Dual-resonance underwater sound absorption superstructure

Abstract

The invention relates to the technical field of underwater sound absorption, in particular to a dual-resonance underwater sound absorption superstructure. The structure comprises a rigid supporting back plate, a containing groove is formed in the rigid supporting back plate, a sound absorption flexible base body is arranged in the containing groove, a balancing weight is embedded in the sound absorption flexible base body, an annular supporting table is arranged at the bottom of the containing groove, a vibration plate is arranged on the annular supporting table, and a local resonance cavity is defined by the bottom of the containing groove, the annular supporting table and the vibration plate. A piezoelectric material layer is attached to the lower side of the vibration plate in the local resonance cavity, and the piezoelectric material layer is connected with an adjustable shunt circuit. By the adoption of the double-resonance underwater sound absorption superstructure, the size is reduced while the sound absorption effect is guaranteed, low-frequency efficient sound absorption under the deep sub-wavelength scale is achieved, sound absorption of variable-frequency-band underwater noise is achieved through the adjustable shunt circuit, two formants are introduced into the frequency band with the low sound absorption coefficient, and the sound absorption efficiency of the underwater sound absorption superstructure is improved. Therefore, the overall sound absorption coefficient is improved.

Description

Technical Field

[0001] This invention relates to the field of underwater sound absorption technology, and more particularly to a dual-resonance underwater sound absorption superstructure. Background Technology

[0002] With the deepening of human activities in the ocean, underwater acoustic stealth capabilities are directly related to the survivability of underwater equipment. Traditional sound-absorbing materials still generally suffer from problems such as weak low-frequency sound absorption performance, narrow effective bandwidth, and excessive structural thickness required in the low-frequency range, making it difficult to meet the urgent needs of modern underwater equipment for lightweight, wide-bandwidth sound absorption technology. Against this backdrop, underwater sound-absorbing metamaterials—which can overcome the limitations of traditional materials to achieve low-frequency, wide-bandwidth, and efficient sound absorption, and possess ultra-thin characteristics at the subwavelength scale—have rapidly become a cutting-edge research hotspot in this field, and their development and application are particularly crucial and urgent. Existing underwater sound-absorbing metamaterials have a simple structure, making it difficult to achieve dual resonance in the low-frequency range. Summary of the Invention

[0003] The purpose of this invention is to provide a dual-resonance underwater sound-absorbing superstructure to solve the above-mentioned technical problems.

[0004] To achieve the above objectives, the present invention provides a dual-resonance underwater sound-absorbing superstructure, comprising a rigid support backplate, a rigid protective support ring extending from the rigid support backplate, the rigid protective support ring and the rigid support backplate forming a receiving groove, a sound-absorbing flexible substrate disposed within the receiving groove, a counterweight embedded within the sound-absorbing flexible substrate, an annular support platform disposed on the rigid support backplate inside the rigid protective support ring, a vibrating plate disposed on the annular support platform, the bottom of the receiving groove, the annular support platform and the vibrating plate forming a local resonant cavity, a piezoelectric material layer attached to the lower side of the vibrating plate within the local resonant cavity, and an adjustable shunt circuit connected to the piezoelectric material layer.

[0005] Preferably, the inner radius of the annular support platform is 22mm-27mm, the outer radius is 25-35mm, the height is 5.5mm, and the material is steel.

[0006] Preferably, the vibrating plate is annular with a radius of 25mm-35mm, a thickness of 0.3mm-0.6mm, and is made of steel.

[0007] Preferably, the rigid support backplate has a thickness of 10-30mm, a radius of 40mm, a depth of 30mm, a radius of 37mm, and is made of steel.

[0008] Preferably, the sound-absorbing flexible matrix is ​​a polyurethane elastomer.

[0009] Preferably, the counterweight is made of lead and is cylindrical in shape with a radius of 1.5mm-3mm and a height of 12mm-18mm. The central axis of the counterweight coincides with the central axis of the sound-absorbing flexible substrate. The bottom of the counterweight is 2.8mm-3mm away from the upper side of the vibrating plate. Sound waves cause the sound-absorbing flexible matrix and counterweight to vibrate. The vibration of the sound-absorbing flexible matrix and counterweight forms a mass-spring system with the local resonant cavity at the bottom. Local resonance occurs at the frequency corresponding to the first resonance peak, converting sound energy into mechanical energy and then into heat energy for dissipation.

[0010] Preferably, the piezoelectric material layer is made of piezoelectric ceramic, with a radius of 14mm-15mm and a thickness of 0.5mm-1mm, and the center of the piezoelectric material layer is on the same axis as the circle of the vibrating plate.

