An underwater self-weighted double-layer thin spherical shell acoustic standard scatterer

Abstract

The present invention discloses an underwater self-weighted double-layer thin spherical shell acoustic standard scatterer, comprising a hoisting device and a spherical double-layer thin spherical shell acoustic scatterer, wherein the spherical double-layer thin spherical shell acoustic scatterer comprises a double-layer sealed spherical shell formed by an inner thick spherical shell and an outer thin spherical shell, and a hoisting ring. The present invention adopts the method of inner thick shell counterweight and inner water-filled counterweight to meet the requirements of the quality and counterweight of the acoustic scatterer during the underwater deployment implementation process; and a water inlet hole is opened inside the connecting load-bearing column to connect the inside of the inner spherical shell of the double-layer spherical shell with the outside of the outer spherical shell, and the water rushed into the inner spherical shell is used to achieve self-weighting, ensuring that the sphere meets the measurement requirements within a depth range of 100m underwater. The present invention not only solves the problem that the underwater position and posture of the scatterer affects the measurement results, but also solves the contradiction between the large size of the underwater high-target intensity spherical acoustic scatterer and the convenience of implementation at sea.

Description

Technical Field

[0001] The invention belongs to the field of hydroacoustics and relates to an underwater self-weighted double-layer thin spherical shell acoustic standard scatterer. Background Art

[0002] The measurement of underwater target acoustic target intensity is of great significance in the fields of underwater target detection and active sonar system design. However, the measurement results of underwater target intensity are often interfered by factors such as measurement equipment, background noise, and target posture, resulting in low repeatability and confidence of the measurement results. Especially for complex-shaped targets, it is impossible to calculate their target intensity theoretically, and the measurement results obtained by simply taking the average value after multiple measurements are still unreliable. To solve the above problems, it is necessary to design an underwater acoustic standard scatterer with known omnidirectional acoustic target intensity. Its characteristics are: the acoustic target intensity is only determined by the radius and the omnidirectional acoustic target intensity is consistent. The acoustic target intensity can be directly calculated by the theoretical formula and can be compared and verified with the experimental measurement results. One of the functions of the acoustic standard scatterer is to compare the measurement results of the complex target with the measurement results of the acoustic standard scatterer, and obtain the acoustic target intensity of the complex target by the comparison method. The second function of the acoustic standard scatterer is to determine the measurement error of the measurement system by measuring the target intensity of the acoustic standard scatterer, thereby realizing the calibration and calibration function of the measurement system and the measurement results.

[0003] The technical conditions required for an excellent underwater acoustic standard scatterer include: high acoustic target intensity, fixed acoustic target intensity value and standard theoretical solution, known target intensity and azimuth relationship, known target intensity and frequency relationship, wide measurable frequency band (applicable to wide frequency band from low frequency to high frequency), stable appearance and structure and can be reused many times, convenient for test deployment and transportation, and adaptable to complex test and application environments at sea. Common underwater acoustic scatterers include corner scatterers, cylindrical, spherical, etc. Due to the asymmetry of the three-dimensional geometric structure, the acoustic field distribution of corner scatterers and cylindrical scatterers has the disadvantage of non-omnidirectionality, and only has high acoustic target intensity in specific directions. Spherical acoustic scatterers have rotational symmetry characteristics, and the scattered echoes in each incident direction are the same. The acoustic target intensity measurement results are insensitive to the azimuth error and position error between the measurement system and the target. Therefore, rigid spheres, hollow spherical shells, and other spheres with large impedance characteristics different from water are more widely used as underwater omnidirectional acoustic standard scatterers.

