A sound absorbing band self-adapting adjustable porous helmholtz resonator

Abstract

This invention discloses a porous Helmholtz resonator with adaptively adjustable sound absorption frequency band, belonging to the fields of noise control and virtual reality technology. It comprises a sound-absorbing structure consisting of a rotating perforated panel, a fixed perforated panel, and a perforated porous material plate arranged sequentially from top to bottom, as well as an adaptive adjustment system composed of a sound pressure sensor, a controller, and a motor. The motor drives the rotating perforated panel to rotate via gear transmission, changing the perforation overlap area; the perforated porous material plate compensates for acoustic impedance, maintaining sound absorption performance. The controller pre-stores spectral data at different rotation angles and selects the optimal rotation angle by comparing the real-time noise spectrum with the pre-stored data. This invention achieves adaptive adjustment of the sound absorption frequency band, maintains a high sound absorption peak value over a wide parameter range, is suitable for large-area deployment, has a compact structure, and low cost, and can be used for noise control and auditory virtual scenes.

Description

Technical Field

[0001] This invention belongs to the field of noise control and virtual reality technology, specifically relating to a multi-hole Helmholtz resonator with adaptive adjustable sound absorption frequency band. Background Technology

[0002] In the field of noise control technology, the noise spectrum changes accordingly with the operating state of mechanical systems. For example, the engine vibration frequency and flow-induced vibration frequency of airplanes, trains, and automobiles differ at different speeds, resulting in different noise frequencies under different operating conditions. Traditional sound-absorbing materials, such as porous materials and micro-perforated plates, have fixed structural parameters and corresponding to fixed frequency-dependent absorption coefficients, making them unsuitable for noise environments with varying frequencies. Therefore, a sound absorber is needed that can adaptively change its sound absorption frequency band according to the external noise frequency. Furthermore, in the field of virtual reality, to achieve virtual hearing indoors, a controllable sound wave reflection boundary needs to be constructed. Tunable sound-absorbing devices can be installed around the indoor environment to achieve controllable sound wave reflection and realize virtual hearing.

[0003] Currently, tunable sound absorbers mainly fall into three categories: (1) Tunable sound absorber based on shunt loudspeaker: The surface acoustic impedance of the loudspeaker is adjusted by the external circuit (i.e. "shunt circuit") of the loudspeaker, so that the incident noise energy is converted into electrical energy and consumed in the external circuit, thereby achieving sound absorption and noise reduction. (2) Tunable sound absorber based on electric / magnetic field adjustment of structural parameters: the geometric or mechanical parameters of the electric / magnetic field sensitive material in the sound absorber are changed by using an external electric / magnetic field, thereby adjusting the sound absorption frequency band; (3) Tunable sound absorber based on mechanical mechanism to adjust structural parameters: the sound absorber's geometry is changed by using a mechanical mechanism, thereby changing the sound absorption frequency band.

[0004] Among them, mechanically tuned sound absorbers are suitable for large-scale applications because they do not require complex electrical equipment and have lower costs. However, they have the following problems: (1) It still relies on manual adjustment and cannot automatically adjust the structural parameters of the sound absorber according to the real-time noise spectrum; (2) When the structural parameters of a traditional adjustable sound absorber are changed, the impedance matching is easily disrupted, making it difficult to maintain a high sound absorption peak during the adjustment process. (3) There is no transmission structure between the sound absorption units, which is not suitable for adjusting the sound absorption structure parameters after large-area laying.

[0005] Therefore, developing a sound-absorbing device and design method that can automatically adjust its own structural parameters and sound absorption frequency band according to the external noise frequency, maintain high sound absorption performance within a wide range of structural parameter adjustments, and has a transmission structure between sound-absorbing units so that it can be laid out over a large area and its parameters can be easily adjusted has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a multi-hole Helmholtz resonator with adaptive adjustable sound absorption frequency band, which addresses the shortcomings of the prior art. This resonator solves the technical problems of existing adjustable sound absorbers requiring manual adjustment, being unable to maintain high sound absorption performance over a wide range of structural parameters, and being unable to uniformly adjust structural parameters after large-area installation.

