A device and method for synergistically regulating sound absorption frequency by neck length and cavity volume

Abstract

This invention relates to the field of noise control and acoustic metamaterials technology, and discloses a device and method for synergistically regulating the sound absorption frequency by adjusting the neck length and cavity volume. The sound-absorbing device includes a Helmholtz main structure and an adjustable neck assembly. The main structure includes a perforated top plate, hexagonal honeycomb sidewalls, rubber lining, and a central base plate, which is connected to a drive device via a push rod. The adjustable neck assembly employs a three-layer nested sleeve design, utilizing a spring return mechanism and a sliding hook slot mechanism to achieve graded adjustment of the neck length. The drive device drives the push rod to raise and lower the central base plate, providing thrust to the adjustable neck assembly and simultaneously changing the cavity volume. This metastructure overcomes the limitations of traditional underwater Helmholtz sound-absorbing structures, which suffer from fixed frequency bands and poor adaptability. By synergistically regulating the sound absorption frequency band with dual parameters, it dynamically responds to changes in the complex underwater acoustic environment, significantly reducing the acoustic target intensity of underwater equipment and providing an efficient solution for acoustic stealth in deep-sea equipment.

Description

Technical Field

[0001] This invention relates to the field of underwater acoustic superstructure and noise control technology, specifically to a device and method for synergistically regulating the sound absorption frequency by adjusting the neck length and cavity volume. Background Technology

[0002] The survivability of deep-sea equipment heavily relies on acoustic stealth technology. The core requirement is to reduce the acoustic intensity of itself by efficiently absorbing active sonar detection waves, thereby avoiding detection and tracking. Low-to-mid-frequency underwater noise is characterized by long propagation distance, slow attenuation, and strong penetration, making it a critical frequency band for underwater detection and counter-detection. Traditional sound-absorbing materials and structures are insufficient for efficient control.

[0003] The Helmholtz resonant sound-absorbing structure is one of the core technologies for underwater low-to-mid-frequency noise control. Its working principle is based on the resonance effect. When the incident sound wave frequency matches the structure's inherent resonant frequency, the water column within the neck vibrates strongly, exchanging energy with the water inside the cavity. Through viscous dissipation, thermal conduction, and rubber damping, the sound energy is converted into heat energy, achieving the sound absorption effect. Its resonant frequency is determined by the neck length, neck cross-sectional area, and water cavity volume parameters.

[0004] Furthermore, existing sound-absorbing structures are only effective for specific frequency bands and cannot adapt to the complex and varied underwater acoustic environment. For example, the frequency distribution of ocean background noise varies in different sea areas, and the detection frequency bands of different types of active sonar are also different. Traditional fixed-frequency sound-absorbing structures are difficult to achieve efficient stealth in all scenarios. In addition, the frequency of self-radiated noise of underwater equipment changes under different navigation states, further exacerbating the problem of insufficient adaptability of traditional structures.

[0005] Therefore, developing an underwater acoustic superstructure that is reliably sealed, has excellent water pressure resistance, and can achieve coordinated control of different frequency bands is of great significance for improving the acoustic stealth capability of deep-sea equipment and is also an urgent need in the field of underwater acoustic technology. Summary of the Invention

[0006] The core objective of this invention is to overcome the shortcomings of existing underwater sound-absorbing structures with fixed frequencies, and to provide a device and method for synergistically controlling the sound absorption frequency by adjusting the neck length and cavity volume. Through innovative structural design, the synergistic dynamic control of the neck length and water cavity volume is achieved. A hexagonal honeycomb structure is adopted to improve space utilization and mechanical stability, simplify the adjustment mechanism, and achieve convenient operation, ultimately meeting the requirements for efficient acoustic stealth in underwater acoustic environments.

[0007] To achieve the above objectives, the present invention provides an underwater sound absorption frequency control device and method based on the coordinated adjustment of neck length and cavity volume, including a Helmholtz main structure as the main body of Helmholtz resonant sound absorption and a dynamic control mechanism.

