Acoustic diffusion structure based on semicircular reflecting surface and design method
By designing a semicircular reflective surface diffusion structure on the sound barrier, using multi-order rectangular blocks and cut arc surfaces to achieve uniform diffusion of sound waves, the problem of multiple reflective diffraction sound is solved and the noise reduction effect of the sound barrier is improved.
Patent Information
- Application Number
- CN202510831567.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-20
- Publication Date
- 2025-08-08
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
During the noise reduction process of traditional sound barriers, multiple reflection diffraction sound problems are significant, especially in dense traffic areas, resulting in poor noise reduction effect.
An acoustic diffusion structure based on a semicircular reflective surface is designed, by distributing multiple rectangular blocks of equal width or height on the substrate, forming a multi-order diffusion, cutting into irregular arc surfaces, achieving uniform diffusion of sound waves, and combining with the interference surface to reduce diffraction sound.
Effectively reduce the multiple reflected sound energy, improve the overall noise reduction effect, and enhance the noise reduction performance of the sound barrier.
Smart Images
Figure CN120452403A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of noise reduction, and in particular to an acoustic diffusion structure based on a semicircular reflecting surface and a design method thereof. Background Art
[0002] When using a sound barrier to reduce noise, the noise in the back-shadow area primarily comes from sound transmitted through the screen and diffracted sound. A significant portion of diffracted sound is generated by multiple reflections between the screen and the vehicle body. This multiple reflection causes sound wave energy to be repeatedly "captured," ultimately bypassing the top or side edges of the barrier to reach the receiving area, significantly reducing the barrier's noise reduction effectiveness. This problem of multiple reflections and diffracted sound is particularly pronounced in dense traffic conditions and with numerous reflective surfaces on vehicles.
[0003] Traditional methods for reducing multi-reflected diffracted sound include adding a top structure to the sound barrier, optimizing the screen structure, and adding a sound-absorbing layer between the sound barrier and the vehicle. This paper proposes a novel diffusing surface structure design method to optimize the screen structure. This method aims to evenly diffuse the multi-reflected sound waves from the sound barrier, thereby reducing the multi-reflected sound energy and diffracted sound. Summary of the Invention
[0004] In order to solve the above technical problems, the present invention provides a diffusion surface structure design method, so that the multiple reflected sound waves of the sound barrier no longer converge but diffuse evenly, thereby reducing the sound energy of the multiple reflections and reducing the diffraction sound.
[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:
[0006] A design method for an acoustic diffusion structure based on a semicircular reflective surface includes a hemispherical base, a rectangular base, and a plurality of rectangular blocks of equal width or height distributed on top of the base. The plurality of rectangular blocks of equal width or height and the base together form a multi-stage diffuser.
[0007] The multi-stage diffuser is formed by cutting the substrate, and the bottom of the substrate is coplanar with the bottom of the base. The peripheral side of the base is exposed by cutting the substrate. The arc surface of the substrate is formed into an irregular arc surface at the top of each rectangular block by cutting to form the diffuser surface. The diffuser surface and the multi-stage diffuser together form an acoustic diffusion structure.
[0008] Preferably, the highest point on the diffuser surface is constrained to:
[0009]
[0010] Where: max(h i ) is the maximum height of the arc surface formed by the top of the i-th order rectangular block; 2l is the width of the acoustic diffusion structure.
[0011] Preferably, the wavelength corresponding to the design center frequency f of the acoustic diffusion structure is The diameter of the substrate is greater than the width of the diffuser.
[0012] Preferably, the radius r of the substrate is:
[0013]
[0014] Wherein, h is the height of the substrate after removing the base, h=rd, and d is the height of the base; l is the width of the base.
