An acoustic covering structure

Abstract

The present invention provides a sound-absorbing covering structure, which relates to the technical field of vibration damping and noise reduction. Specifically, the sound-absorbing covering structure includes a first covering layer and a second covering layer that are adhesively connected. The first covering layer is used to adhere to the surface of the covering target. A number of cavity units for absorbing sound waves are provided inside the first covering layer, and the cavity units are arranged periodically. The second covering layer is disposed on the side of the first covering layer away from the covering target surface. Among them, the impact toughness of the second covering layer is greater than that of the first covering layer, and the acoustic impedances of the first covering layer, the second covering layer and the water medium are matched. The present invention can improve the vibration damping and sound absorption effects of the sound-absorbing covering structure under high hydrostatic pressure or impact pressure.

Description

Technical Field

[0001] The present invention relates to the technical field of vibration and noise reduction, and more specifically, to a sound-absorbing covering structure. Background Art

[0002] Underwater vehicles usually adopt sound-absorbing covering structures for underwater noise control and stealth. For example, in order to avoid sonar detection by the enemy, underwater ships usually lay a layer of sound-absorbing covering structure on their outer surfaces to absorb the sound waves emitted by sonars, reduce the reflection intensity of the sound waves, and improve the stealth performance of the ships.

[0003] Traditional sound-absorbing covering structures are usually prepared from rubbers with relatively high loss factors. However, due to the low Young's modulus of rubbers, when subjected to relatively high hydrostatic pressure or impact pressure, the internal cavity structure of the sound-absorbing covering structure is prone to large deformation, resulting in the destruction of the sound-absorbing performance and the inability to guarantee the sound-absorbing effect. Summary of the Invention

[0004] The problem solved by the present invention is to improve the vibration and noise reduction effect of the sound-absorbing covering structure under high hydrostatic pressure or impact pressure.

[0005] To solve the above problems, the present invention provides a sound-absorbing covering structure, including: a first covering layer and a second covering layer that are adhesively connected, and the first covering layer is used to adhere to the surface of the covering target;

[0006] A number of cavity units for absorbing sound waves are provided inside the first covering layer, and the cavity units are arranged periodically;

[0007] The second covering layer is arranged on the side of the first covering layer away from the surface of the covering target;

[0008] Wherein, the impact toughness of the second covering layer is greater than that of the first covering layer, and the acoustic impedances of the first covering layer, the second covering layer and the water medium are matched.

[0009] Optionally, the material of the first covering layer is a viscoelastic body including rubber, polyurethane, or a composite material based on a viscoelastic material.

[0010] Optionally, the thickness of the first covering layer is 24 mm to 36 mm, and the thickness of the second covering layer is 4 mm to 6 mm.

[0011] Optionally, the material of the second covering layer is a polyurea elastomer.

[0012] Optionally, a number of metal particles for enhancing the impact toughness are arranged periodically inside the second covering layer.

[0013] Optionally, a rubber coating is provided on the surface of the metal particles.

[0014] Optionally, the metal particles are porous metal particles, and the filling amount of the porous metal particles in the second covering layer increases in a gradient manner along the direction from the second covering layer to the first covering layer.

[0015] Optionally, the porous metal particles and the cavity units are correspondingly arranged in the thickness direction of the first covering layer.

[0016] Optionally, the acoustic covering structure further includes an adhesive layer that bonds the first covering layer and the second covering layer. The acoustic impedance of the adhesive layer matches that of the water medium, and the material of the adhesive layer is polyurethane foam or epoxy resin.

[0017] Optionally, the cavity units are one or more combinations of cylindrical cavities, conical cavities, and horn-shaped cavities.

[0018] The beneficial effects of the acoustic covering structure of the present invention are as follows: The acoustic covering structure includes a first covering layer and a second covering layer that are adhesively connected. Periodically arranged cavity units are provided inside the first covering layer. When sound waves pass through the second covering layer and pass through the cavity units of the first covering layer, multiple scattering, cavity resonance, waveform conversion, and sound wave conversion occur, thereby reducing the transmission of sound waves and achieving the effect of sound absorption. The second covering layer is provided on the side of the first covering layer away from the surface of the covering target. In an environment of high hydrostatic pressure or impact pressure, the second covering layer with higher impact toughness can relieve most of the hydrostatic pressure and / or impact pressure, thereby protecting the first covering layer to avoid a decrease in sound absorption performance caused by the deformation of the cavity units. Moreover, the characteristic that the water characteristic impedances of the second covering layer, the first covering layer, and the water medium match makes it easier for sound waves to enter the interior of the acoustic covering structure without reflection on the surface of the second covering layer, further improving the sound absorption effect of the acoustic covering structure. Description of the Drawings

[0019] Figure 1 is a schematic structural diagram of a sound absorption covering structure according to an embodiment of the present invention;

[0020] Figure 2 is a schematic structural diagram of a sound absorption covering structure according to another embodiment of the present invention;

[0021] Figure 3 is a schematic structural diagram of a sound absorption covering structure according to still another embodiment of the present invention.