[0007] The present invention adopts the following technical solution: A multi-hole Helmholtz resonator with adaptive adjustable sound absorption frequency band includes a sound-absorbing structure and an adaptive adjustment system; The sound-absorbing structure is provided from top to bottom with a rotating perforated panel, a fixed perforated panel, and a perforated porous material plate; The edge portion of the rotating perforated panel is provided with a gear transmission mechanism; The adaptive adjustment system includes a sound pressure sensor, a motor, and a controller. The sound pressure sensor is signal-connected to the controller, and the controller is control-connected to the motor. The end of the motor shaft is provided with a gear transmission mechanism, which meshes with the gear transmission mechanism of the rotating perforated panel to drive the rotating perforated panel to rotate relative to the fixed perforated panel, thereby changing the overlap area of ​​the perforations of the two. The perforated porous material plate is used to compensate for acoustic resistance and maintain sound absorption performance when the perforation overlap area of ​​the rotating perforated panel and the fixed perforated panel changes.

[0008] Preferably, the perforated porous material plate is made by periodically perforating a uniform porous material plate, and the diameter of the perforated pores on the perforated porous material plate is more than 10 times the diameter of the micropores in the uniform porous material plate.

[0009] Preferably, the perforation diameter on the fixed perforated panel is smaller than the perforation diameter on the perforated porous material plate.

[0010] Preferably, the diameter of the perforation on the rotating perforated panel is not greater than the diameter of the perforation on the fixed perforated panel.

[0011] Preferably, the arc of the gear transmission mechanism is not less than the maximum rotation angle of the rotating perforated panel.

[0012] Preferably, a gap is provided between the rotating perforated panel and the fixed perforated panel to ensure relative rotation between the rotating perforated panel and the fixed perforated panel.

[0013] Preferably, the system includes multiple sound-absorbing structures, which are connected in parallel and / or in series to broaden the adjustment range of the sound absorption frequency band.

[0014] Preferably, both the fixed perforated panel and the rotating perforated panel are made of rigid material with a density much greater than that of air.

[0015] Preferably, the controller pre-stores the sound absorption coefficient spectrum and sound pressure reflection coefficient spectrum of the sound absorber at different rotation angles of the rotating perforated panel; during operation, the controller receives the real-time noise spectrum collected by the sound pressure sensor, multiplies it by each pre-stored sound pressure reflection coefficient spectrum and calculates the A-weighted sound pressure level, selects the rotation angle corresponding to the lowest A-weighted sound pressure level, and controls the motor to drive the rotating perforated panel to rotate to that angle.

[0016] Preferably, the perforated porous material plate, the fixed perforated panel, and the rotating perforated panel are all provided with a plurality of symmetrically and evenly distributed perforations.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: A multi-hole Helmholtz resonator with adaptive and adjustable sound absorption frequency band organically integrates the sound absorption structure with an adaptive adjustment system. Through a three-layer structure consisting of a rotating perforated panel, a fixed perforated panel, and a perforated porous material plate, coupled with a motor and gear transmission, it fundamentally solves the problem of existing mechanically tuned sound absorbers relying on manual adjustment, achieving the core function of automatically adapting the sound absorption frequency band to the noise spectrum. Simultaneously, it clarifies the acoustic impedance compensation effect of the perforated porous material plate, specifically addressing the problems of impedance mismatch and decreased sound absorption peak value when the structural parameters of traditional adjustable sound absorbers change. The gear transmission design provides a structural basis for unified adjustment after large-area deployment, avoiding the cumbersome process of independent adjustment of each sound absorption unit.

[0018] Furthermore, the design of periodically perforating a uniform porous material plate with perforation diameters 10 times larger than micropore diameters utilizes the sound diffusion effect of sound waves entering the micropores through the large-diameter perforations, significantly enhancing low-frequency sound absorption performance and compensating for the shortcomings of traditional porous materials in low-frequency sound absorption. Simultaneously, this structural design, combined with the rational selection of substrate material parameters and thickness, ensures that the ratio of the real part of the surface acoustic impedance of the porous material substrate to the characteristic impedance of air is greater than 1 in the target low-frequency range. This guarantees sufficient sound energy dissipation capacity even after perforation, providing a material basis for the subsequent implementation of acoustic impedance compensation mechanisms.