[0011] Preferably, electrodes are provided on the upper and lower sides of the piezoelectric material layer. The electrodes are connected to an adjustable shunt circuit via wires. The adjustable shunt circuit is an adjustable LC oscillation circuit. The adjustable LC oscillation circuit includes a pluggable capacitor and a pluggable inductor connected in series. By replacing the pluggable capacitor and the pluggable inductor, the capacitance and inductance values ​​can be adjusted, thereby achieving continuous translational adjustment of the position of the second resonance peak.

[0012] Preferably, the local resonance cavity is filled with air.

[0013] Therefore, the underwater sound-absorbing superstructure with dual resonance described above has the following beneficial effects: (1) Traditional underwater sound-absorbing materials (such as pure rubber or polyurethane) usually rely on material thickness to dissipate sound energy. To absorb low-frequency (such as below 1000Hz) noise, they often require extremely large and heavy structures, making them difficult to apply to the surface of underwater vehicles with limited space. This invention uses a mechanical mass-spring system consisting of a rigid support backplate, a sound-absorbing flexible substrate, a counterweight, and a local resonant cavity. By introducing the high acoustic compliance of the local resonant cavity, a low-frequency local resonance of about 950Hz is successfully generated in an ultra-thin dimension with an overall thickness of only 40mm. This greatly reduces the thickness of the sound-absorbing structure and achieves high-efficiency low-frequency sound absorption at the deep subwavelength scale.

[0014] (2) The equivalent mechanical stiffness of the steel plate is dynamically changed by the adjustable shunt circuit. This electromechanical coupling process not only provides an additional sound absorption peak at 1450Hz, but also allows the position of the sound absorption peak to be continuously shifted by simply adjusting the inductance and capacitance values ​​in the external circuit, thus achieving precise strike against underwater noise in multiple frequency bands.

[0015] (3) A single local resonance mechanism usually exhibits narrow-band sound absorption, which is difficult to cope with the complex underwater noise environment with a wide frequency band. This invention integrates passive local resonance (around 950Hz) and semi-active piezoelectric shunt electromechanical resonance (around 1450Hz and adjustable range) into a single microstructure unit, which can introduce another peak in the frequency band with a low sound absorption coefficient, thereby improving the overall sound absorption coefficient.

[0016] (4) The rigid shell is constructed by using an external thick steel plate (10mm thick base and outer wall), which not only provides a solid physical support and underwater sealing guarantee for the entire metamaterial unit cell, but also effectively isolates the direct compression of the internal local resonant cavity and piezoelectric material layer by the deep water hydrostatic pressure, ensuring that the invention can still maintain stable acoustic control performance in complex and high-pressure real underwater engineering environments.

[0017] 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

[0018] Figure 1 This is a schematic diagram of a dual-resonance underwater sound-absorbing superstructure according to the present invention; Figure 2 This is a schematic diagram of the rigid support backplate structure of the present invention; Figure 3 This is a schematic diagram of an adjustable shunt circuit. Figure 4 This is a graph showing the sound absorption coefficient versus the incident wave frequency in this embodiment. Figure 5 The graph shows the sound absorption coefficient versus incident wave frequency for plugged-in capacitors with different capacitance values. Figure 6 The graph shows the sound absorption coefficient versus incident wave frequency for plug-in inductors with different inductance values. Figure 7 The graph shows the sound absorption coefficient versus incident wave frequency for plugged-in capacitors and plugged-in inductors with different capacitance and inductance values. Figure 8 The graphs show the sound absorption coefficient versus incident wave frequency for this embodiment and the control group. Figure 9 The graph shows the sound absorption coefficient versus incident wave frequency when the capacitance value is changed, serving as a control group.

[0019] Figure Labels 1. Rigid support backplate; 11. Receiving groove; 12. Annular support platform; 13. Vibrating plate; 2. Sound-absorbing flexible substrate; 3. Counterweight; 4. Local resonant cavity; 5. Piezoelectric material layer; 6. Adjustable shunt circuit; 61. Plug-in capacitor; 62. Plug-in inductor. Detailed Implementation