[0004] According to the theory of hydroacoustics, in the case where geometric scattering is the main echo contribution, the target intensity of underwater acoustic scatterers is proportional to the linear size of the target. The design and implementation of acoustic scatterers face the contradiction between the maximum target intensity and the physical size of the target. For example, in order to achieve an acoustic target intensity of 0 dB, the diameter of the spherical acoustic scatterer will reach 4 meters. If the density is 7900 kg / m 3The stainless steel material has a mass of about 264.7 tons. Obviously, it is very difficult to implement the above-mentioned solid spherical acoustic scatterer at sea. In order to meet the control requirements of the quality of the acoustic scatterer for transportation and offshore placement, a hollow thin spherical shell is often used as the acoustic scatterer. However, to completely sink a hollow thin spherical shell with a diameter of 4 meters to a certain depth underwater, it is necessary to overcome the buoyancy of 33.5 tons (measured in terms of the mass of the water displaced, the same below), which is also very difficult. Internationally, there are spherical acoustic standard bodies produced by Sonerbell Company, which can achieve large target intensity with a smaller volume. However, a single small-sized acoustic standard sphere can only achieve a large target intensity at a certain frequency, which cannot meet the needs of broadband measurement. Therefore, it is necessary to design a spherical acoustic standard scatterer that can not only meet the requirements of high target intensity for large size, but also have the feasibility of offshore deployment and recovery.

[0005] Patent document CN111212359A discloses an underwater pressure-maintaining flexible air column acoustic scatterer with the following main disadvantages: 1. The acoustic target intensity of the columnar structure is not only related to its radius, but also to the length of the cylinder. The flexible PVC material is selected as the cylindrical shape-maintaining material, which is easily affected by temperature and causes the radius and length to change, thereby affecting the target intensity value; 2. The air column acoustic scatterer has an elongated cylindrical appearance, and the acoustic scattering intensity formed in the vertical direction has a sharp directivity. It has a large target intensity only at a specific angle, and the designed acoustic target intensity cannot be obtained in other directions, and the requirement of strong scattering at all angles cannot be met. Especially when implemented at sea, the air column scatterer is easily affected by the ocean current and causes shaking, which will make it difficult to receive the echo signal; 3. The pressure-maintaining flexible air column acoustic scatterer is dense as a whole. Sealing structure, internal inflation, if it is placed underwater and kept in a vertical posture, a large amount of counterweights are required, which makes it difficult to implement it at sea; third, the working depth of the pressure-maintaining flexible air column acoustic scatterer is a single fixed depth, set to 65m underwater, and the flexible air column acoustic scatterer only maintains the set properties at this working depth. When its working depth changes, the shape of the flexible air column acoustic scatterer will also change due to changes in water pressure, resulting in deviations in the acoustic scattering measurement results; fourth, the pressure-maintaining flexible air column acoustic scatterer is made of PU hose material, which is easily affected by changes in seawater temperature, resulting in differences in its scattered wave measurement results in different seasons; fifth, the PU hose of the flexible air column acoustic scatterer and the upper and lower watertight connectors are connected by vulcanization technology, which is prone to water leakage, resulting in a low reuse rate of the air column scatterer. The present invention only needs to place the scatterer underwater, eliminating the processes of hanging counterweights, inflating the scatterer, and checking the inflation amount of the scatterer. The hanging process is simpler, and the posture of the scatterer underwater does not affect the measurement results. Therefore, when hanging, you only need to place the scatterer at the specified depth, and there is no need to confirm the scatterer posture and modulation posture. Summary of the invention

[0006] The present invention provides an underwater self-weighted double-layer thin spherical shell acoustic standard scatterer, which can achieve the same acoustic target intensity as a hollow sphere of the same size, has the characteristic of knowing the omnidirectional acoustic target intensity, meets the needs of broadband and deep-depth measurement, can be used as an acoustic standard body to calculate the acoustic target intensity of other complex targets, and can also be used to calibrate and calibrate the measurement system, while solving the problem that it is difficult and unfeasible to test large-sized spherical acoustic scatterers at sea.