[0019] Furthermore, the perforation diameter of the fixed perforated panel is no larger than that of the perforated porous material plate, so that the mass block formed by the overlapping area of ​​the perforations of the fixed and rotating perforated panels, together with the air spring formed by the air within the perforated area of ​​the perforated porous material plate, constitutes a matched acoustic resonance system. When the external noise frequency matches the natural frequency of the resonance system, it can cause a sharp increase in particle velocity and sound pressure. On the one hand, this enhances the frictional dissipation between the air and the perforation boundary, and on the other hand, it promotes the diffusion of sound waves into the interior of the porous material, thus doubly improving the sound absorption efficiency.

[0020] Furthermore, the diameter of the rotating perforated panel is no larger than that of the fixed perforated panel, ensuring that there is no useless rotational travel during the process of the rotating perforated panel changing the overlapping area with the fixed perforated plate by rotating (or during the process of changing the diameter of the rotating perforated panel by using mechanical structures such as iris structures to change the overlapping area with the fixed perforated plate).

[0021] Furthermore, the curvature of the gear tooth area is not less than the maximum rotation angle of the rotating perforated panel, ensuring that the rotating perforated panel maintains effective engagement with the motor's gear transmission mechanism throughout the entire adjustment stroke, preventing adjustment interruption or transmission failure due to insufficient gear tooth length. This design specifically addresses the problems of existing sound-absorbing units lacking effective transmission structures and being difficult to adjust uniformly after large-area deployment. It enables multiple sound-absorbing units to achieve synchronous tuning through gear tooth linkage, significantly improving the practicality and ease of operation of the device in large-space applications. Simultaneously, the stable meshing transmission relationship ensures the consistency of the rotation angle of each sound-absorbing unit, preventing uneven overall sound absorption due to adjustment differences and ensuring acoustic performance stability in large-area application scenarios.

[0022] Furthermore, by clarifying the role of the gap under different overlapping area conditions, the calculation deviation of the sound absorption frequency caused by neglecting the gap is avoided. When the overlapping area and the gap size are on the same order of magnitude, the gap is equivalent to expanding the overlapping area, thus increasing the peak sound absorption frequency. When the overlapping area is much larger than the gap size, the effect of the gap on the peak sound absorption frequency can be ignored.

[0023] Furthermore, by combining multiple sound-absorbing structures, multiple different resonant structures are created, resulting in resonant absorption peaks at multiple different frequencies. This allows for the superposition of different frequency band coverages, significantly widening the overall sound absorption frequency range and adapting to more complex noise scenarios. In addition, compatible with gear transmission structures, multiple sound-absorbing units can be synchronously adjusted through linkage. This ensures the ease of adjustment of the combined structure while further optimizing sound absorption performance through the synergistic effect between units, overcoming the technical bottleneck of insufficient frequency band coverage of a single sound-absorbing unit.

[0024] Furthermore, using rigid materials with a density far greater than that of air reduces the interference of panel vibration on acoustic characteristics, ensuring the structural stability of the panel as a mass carrier and preventing frequency shifts due to panel vibration. Simultaneously, the rigidity of the material guarantees the stability of the perforation shape and size, preventing deviations in overlapping area calculations caused by deformation during long-term use, thus affecting adjustment accuracy and extending the device's lifespan and reliability. Most importantly, the high-density material significantly hinders sound wave penetration through the panel, allowing most sound waves to enter the sound-absorbing structure through the designed air channels, forming an acoustic resonance system and improving low-frequency sound absorption performance.

[0025] Furthermore, the controller pre-stores spectral data at different rotation angles. During operation, it compares the real-time noise spectrum with the pre-stored data to quickly and accurately select the optimal rotation angle, solving the problems of lag and insufficient accuracy in traditional adjustment methods. The control strategy of multiplying the noise spectrum with the sound pressure reflection coefficient spectrum and calculating the A-weighted sound pressure level can accurately match the auditory characteristics of the actual noise scene, ensuring that the selected sound absorption parameters achieve the optimal sound absorption effect in the frequency band sensitive to the human ear, thus enhancing the practical value of the device. This design upgrades adaptive adjustment from passive perception to active optimization, achieving real-time dynamic tuning without manual intervention, perfectly matching application scenarios with dynamic changes in the noise spectrum.

[0026] In summary, this invention features a simple structure and convenient operation, enabling adaptive dynamic adjustment of the sound absorption frequency band and resolving the pain point of manual reliance. Through designs such as aperture matching and acoustic impedance compensation, it maintains a high sound absorption peak value over a wide parameter range. The gear transmission and multi-unit assembly are well-suited for large-area application, resulting in low cost, easy promotion, and comprehensive optimization of noise control and acoustic performance in virtual reality scenarios.