[0020] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used 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. Therefore, they should not be construed as limitations on the invention. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" 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 communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0022] like Figures 1-2As shown, a dual-resonance underwater sound-absorbing superstructure includes a rigid support backplate 1, which provides physical sealing and support. The rigid support backplate 1 and the rigid protective support ring extending from it constitute the rigid shell and acoustic hard boundary of the entire superstructure, providing excellent support under underwater pressure and preventing the soft sound-absorbing flexible matrix 2 inside from being damaged by pressure. The rigid support backplate 1 has a receiving groove 11. The rigid support backplate 1 is 10mm thick and has an outer radius of 40mm. The receiving groove 11 is 30mm deep and has a radius of 37mm. The rigid support backplate 1 is made of steel (304 steel). The sound-absorbing flexible matrix 2 is disposed inside the receiving groove 11. The sound-absorbing flexible matrix 2 is a polyurethane elastomer with a damping coefficient as high as 0.8, serving as the main medium for absorbing incident sound waves. A counterweight 3 is embedded within the sound-absorbing flexible substrate 2. The counterweight 3 is made of lead and is cylindrical in shape with a radius of 2.5 mm and a height of 18 mm. The central axis of the counterweight 3 coincides with the central axis of the sound-absorbing flexible substrate 2, and is used to adjust the overall mass distribution of the system. An annular support platform 12 is provided at the bottom of the receiving groove 11. The annular support platform 12 has an inner radius of 27 mm, an outer radius of 30 mm, and a height of 5.5 mm, and is made of steel (304 stainless steel). A vibrating plate 13 is provided on the annular support platform 12. The vibrating plate 13 is annular with a radius of 30 mm and a thickness of 0.5 mm. Because the vibrating plate 13 is relatively thin, it is more sensitive to vibration. The bottom of the counterweight 3 is 3 mm away from the top of the vibrating plate 13. The bottom of the receiving groove 11, the annular support platform 12, and the vibrating plate 13 form a local resonance cavity 4, which is filled with air. The sound waves cause the sound-absorbing flexible substrate 2 and the counterweight 3 to vibrate. The vibration of the sound-absorbing flexible substrate 2 and the counterweight 3 forms a mass-spring system with the local resonance cavity 4 at the bottom. Local resonance occurs at the frequency corresponding to the first resonance peak, converting sound energy into mechanical energy and then into heat energy for dissipation.

[0023] A piezoelectric material layer 5 is attached to the lower side of the vibrating plate 13 within the local resonant cavity 4. The piezoelectric material layer 5 is connected to an adjustable shunt circuit 6. The piezoelectric material layer 5 is made of piezoelectric ceramic, has a radius of 14 mm, and a thickness of 1 mm. The center of the piezoelectric material layer 5 is collinear with the circle of the vibrating plate 13. Electrodes are provided on the upper and lower sides of the piezoelectric material layer 5. The piezoelectric material layer 5 is made of PZT-5H and has inherent capacitance, calculated using the following formula: ; in, Where is the dielectric constant. The end face area of ​​the piezoelectric material layer. The distance between the two electrodes.

[0024] The electrode is connected to an adjustable shunt circuit 6 via a wire, such as... Figure 3As shown, the adjustable shunt circuit 6 is an adjustable LC oscillation circuit. The adjustable LC oscillation circuit includes a pluggable capacitor 61 and a pluggable inductor 62 connected in series, as shown below. Figure 4 , Figure 5 , Figure 6 as well as Figure 7 As shown, by replacing the plug-in capacitor 61 and the plug-in inductor 62, the capacitance or inductance value can be adjusted, directly changing the equivalent stiffness of the mass-spring system. This allows for continuous translational adjustment of the position of the second resonance peak (1450Hz) to adapt to the sound absorption requirements of different frequency bands. The technical solution of this embodiment achieves dual resonance peaks in the low frequency range (500Hz-2000Hz).

[0025] Underwater sound waves are incident from above. After passing through the sound-absorbing flexible substrate 2, the sound waves act on the lead counterweight 3 at the center and the steel vibrating plate 13 below. The piezoelectric material layer 5 is directly mechanically coupled to the steel vibrating plate 13. Sound energy is dissipated through a passive + semi-active dual mechanism.

[0026] Passive local resonance: Sound waves induce vibrations in the sound-absorbing flexible matrix 2 (TPU) and the counterweight 3 (lead). The localized resonant cavity 4 at the bottom provides excellent acoustic compliance (equivalent to an acoustic spring). This forms a mass-spring system that exhibits intense localized resonance at a specific frequency. Under the current structural parameters, this passive resonance produces its first high absorption peak around 950Hz, converting acoustic energy into heat energy for dissipation. Localized resonance calculation formula: ; in, The local resonant frequency, in Hz. The equivalent stiffness of the localized oscillator is expressed in Newtons per meter (N / m). The equivalent mass of the local oscillator is expressed in kilograms. Pi is the mathematical constant of a circle.

