics, enabling targeted sound absorption and noise reduction.

[0066] Figure 6 (a) shows a simulated sound field distribution diagram of the sound wave absorbing structure 100 with a first inclination angle of 45° when the sound wave is incident at ±45°. It can be seen that the reflection phenomenon is eliminated in both cases, and when the sound wave is incident at -45°, a nearly perfect absorption phenomenon can be observed. Figure 6 (b) shows a simulated sound field distribution diagram of the sound 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 to prepare a super-structured blind as shown in Figure 7. The super-structured blind can provide a quiet area on only one side, while achieving normal sound transmission on the other side, which has important application value in some specific scenarios.

[0067] The following will refer to Figures 8 and 9 to conduct relevant experimental verification on the above-mentioned super-structure blinds.

[0068] In the experiments of FIG8 and FIG9 , steel MPPs with periodically arranged triangular tapered holes were used. Under vertical incidence, the absorption rate at the operating frequency was about 30%.

[0069] The experimental setup of the Gaussian beam is shown in Figure 8(a), where the xy planes are the two measurement areas on the reflection side and the transmission side, respectively. They are represented by gray rectangular areas, each with a size of 32*30 cm. 2 , 3 cm from the sample. The inset shows a photograph of an actual sample. The MPP tilt angle (i.e., the first tilt angle β) was 45°, and the spacing ω was 3 cm. To generate a quasi-Gaussian acoustic beam, a loudspeaker array with parabolic mirrors was constructed. The microphone was then mounted on a mobile stage, scanning the sound field distribution with a step size of 10 mm. The experiments were conducted in an anechoic chamber to minimize reflections and noise.

[0070] Figure 8 (b) shows the curves of reflectivity, transmittance and absorptivity as a function of frequency when the sound wave is incident on the meta-louver 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 and there is 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 to be about 60%. Optionally, an MPP with a higher absorptivity can be used or the thickness of the sound wave absorbing structure can be increased to further improve the absorptivity. It can be understood that when the thickness of the sound wave absorbing structure increases, the distance that the sound wave travels in the sound wave absorbing 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 the Gaussian beam.

[0071] Figure 8(c) shows the transmitted acoustic field distribution when sound waves of different frequencies are incident on the metastructured louver sample at 45°, while Figure 8(d) shows the reflected acoustic field distribution when sound waves of different frequencies are incident on the metastructured louver 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. When the sound waves are incident at -45°, the sound wave absorption structure exhibits excellent sound absorption effects at different frequencies.

[0072] The experimental structure of the point sound source is shown in Figure 9 (a). The measurement area is marked by a black box in the figure, and its size is 40*20cm. 2 The distance between the measurement area and the sound absorption structure is 2 cm, and the distance between the speaker and the sound absorption structure is 2 cm. Figure 9(b) shows the transmitted sound field distribution of a point sound source without the meta-louver sample (top) and with the meta-louver sample (bottom). It can be seen that the left half of the transmitted sound field exhibits greater absorption, while the right half exhibits greater transmission.

[0073] 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.

[0074] In some embodiments, by adjusting boundary conditions and simultaneously incorporating the reciprocity principle and the complex resonance principle, ultra-wideband omnidirectional sound absorption performance can be achieved. Specifically, as shown in FIG10(a), the sound wave absorbing material (MPP) includes a first end near the sound wave incident side and a second end near the sound wave exit side. The sound wave absorbing structure also includes a first rigid boundary disposed near the second end, and at least a portion of the first rigid boundary extends in a direction parallel to the predetermined axis. In this manner, a first-class omnidirectional sound wave absorbing structure 200 is formed. Due to the addition of the first rigid boundary, transmitted sound waves are reflected back to the sound wave absorbing structure and continue to be dissipated by the sound wave absorbing material, thereby achieving an omnidirectional sound absorption effect.

[0075] In some embodiments, the second end of at least a portion of the sound wave absorbing material is disposed in contact with the first rigid boundary. Direct contact between the first rigid boundary and the second end facilitates reducing the thickness of the sound wave absorbing structure, making the sound wave absorbing structure thinner.

[0076] In some embodiments, as shown in Figure 11(a), the sound absorbing structure further includes a second rigid boundary that intersects the first rigid boundary or an extension of the first rigid boundary, and at least a portion of the second rigid boundary is located on the side of the first rigid boundary closest to the sound absorbing material. This creates a second type of omnidirectional sound absorbing structure 300. The addition of the first and second rigid boundaries allows for complex resonances, further enhancing the sound absorption performance of the omnidirectional sound absorbing structure. Optionally, a gap may be provided between the second rigid boundary and the sound absorbing material to further enhance sound dissipation.