[0022] Description of the Reference Numerals:

[0023] 1 - First covering layer; 11 - Cavity unit; 2 - Second covering layer; 21 - Metal particle; 22 - Rubber inclusion; 3 - Adhesive layer. Detailed Embodiments

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] Referring to "embodiments" herein means that specific features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment of the present invention. The phrase appears in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0026] The following describes an acoustic covering structure provided by an embodiment of the present invention.

[0027] As Figure 1 shown, an acoustic covering structure provided by an embodiment of the present invention includes a first covering layer 1 and a second covering layer 2 that are adhesively connected. The first covering layer 1 is used to adhere to the surface of the covering target.

[0028] A plurality of cavity units 11 for absorbing sound waves are formed inside the first covering layer 1, and the cavity units 11 are arranged periodically.

[0029] The second covering layer 2 is disposed on the side of the first covering layer 1 away from the surface of the covering target.

[0030] Wherein, the impact toughness of the second covering layer 2 is greater than that of the first covering layer 1, and the acoustic impedances of the first covering layer 1 and the second covering layer 2 match that of the water medium.

[0031] It should be explained that impact toughness is the ability of a material to resist external impacts or impact loads, which measures the deformation and damage ability of the material when subjected to high-energy impacts, and can usually be reflected by the impact absorption ability.

[0032] Whether the acoustic impedances of two media match or not characterizes the impedance change caused by the difference in the properties of the two media when sound waves propagate between two different media. In this embodiment, the acoustic impedance matching means that the acoustic impedances of the water medium, the first covering layer 1 and the second covering layer 2 are approximately equal; when sound waves propagate from one medium to another, if the acoustic impedances of the two media are equal, reflection and energy loss can be minimized to achieve the most effective sound energy transfer. Therefore, the acoustic impedances of the water medium, the first covering layer 1 and the second covering layer 2 are approximately equal, that is, when sound waves pass through these three media at one time, the reflection and energy loss are small.

[0033] Furthermore, the acoustic impedances being approximately equal means that when the relative difference between the acoustic impedances of two media is less than 5%, the acoustic impedances of the two media are considered to be approximately equal.

[0034] In this embodiment: The sound-absorbing covering structure can be laid on the outer surface of the underwater vehicle. When the detection sound waves emitted by the sound wave detection device reach the sound-absorbing covering structure, they enter through the outer surface of the second covering layer 2, pass through the second covering layer 2 and the first covering layer 1 in sequence. When passing through the cavity unit 11 of the first covering layer 1, since the acoustic impedance of the first covering layer 1 is quite different from the cavity acoustic impedance, the sound waves are reflected at the cavity boundary, which can effectively increase the propagation distance of the sound waves, thereby reducing the sound wave transmission. The coupled resonance between multiple cavity units 11 can increase the structural resonance mode density within a certain frequency range, and then generate more new resonance modes within a certain frequency range, thereby broadening the sound-absorbing frequency band of the structure. At the same time, the coupled resonance effect between the cavities can enhance the dissipation of the sound wave energy in the covering layer, converting the sound wave energy into heat energy and dissipating it. Since the impact toughness of the second covering layer 2 is greater than that of the first covering layer 1, in a high hydrostatic pressure or impact pressure environment, the second covering layer 2 with higher impact toughness can relieve most of the hydrostatic pressure and / or impact pressure, thereby protecting the first covering layer 1 to avoid the reduction of the sound-absorbing performance caused by the deformation of the cavity unit 11. Moreover, the characteristic that the second covering layer 2, the first covering layer 1 and the water characteristic impedance of the water medium match makes it easier for sound waves to enter the interior of the acoustic covering structure without reflection occurring on the surface of the second covering layer 2. Through the material damping characteristics of the second covering layer 2 and the first covering layer 1, the sound waves are converted into heat energy and dissipated under the action of elastic relaxation, internal friction, etc., further enhancing the sound-absorbing effect of the acoustic covering structure.

[0035] In one embodiment, the material of the first covering layer 1 is a viscoelastic body including rubber, polyurethane, or a composite material based on a viscoelastic material. Since viscoelastic bodies including rubber and polyurethane, or composite materials based on viscoelastic materials have a high loss factor, the material itself can increase the dissipation of sound waves through mechanisms such as friction, viscosity, bending, and torsion. Moreover, viscoelastic bodies including rubber and polyurethane, or composite materials based on viscoelastic materials also have a similar acoustic impedance to the water medium, which can reduce the reflection of sound waves at the boundary of the first covering layer 1, thereby enhancing the sound wave absorption ability. In addition, the macromolecular structure of viscoelastic materials is complex with a wide variety of chain segment motions, a wide distribution of relaxation and hysteresis times, and a large frequency range for sound wave absorption.

