A middle-low frequency mixed wideband sound absorber

Abstract

This invention discloses a mid-to-low frequency hybrid broadband sound absorber, comprising: a first Helmholtz resonator with a first absorption peak frequency band; a second Helmholtz resonator with a second absorption peak frequency band; the second absorption peak frequency band being higher than the first absorption peak frequency band; and a plurality of discrete porous material blocks; the first and second Helmholtz resonators are spatially separated by at least one of the plurality of porous material blocks. This invention achieves effective extension of low-frequency sound absorption to mid-frequency; it achieves effective connection and fusion of optimized mid-to-high frequency sound absorption bands with extended low-to-mid frequency sound absorption bands; the sound absorber of this invention forms continuous, flat, and efficient broadband sound absorption performance within the target frequency band. Simulation verification shows that the average sound absorption coefficient in the 400Hz-2000Hz frequency band can exceed 0.8.

Description

Technical Field

[0001] This invention relates to the field of sound absorption and noise reduction technology, and in particular to a mid-to-low frequency hybrid broadband sound absorber. Background Technology

[0002] Porous materials are a common type of sound-absorbing material, exhibiting excellent sound absorption performance in the mid-to-high frequencies. However, their sound absorption performance deteriorates as the noise frequency decreases, resulting in limited effectiveness in controlling low-frequency noise. Helmholtz resonators are a common material used for low-frequency sound absorption, offering excellent sound absorption performance and a high degree of design freedom, allowing for targeted design and application based on specific needs.

[0003] To achieve broadband sound absorption in the mid-to-low frequencies, existing technologies typically combine porous materials with a Helmholtz resonator in a side-by-side design, such as... Figure 1 As shown.

[0004] However, in the process of implementing the technical solution of the present application, the inventors of this application discovered that the above-mentioned technology has at least the following technical problems: when the porous material is used as part of the mixed sound-absorbing material, its mid-frequency sound absorption performance will be compressed, resulting in a serious deterioration of the sound absorption performance in the frequency band after the first sound absorption peak, which seriously affects the overall performance of the material. Summary of the Invention

[0005] This invention provides a mid-to-low frequency hybrid broadband sound absorber, which solves the problem in the prior art where the mid-frequency sound absorption performance decreases after the first sound absorption peak frequency when porous materials are combined with a Helmholtz resonator.

[0006] To address the aforementioned technical problems, this invention provides a mid-to-low frequency hybrid broadband sound absorber, comprising: The first Helmholtz resonant cavity has the first sound absorption peak frequency band; The second Helmholtz resonant cavity has a second sound absorption peak frequency band; the second sound absorption peak frequency band is higher than the first sound absorption peak frequency band. Multiple porous material blocks that are independent of each other; The first Helmholtz resonant cavity and the second Helmholtz resonant cavity are spatially separated by at least one of the plurality of porous material blocks; The porous material block, the first Helmholtz resonator, and the second Helmholtz resonator are combined in an acoustic parallel manner, so that the first sound absorption peak frequency band and the second sound absorption peak frequency band are connected with the sound absorption frequency band of the porous material block, together forming a broadened continuous sound absorption frequency band.

[0007] In a preferred embodiment of the present invention, the first Helmholtz resonant cavity, the second Helmholtz resonant cavity, and the plurality of porous material blocks are arranged alternately along a one-dimensional direction.

[0008] In a preferred embodiment of the present invention, the plurality of porous material blocks are of the same size and are arranged at equal intervals along the one-dimensional direction.

[0009] In a preferred embodiment of the present invention, the first absorption peak frequency band of the first Helmholtz resonator is below 600Hz, and the second absorption peak frequency band of the second Helmholtz resonator is above 600Hz.

[0010] In a preferred embodiment of the present invention, the width of the first Helmholtz resonant cavity is smaller than the width of the second Helmholtz resonant cavity.

[0011] In a preferred embodiment of the present invention, the width of the first Helmholtz resonant cavity is 10-16 mm, and the width of the second Helmholtz resonant cavity is 26-30 mm.