[0015] Preferably, when multiple rectangular blocks are distributed on the base with equal width, the height of each rectangular block in the multi-stage diffuser is:
[0016]
[0017] At this time h i Maximum height h i，max for:
[0018]
[0019] The width of the arc cut at the top of each rectangular block is:
[0020]
[0021] Where: l i h is the width of the arc cut at the top of the i-th rectangular block; i is the height of the i-th rectangular block; n is the order of the diffuser, and n≥2; i=1,2,…,n.
[0022] Preferably, when multiple rectangular blocks are distributed on the base at equal heights, the height of each rectangular block in the multi-stage diffuser is:
[0023]
[0024] at this time,
[0025]
[0026] d=rn·h i
[0027] The height of the arc cut at the top of each rectangular block is:
[0028]
[0029] The width of the arc cut at the top of each rectangular block is:
[0030]
[0031] Where, l i is the width of the i-th rectangular block; n is the order of the diffuser; l is the width of the base, h i is the height of the arc cut from the top of the i-th rectangular block; j.
[0032] Compared with the prior art, the present invention has the following beneficial effects:
[0033] The surface diffusion structure of the present invention allows the incident sound on the surface to be evenly diffused, reducing the diffraction sound caused by multiple reflections of the sound barrier. At the same time, the diffusion structure is combined with the interference surface to further reduce the surface diffraction sound, thereby improving the overall noise reduction effect. BRIEF DESCRIPTION OF THE DRAWINGS
[0034] Figure 1 This is a schematic diagram of the base and the design position of the base;
[0035] Figure 2 It is a schematic diagram of the design of multiple rectangular blocks with equal width;
[0036] Figure 3 It is a schematic diagram of cutting multiple rectangular blocks with equal width;
[0037] Figure 4 This is a schematic diagram of an acoustic diffusion structure formed by cutting multiple rectangular blocks of equal width.
[0038] Figure 5 It is a schematic diagram of the design of multiple rectangular blocks with equal height distribution;
[0039] Figure 6 It is a cutting diagram of multiple rectangular blocks of equal height;
[0040] Figure 7 It is a schematic diagram of the acoustic diffusion structure formed by cutting multiple rectangular blocks of equal height;
[0041] Figure 8 It is made of ECP cement board and is equipped with a schematic diagram of the acoustic diffusion structure with a cavity.
[0042] Figure symbols: 1. base, 2. base, 3. rectangular block. DETAILED DESCRIPTION
[0043] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples and drawings. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.
[0044] Suppressing diffracted sound caused by multiple reflections can effectively improve the noise reduction effect. The existing technology mainly uses the following methods to reduce multiple reflections:
[0045] Method 1: Add a top structure to the sound barrier;
[0046] Method 2: Optimize the screen structure;
[0047] Method 3: Add a sound-absorbing layer between sound barrier vehicles.
[0048] The present invention proposes a design method for an acoustic diffusion structure based on a semicircular reflecting surface on the basis of optimizing the screen structure, so that the multiple reflected sound waves of the sound barrier no longer converge and can be evenly diffused, thereby reducing the sound energy of multiple reflections to reduce diffraction sound. In the implementation process, it can also cooperate with the method of adding a sound-absorbing layer between the top structure of the sound barrier and the sound barrier vehicle.
[0049] 1. Acoustic diffusion structure of semicircular Fresnel reflector (Fresnel structure)
[0050] Fresnel structures were originally used in optical lenses. By discretizing continuous curved surfaces into stepped annular regions, they reduce thickness while maintaining functionality. In acoustics, similar principles are used to manipulate the phase of sound waves, achieving directional scattering of sound waves through stepped or segmented geometric structures. Semicircular substrates provide symmetrical scattering properties, suitable for diffusing sound waves from different directions while reducing acoustic energy loss caused by geometric abrupt changes.
[0051] The depth Δd of each Fresnel step is related to the wavelength λ of the target frequency f, satisfying Where n is the number of steps. By adjusting the step height, the phase difference of the reflected sound waves is made close to 180°, forming destructive interference to destroy the mirror reflection.