[0027] Semi-active piezoelectric shunt control: When the structure deforms, the piezoelectric material layer 5 (PZT-5H) generates an alternating current signal due to the positive piezoelectric effect. This signal is input to an external adjustable shunt circuit 6. When the electrical resonant frequency of the adjustable shunt circuit 6 matches the mechanical vibration frequency, a strong electromechanical coupling effect is generated. This macroscopically alters the equivalent dynamic stiffness of the vibrating plate 13 and the local system, thereby exciting a second resonant absorption peak at 1450Hz. Resonant frequency calculation formula: ; in, The resonant frequency is expressed in Hertz (Hz). This is the inductance value, expressed in Henry (H). The capacitance value is expressed in farads (F).

[0028] To verify the effectiveness of the technical solution in this embodiment, a control group was set up (without a local resonant cavity, and the local resonant cavity in this embodiment was filled with TPU material), such as... Figure 8 As shown, compared to a structure without a cavity, adding a cavity can increase an absorption peak (950Hz) at low frequencies. Figure 9 As shown, in the absence of a cavity structure, changing the value of the capacitor (solid line capacitor and inductor parameters are (1, 0.1), and the dashed line capacitor and inductor parameters are (0.6, 0.1), it can be seen that the sound absorption coefficient remains basically unchanged. This is because the TPU suppresses the deformation of the piezoelectric sheet, which in turn suppresses the effect of its external circuit.

[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A dual-resonance underwater sound-absorbing superstructure, characterized in that: It includes a rigid support back plate, from which a rigid protective support ring extends. The rigid protective support ring and the rigid support back plate form a receiving groove. A sound-absorbing flexible substrate is installed in the receiving groove, and a counterweight is embedded in the sound-absorbing flexible substrate. An annular support platform is installed on the rigid support back plate inside the rigid protective support ring, and a vibrating plate is installed on the annular support platform. The bottom of the receiving groove, the annular support platform, and the vibrating plate form a local resonant cavity. A piezoelectric material layer is attached to the lower side of the vibrating plate in the local resonant cavity, and the piezoelectric material layer is connected to an adjustable shunt circuit.

2. The underwater sound-absorbing superstructure with dual resonance according to claim 1, characterized in that: The inner radius of the annular support platform is 22mm-27mm, the outer radius is 25-35mm, the height is 5.5mm, and the material is steel.

3. The underwater sound-absorbing superstructure with dual resonance according to claim 2, characterized in that: The vibrating plate is annular with a radius of 25mm-35mm and a thickness of 0.3mm-0.6mm, and is made of steel.

4. The underwater sound-absorbing superstructure with dual resonance according to claim 3, characterized in that: The rigid support backplate has a thickness of 10-30mm, a radius of 40mm, a depth of 30mm, a radius of 37mm, and is made of steel.

5. The underwater sound-absorbing superstructure with dual resonance according to claim 4, characterized in that: The sound-absorbing flexible matrix is ​​a polyurethane elastomer.

6. The underwater sound-absorbing superstructure with dual resonance according to claim 5, characterized in that: The counterweight is made of lead and is cylindrical in shape with a radius of 1.5mm-3mm and a height of 12mm-18mm. The central axis of the counterweight coincides with the central axis of the sound-absorbing flexible substrate. The bottom of the counterweight is 2.8mm-3mm away from the upper side of the vibrating plate. Sound waves cause the sound-absorbing flexible matrix and counterweight to vibrate. The vibration of the sound-absorbing flexible matrix and counterweight forms a mass-spring system with the local resonant cavity at the bottom. Local resonance occurs at the frequency corresponding to the first resonance peak, converting sound energy into mechanical energy and then into heat energy for dissipation.

7. The underwater sound-absorbing superstructure with dual resonance according to claim 6, characterized in that: The piezoelectric material layer is made of piezoelectric ceramic, with a radius of 14mm-15mm and a thickness of 0.5mm-1mm. The center of the piezoelectric material layer is on the same axis as the circle of the vibrating plate.

8. The underwater sound-absorbing superstructure with dual resonance according to claim 7, characterized in that: Electrodes are provided on the upper and lower sides of the piezoelectric material layer. The electrodes are connected to an adjustable shunt circuit via wires. The adjustable shunt circuit is an adjustable LC oscillation circuit. The adjustable LC oscillation circuit includes a pluggable capacitor and a pluggable inductor connected in series. By replacing the pluggable capacitor and pluggable inductor, the capacitance and inductance values ​​can be adjusted, thereby achieving continuous translation adjustment of the position of the second resonance peak.

9. The underwater sound-absorbing superstructure with dual resonance according to claim 8, characterized in that: The cavity containing the local resonance is filled with air.

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