[0007] To solve the above technical problems, the present invention is achieved through the following technical solutions:

[0008] An underwater self-weighted double-layer thin spherical shell acoustic standard scatterer comprises a hanging device and a spherical double-layer thin spherical shell acoustic scatterer, wherein the spherical double-layer thin spherical shell acoustic scatterer comprises a double-layer sealed spherical shell formed by an inner thick spherical shell and an outer thin spherical shell, and a hanging ring;

[0009] The upper and lower ends of the connecting load-bearing column are respectively provided with waist-shaped holes, which extend from the inner thick spherical shell to the outside of the outer thin spherical shell, and penetrate the upper and lower ends of the double-layer sealed spherical shell; the part of the connecting load-bearing column inside the inner thick spherical shell is provided with a plurality of water inlet holes, so that water flows from the waist-shaped holes through the water inlet holes into the inner thick spherical shell, thereby realizing automatic water filling in the inner thick spherical shell;

[0010] The hoisting ring is fixed on the upper end of the double-layer sealing spherical shell and is used to be connected with the hoisting device to realize the deployment and recovery of the double-layer sealing spherical shell.

[0011] There is air between the inner thick spherical shell and the outer thin spherical shell, which is used to ensure that the target intensity of the scatterer is the same as that of a hollow sphere of the same size.

[0012] A counterweight ring is also provided at the lower end of the double-layer sealed spherical shell for connecting a counterweight object.

[0013] The counterweight may be a high-density streamlined weight such as a lead fish, which is used to increase the underwater mass of the sound scatterer according to the placement requirements of the sound scatterer, so that it remains stable when being towed by the ship.

[0014] The radius r of the outer thin spherical shell is outside , the following conditions are met:

[0015]

[0016] Among them, TS is the target strength to be measured.

[0017] The mass of the inner thick spherical shell is M inside The following conditions must be met:

[0018] M inside =Mf +M z -M outside (2)

[0019] Among them, M f is the mass of water displaced by the sound scatterer, M z is the self-weight of the sound scatterer, M outside is the mass of the outer thin spherical shell of the sound scatterer.

[0020] The radius r of the inner thick spherical shell inside , the following conditions are met:

[0021] r inside =r outside -h outside -h air (3)

[0022] Where, h is the thickness of the outer thin spherical shell outside ,h air is the thickness of the air cavity between the inner spherical shell and the outer spherical shell.

[0023] The thickness of the inner spherical shell h inside , the following conditions are met:

[0024]

[0025] The hoisting device comprises a crane, a connecting cable and a winch; the hoisting ring is connected to the crane and the winch through the connecting cable.

[0026] The hoisting ring is welded to the outer part of the connecting load-bearing column extending to the double-layer sealed spherical shell, or is welded to the connecting part of the connecting load-bearing column and the outer thin spherical shell.

[0027] The counterweight lifting ring is welded to the portion of the connecting load-bearing column extending outside the double-layer sealed spherical shell, or is welded to the connecting portion of the connecting load-bearing column and the outer thin spherical shell.

[0028] When in use, water automatically enters the inner thick spherical shell through the water inlet hole, achieving the self-weighting effect of the inner space. There is air between the outer spherical shell and the inner spherical shell, which is used to ensure that the target strength of the scatterer is the same as that of a hollow ball of the same size; the lifting ring is cylindrical, located at the upper opening of the sealed double-layer spherical shell, and welded to the outer wall of the upper end of the waist-shaped connecting load-bearing column passing through the center of the sphere, and is used for the deployment and recovery of the sound scatterer; the counterweight lifting ring is located at the lower opening of the sealed double-layer spherical shell, and is welded to the outer wall of the lower end of the waist-shaped connecting load-bearing column passing through the center of the sphere, and is used to connect the counterweight; the counterweight can be optionally equipped with high-density streamlined heavy objects such as lead fish, and its function is to increase the underwater mass of the sound scatterer according to the deployment requirements of the sound scatterer, so that it can remain stable when towed with the ship.

[0029] Connect the lifting ring of the acoustic scatterer through the ship-mounted crane and place it in the water. Before placing it, tie the weight to the bottom of the weight lifting ring with a rope, slowly release the rope of the crane, wait for water to enter the inner spherical shell, and wait until the acoustic scatterer is completely submerged in the water. According to the depth requirements, mark the lifting rope and place the self-weighted double-layer thin spherical shell acoustic standard scatterer at the specified depth.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1) The spherical structure can form echo signals of equal intensity in all spatial directions. Even if the scatterer is shaken by the ocean current, it will not affect the measurement results of the scatterer. The intensity value of the acoustic target is only related to the radius r, which can greatly simplify the structure of the acoustic standard body.