[0052] The core design basis of the step height is the target frequency Wavelength rule, the specific implementation process is as follows:
[0053] S1. Determine the target frequency f and the wavelength corresponding to f Where c is the speed of sound;
[0054] S2. Calculate the path difference required to produce a 180° phase difference
[0055] S3. Since the reflected sound wave experiences a round trip path, the actual step height must meet
[0056] S4, achieve full phase coverage 0-2π through multi-step superposition.
[0057] This discretization allows The phase is regulated within the wavelength scale, and the sudden reflection is reduced by impedance gradient. In the actual design, a multi-band optimization method is adopted: the reflecting surface is divided into different annular areas, each area is designed for a specific center frequency.
[0058] 2. Semicircular curvature combined with Fresnel steps
[0059] Disperse incident sound energy into a wider solid angle to avoid sound energy concentration. The highest operating frequency is determined by the minimum step width to avoid sound wave diffraction, and the lowest frequency is determined by the overall structure depth.
[0060] Specifically, the relationship between the semicircular base curvature radius R and the Fresnel partition is determined by the sound ray tracing method, and the sound wave incident angle θ and reflection angle are established. The mapping relationship.
[0061] Discretize the semicircle into N Fresnel rings, and the boundary angle of the kth ring satisfies:
[0062]
[0063] Optimize the ring belt width wk to satisfy:
[0064]
[0065] To ensure the diffusion effect of the highest operating frequency.
[0066] This design principle stems from the wavelength-geometry matching condition and phase modulation limit of sound waves. The acoustic function of the Fresnel step is essentially the discrete sampling of the continuous phase plane. According to the spatial sampling theorem, to effectively control the sound wave of frequency f, the step width w must satisfy:
[0067]
[0068] Where λ is the wavelength and c is the speed of sound (about 343 m / s in air).
[0069] If the step width is greater than half a wavelength, a spatial aliasing effect will occur, causing phase modulation to fail; each step must produce a local phase mutation on the acoustic wave front; when the step width exceeds half a wavelength, the acoustic wave phase difference at different positions in the same step area exceeds 180°, resulting in a mixture of constructive and destructive interference, destroying the designed phase gradient.
[0070] Depend on The highest effective frequency can be obtained: At the lowest frequency f min To achieve effective phase modulation, the overall structure depth D must be sufficient The wavelength condition ensures that the acoustic path difference between adjacent steps is sufficient to produce a significant phase difference of ≥90°, thereby forming destructive interference. If the structure depth is insufficient, the wavelength of the low-frequency sound wave is too long, and the phase difference between the steps approaches zero, causing the reflected wave to be close to mirror reflection and unable to diffuse.
[0071]
[0072] To overcome the depth limitations of single-layer structures, Helmholtz resonant cavities or elastic membrane coupling structures can be used to enhance low-frequency diffusion through resonance effects. For example, cavities can be set inside the substrate, or porous materials (such as micro-perforated plates) can be combined to broaden the low-frequency response through viscous losses.
[0073] The interference surface uses periodic or pseudo-randomly distributed concave and convex structures (such as hemispherical and pyramidal units) to make the acoustic wave path difference (ΔL) meet the following conditions: Where k is an integer, it leads to destructive interference, destroying the coherent sound field. The semicircular Fresnel structure dominates low-frequency diffusion, dispersing acoustic energy through large-scale phase modulation. Subwavelength interference elements attached to the microsurface enhance scattering at mid- and high-frequency frequencies.
[0074] The core of large-scale phase modulation is to perform segmented phase delay on the wavefront of the incident sound wave through a discrete geometric structure, so that the reflected sound wave forms controllable destructive interference and energy dispersion in space.
[0075] Select the dominant frequency band, such as the sound barrier center frequency of 500Hz, or others.
[0076] The height of each step h n The two-way path difference of the reflected sound wave must be satisfied to produce the target phase difference. The phase delay of the reflected wave increases by 180° (the round trip path is 2h n ).