[0008] It includes the Helmholtz main structure, the neck adjustment assembly, and the drive device. The neck adjustment assembly is embedded in the central area of ​​the Helmholtz main structure, and the drive device is connected to the central base plate of the Helmholtz main structure through a push rod. The main structure of the Helmholtz system includes a top plate, hexagonal honeycomb side walls, a central bottom plate, and a closed hexagonal prism cavity. The inner surface of the side walls is covered with a rubber layer, and the central bottom plate has a bottom rubber layer. The Helmholtz main structure forms the basic sound absorber, which includes a top plate, side walls, a central bottom plate, and rubber applied to the inner surface of the side walls and the upper surface of the central bottom plate, together forming a closed resonant cavity. The top plate has a hole machined in the center for mounting the neck assembly.

[0009] The dynamic control mechanism is the core of frequency regulation and consists of two parts: the neck adjustment component and the cavity volume adjustment component.

[0010] The neck adjustment assembly includes an outer sleeve, an inner sleeve, a middle sleeve, a spring, a slide rail, and a sliding hook. The outer sleeve and the inner sleeve are coaxial and of the same length. The middle sleeve is movably nested between the outer sleeve and the inner sleeve. The axes of the three components coincide with the center line of the cavity of the Helmholtz main structure. A slide rail is provided axially on the outer wall of the middle sleeve. One side of the slide rail has evenly spaced slots along its length, while the other side is smooth without slots. The spring is installed at the top of the middle sleeve, and the top of the spring is fixedly connected to the lower surface of the top plate. In its natural state, the spring is in an extended state under the action of gravity, causing the lower end of the middle sleeve to extend beyond the bottom of the outer sleeve and the inner sleeve. A sliding hook is fixedly installed on the lower part of the inner wall of the outer sleeve. The sliding hook consists of a hook head, a support rod, and a positioning pin. The positioning pin is used to fix the sliding hook to the inner wall of the outer sleeve. The hook head is adapted to the slot of the slide rail, and the support rod connects the hook head and the positioning pin. The drive device is a linear hydraulic push rod mechanism. The output end of the drive device is fixedly connected to the push rod, and the top of the push rod is fixedly welded to the center of the lower surface of the center base plate. The drive device can drive the center base plate to rise and fall in the vertical direction.

[0011] The adjustable neck assembly employs a three-layer nested sleeve design. The upper ends of the outer and inner sleeves are fixed to the top plate, and their lengths are identical. The middle sleeve slides between the inner and outer sleeves. A sliding hook is fixedly installed on the inner wall of the outer sleeve. A specially designed slide rail is machined on the outer wall of the middle sleeve. One side is a slot area, which has several uniformly sized slots evenly spaced along the axial direction, with the slot openings facing downwards. The other side is a smooth guide area, the surface of which is polished and has no protrusions or groove structures. There is a difference in the axial starting height between the slot area and the smooth guide area; the starting end of the slot area is lower than the starting end of the smooth guide area, creating a height difference. This allows the hook to slide along one side of the slot when the neck is pushed upwards. A spring is installed between the top of the middle sleeve and the top plate. The spring is stretched by gravity, and when the sliding hook is at the top of the slide rail, the maximum neck length is reached. When the neck needs to be shortened, the drive mechanism drives the push rod upward, pushing the center base plate and bottom rubber upward, causing the intermediate sleeve to slide upward against the spring force, and the hook moves along the slide rail on the slot side. When the hook head moves to and engages with any slot, the external force is removed, and the intermediate sleeve is locked in that position, fixing the neck length to a shortened value. To restore the maximum length, a sufficiently large upward thrust is applied again, causing the hook to move to the groove near the smooth side of the bottom of the slide rail. The thrust is then released, and under the action of gravity, the hook head slides back to the starting position along the smooth guide surface, thereby changing the neck length.