[0077] In some embodiments, referring again to Figure 11(a), multiple second rigid boundaries are arranged circumferentially around the first rigid boundary. Together with the first rigid boundary, these second rigid boundaries form a cavity open toward the sound wave incident side for accommodating multiple sound absorbing materials. This arrangement facilitates the formation of a three-dimensional, omnidirectional sound absorber, allowing sound waves to be more fully absorbed by the sound absorbing materials, thereby further improving sound absorption performance.

[0078] 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, where 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 relating a given absorption spectrum to the sample thickness d:

[0079] Where 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 minimized 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 lighter and thinner sound wave absorbing structure while satisfying the causal law.

[0080] In some embodiments, the sound wave absorbing structure further includes a first adjustment mechanism coupled to the plurality of sound wave absorbing materials for adjusting a first inclination angle; and / or a second adjustment mechanism coupled to the plurality of sound wave absorbing materials for adjusting the distance between two adjacent sound wave absorbing materials. The first adjustment mechanism can adjust the first inclination angle of the sound wave absorbing material, thereby facilitating adjustment of the first inclination angle to a corresponding absorption inclination angle based on the second inclination angle of the incident sound wave, thereby achieving a better sound absorption effect. The second adjustment mechanism can adjust the distance between two adjacent sound wave absorbing materials, thereby facilitating widening the operating frequency range of the sound wave absorbing structure and meeting the application requirements of higher operating frequencies. Exemplarily, the first adjustment mechanism can achieve adjustment of the first inclination angle by connecting the sound wave absorbing material to the pivot structure or a motor. Exemplarily, the second adjustment mechanism can achieve adjustment of the distance by connecting the sound wave absorbing material to the screw thread, screw rod or motor.

[0081] Specific embodiments that reflect the inventive concept of the present application will be further described below with reference to FIG. 10 to FIG. 12 .

[0082] As shown in Figure 10 (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. 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 1 cm, the length D of the first rigid boundary is 10 cm, the thickness of the first rigid boundary is 2 mm, the thickness H of the sound wave absorbing structure is 10 cm, and the periodic boundary represents the infinite boundary during simulation. Among them, the parameters of MPP are an aperture (diameter) of 0.2 mm, a plate thickness of 0.1 mm, and a porosity of 2%. Figure 10 (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 Within the range of |≤60°, sound waves from 800Hz to 16800Hz can achieve a high absorption rate.

[0083] As shown in Figure 11(a), the second type of omnidirectional sound wave absorbing structure 300 (Case 2) also has rigid boundaries (i.e., second rigid boundaries) set 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 within the sound wave absorbing structure, which is conducive to further improving the absorption rate. In addition, an opening with a distance of s = 5 mm is set on the left side of the second type of omnidirectional sound wave absorbing structure 300 to enhance sound dissipation. Figure 11(b) shows the absorption rate of Case 1, Case 2, and the microperforated plate under vertical incidence of sound waves as a function of frequency. The back cavity depth corresponding to the microperforated plate is 9.8 cm (the total thickness is 10 cm). It can be seen that Case 2 shows significantly better sound absorption performance than the other two. In order to intuitively illustrate the complex resonance supported by Case 2, Figure 11(c) shows the normalized sound intensity (|P|) of Case 1 and Case 2 at 330 Hz. 2 ) and velocity field (indicated by white arrows). It can be seen that in Case 1 (M), the sound 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.

[0084] Figure 12 (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 Case 2 and will not be repeated here. Optionally, the bottom surface of the three-dimensional omnidirectional sound absorber is a square. For the sake of clarity, the front panel of the three-dimensional omnidirectional sound absorber is rendered transparent to observe the internal details. Figure 12 (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, in When the sound wave has a frequency of 370Hz, the absorption rate reaches 90%, and the average absorption rate in the frequency band of 370Hz to 12000Hz is 92.4%. Under the condition that the second inclination angle is symmetrical with the first inclination angle about the preset axis, the average absorption rate of the sound wave in the frequency band of 370Hz to 12000Hz can reach 97.1%. Figure 12 (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 aforementioned 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.

[0085] The following will refer to FIG13 to conduct relevant experimental verification on the above three-dimensional omnidirectional sound absorber.