[0077]
[0078] Where n = 1, 2, 3, … N.
[0079] Map step heights to radial depths of a semicircular base:
[0080]
[0081] Where R is the radius of the semicircular base; ω n is the microstructure width.
[0082] By adjusting ω n Make the sound path difference between adjacent steps meet the phase condition.
[0083] Width ω n The sampling theorem of the highest operating frequency must be met.
[0084] In actual engineering, in order to avoid the structure being too thick, phase folding is used to reduce the theoretical height h n right Modulo, the equivalent phase delay remains unchanged, but the physical depth is reduced, and the height after compression is:
[0085]
[0086] Diffusion Index:
[0087]
[0088] Where, L i is the sound pressure level in each direction, is the average value, the ideal value D θ →1.
[0089] In summary, this embodiment discloses a design method for an acoustic diffusion structure based on a semicircular reflective surface, so that the multiple reflected sound waves of the sound barrier no longer converge and diffuse evenly, thereby reducing the sound energy of the multiple reflections and reducing the diffraction sound. Specifically, it includes a hemispherical base 1, a rectangular base 2, and a plurality of rectangular blocks 3 of equal width or height distributed on the top of the base 2, wherein the plurality of rectangular blocks 3 of equal width or height and the base 2 together form a multi-order diffuser; the multi-order diffuser is formed by cutting the base 1, and the bottom of the base 1 is coplanar with the bottom of the base 2, the circumference of the base 2 is exposed by cutting the base 1, and the arc surface of the base 1 is formed into an irregular arc surface on the top of each rectangular block 3 by cutting to form a diffuser surface, and the diffuser surface and the multi-order diffuser together form an acoustic diffusion structure; according to the reflected sound line, the structure of the acoustic diffusion structure and the curvature of the diffuser surface, the multiple reflected sound waves of the sound barrier no longer form a convergence point, thereby reducing the sound energy of the multiple reflections and reducing the diffraction sound, just like light cannot converge when passing through a concave lens.
[0090] The highest point on the diffuser surface is constrained by:
[0091]
[0092] Where: max(h i ) is the maximum height of the arc surface formed at the top of the i-th order rectangular block 3; 2l is the width of the acoustic diffusion structure.
[0093] The wavelength corresponding to the design center frequency f of the acoustic diffusion structure The diameter of the substrate 1 is larger than the width of the diffuser.
[0094] like Figure 1 As shown, the radius r of the substrate 1 is:
[0095]
[0096] Wherein, h is the height of the base 1 after removing the base 2, h=rd, and d is the height of the base 2; l is the width of the base 2.
[0097] The order of the above diffuser is n, with Figure 2 The 2(n-1) rectangular blocks 3 shown, when multiple rectangular blocks 3 are distributed on the base 2 with equal width:
[0098] l1=l2=…=l i
[0099]
[0100] The height of each rectangular block 3 in the multi-stage diffuser is:
[0101]
[0102] At this time h i Maximum height h i，max for:
[0103]
[0104] Where: l i h is the width of the arc cut at the top of the i-th rectangular block 3; i is the height of the i-th rectangular block 3; n is the order of the diffuser, and n≥2; i=1,2,…,n.
[0105] Pick at this time The corresponding diffuser shape is a semicircle and the shape of n rectangular blocks 3 cut as follows Figure 3-4 shown.
[0106] The order of the diffuser is n, and it has 2(n-1) rectangular blocks 3, such as Figure 5 As shown, when multiple rectangular blocks 3 are distributed on the base 2 at equal heights:
[0107]
[0108] h1=h2=…=h n
[0109]
[0110] The height of each rectangular block 3 in the multi-stage diffuser is:
[0111]
[0112] at this time,
[0113]
[0114] d=rn·h i
[0115] The width of the arc cut at the top of each rectangular block 3 is:
[0116]
[0117] Where, l i is the width of the i-th rectangular block 3; n is the order of the diffuser; l is the width of the base 2, h i is the height of the arc cut at the top of the i-th rectangular block 3; j.