[0012] The drive unit is fixedly installed at the bottom of the sound-absorbing structure, and its output end is connected to a push rod. The upper end of the push rod is connected to the center of the central base plate of the Helmholtz resonator unit. By controlling the drive unit, the push rod can be precisely driven to perform vertical extension and retraction, thereby pushing the entire central base plate and the bottom rubber attached to it to move up and down. The movement of the central base plate directly changes the internal height of the resonator cavity, thus realizing effective volume adjustment of the cavity and providing thrust for neck length control.

[0013] Optionally, the center base plate, top plate, side walls, and neck adjustment assembly are all made of stainless steel.

[0014] Optionally, both the center base plate and the bottom rubber are hexagonal prisms, and the side lengths of the hexagonal cross sections of the center base plate and the bottom rubber are the same. The thickness of the bottom rubber and the rubber layer applied to the inner side of the side wall is the same, and the bottom rubber and the center base plate, as well as the side wall and the rubber layer, are bonded together with a special adhesive that is resistant to water pressure and corrosion.

[0015] Alternatively, the specialty adhesives include epoxy resin-based or polyurethane-based underwater structural adhesives.

[0016] Optionally, the slide rail has an asymmetrical structure, with the starting end of the slot area lower than the starting end of the smooth guide area, forming a height difference to ensure that the hook of the neck adjustment component slides downward along the side with the slot under force.

[0017] Optionally, a sealing ring is provided on the sliding mating surface of the intermediate sleeve and the outer and inner sleeves to prevent liquid from entering the sliding gap between the sleeves.

[0018] Optionally, the intermediate sleeve is stepped. In the initial state, the thickness of the part of the intermediate sleeve extending out of the inner and outer sleeves is greater than the thickness between the inner and outer sleeves, so as to prevent water from entering between the inner and outer sleeves. The top of the intermediate sleeve is fixedly connected to a spring to provide a reset force. The hook head and the cooperation of different slots realize the graded fixation of the neck length.

[0019] This application also provides a method for coordinating the sound absorption frequency of the neck length and cavity volume, which is carried out using any of the aforementioned devices for coordinating the sound absorption frequency of the neck length and cavity volume. The driving device drives the push rod to move upward in a straight line, pushing the central base plate and the bottom rubber upward to provide an upward thrust to the intermediate sleeve of the neck adjustment assembly, thereby controlling the length adjustment of the neck. The volume of the hexagonal prism cavity is changed based on the final position of the central base plate and the bottom rubber layer.

[0020] The beneficial effects of the device for coordinating the neck length and cavity volume to regulate the sound absorption frequency provided in this application are as follows: (1) Dual-parameter control: The neck length and cavity volume are independently controlled by mechanical structure, and the two together determine the Helmholtz resonance frequency, thus realizing the dynamic control of the sound absorption frequency.

[0021] (2) Reliable and compact mechanism: The hexagonal honeycomb structure improves space utilization and mechanical stability, and is easy to cascade design. The neck adjustment adopts a spring buckle mechanism, which can maintain the locked state without continuous power supply. The structure is simple and easy to control. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0023] Figure 1 This is a schematic diagram of the sound-absorbing structure in an embodiment of the present invention; Figure 2 This is a schematic diagram of the neck of the sound-absorbing structure in an embodiment of the present invention; Figure 3 This is a schematic diagram of the sound-absorbing structure sliding hook in an embodiment of the present invention; Figure 4 This is a graph showing the sound absorption coefficient of the sound-absorbing structure under three conditions in an embodiment of the present invention.

[0024] The attached figures are labeled as follows: 1-Neck adjustment assembly; 11-Outer sleeve; 12-Spring mounting position; 13-Inner sleeve; 14-Slide rail; 15-Slide hook; 151-Positioning pin; 152-Support rod; 153-Hook head; 16-Intermediate sleeve; 2-Top plate; 3-Side wall; 4-Bottom rubber; 5-Rubber layer; 6-Push rod; 7-Central base plate; 8-Drive device; 9-Outer base plate. Detailed Implementation

[0025] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0026] This embodiment provides a device and method for coordinating the neck length and cavity volume to regulate the sound absorption frequency. The core of this method is to achieve dynamic adaptation and adjustment of the sound absorption frequency through the synergistic effect of power drive and spring latching mechanism, so as to cope with the complex and ever-changing underwater acoustic environment.