[0032] 2) The acoustic standard scatterer adopts a pre-formed processing technology, has good shape retention characteristics, and can work at any depth within 100m underwater, and will not be deformed by the impact of ocean currents;

[0033] 3) The self-weighted double-layer structure ensures the target strength and uses the inner shell to automatically fill with water as the weight, which reduces the need for external weight and facilitates deployment and recovery at sea;

[0034] 4) The radius of the outer spherical shell of the self-weighted double-layer thin spherical shell acoustic standard scatterer is calculated according to the actual target intensity using the calculation formula (1). The thickness of the outer thin spherical shell is determined by the actual required working depth. The thinner the better while ensuring the shape stability.

[0035] 5) Due to the use of a double-layer spherical shell to form a sealed air cavity between the inner spherical shell and the outer spherical shell, the acoustic target intensity of a hollow sphere of the same size is achieved, meeting the demand for high target intensity for a large-sized sphere;

[0036] 6) The combination of inner thick shell weight and inner water-filled weight is adopted to meet the requirements of acoustic scatterer mass and weight during underwater deployment. This solves the contradiction between the large size of underwater high-target intensity spherical acoustic standard scatterers and the convenience of offshore implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the internal structure of the underwater self-weighted double-layer thin spherical shell acoustic standard scatterer of the present invention.

[0038] In the figure, there is an outer thin spherical shell 1, an inner thick spherical shell 2, a connecting load-bearing column 3, a water inlet 4, a crane 5, a lifting ring 6, a counterweight lifting ring 7, a connecting cable 8, and a winch 9.

[0039] Figure 2It is a schematic diagram of a spherical double-layer thin shell acoustic scatterer, where a is a front view and b is a cross-sectional view of a. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0041] like Figure 1 As shown, an underwater self-weighted double-layer thin spherical shell acoustic standard scatterer includes a spherical double-layer thin spherical shell acoustic scatterer, a hanging device, a hanging cable and a counterweight, wherein the spherical double-layer thin spherical shell acoustic scatterer includes: an outer thin spherical shell 1, an inner thick spherical shell 2, a connecting load-bearing column 3, a water inlet hole 4, a hanging ring 6, and a counterweight hanging ring 7; the hanging device includes: a crane 5, a cable 8, and a winch 9; the hanging connecting cables include a hanging cable and a counterweight cable, both of which are Kevlar ropes; the counterweight is an optional accessory. In the case of large interference from underwater ocean currents, a lead fish or other streamlined structures with a higher density can be used to maintain the posture stability of the spherical scatterer.

[0042] The outer thin spherical shell 1 and the inner thick spherical shell 2 form a sealed double-layer spherical shell, and there is a cavity between the inner and outer spherical shells; the connecting load-bearing column 3 passes through the upper and lower ends of the sealed double-layer spherical shell, extends from the inner thick spherical shell 2 to the outside of the outer thin spherical shell 1, and the upper end is welded to the lifting ring 6, and the lower end is welded to the counterweight lifting ring 7; the water inlet hole 4 is located inside the connecting load-bearing column 3, and the water outside the outer spherical shell enters the inner spherical shell through the water inlet hole 4, so that the inner spherical shell is self-balanced; the lifting cable 8 passes through the crane 5, one end is connected to the cable storage drum of the winch 9, and the other end is connected to the lifting ring 6; one end of the counterweight cable is connected to the counterweight lifting ring 7, and the other end is connected to the counterweight (lead fish); the counterweight is an optional accessory, the spherical scatterer has self-weighting, and there is no need to add counterweight under good measurement conditions. Only when encountering large interference from underwater currents, lead fish or other streamlined structures with higher density can be used to maintain the posture stability of the spherical scatterer; the system deployment is completed by the cooperation of the crane and the winch.