[0012] In a preferred embodiment of the present invention, the width of the first Helmholtz resonant cavity is 13 mm, and the width of the second Helmholtz resonant cavity is 28 mm.

[0013] In a preferred embodiment of the present invention, there are two first Helmholtz resonant cavities, which are located at both ends of the entire sound absorber along the arrangement direction.

[0014] In a preferred embodiment of the present invention, the width of the porous material block is 18-22 mm, and the center-to-center distance between adjacent porous material blocks is 28-33 mm.

[0015] In a preferred embodiment of the present invention, the width of the porous material block is 20 mm, and the center-to-center distance between adjacent porous material blocks is 30 mm.

[0016] The beneficial effects of this invention are as follows: This invention provides a mid-to-low frequency hybrid broadband sound absorber. By dividing a traditional continuous porous material into multiple discrete and spaced blocks and introducing at least two Helmholtz resonators with different structural parameters, it is designed for frequency bands below 600Hz and above 600Hz respectively, achieving effective extension of low-frequency sound absorption to mid-frequency. By coordinating the spatial arrangement of the Helmholtz resonators and the discrete porous material blocks, the acoustic coupling effect is controlled, effectively connecting and integrating the optimized mid-to-high frequency sound absorption band with the extended low-to-mid frequency sound absorption band. The sound absorber of this invention forms continuous, flat, and efficient broadband sound absorption performance within the target frequency band. Simulation verification shows that the average sound absorption coefficient in the 400Hz-2000Hz frequency band can exceed 0.8. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the combination of porous materials and Helmholtz resonant cavities in existing technologies; Figure 2 This is a schematic diagram of the combination of porous material and Helmholtz cavity resonant cavity in a preferred embodiment 1 of the present invention; Figure 3 This is a schematic diagram showing the control of the sound absorption performance of porous materials obtained by combining polyurethane foam with a Helmholtz resonant cavity according to existing technology and specific embodiment 1 of the present invention. Figure 4 This is a schematic diagram of the sound absorption simulation results of a mid-low frequency hybrid broadband sound absorber according to a preferred embodiment 1 of the present invention; The components in the attached diagram are labeled as follows: 100. Polyurethane foam; 10. The first Helmholtz resonator; 20. Second Helmholtz resonator; 30. Porous material block. Detailed Implementation

[0018] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0019] This invention discloses a mid-to-low frequency hybrid broadband sound absorber. Without changing the volume ratio of the porous material, it is divided into multiple parts and then combined with a Helmholtz cavity in an acoustic parallel manner. Through the design of relative parameters and positions, this invention solves the problem in the prior art where the porous material is treated as a whole and combined with the Helmholtz cavity once, resulting in a severe fragmentation of the sound absorption performance in the frequency band after the first sound absorption peak, which seriously affects the overall performance of the sound absorber.

[0020] The technical solution of the present invention will be described in detail below through specific embodiments.

[0021] Example 1 In this embodiment, the mid-to-low frequency hybrid broadband sound absorber has a cuboid structure. For example... Figure 2 As shown, all components are arranged alternately along a one-dimensional direction, which is defined as the arrangement direction. The dimension in the arrangement direction is called the width of the component. The dimension perpendicular to the arrangement direction and within the main plane of the sound absorber is called the length. The dimension perpendicular to the main plane is called the height or thickness. In this embodiment, all components have the same length of 38.8 mm and a height of 50 mm.

[0022] Specifically, the mid-low frequency hybrid broadband sound absorber includes a first Helmholtz resonant cavity 10, a second Helmholtz resonant cavity 20, and multiple porous material blocks 30 that are independent of each other.

[0023] The system comprises two first Helmholtz resonant cavities 10, located at opposite ends of the mid-to-low frequency hybrid broadband sound absorber along its arrangement direction. Each first Helmholtz resonant cavity 10 has a width of 13 mm and a length of 38.8 mm; this length can be adjusted according to the target frequency band and cavity volume requirements. The primary absorption peak, or first absorption peak frequency band, generated by the first Helmholtz resonant cavity 10 is located in the low-frequency region below 600 Hz.