[0027] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structural composition of the adaptive adjustable sound absorption frequency band system of the present invention; Figure 2 In this invention, the rotating perforated panel and the fixed perforated panel are at different rotation angles. θ Schematic diagram of the overlapping state of the perforation area; Figure 3 A three-dimensional schematic diagram of the sound absorber assembly unit; Figure 4 This is a graph showing the sound absorption coefficient of the sound absorber when the perforated plate is rotated at different rotation angles.

[0029] The components include: 1. a perforated porous material plate; 2. a fixed perforated panel; 3. a rotating perforated panel; 4. a sound pressure sensor; 5. a motor with a gear at the end of the shaft; and 6. a controller. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "one side," "one end," and "one side," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. 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 indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0032] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0034] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0035] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0036] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0037] This invention provides a multi-hole Helmholtz resonator with adaptive adjustable sound absorption frequency band. By integrating acoustic sensors, controllers, actuators, and sound-absorbing structures, the system can sense changes in the noise spectrum in real time and automatically adjust structural parameters to achieve optimal sound absorption without manual intervention, realizing the transformation from manual tuning to adaptive tuning. The overall thickness of the entire sound-absorbing unit remains unchanged, making it suitable for space-constrained applications. The stepper motor, microphone, and other components used are all conventional devices, resulting in relatively low system construction costs and facilitating engineering applications and promotion.

[0038] Please see Figure 1 The present invention provides a multi-hole Helmholtz resonator with adaptive adjustable sound absorption frequency band, comprising a sound absorption structure and an adaptive adjustment system; The sound-absorbing structure is provided with a rotating perforated panel 3, a fixed perforated panel 2 and a perforated porous material plate 1 from top to bottom. A gear transmission mechanism is provided on part of the edge of the rotating perforated panel 3. A gear transmission mechanism is added at the edge of each sound-absorbing unit, thereby realizing the rotational transmission between each unit and facilitating the adjustment of the sound-absorbing structure parameters after laying out a large area of ​​sound-absorbing units.

[0039] The adaptive adjustment system includes a sound pressure sensor 4, a controller 6, and a motor 5. The sound pressure sensor 4 is signal-connected to the controller 6, and the controller 6 is control-connected to the motor 5. The end of the shaft of the motor 5 is provided with a gear transmission mechanism, which meshes with the gear transmission mechanism of the rotating perforated panel 3 to drive the rotating perforated panel 3 to rotate relative to the fixed perforated panel 2 to change the overlapping area of ​​the perforations of the two. Preferably, the perforated porous material plate 1 is made of ceramic fiber, and when it is not perforated, the ratio of the real part of its surface acoustic impedance to the characteristic impedance of air is greater than 1 in the target low frequency band.

[0040] The perforated porous material plate 1 is used to compensate for acoustic resistance and maintain sound absorption performance when the overlapping area of ​​the perforations of the rotating perforated panel 3 and the fixed perforated panel 2 changes.

[0041] The perforated porous material plate 1 is made by periodically perforating a uniform porous material plate, and the diameter of the perforated holes on the perforated porous material plate 1 is more than 10 times the diameter of the micropores in the uniform porous material plate.

[0042] The perforation diameter on the fixed perforated panel 2 is smaller than the perforation diameter on the perforated porous material plate 1.

[0043] The diameter of the perforated hole on the rotating perforated panel 3 is not greater than the diameter of the perforated hole on the fixed perforated panel 2.

[0044] The arc of the gear transmission mechanism is greater than or equal to the maximum rotation angle of the rotating perforated panel 3.

[0045] A gap is provided between the rotating perforated panel 3 and the fixed perforated panel 2. When the overlapping area of ​​the perforations and the size of the gap are on the same order of magnitude, the gap is used to increase the peak frequency of sound absorption.

[0046] The fixed perforated panel 2 and the rotating perforated panel 3 are made of plexiglass.

[0047] It also includes multiple sound-absorbing structures, which are connected in parallel and / or in series to broaden the adjustment range of the sound absorption frequency band. The sound-absorbing structure is a hexagonal cell.

[0048] The perforated porous material plate 1, the fixed perforated panel 2, and the rotating perforated panel 3 are all provided with multiple symmetrically distributed through holes.