[0027] like Figure 1 As shown, this embodiment provides a device and method for coordinating the neck length and cavity volume to regulate the sound absorption frequency. Its outer shell is welded together from a top plate 2, hexagonal honeycomb sidewalls 3 and an outer bottom plate 9. The top plate has perforations for connecting the adjustable neck structure. The top plate 2 has a central opening for installing a variable length neck adjustment component 1. A rubber layer 5 is applied to the sidewalls 3, and a bottom rubber 4 is applied to the upper surface of the central bottom plate 7.

[0028] like Figure 2 As shown, the neck adjustment assembly 1 includes an outer sleeve 11, an inner sleeve 13, and a middle sleeve 16. The upper ends of the outer sleeve 11 and the inner sleeve 13 are fixed to the top plate 2 by welding. The middle sleeve 16 is positioned between the two and can slide axially. The outer wall of the middle sleeve 16 is machined with a slide rail 14, which has several evenly distributed slots on one side and a smooth guide surface on the other side. A sliding hook 15 is fixed to the inner wall of the outer sleeve 11, and the top end of the middle sleeve 16 is connected to the top plate 2 by a spring. Figure 3 As shown, the sliding hook 15 consists of a hook head 153, a support rod 152 and a positioning pin 151. The positioning pin 151 is used to fix the sliding hook 15 so that it is located on the inner wall of the outer sleeve 11. The hook head 153 is adapted to the groove of the slide rail 14. The support rod 152 connects the hook head 153 and the positioning pin 151.

[0029] The intermediate sleeve 16 is stepped. In the initial state, the thickness of the part of the intermediate sleeve 16 extending out of the inner and outer sleeves is greater than the thickness between the inner and outer sleeves, so as to prevent water from entering between the inner and outer sleeves. The part of the intermediate sleeve 16 extending out of the inner and outer sleeves refers to the part of the intermediate sleeve 16 that contacts the lower edge of the outer sleeve 11 and the inner sleeve 13, as well as the part that extends away from the lower edge of the outer sleeve 11 and the inner sleeve 13. "The intermediate sleeve 16 is stepped" means that the intermediate sleeve 16 has an upper and lower part with different thicknesses. The upper part of the intermediate sleeve 16 refers to the part that is located above the lower edge of the outer sleeve 11 and the inner sleeve 13 under all working conditions, while the lower part of the intermediate sleeve 16 refers to the part that contacts the lower edge of the outer sleeve 11 and the inner sleeve 13, as well as the part that extends away from the lower edge of the outer sleeve 11 and the inner sleeve 13. In this embodiment, the natural thickness ratio of the upper part to the lower part of the intermediate sleeve 16 is 1:2. The upper part is used to leave space for the movement of the sliding hook 15, and the lower part is used to seal the internal space between the outer sleeve 11 and the inner sleeve 13 to prevent water from entering between the inner and outer sleeves.

[0030] The drive unit 8 and push rod 6 reciprocate linearly against the central base plate 7 and the bottom rubber 4 to control the internal volume of the cavity. The drive unit 8 is fixed to the bottom of the sound-absorbing structure, and the lower end of the push rod 6 is connected to the output end of the drive unit 8, while the upper end is welded to the center of the central base plate 7. By controlling the extension and retraction of the drive unit 8, the stroke of the push rod 6 can be precisely controlled. When the drive unit 8 pushes the push rod 6 upward, it pushes the central base plate 7 and the bottom rubber 4 upward, reducing the volume of the water cavity, and vice versa.