[0043] This embodiment takes the underwater large depth range self-weighted double-layer thin spherical shell acoustic standard scatterer as an example. The specific technical requirements of the device are as follows: double-layer spherical shell structure, water filling inside the inner shell, target strength -6dB, underwater negative buoyancy M z =500kg (i.e. the self-weight of the acoustic standard scatterer M z), the deployment depth is not greater than any depth of 100m; the outer radius of the outer thin spherical shell is 1m, the thickness is 10mm, and the material is stainless steel; the outer radius of the inner thin spherical shell is 0.77m, the thickness is 21.3mm, and the material is stainless steel; the size of the waist-shaped connecting load-bearing column is 2×0.15×φ0.05m (length 2m, width 0.15m, round head radius 0.05m), thickness 6mm; the size of the lifting ring and the load-bearing ring is 0.1×0.05m (length 0.1m, diameter 0.05m); the total weight of the counterweight is not less than 50kg; the diameter of the lifting cable is not less than 25mm, and the normal tension is not less than 5000kg; the diameter of the counterweight cable is not less than 10mm, and the normal tension is not less than 500kg.

[0044] The specific implementation steps are as follows:

[0045] 1. Design method of underwater self-weighted double-layer thin spherical shell acoustic standard scatterer

[0046] If the target intensity is -6dB, the outer radius of the spherical sound scatterer can be calculated according to the following formula:

[0047]

[0048] Among them, TS is the target strength, r outside is the target shell radius. The shell radius r of the double-layer spherical shell is calculated by the above formula (1): outside =1m, in order to meet the condition of shape stability within a depth of 100m, the thickness h is adopted outside =10mm stainless steel material is used as the outer thin shell material, and the density is ρ=7900kg / m 3 , then the mass of the outer shell M outside =982.9kg.

[0049] In order to achieve the same target strength as the hollow sphere of the same size, the cavity thickness h between the two spherical shells in this embodiment is air You can take 22% of the outer diameter, that is, h air =0.22m. According to the thickness of the air layer h air The outer radius of the inner spherical shell can be determined using the following formula:

[0050] r inside =r outside -h outside -h air (2)

[0051] The radius of the inner spherical shell is r inside =0.77m. Since the innermost spherical shell is filled with water, the buoyancy generated by the above cavity contributes to the entire buoyancy of the underwater self-weighted double-layer thin spherical shell acoustic standard scatterer. The buoyancy of the acoustic scatterer is calculated to be M f=1700.1kg.

[0052] In the embodiment, the connecting load-bearing column is a waist-shaped column, and its external dimensions are 0.15m×φ0.05m (width 0.15m, round head radius 0.05m). The connecting load-bearing column uses a hollow waist-shaped column with a wall thickness of 6mm to connect the upper and lower waist-shaped openings of the inner and outer spherical shells; the lifting ring and the counterweight ring are solid cylinders with a diameter of 0.05m, which are welded on the hollow waist-shaped column and the waist-shaped hole of the outer spherical shell; the load-bearing column and the lifting ring have little effect on the overall mass, and the influence of the load-bearing column and the lifting ring is ignored when calculating the overall mass and buoyancy. Therefore, the mass of the inner spherical shell of the double-layer thin spherical shell can be calculated according to the relationship between the mass of the inner and outer shells and the buoyancy, specifically:

[0053] M inside =M f +M z -M outside (3)

[0054] The mass M of the inner thick spherical shell is calculated inside =1217.2kg.

[0055] Next, we can calculate the mass of the inner thick spherical shell and the thickness of the inner spherical shell h. inside , specifically calculated using the following formula:

[0056]

[0057] The thickness of the inner spherical shell is calculated to be 21.3 mm by formula (4), and the inner radius of the inner spherical shell is further calculated to be 0.7487 m.