[0049] Both the fixed perforated panel 2 and the rotating perforated panel 3 are made of rigid materials with a density much greater than that of air.

[0050] The controller 6 pre-stores the sound absorption coefficient spectrum and sound pressure reflection coefficient spectrum of the sound absorber at different rotation angles of the rotating perforated panel 3. During operation, the controller 6 receives the real-time noise spectrum collected by the sound pressure sensor 4, multiplies it by each pre-stored sound pressure reflection coefficient spectrum and calculates the A-weighted sound pressure level, selects the rotation angle corresponding to the lowest A-weighted sound pressure level, and controls the motor 5 to drive the rotating perforated panel 3 to rotate to that angle.

[0051] First, the absorption coefficient spectrum and sound pressure reflection coefficient spectrum of the sound absorber under different structural parameters are measured and stored in the controller. Then, the noise spectrum obtained in real time is multiplied by the sound pressure reflection coefficient spectrum under different structural parameters and the A-weighted sound pressure level is calculated. The structural parameters of the sound absorber corresponding to the lowest A-weighted sound pressure level are selected.

[0052] An energy dissipation compensation mechanism is introduced into the frequency band adjustable sound absorber to ensure that a high sound absorption peak is maintained during the adjustment of the sound absorber's structural parameters: when the overlapping area of ​​the openings of the rotating panel and the fixed panel is too large, resulting in insufficient acoustic resistance in this part, the perforated porous material on the back can compensate for the required acoustic resistance, thereby ensuring that the system can maintain a good match with the characteristic impedance of air within a wide range of geometric configuration changes, thereby maintaining near-perfect sound absorption (such as the sound absorption peak coefficient being greater than 0.989 during the rotation angle change from 0° to 37.8° in the embodiment).

[0053] The perforated porous material plate 1, the fixed perforated panel 2, and the rotating perforated panel 3 are all provided with multiple symmetrically and evenly distributed perforations.

[0054] The method for fabricating a multi-hole Helmholtz resonator with adaptive adjustable sound absorption frequency band according to the present invention is as follows: S1. Construct a tunable sound-absorbing structure; S101, Preparation of perforated porous material plate 1 A perforated porous material plate 1 is obtained by periodically perforating a uniform porous material plate (i.e., a porous material substrate). The perforation diameter is generally 10 times larger than the micropore diameter in the porous material. This utilizes the sound diffusion effect during the sound wave propagation process from the larger perforation into the micropore to enhance low-frequency sound absorption performance. Simultaneously, by rationally selecting the parameters of the porous material substrate and its thickness, the ratio of the real part of the surface acoustic impedance of the non-perforated porous material substrate to the characteristic impedance of air is ensured to be greater than 1 in the target low-frequency range, thereby guaranteeing that the perforated porous material plate 1 possesses sufficient sound energy dissipation capability.

[0055] S102. Prepare the fixed perforated panel 2 and place it above the perforated porous material plate 1. The panel material should be a rigid material with a density much greater than that of air. The perforation diameter on the fixed perforated panel 2 should be smaller than the perforation diameter on the perforated porous material board 1. The thickness of the fixed perforated panel 2 should be determined based on the actual available installation space; the thicker the panel, the lower the peak sound absorption frequency will shift.

[0056] S103. Prepare multiple rotating perforated panels 3 and place them above the fixed perforated panel 2. The panel material is made of a rigid material with a density much greater than that of air. The perforation diameter on the rotating perforated panel 3 should not be greater than the perforation diameter on the fixed perforated panel 2. Part of the edge of the rotating perforated panel 3 has a gear transmission mechanism, which can realize the unified scheduling of multiple rotating panels. The curvature of the gear tooth area is determined according to the rotation angle range of the rotating perforated panel 3, and the curvature of the gear tooth area is not less than the rotation angle of the perforated panel 3.