[0036] In one embodiment, the thickness of the first covering layer 1 is 24 mm to 36 mm, and the thickness of the second covering layer 2 is 4 mm to 6 mm.

[0037] By restricting the thickness of the first covering layer 1, the pressure resistance can be improved while maintaining the sound wave absorption efficiency. By restricting the thickness of the second covering layer 2, the energy absorption ability of the sound absorption covering structure can be enhanced while avoiding the excessive thickness of the second covering layer 2 from affecting the performance and stability of the underwater vehicle.

[0038] In one embodiment, the material of the second covering layer 2 is a polyurea elastomer.

[0039] It should be explained that due to the unique molecular structure of the polyurea elastomer, it has good mechanical properties. The polyurea elastomer can absorb part of the energy through the breakage of hydrogen bonds in the hard segment of the microstructure. The polyurea elastomer presents a rubber state at a low strain rate and a leathery or glassy state under high strain rate loading conditions. At the same time, the stress-strain behavior of the polyurea elastomer shows strong strain rate sensitivity at high strain rates. When the polyurea is subjected to an impact load, it will change from a rubber state to a glassy state and consume a large amount of energy during the tensile deformation process, which can effectively prevent the rubber cavity structure inside the covering layer from deforming and maintain the original sound absorption effect. Moreover, the acoustic impedance of the polyurea elastomer matches that of the water medium. The second covering layer 2 made of the polyurea elastomer can play a buffering and protecting role for the first covering layer 1 while absorbing sound waves, thereby improving the vibration and sound absorption ability of the sound absorption covering structure.

[0040] Furthermore, the material of the first covering layer is a polyurea elastomer, the density of the polyurea elastomer is 1000 kg / m 3 ~1040 kg / m 3 , and the material of the second covering layer is rubber, the density of the rubber material is 920 kg / m 3 ~960 kg / m 3 , and the density of water is 1000 kg / m 3, the calculation formula of water impedance is: Z = ρc, where Z represents acoustic impedance, ρ represents medium density, and c represents medium sound velocity, so that the acoustic impedance characteristics of the first covering layer, the second covering layer and the water medium are matched.

[0041] As Figure 2 shown, there are several metal particles 21 for enhancing impact toughness arranged periodically in the second covering layer 2.

[0042] It should be explained that the energy absorption capacity of the second covering layer 2 increases with the increase of its thickness, but if the thickness of the second covering layer 2 is too large, the performance and stability of the underwater vehicle will be reduced. In this embodiment, metal particles 21 are arranged periodically in the second covering layer 2 to improve the energy absorption capacity of the second covering layer 2, thereby improving the pressure resistance of the sound absorption covering structure.

[0043] Moreover, the metal particles 21 in the second covering layer 2 can themselves become scatterers of sound waves, which can not only increase the propagation distance of sound waves, but also couple and resonate with the cavity units 11 of the first covering layer 1, enhancing the coupling resonance effect inside the sound absorption covering structure, thereby improving the sound absorption performance.

[0044] When sound waves are reflected at the boundary of the cavity units 11, the metal particles 21 in the second covering layer 2 can dissipate the energy of the sound waves twice, thus achieving multiple effects with one action.

[0045] Furthermore, a rubber wrapping 22 is provided on the surface of the metal particles 21.

[0046] By providing a rubber wrapping 22 on the surface of the metal particles 21, due to the different natural frequencies between different metal particles 21, coupled resonance is generated between multiple metal particles 21, effectively broadening the sound absorption frequency range of the sound absorption covering structure, thereby improving the sound absorption performance.

[0047] Referring to Figure 3 , the metal particles 21 are porous metal particles 21, and the filling amount of the porous metal particles 21 in the second covering layer 2 increases in a gradient along the direction from the second covering layer 2 to the first covering layer 1.

[0048] Due to the porous characteristics, the porous metal particles 21 have a better sound absorption effect than the metal particles 21. The filling amount of the porous metal particles 21 in the second covering layer 2 increases in a gradient along the direction from the second covering layer 2 to the first covering layer 1, thus avoiding the stepped attenuation of sound waves when entering the protective layer and improving the stealth performance of the sound absorption covering structure.

[0049] In one embodiment, the porous metal particles 21 and the cavity units 11 are arranged corresponding to each other in the thickness direction of the first covering layer 1.

[0050] Since the porous metal particles 21 and the cavity unit 11 have different materials and shapes, they will have different resonance characteristics at different angles. They are arranged correspondingly in the thickness direction of the first covering layer 1, so as to enhance the coupled resonance between the porous metal particles 21 and the cavity unit 11, and further increase the energy dissipation of the sound wave, thereby improving the sound absorption and energy absorption of the overall sound absorption covering structure.