[0031] The neck 1 is at its longest length in the initial state. The spring naturally extends under gravity. The hook 15 is located at the bottom of the slide rail 14. When frequency adjustment is required, the drive device 8 moves upward, and the control push rod 6 drives the center base plate 7 and the bottom rubber 4 to move upward, thereby providing thrust to the intermediate sleeve 16. The intermediate sleeve 16 compresses the spring and moves upward. The hook head 153 moves downward relative to the intermediate sleeve 16 along the grooved side of the slide rail 14, reaching the target slot. The drive device moves downward, removing the thrust. The hook 15 is locked in the target slot, and the intermediate sleeve cannot fall back under gravity. The neck length is fixed at the shortened length value. When the length needs to be reset, the drive device 8 applies an upward thrust again, causing the hook 15 to move along the slide rail to the groove near the smooth side at the lowest end. Then, the force is quickly released, and the neck moves downward under gravity. The hook head 153 of the hook 15 slides along the smooth guide surface until it returns to the initial position at the top of the slide rail.

[0032] In practical applications, the neck length can be locked at a specific length by the drive device 8 based on the sonar frequency prediction, and then the volume of the hexagonal prism cavity can be adjusted to a suitable size to adjust the resonance frequency, so that the structural resonance frequency domain matches the target sonar frequency and achieves the best sound absorption state.

[0033] Furthermore, finite element models of the sound-absorbing structure in three states were established in Comsol. States A, B, and C represent the sound-absorbing structures of the hook 153 at positions one, two, and three, respectively. The slot numbers on the slide rail, from bottom to top, are slot one, slot two, and slot three. The ratio of the cavity volume of states A, B, and C is 1.279:1.040:1, respectively. The maximum volume of the underwater sound-absorbing frequency control device based on the coordinated adjustment of neck length and cavity volume provided in this embodiment is 1.36 times the cavity volume of state C. Finite element simulations of the sound-absorbing structures in the three states were performed by coupling pressure acoustics, thermoviscous acoustics, and solid mechanics modules, resulting in... Figure 4 The sound absorption coefficient curves shown in the figure indicate that the peak frequencies of the sound absorption structure in the three states are 219Hz, 255Hz, and 298Hz, respectively. Therefore, changes in length and cavity volume can effectively control the peak frequency of the sound absorption structure.

[0034] Each unit of this device can serve as a standard sound-absorbing module. Utilizing its hexagonal shape, it can be arranged closely like a honeycomb and spliced ​​on a large scale by sharing sidewalls to cover the surface of underwater vehicles, forming an intelligent acoustic stealth layer with unified or zoned frequency control. It is suitable for low- and mid-frequency noise control and acoustic stealth of underwater platforms such as deep-sea equipment and underwater vehicles, and is especially suitable for complex acoustic environments where underwater noise frequencies change dynamically.