[0024] There are three second Helmholtz resonators 20, all located between the two first Helmholtz resonators 10. Each second Helmholtz resonator 20 has a width of 28 mm and a length of 38.8 mm, the same as the first Helmholtz resonators 10, but can also be independently varied according to design requirements. The main absorption peak, i.e., the second absorption peak frequency band, generated by the second Helmholtz resonator 20 is located in the high-frequency region above 600 Hz.

[0025] In this embodiment, polyurethane foam is used as the porous material, and it is divided into four completely independent cuboid blocks of the same size, namely porous material blocks 30. Each porous material block 30 has a width of 20mm, and its length and height are the same as those of the first Helmholtz resonator 10 or the second Helmholtz resonator 20, respectively. The center-to-center distance between any two adjacent porous material blocks 30 is 30mm. The four porous material blocks 30 are inserted between the five Helmholtz resonators, so that the mid-low frequency mixed broadband sound absorber, from left to right, is the first Helmholtz resonator 10, porous material block 30, second Helmholtz resonator 20, porous material block 30, second Helmholtz resonator 20, porous material block 30, and first Helmholtz resonator 10, combined in an acoustic parallel manner. This structural design, by optimizing the sound absorption curve of porous materials in the mid-frequency range, suppresses the performance degradation near the first sound absorption peak, thereby effectively extending the overall operating frequency band of the mid-low frequency hybrid broadband sound absorber to low and high frequencies. It also connects the first sound absorption peak frequency band of the first Helmholtz resonator 10, the second sound absorption peak frequency band of the second Helmholtz resonator 20, and the sound absorption frequency band of the porous material block 30, together forming a broadened continuous sound absorption frequency band, thus broadening the mid-low frequency sound absorption performance.

[0026] like Figure 2 As shown, five Helmholtz resonant cavities and four discrete porous material blocks are arranged alternately along the length of the sound absorber. This alternating arrangement allows sound waves, when incident perpendicular to the arrangement direction, to simultaneously and directly reach the opening of each resonant cavity and the surface of each porous material block. All components are acoustically parallel, meaning that sound waves can act on each resonant cavity and each porous material block simultaneously and independently.

[0027] The polyurethane foam and two specifications of Helmholtz resonant cavities used in this embodiment are arranged according to... Figure 1 The structural combination shown further divides the polyurethane foam used in this embodiment into four porous material blocks, and then combines them with two specifications of Helmholtz resonant cavities according to... Figure 2 The structural combinations shown were then tested, and the sound absorption performance of the two combinations was measured separately. A schematic diagram illustrating the sound absorption performance control of the resulting polyurethane foam is attached. Figure 3 As shown in the attached figure, the simulation results of the sound absorption coefficient of the sound absorber obtained in this specific embodiment 1 are as follows. Figure 4 As shown.

[0028] The working principle of the mid-low frequency hybrid broadband sound absorber designed above is as follows: Compared to traditional structures that use porous materials as a continuous whole (such as...) Figure 1 This invention, by dividing the material into multiple discrete porous material blocks 30 and arranging them alternately with a Helmholtz resonant cavity, significantly optimizes the propagation path and acoustic impedance distribution of sound waves in the composite structure through the air gaps between the porous material blocks 30 and their acoustic coupling with the resonant cavity. This effectively weakens the mid-frequency sound absorption trough caused by unfavorable acoustic interference within the original continuous porous material. Beneficial acoustic coupling is generated between the discretely arranged porous material blocks and between the porous material blocks and the cavity, suppressing the mid-frequency sound absorption trough that occurs when the porous material is used as a whole (e.g., ...). Figure 3 As shown in the figure, this makes its sound absorption curve flatter.

[0029] Two different widths of Helmholtz resonators provide absorption peaks at different center frequencies. The 13mm wide cavity provides deep low-frequency absorption, while the 28mm wide cavity provides mid-frequency absorption. The absorption peak frequency bands of both cavityes connect with and partially overlap with the optimized sponge absorption frequency band.