[0051] Optionally, the sound absorption covering structure further includes an adhesive layer 3 that bonds the first covering layer 1 and the second covering layer 2. The adhesive layer 3 is matched with the acoustic impedance of the water medium, and the material of the adhesive layer 3 is polyurethane foam or epoxy resin.

[0052] Furthermore, taking the adhesive layer 3 made of polyurethane foam material as an example, it has good sound absorption performance and elasticity, and can reduce the sound wave propagation loss. Polyurethane foam is a lightweight material, which helps to reduce the weight of the sound absorption covering structure, and has good elasticity, which can absorb and disperse external impact forces, improving the seismic resistance and impact resistance of the underwater structure. Moreover, polyurethane foam has good chemical stability in the underwater environment, can resist underwater corrosion and other chemical actions, and prolong the service life of the sound absorption covering structure. In addition, due to its good water resistance, polyurethane foam is not easy to absorb water, which helps to maintain the stability and performance of the sound absorption covering structure.

[0053] In one embodiment, the cavity unit 11 is one or a combination of a cylindrical cavity, a conical cavity, and a horn-shaped cavity. Different structures of the cavity unit 11 can generate different additional reflection phases, and the corresponding sound absorption frequencies are also different. By setting a single or a combination of different types of cavity units 11, the requirements for different sound absorption frequencies can be met. Therefore, the type and structure of the cavity unit 11 can be flexibly set according to the actual situation, and no specific limitation is made here.

[0054] Furthermore, in one embodiment, the cavity unit 11 is a horn-shaped cavity, the cross-sectional shape of the cavity unit along the thickness direction is an isosceles trapezoid, the upper base of the cavity unit 11 is 4 mm, the lower base is 8 mm, and the height is 10 mm.

[0055] It can be understood that when a horn-shaped cavity is provided in the first covering layer 1 made of a viscoelastic material, due to the shear deformation at the viscoelastic body-cavity interface, the incident plane longitudinal wave is converted into an elastic shear wave, thereby increasing the sound energy loss. The geometric shape of the horn-shaped cavity causes the sound wave to undergo multiple geometric reflections and scatterings in the second covering layer, which causes the sound wave to propagate along different paths, increasing the propagation path of the sound wave, and thus also increasing the loss of the sound wave, improving the sound absorption performance of the sound absorption covering structure.

[0056] In one embodiment, the inside of the cavity unit 11 is normal pressure air.

[0057] Although the present invention is disclosed as above, the scope of protection of the present invention is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will all fall within the scope of protection of the present invention.

Claims

1. An acoustic covering structure, characterized in that, Comprising: A first covering layer (1) and a second covering layer (2) which are adhesively connected, and the first covering layer (1) is used for adhering to the surface of the covering target; A plurality of cavity units (11) for absorbing sound waves are formed inside the first covering layer (1), and the cavity units (11) are arranged periodically; The second covering layer (2) is arranged on the side of the first covering layer (1) away from the surface of the covering target; Wherein, the impact toughness of the second covering layer (2) is greater than that of the first covering layer (1), and the acoustic impedances of the first covering layer (1) and the second covering layer (2) match that of the water medium; The material of the second covering layer (2) is a polyurea elastomer; There are a plurality of metal particles (21) for enhancing the impact toughness arranged periodically in the second covering layer (2), the metal particles (21) are porous metal particles (21), and the filling amount of the porous metal particles (21) in the second covering layer (2) increases in a gradient along the direction from the second covering layer (2) to the first covering layer (1); The thickness of the first covering layer (1) is 24 mm to 36 mm, and the thickness of the second covering layer (2) is 4 mm to 6 mm; It further includes an adhesive layer (3) for bonding the first covering layer (1) and the second covering layer (2), the adhesive layer (3) matches the acoustic impedance of the water medium, and the material of the adhesive layer (3) is polyurethane foam or epoxy resin.

2. The sound-absorbing covering structure according to claim 1, wherein, The material of the first covering layer (1) is a viscoelastic body including rubber and polyurethane or a composite material based on a viscoelastic material.

3. The sound-absorbing covering structure according to claim 1, characterized in that, A rubber wrapper (22) is arranged on the surface of the metal particles (21).

4. The sound-absorbing covering structure according to claim 1, characterized in that, The porous metal particles (21) and the cavity units (11) are correspondingly arranged in the thickness direction of the first covering layer (1).

5. The sound-absorbing covering structure according to any one of claims 1-4, characterized in that, The cavity unit (11) is one or a combination of a cylindrical cavity, a conical cavity, and a horn-shaped cavity.

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