[0057] S104. The sound-absorbing structure constructed from the perforated porous material plate 1, the fixed perforated panel 2, and the rotating perforated panel 3 can be regarded as a porous Helmholtz resonator. The air in the overlapping perforated area of ​​the fixed perforated panel 2 and the rotating perforated panel 3 acts as the "mass" of this Helmholtz resonator; the air in the perforated area of ​​the perforated porous material plate 1 acts as the "air spring" of this Helmholtz resonator. When the external noise frequency is the same as the natural frequency of this sound-absorbing structure, the particle velocity and sound pressure in the entire sound-absorbing structure will increase sharply. Both the "mass" and the "air spring" will vibrate strongly, which on the one hand increases the friction between the air in the overlapping perforated area of ​​the fixed perforated panel 2 and the rotating perforated panel 3 and the perforation boundary; on the other hand, the particle velocity and sound pressure in the air area in the perforations of the perforated porous material plate 1 will increase sharply, and the sound waves will strongly diffuse into the interior of the surrounding porous material, enhancing the dissipation of sound energy.

[0058] S105. Because it has the above two sound absorption enhancement mechanisms, this band-adjustable sound absorber has an energy dissipation compensation mechanism to ensure that a high sound absorption peak is always maintained during the adjustment of the sound absorber's structural parameters: When the overlapping area of ​​the openings of the rotating panel and the fixed panel is too large, resulting in insufficient acoustic resistance in this part, the perforated porous material on the back can compensate for the required acoustic resistance, thereby ensuring that the system can maintain a good match with the characteristic impedance of air within a wide range of geometric configuration changes, thus maintaining near-perfect sound absorption.

[0059] S106. By rotating the perforated panel 3, the overlapping area formed by the perforations on the rotating perforated panel 3 and the perforations on the fixed perforated panel 2 can be changed, thereby adjusting the peak frequency of sound absorption.

[0060] When the overlapping area decreases, the peak frequency of sound absorption decreases. There are several ways to change the overlapping area, such as by rotating the perforated panel 3 as in Example 1, or by changing the overlapping area through methods such as a mechanical iris mechanism.

[0061] S107. Due to the relative movement between the rotating perforated panel 3 and the fixed perforated panel 2, there is a certain gap.

[0062] When the overlapping area formed by the perforations on the rotating perforated panel 3 and the perforations on the fixed perforated panel 2 is much larger than the gap size, the gap has little effect on the sound absorption performance of the porous Helmholtz resonator. When the overlapping area and the gap size are on the same order of magnitude, compared with the sound absorption peak frequency without gap, the presence of gap is equivalent to expanding the overlapping area, which will increase the sound absorption peak frequency.

[0063] S108. To broaden the adjustment range of the sound absorption frequency band, it can be achieved by connecting multiple different multi-hole Helmholtz resonators in parallel and series.

[0064] S2. Constructing a sound absorption frequency band adaptive system S201: Integrate the sound-absorbing structure with the sound pressure sensor 4, controller 6 and motor 5.

[0065] S202: One or more sound pressure sensors 4 are placed near the noise source or in the direction of sound wave incidence. The noise collected by the sound pressure sensors 4 is transmitted to the controller 6 for analysis. Based on the noise spectrum, the controller outputs the optimal rotation angle to the motor 5. The end of the shaft of the motor 5 has a gear transmission mechanism, which meshes with the gear teeth on the edge of the rotating perforated panel 3 to drive the rotating perforated panel 3 to rotate, thereby adjusting the sound absorption frequency band of the sound absorber.

[0066] S3. Construct the control algorithm in the controller.

[0067] First, the sound absorption coefficient spectrum and sound pressure reflection coefficient spectrum of the rotating perforated panel 3 at different rotation angles are measured. Alternatively, based on the transmission ratio between the end gear of motor 5 and the edge teeth of the rotating perforated panel 3, the sound absorption coefficient spectrum and sound pressure reflection coefficient spectrum at different motor rotation angles can be established and stored in the controller. In actual operation of the sound absorber, the noise spectrum obtained in real time by the sound pressure sensor 4 is multiplied by the sound pressure reflection coefficient spectrum at different rotation angles, and the A-weighted sound pressure level is calculated. The controller automatically selects the rotation angle corresponding to the lowest A-weighted sound pressure level and transmits the command to motor 5 to rotate the rotating perforated panel 3 to the target angle.

[0068] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0069] Example 1 Please see Figure 1 A schematic diagram of the structure of the sound absorption frequency band adaptive adjustable system, showing the thickness of the perforated porous material plate 1. H =50mm. The porous material substrate is a ceramic fiber with a porosity of 0.89 and a static flow resistance of 421535.5 N·s / m. 4 The tortuosity is 2.835, the viscous feature length is 11.65 μm, and the thermal feature length is 38.38 μm.