[0118] The corresponding diffuser is Figure 6-7 As shown, the shape is a hemisphere cut with n rectangles.
[0119] When 2l = 1m, the diffusion coefficient (dimensionless) is as follows:
[0120] Table 1 Acoustic diffusion structure formed by multiple rectangular blocks distributed at equal heights on a substrate
[0121]
[0122] Table 2 Acoustic diffusion structure formed by multiple rectangular blocks with equal width distributed on the substrate
[0123]
[0124]
[0125] In the application process, the above acoustic diffusion structure can break through the depth limitation of the single-layer structure by using a Helmholtz resonance cavity or an elastic membrane coupling structure to enhance low-frequency diffusion through the resonance effect, such as setting a cavity inside the base 2, or combining porous materials (such as micro-perforated plates) to use viscous loss to broaden the low-frequency response. For example, the above acoustic diffusion structure made of ECP cement board is as follows: Figure 8 As shown, a cavity is provided inside the base 2, so that the sound insulation exceeds 39dB. Compared with the appearance without shape, the average insertion loss is improved by 1.5 to 2dB in actual use.
[0126] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.
Claims
1. A design method for an acoustic diffusion structure based on a semicircular reflective surface, characterized in that: The invention comprises a hemispherical base (1), a rectangular base (2), and a plurality of rectangular blocks (3) of equal width or equal height distributed on the top of the base (2), wherein the plurality of rectangular blocks (3) of equal width or equal height and the base (2) together form a multi-stage diffuser; The multi-stage diffuser is formed by cutting the base (1), and the bottom of the base (1) is coplanar with the bottom of the base (2), the peripheral side of the base (2) is exposed by cutting the base (1), and the arc surface of the base (1) is formed into an irregular arc surface at the top of each rectangular block (3) by cutting to form a diffuser surface, and the diffuser surface and the multi-stage diffuser together form an acoustic diffusion structure.
2. The acoustic diffusion structure and design method based on a semicircular reflective surface according to claim 1, characterized in that: The highest point on the diffuser surface is constrained to: Where: max(h i ) is the maximum height of the arc surface formed at the top of the rectangular block (3) of the i-th order; 2l is the width of the acoustic diffusion structure.
3. The acoustic diffusion structure and design method based on a semicircular reflective surface according to claim 2, characterized in that: The wavelength corresponding to the design center frequency f of the acoustic diffusion structure The diameter of the substrate (1) is greater than the width of the diffuser.
4. The acoustic diffusion structure and design method based on a semicircular reflective surface according to claim 3, characterized in that: The radius r of the substrate (1) is: In the formula, h is the height of the base (1) after removing the base (2), h=rd, and d is the height of the base (2); l is the width of the base (2).
5. The acoustic diffusion structure and design method based on a semicircular reflective surface according to claim 4, characterized in that: When a plurality of rectangular blocks (3) are distributed on the base (2) with equal width, the height of each rectangular block (3) in the multi-stage diffuser is: At this time h i Maximum height h i，max for: The width of the cutting arc at the top of each rectangular block (3) is: Where: l i h is the width of the arc cut at the top of the i-th rectangular block (3); i is the height of the i-th rectangular block (3); n is the order of the diffuser, and n≥2; i=1, 2, ..., n.
6. The acoustic diffusion structure and design method based on a semicircular reflective surface according to claim 4, characterized in that: When a plurality of the rectangular blocks (3) are distributed at equal heights on the base (2), the height of each rectangular block (3) in the multi-stage diffuser is: at this time, d=r-n·h i The height of the cutting arc at the top of each rectangular block (3) is: The width of the cutting arc at the top of each rectangular block (3) is: Where, l i is the width of the i-th rectangular block (3); n is the order of the diffuser; l is the width of the base (2), h i is the height of the arc cut at the top of the i-th rectangular block (3).