[0035] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A device for coordinating the neck length and cavity volume to regulate the sound absorption frequency, characterized in that: It includes a Helmholtz main structure, a neck adjustment component (1), and a drive device. The neck adjustment component (1) is embedded in the central area of ​​the Helmholtz main structure, and the drive device (8) is connected to the central base plate (7) of the Helmholtz main structure through a push rod (6). The Helmholtz main structure includes a top plate (2), hexagonal honeycomb sidewalls (3), a central bottom plate (7), and a closed hexagonal prism cavity. The inner surface of the sidewalls (3) is covered with a rubber layer (5), and the central bottom plate (7) has a bottom rubber layer (4). The neck adjustment assembly (1) includes an outer sleeve (11), an inner sleeve (13), a middle sleeve (16), a spring, a slide rail (14), and a hook (15). The outer sleeve (11) and the inner sleeve (13) are coaxial and have the same length. The middle sleeve (16) is movably nested between the outer sleeve (11) and the inner sleeve (13). The axes of the three components coincide with the center line of the cavity of the Helmholtz main structure. The outer wall of the middle sleeve (16) is provided with a slide rail (14) along the axial direction. The slide rail (14) has slots evenly opened on one side along the length direction, and the other side is smooth without slots. The spring installation position (12) is located in the middle sleeve (16). At the top, the top of the spring is fixedly connected to the lower surface of the top plate (2). In its natural state, the spring is in an extended state under the action of gravity, so that the lower end of the middle sleeve (16) extends out of the bottom of the outer sleeve (11) and the inner sleeve (13). The lower part of the inner wall of the outer sleeve (11) is fixedly installed with a sliding hook (15). The sliding hook (15) consists of a hook head (153), a support rod (152) and a positioning pin (151). The positioning pin (151) is used to fix the sliding hook (15) so that it is located on the inner wall of the outer sleeve (11). The hook head (153) is adapted to the groove of the slide rail (14). The support rod (152) connects the hook head (153) and the positioning pin (151). The driving device (8) is a linear hydraulic push rod mechanism. The output end of the driving device (8) is fixedly connected to the push rod (6). The top end of the push rod (6) is fixedly welded to the center of the lower surface of the center base plate (7). The driving device (8) can drive the center base plate (7) to rise and fall in the vertical direction.

2. The device for coordinating the neck length and cavity volume to regulate the sound absorption frequency according to claim 1, characterized in that: The center base plate (7), top plate (2), side wall (3) and neck adjustment assembly (1) are all made of stainless steel.

3. The device for coordinating the neck length and cavity volume to regulate the sound absorption frequency according to claim 1, characterized in that: Both the central base plate (7) and the bottom rubber (4) are hexagonal prisms, and the cross-sectional hexagonal side lengths of the central base plate (7) and the bottom rubber (4) are the same. The bottom rubber (4) and the rubber layer (5) applied to the inner side of the side wall are of the same thickness. The bottom rubber (4) and the central base plate (7) and the side wall (3) and the rubber layer (5) are bonded together with a special adhesive that is resistant to water pressure and corrosion.

4. The device for coordinating the neck length and cavity volume to regulate the sound absorption frequency according to claim 3, characterized in that: The special adhesives include epoxy resin-based or polyurethane-based underwater structural adhesives.

5. The device for coordinating the neck length and cavity volume to regulate the sound absorption frequency according to claim 1, characterized in that: The slide rail (14) has an asymmetrical structure, with the starting end of the slot area lower than the starting end of the smooth guide area, forming a height difference, which ensures that the hook (153) of the neck adjustment component (1) slides downward along the side with the slot under the action of force.

6. The device for coordinating the neck length and cavity volume to regulate the sound absorption frequency according to claim 1, characterized in that: The sliding mating surfaces of the intermediate sleeve (16) and the outer sleeve (11) and inner sleeve (13) are provided with sealing rings to prevent liquid from entering the sliding gap between the sleeves.

7. The device for coordinating the neck length and cavity volume to regulate the sound absorption frequency according to claim 1, characterized in that: The intermediate sleeve (16) is stepped. In the initial state, the thickness of the part of the intermediate sleeve (16) extending out of the inner and outer sleeves is greater than the thickness between the inner and outer sleeves, so as to prevent water from entering between the inner and outer sleeves. The top of the intermediate sleeve (16) is fixedly connected to the spring to provide a reset force. The hook (153) and the cooperation of different slots realize the graded fixation of the neck length.

8. A method for coordinating the neck length and cavity volume to regulate the sound absorption frequency, characterized in that: The device for coordinating the adjustment of the neck length and cavity volume to regulate the sound absorption frequency is used as described in any one of claims 1-7. The driving device (8) drives the push rod (6) to move upward in a straight line, pushing the center base plate (7) and the bottom rubber (4) upward to provide an upward thrust to the middle sleeve (16) of the neck adjustment assembly (1), thereby controlling the adjustment of the neck length and changing the volume of the hexagonal prism cavity based on changing the final position of the center base plate (7) and the bottom rubber layer (5).

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