[0070] Please see Figure 2 Rotating perforated panels and fixed perforated panels at rotation angles θ Schematic diagram of overlapping state of the perforation area and Figure 3 A 3D schematic diagram of the sound absorber assembly unit. A typical assembly unit is a hexagonal cell with an inscribed circle diameter of 100mm. Four symmetrically and evenly distributed through holes are formed within the perforated porous material plate 1, the fixed perforated panel 2, and the rotating perforated panel 3. The distance between the centers of two diagonally opposite perforated circles is 50mm. The diameter of the four perforations on the perforated porous material plate 1 is... d m =28.5mm. Both the fixed perforated panel 2 and the rotating perforated panel 3 are made of acrylic sheet. The thickness of the fixed perforated panel 2 is... T f =9mm, the thickness of the rotating perforated panel 3 is T r =2mm. The diameter of the eight perforations on both the fixed perforated panel 2 and the rotating perforated panel 3 is 2mm. d p =20mm. The rotating perforated panel 3 rotates around the center of the hexagonal cell.

[0071] Please see Figure 4 The sound absorption coefficient curves of the sound absorber at different rotation angles of the rotating perforated panel 3. θ In 5.4° increments, increasing from 0° to 37.8°, the peak absorption frequency decreased from 670Hz to 426Hz, with all peak absorption coefficients exceeding 0.989. Even at 43.2°, the absorption coefficient at 400Hz remained as high as 0.967. This demonstrates that the porous Helmholtz resonator can achieve near-perfect sound absorption through tuning within a frequency range of 426-670Hz, a bandwidth of 244 Hz.

[0072] Example 2 Please see Figure 1 The material and structural parameters in Example 1 were used as default values. The rotation of the perforated plate was measured at 5.4° intervals. θThe sound pressure reflection coefficient spectrum of the sound absorber from 0° to 43.2° is stored in controller 6, which is controlled by a computer. A narrowband noise with a center frequency of approximately 622Hz is emitted by a loudspeaker. The sound pressure signal collected by sound pressure sensor 4 is sent to a data acquisition card and then to the computer. The noise spectrum is multiplied by the sound pressure reflection coefficient spectrum of the rotating perforated panel at different rotation angles stored in the computer, and the A-weighted sound pressure level is calculated. The computer automatically selects the rotation angle corresponding to the lowest A-weighted sound pressure level. The computer sends a command to motor 5 via RS485 serial port. Motor 5 is a stepper motor. Motor 5 rotates a certain angle according to the transmission ratio between its end gear and the edge gear teeth of the rotating perforated panel 3, causing the rotating perforated panel 3 to rotate 16.2°. The measured sound absorption coefficient at this angle near 622Hz exceeds 0.99.

[0073] Example 3 Please see Figure 1 Using the material and structural parameters from Example 1 as default values ​​and the control strategy from Example 2 as the default control strategy, the system automatically adjusts the rotating perforated panel 3 to a position where a narrowband noise with a center frequency of approximately 593Hz is emitted by a loudspeaker. θ =21.6°, and the measured sound absorption coefficient at this angle near 593Hz exceeds 0.99.

[0074] Example 4 Please see Figure 1 Using the material and structural parameters from Example 1 as default values ​​and the control strategy from Example 2 as the default control strategy, the system automatically adjusts the rotating perforated panel 3 to a position where a narrowband noise with a center frequency of approximately 559Hz is emitted by a loudspeaker. θ =27°, and the measured sound absorption coefficient at this angle near 559Hz exceeds 0.99.

[0075] Example 5 Please see Figure 1 Using the material and structural parameters from Example 1 as default values ​​and the control strategy from Example 2 as the default control strategy, the system automatically adjusts the rotating perforated panel 3 to a position where a narrowband noise with a center frequency of approximately 497Hz is emitted by a loudspeaker. θ =32.4°, and the measured sound absorption coefficient at this angle near 497Hz exceeds 0.99.