[0030] Ultimately, as Figure 4 As shown in the simulation curves, the hybrid sound absorber in this embodiment maintains a high sound absorption coefficient in a wide frequency range of 400Hz to 2000Hz, with an average sound absorption coefficient exceeding 0.8, achieving excellent mid-to-low frequency broadband sound absorption performance.

[0031] Example 2 The difference between this and the mid-low frequency hybrid broadband sound absorber in Example 1 is that the first Helmholtz resonator 10 and the second Helmholtz resonator 20 have different sizes to demonstrate the adjustability of the parameters.

[0032] Specifically, the width of the first Helmholtz resonant cavity 10 is 16 mm.

[0033] The width of the second Helmholtz resonant cavity 20 is 30 mm.

[0034] By adjusting the cavity width, its resonant frequency can be fine-tuned to adapt to different target frequency band requirements. Simulations show that this structure can still maintain good sound absorption performance over a similar wide frequency range.

[0035] Example 3 The difference between this and the low-frequency hybrid broadband sound absorber in Example 1 is that the porous material block 30 has a width of 22mm and a center-to-center spacing of 32mm.

[0036] Simulations show that this structure can still maintain good sound absorption performance over a similar wide frequency band.

[0037] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A mid-to-low frequency hybrid broadband sound absorber, characterized in that, include: The first Helmholtz resonant cavity has the first sound absorption peak frequency band; The second Helmholtz resonant cavity has a second sound absorption peak frequency band; the second sound absorption peak frequency band is higher than the first sound absorption peak frequency band. Multiple porous material blocks that are independent of each other; The first Helmholtz resonant cavity and the second Helmholtz resonant cavity are spatially separated by at least one of the plurality of porous material blocks; The porous material block, the first Helmholtz resonator, and the second Helmholtz resonator are combined in an acoustic parallel manner, so that the first sound absorption peak frequency band and the second sound absorption peak frequency band are connected with the sound absorption frequency band of the porous material block, together forming a broadened continuous sound absorption frequency band.

2. The mid-low frequency hybrid broadband sound absorber according to claim 1, characterized in that, The first Helmholtz resonant cavity, the second Helmholtz resonant cavity, and the plurality of porous material blocks are arranged alternately along a one-dimensional direction.

3. The mid-low frequency hybrid broadband sound absorber according to claim 2, characterized in that, The multiple porous material blocks are of the same size and are arranged at equal intervals along the one-dimensional direction.

4. The mid-low frequency hybrid broadband sound absorber according to claim 1, characterized in that, The first absorption peak frequency band of the first Helmholtz resonator is below 600Hz, and the second absorption peak frequency band of the second Helmholtz resonator is above 600Hz.

5. A mid-to-low frequency hybrid broadband sound absorber according to claim 4, characterized in that, The width of the first Helmholtz resonant cavity is smaller than the width of the second Helmholtz resonant cavity.

6. A mid-to-low frequency hybrid broadband sound absorber according to claim 5, characterized in that, The width of the first Helmholtz resonant cavity is 10-16 mm, and the width of the second Helmholtz resonant cavity is 26-30 mm.

7. A mid-to-low frequency hybrid broadband sound absorber according to claim 6, characterized in that, The width of the first Helmholtz resonant cavity is 13 mm, and the width of the second Helmholtz resonant cavity is 28 mm.

8. A mid-to-low frequency hybrid broadband sound absorber according to any one of claims 5 to 7, characterized in that, There are two first Helmholtz resonant cavities, located at opposite ends of the entire sound absorber along its arrangement direction.

9. A mid-to-low frequency hybrid broadband sound absorber according to claim 8, characterized in that, The width of the porous material block is 18-22mm, and the center-to-center distance between adjacent porous material blocks is 28-33mm.

10. A mid-to-low frequency hybrid broadband sound absorber according to claim 9, characterized in that, The width of the porous material block is 20mm, and the center-to-center distance between adjacent porous material blocks is 30mm.

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