[0086] As shown in Figure 13(a), the impedance tube method was used for the experiment. Figure 13(b) shows a photograph of a real sample (Sample 1) fabricated using steel plate etching technology. To measure sound absorption performance at higher frequencies, a smaller sample (Sample 2) was also fabricated. Figure 13(c) shows the structure of Sample 2. The relevant parameters for Sample 2 are that the complementary angle α of the first inclination angle is 60°, resulting in a first inclination angle β of 30°; the spacing ω between two adjacent sound wave absorbing materials (MPPs) is 1 cm; the bottom surface of Sample 2 is square, with the length D of the first rigid boundary being 5 cm; the length D of the second rigid boundary perpendicular to the predetermined axis being 5 cm, and the spacing s between the two adjacent sound wave absorbing materials being 3 mm; and the thickness H of Sample 2 being 10 cm. The MPP parameters can be found in Example 1. The experimental apparatus consists of 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. Measurements above these frequencies become inaccurate. The large image in Figure 13(d) shows the absorptivity curves of Samples 1 and 2 under simulation, with Sample 1 (simulation) represented by solid circles and Sample 2 (simulation) represented by solid squares. The inset in the large image shows both the absorptivity curves of Samples 1 and 2 in the gray area of ​​the large image and the absorptivity curves of Samples 1 and 2 under experimental measurements, with Sample 1 (experimental) represented by hollow circles and Sample 2 (experimental) represented by hollow squares. It can be seen that the experimental measurement results are very close to the simulation results, and Samples 1 and 2 can even achieve high sound absorption in the frequency range of 10,000 Hz and above under simulation. In addition, for comparison, the inset also includes the absorptivity curves of an MPP with a back cavity depth of 9.8 cm (total thickness 10 cm) under simulation and experimental measurements, with MPP (simulation) represented by solid triangles and MPP (experimental) represented by hollow triangles. Clearly, compared to traditional MPPs, the three-dimensional omnidirectional sound absorber of this application demonstrates superior sound absorption performance.

[0087] The present application also provides a method for preparing a sound wave absorbing structure.

[0088] In one embodiment, the preparation method comprises the following steps:

[0089] 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, where t represents the thickness of the sound wave absorbing material, and λ represents the wavelength of the incident sound wave.

[0090] Exemplarily, the sound wave absorbing material includes at least one of a micro-perforated plate, a textile sound absorbing material, and a foam metal.

[0091] 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. 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.

[0092] For example, when the first tilt angle and the second tilt angle are symmetrical about a preset axis, a broadband impedance matching characteristic can be achieved based on the reciprocity principle.

[0093] S300 , tilting at least a portion of the sound wave absorbing material relative to the preset axis within a range of an absorption inclination angle plus or minus a preset angle.

[0094] Exemplarily, the upper limit of the preset angle may be 15°. Exemplarily, the preset angle may be 3°, 5°, 8°, 10°, or 15°.

[0095] The above-mentioned method for preparing a sound-absorbing structure calculates the absorption angle of the sound-absorbing material based on the second inclination angle of the incident sound wave relative to a predetermined axis. This absorption angle is then used to set the first inclination angle of the sound-absorbing material relative to the predetermined axis, thereby producing the above-mentioned sound-absorbing structure. This method can produce a sound-absorbing structure designed based on the propagation direction of the incident sound wave, achieving directional sound absorption.

[0096] In some embodiments, the preparation method further comprises:

[0097] S10. Obtaining the operating frequency f of the sound wave absorbing structure w ;

[0098] S20, according to the operating frequency f w Adjust the distance ω between two adjacent sound wave absorbing materials; where f w Negatively correlated with ω.

[0099] In this way, the spacing between two adjacent sound wave absorbing materials can be adjusted according to the frequency of the incident sound wave, thereby helping to meet customized sound absorption requirements. Optionally, these two steps can be arranged before step S100 or after step S100. This application does not impose any restrictions on this.

[0100] 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:

[0101] 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.

[0102] 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.

[0103] Furthermore, the preparation method further comprises:

[0104] S500 , setting a second rigid boundary intersecting 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.

[0105] In this way, the transmitted sound waves will be reflected by both the first rigid boundary and the second rigid boundary, thereby forming a complex resonance within the sound wave absorbing structure, which is beneficial to further enhance the sound absorption effect of the omnidirectional sound wave absorbing structure.

[0106] The present application also provides a sound transmitting device.

[0107] 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.

[0108] For example, the microphone device can be used in a directional communication device and an encrypted communication device.

[0109] 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 embodiments, thereby achieving an asymmetric sound transmission effect.

[0110] The present application also 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.

[0111] Some devices may generate a lot of noise during operation. 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.

[0112] 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 as being modified by the terms "roughly", "about", "approximately" or "substantially" in some cases. For example, unless otherwise stated, "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 characteristics 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 fields and parameters used to confirm the breadth of their range in some embodiments of the present application are approximate values, in specific embodiments, the settings of such numerical values ​​are as accurate as possible within the feasible range.

[0113] It should be understood that the above embodiments are exemplary and are not intended to encompass all possible implementations of the claims. Various modifications and variations may be made to the above embodiments without departing from the scope of this disclosure. Similarly, the various technical features of the above embodiments may be arbitrarily combined to form additional embodiments of the present invention that may not be explicitly described. Therefore, the above embodiments merely illustrate several implementations of the present invention and do not limit the scope of protection of the patent of this 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 the 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 the first inclination angle and the second inclination angle are about the preset axis. When the axis is preset to be symmetrical, 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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