[0076] In summary, this invention presents a multi-hole Helmholtz resonator with adaptive adjustable sound absorption frequency band, effectively solving the problems of manual adjustment, unstable sound absorption performance over a wide parameter range, and difficulty in adjustment after large-area deployment in existing adjustable sound absorbers. By integrating the sound absorption structure with an adaptive adjustment system, real-time noise spectrum sensing and automatic tuning are achieved without manual intervention. Utilizing the acoustic impedance compensation mechanism of the perforated porous material, the peak sound absorption coefficient exceeds 0.989 within a rotation angle range of 0°-37.8°, maintaining near-perfect sound absorption within a bandwidth of 426-670Hz. The gear-tooth transmission design is suitable for unified adjustment after large-area deployment, and the compact structure, use of conventional components, low cost, and ease of promotion make it suitable for various scenarios such as noise control and virtual reality.

[0077] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A multi-hole Helmholtz resonator with adaptively adjustable sound absorption frequency band, characterized in that, Including sound-absorbing structures and adaptive adjustment systems; The sound-absorbing structure is provided with a rotating perforated panel (3), a fixed perforated panel (2) and a perforated porous material plate (1) from top to bottom. The edge portion of the rotating perforated panel (3) is provided with a gear transmission mechanism; The adaptive adjustment system includes a sound pressure sensor (4), a motor (5) and a controller (6). The sound pressure sensor (4) is connected to the controller (6) via a signal, and the controller (6) is connected to the motor (5) via a control. The end of the shaft of the motor (5) is provided with a gear transmission mechanism, which meshes with the gear transmission mechanism of the rotating perforated panel (3) to drive the rotating perforated panel (3) to rotate relative to the fixed perforated panel (2) so as to change the overlapping area of ​​the perforations of the two. The perforated porous material plate (1) is used to compensate for acoustic resistance and maintain sound absorption performance when the perforation overlap area of ​​the rotating perforated panel (3) and the fixed perforated panel (2) changes.

2. The multi-hole Helmholtz resonator with adaptive and adjustable sound absorption frequency band according to claim 1, characterized in that, The perforated porous material plate (1) is made by periodically perforating a uniform porous material plate, and the diameter of the perforated holes on the perforated porous material plate (1) is 10 times larger than the diameter of the micropores in the uniform porous material plate.

3. The multi-hole Helmholtz resonator with adaptive and adjustable sound absorption frequency band according to claim 1, characterized in that, The diameter of the perforation on the fixed perforated panel (2) is not greater than the diameter of the perforation on the perforated porous material plate (1).

4. The multi-hole Helmholtz resonator with adaptive adjustable sound absorption frequency band according to claim 3, characterized in that, The diameter of the perforation on the rotating perforated panel (3) is not greater than the diameter of the perforation on the fixed perforated panel (2).

5. The multi-hole Helmholtz resonator with adaptive adjustable sound absorption frequency band according to claim 1, characterized in that, The arc of the gear transmission mechanism is not less than the maximum rotation angle of the rotating perforated panel (3).

6. The multi-hole Helmholtz resonator with adaptive and adjustable sound absorption frequency band according to claim 1, characterized in that, A gap is provided between the rotating perforated panel (3) and the fixed perforated panel (2) to ensure relative rotation between the rotating perforated panel (3) and the fixed perforated panel (2).

7. The multi-hole Helmholtz resonator with adaptive adjustable sound absorption frequency band according to claim 1, characterized in that, It includes multiple sound-absorbing structures, which are connected in parallel and / or in series to broaden the adjustment range of the sound absorption frequency band.

8. The multi-hole Helmholtz resonator with adaptive adjustable sound absorption frequency band according to claim 1, characterized in that, Both the fixed perforated panel (2) and the rotating perforated panel (3) are made of rigid materials with a density much greater than that of air.

9. The multi-hole Helmholtz resonator with adaptive adjustable sound absorption frequency band according to claim 1, characterized in that, The controller (6) pre-stores the sound absorption coefficient spectrum and sound pressure reflection coefficient spectrum of the sound absorber at different rotation angles of the rotating perforated panel (3). During operation, the controller (6) receives the real-time noise spectrum collected by the sound pressure sensor (4), multiplies it with each pre-stored sound pressure reflection coefficient spectrum, calculates the A-weighted sound pressure level, selects the rotation angle corresponding to the lowest A-weighted sound pressure level, and controls the motor (5) to drive the rotating perforated panel (3) to rotate to that angle.

10. The multi-hole Helmholtz resonator with adaptive adjustable sound absorption frequency band according to claim 1, characterized in that, The perforated porous material plate (1), the fixed perforated panel (2), and the rotating perforated panel (3) are all provided with multiple symmetrically and evenly distributed perforations.

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