[0058] 2. Steps for making underwater self-weighted double-layer thin spherical shell acoustic standard scatterer

[0059] According to the design results in Example 1, considering the general specifications of the steel plate material, a 22mm thick stainless steel material is selected to be welded into an inner thick spherical shell 2 with an outer radius of 0.77m; waist-shaped holes with a size of 0.15m×φ0.05m are opened directly above and directly below the inner thick spherical shell 2, and a stainless steel waist-shaped column with a thickness of 6mm and a size of 0.15m×φ0.05m×2m is selected to pass through the upper and lower through holes of the inner spherical shell and is welded on the inner thick spherical shell as a connecting load-bearing column 3 connecting the inner and outer spherical shells; a water inlet hole 4 for water inlet is opened on the straight wall on one side of the waist-shaped column; and each welding diameter is 0.15m×φ0.05m on the upper and lower hole boundaries. A solid stainless steel cylinder with a diameter of 0.05m and a length of 0.1m is used as the load-bearing ring 5 and the counterweight ring 6; a 10mm thick stainless steel material is selected to be welded into the upper and lower hemispheres of the outer thin spherical shell 1 with a radius of 1m, and a waist-shaped hole of 0.15m×φ0.05m is opened at the center of the upper and lower hemispheres of the outer thin spherical shell 1; the circular holes of the upper and lower hemispheres of the outer thin spherical shell 1 are respectively sleeved on the upper and lower ends of the connecting load-bearing column 3 and welded into one body, and at the same time, the upper and lower hemispheres of the outer thin spherical shell 1 are closed and welded into one body; so far, the outer thin spherical shell 1, the inner thick spherical shell 2, and the connecting load-bearing column 3 form a closed double-layer thin spherical shell. Water flows in through the waist-shaped through holes at the lifting ring 6 and the counterweight ring 7, and then enters the inner thick spherical shell 2 through the water inlet hole 4 inside the connecting load-bearing column 3, thereby realizing the self-weighting effect of the inner spherical shell. The lifting ring 6 is connected to the crane and winch of the deploying vessel through a Kevlar rope with a length greater than 100m and a normal tension greater than 5000kg; the counterweight (50kg lead fish) is connected to the counterweight lifting ring 7 through a Kevlar rope with a length of 10m and a normal tension greater than 500kg.

[0060] 3. Deployment and recovery of underwater self-weighted double-layer thin spherical shell acoustic standard scatterer

[0061] The hoisting ring 6 at the upper end of the scatterer is connected to the crane 5 and winch 9 of the deployment ship through the hoisting cable 8. A clear mark is made on the connecting cable 8 at a distance of 99m from the hoisting ring (the radius of the double-layer thin spherical shell is 1m, and the sum of the two is the deployment depth of 100m); then the connecting cable 8 is wound around the winch of the winch 9. When hoisting, first use the crane to hoist the double-layer thin spherical shell acoustic standard scatterer from the ship deck to the water surface, then slowly release the cable until the double-layer thin spherical shell is completely submerged in the water, unhook the crane, and at this time, the connecting cable 8 is provided with tension by the winch 9; use the winch 9 on the ship to slowly release the cable, place the double-layer thin spherical shell acoustic scatterer to a depth of 100 meters underwater, turn off the winch 9, and the scatterer is deployed. During recovery, the hoisting cable 8 is first recovered by the winch 9 until the sound scatterer rises to the water surface. After all the water inside the inner spherical shell 2 flows out, it is recovered to the designated position on the deck by the crane 5, and the crane 5 is unhooked; the recovery of the scatterer is completed.

[0062] If a counterweight is added, it is only necessary to connect the counterweight to the counterweight ring 7 by means of a cable, and then the placement and recovery of the scatterer is completed according to the above placement and recovery sequence.

[0063] 4. Underwater self-weighted double-layer thin spherical shell acoustic standard scatterer deployment control

[0064] (1) Depth control: The working depth of the acoustic scatterer can be modulated within the range of 0-100m. The depth is adjusted by a winch using the mark on the hanging cable.

[0065] (2) Attitude control: In this embodiment, the acoustic scatterer has a negative buoyancy of 500 kg. Under normal circumstances, it can be deployed underwater without relying on weights, and it should have a stable attitude underwater. However, when the ocean current is strong, there is a possibility of deviation from the test position. The attitude stability of the acoustic scatterer can be achieved by adding weights.

Claims

1. An underwater self-weighted double-layer thin spherical shell acoustic standard scatterer, comprising a hanging device and a spherical double-layer thin spherical shell acoustic scatterer, characterized in that: The spherical double-layer thin spherical shell sound scatterer comprises a double-layer sealed spherical shell formed by an inner thick spherical shell (2) and an outer thin spherical shell (1), and a lifting ring (6); The upper and lower ends of the connecting load-bearing column (3) are respectively provided with waist-shaped holes, which extend from the inner thick spherical shell (2) to the outside of the outer thin spherical shell (1), and penetrate the upper and lower ends of the double-layer sealed spherical shell; the portion of the connecting load-bearing column (3) inside the inner thick spherical shell (2) is provided with a plurality of water inlet holes (4), so that water flows from the waist-shaped holes through the water inlet holes (4) into the inner thick spherical shell (2), thereby realizing automatic water filling in the inner thick spherical shell (2); The hoisting ring (6) is fixed to the upper end of the double-layer sealing spherical shell and is used to be connected to the hoisting device to realize the deployment and recovery of the double-layer sealing spherical shell; There is air between the inner thick spherical shell (2) and the outer thin spherical shell (1), which is used to ensure that the target intensity of the scatterer is the same as that of a hollow sphere of the same size.

2. The underwater self-weighted double-layer thin spherical shell acoustic standard scatterer according to claim 1 is characterized in that: A counterweight ring (7) is also provided at the lower end of the double-layer sealed spherical shell for connecting a counterweight object.

3. The underwater self-weighted double-layer thin spherical shell acoustic standard scatterer according to claim 2 is characterized in that: The counterweight may be a high-density streamlined weight such as a lead fish, which is used to increase the underwater mass of the sound scatterer according to the placement requirements of the sound scatterer, so that it remains stable when being towed by the ship.

4. The underwater self-weighted double-layer thin spherical shell acoustic standard scatterer according to claim 1 is characterized in that: The radius r of the outer thin spherical shell (1) is outside , the following conditions are met: Among them, TS is the target strength to be measured.

5. The underwater self-weighted double-layer thin spherical shell acoustic standard scatterer according to claim 1 is characterized in that: The radius r of the inner thick spherical shell inside , the following conditions are met: r inside =r outside -h outside -h air (3) Among them, h outside is the thickness of the outer thin spherical shell, route is the radius of the outer thin spherical shell (1), h air is the thickness of the air cavity between the inner spherical shell and the outer spherical shell.

6. The underwater self-weighted double-layer thin spherical shell acoustic standard scatterer according to claim 5 is characterized in that: The thickness of the inner spherical shell h inside , the following conditions are met: Among them, M inside is the mass of the inner thick spherical shell, and ρ is the density of the outer thin shell material.

7. The underwater self-weighted double-layer thin spherical shell acoustic standard scatterer according to claim 6 is characterized in that: The mass M of the inner thick spherical shell inside , the following conditions are met: M inside =M f +M z -M outside (2) Among them, M f is the mass of water displaced by the sound scatterer, M z is the self-weight of the sound scatterer, Moutside is the mass of the outer shell, and M z =M Target -M water , M Target >M water , M Target =M inside +M outside , that is, the sum of the masses of the inner thick shell and the outer thin shell M Target Greater than the mass M of the water displaced by the enclosing outer spherical shell water .

8. The underwater self-weighted double-layer thin spherical shell acoustic standard scatterer according to any one of claims 1 to 7, characterized in that: The hoisting device comprises a crane (5), a connecting cable (8) and a winch (9); the hoisting ring (6) is connected to the crane (5) and the winch (9) via the connecting cable (8).

9. The underwater self-weighted double-layer thin spherical shell acoustic standard scatterer according to any one of claims 1 to 7, characterized in that: The hoisting ring (6) is welded to the outer part of the connecting load-bearing column (3) extending to the double-layer sealed spherical shell, or is welded to the connecting part of the connecting load-bearing column (3) and the outer thin spherical shell (1).

10. The underwater self-weighted double-layer thin spherical shell acoustic standard scatterer according to any one of claims 1 to 7, characterized in that: The counterweight lifting ring (7) is welded to the portion of the connecting load-bearing column (3) extending outside the double-layer sealed spherical shell, or is welded to the portion connecting the connecting load-bearing column (3) and the outer thin spherical shell (1).

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