Sound tube test method for decoupling performance of an acoustic covering layer

Abstract

The present invention discloses an acoustic tube testing method for the decoupling performance of an acoustic covering layer, comprising the following steps: S1. Prepare a sample to be tested; the sample to be tested includes: a test sample and an acoustic covering layer sample, wherein the outer diameters of the test sample and the acoustic covering layer sample are the same and are adapted to the inner diameter of the acoustic tube; S2. Lay the acoustic covering layer sample on one side surface of the test sample to form a new sample to be tested, respectively set the test sample and the new sample to be tested in the acoustic tube, and respectively test and obtain the complex reflection coefficient and the complex transmission coefficient of the test sample and the new test sample under incident sound waves of different frequencies; S3. Respectively obtain the radiation sound pressure transfer coefficients of the test sample and the new sample to be tested; S4. Calculate the radiation sound pressure insertion loss according to the ratio of the radiation sound pressure transfer coefficients of the new sample to be tested and the test sample, and characterize the decoupling performance of the acoustic covering layer by the radiation sound pressure insertion loss.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater acoustic testing, and particularly relates to a sound tube testing method for the decoupling performance of an acoustic covering layer. Background Art

[0002] An acoustic covering layer refers to a special underwater acoustic material or component laid or installed on the surface of a submarine hull for reducing the radiated noise and target strength of the submarine. It is usually a type of polymer viscoelastic material containing an internal acoustic structure, with functions such as sound absorption, vibration suppression, sound insulation, and decoupling. It is a key component on a submarine that can effectively counter both active and passive sonars of the enemy. Conducting experimental tests and evaluations on the decoupling performance of the acoustic covering layer is the most direct means to verify the accuracy of relevant design theory methods and to test the effectiveness of design schemes.

[0003] Among them, the decoupling performance of the acoustic covering layer describes the ability of the acoustic covering layer laid on the structure surface to suppress the radiated noise of the structure by effectively "removing" the "coupling effect" between the structure surface and the external fluid medium. In the theoretical analysis process, the decoupling characteristics of the acoustic covering layer are usually characterized by the insertion loss of the radiated sound pressure (or radiated sound power) of an infinite plate excited by a harmonic point force before and after laying the acoustic covering layer. Therefore, in order to be as consistent as possible with the conditions in the theoretical analysis, the experimental test process also mainly uses an exciter to simulate the point force excitation method, and the decoupling performance of the measured acoustic covering layer is characterized by comparing the insertion loss of the radiated sound pressure (or radiated sound power) of the excited structure before and after laying the acoustic covering layer. However, this "formally" consistent excitation method brings difficulties to the test of the decoupling performance of the acoustic covering layer. In order to approximate the infinite plate assumption as much as possible, it is usually necessary to manufacture a flat plate with a sufficiently large lateral size (length and width), install an exciter with sufficient power at the center of the plate, and place the device to be tested in an anechoic pool to carry out relevant test work. If test results under pressurized conditions are required, the structure to be excited needs to be designed as a pressure-resistant container, the exciter is placed inside the container, and relevant experimental tests can only be carried out in an anechoic pressure water tank. The entire test process includes links such as the design of the pressure-resistant container, the laying of the acoustic covering layer, the installation of sensors, and the hoisting of experimental samples. This not only places high requirements on the design of the pressure-resistant container, but also requires a large amount of manpower, material resources, and time costs. Moreover, the boundary conditions at this time have deviated from the original theoretical model, seriously restricting the rapid iterative design of the decoupling performance of the acoustic covering layer.

[0004] To solve the problems of difficult preparation of test specimens, complex process of setting up the test environment, long test cycle, and high cost in the above-mentioned large-sample model test method, there is also a small-sample sound tube test method in the prior art, including sound insulation measurement and excitation test with a sound tube exciter. In the former, the sound insulation of the acoustic covering layer is directly measured in an underwater sound tube as an index to evaluate its decoupling performance, and the measurement of sound insulation refers to the national standard GB / T 14369-2011 "Measurement Methods for Insertion Loss, Echo Reduction and Absorption Coefficient of Underwater Acoustic Material Specimens"; in the latter, a cylindrical steel plate is excited by an exciter at the end of the sound tube, and the radiation sound pressure before and after the acoustic covering layer is attached to the surface of the steel plate is measured. The insertion loss of the radiation sound pressure measured before and after attaching the covering layer is used to measure the decoupling performance of the acoustic covering layer. For these two methods, the sound insulation index used in the former is not equivalent to the decoupling performance of the acoustic covering layer, and the latter requires a relatively complex installation of the exciter at the end of the sound tube and it is difficult to conduct measurements under pressurized conditions. Summary of the Invention

[0005] In view of this, the present invention provides a sound tube test method for the decoupling performance of an acoustic covering layer, which is used to at least solve the problems of insufficient accuracy in the test of the decoupling performance of the acoustic covering layer, difficulty in conducting tests under pressurized conditions, and complex process of setting up the test environment in the prior art.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A sound tube test method for the decoupling performance of an acoustic covering layer, comprising the following steps:

[0008] S1. Prepare a test specimen to be measured; the test specimen to be measured includes: a test specimen and an acoustic covering layer specimen, wherein the outer diameters of the test specimen and the acoustic covering layer specimen are the same and are adapted to the inner diameter of the underwater sound tube;

[0009] S2. Lay the acoustic covering layer specimen on one side surface of the test specimen to form a new test specimen to be measured, respectively set the test specimen and the new test specimen to be measured in the underwater sound tube, and respectively test to obtain the complex reflection coefficient and complex transmission coefficient of the test specimen and the new test specimen under incident sound waves of different frequencies;

[0010] S3. Respectively obtain the radiation sound pressure transfer coefficient of the test specimen and the new test specimen to be measured, wherein the specific calculation method of the radiation sound pressure transfer coefficient is:

[0011] ,

[0012] In the formula, is the radiation sound pressure transfer coefficient, and are the complex transmission coefficient and the complex reflection coefficient respectively;

[0013] S4. Calculate the radiation sound pressure insertion loss according to the ratio of the radiation sound pressure transfer coefficients of the new sample to be measured and the test sample, and characterize the decoupling performance of the acoustic covering layer by the radiation sound pressure insertion loss.

[0014] Preferably, the specific contents of the complex reflection coefficient and the complex transmission coefficient of the test sample under incident sound waves of different frequencies obtained in S2 include:

[0015] Place the test sample in the acoustic tube, and the axis direction of the test sample is consistent with that of the acoustic tube, so that both ends of the test sample are water, and the complex reflection coefficient of the test sample under incident sound waves of different frequencies is obtained by testing. And the complex transmission coefficient .

[0016] Preferably, the specific contents of the complex reflection coefficient and the complex transmission coefficient of the new test sample under incident sound waves of different frequencies obtained in S2 include:

[0017] Lay the acoustic covering layer sample on one side surface of the test sample to form a new sample to be measured, place the new sample to be measured in the acoustic tube, and the axis direction of the test sample is consistent with that of the acoustic tube, so that both ends of the sample to be measured are water, and the complex reflection coefficient of the new sample to be measured under incident sound waves of different frequencies is obtained by testing. And the complex transmission coefficient .

[0018] Preferably, the specific calculation method of the radiation sound pressure insertion loss in S4 is:

[0019] ,

[0020] In the formula, Radiation sound pressure insertion loss, And Are the radiation sound pressure transfer coefficients of the new sample to be measured and the test sample respectively.

[0021] Preferably, a transmitting transducer is arranged at the opening of the acoustic tube, and hydrophones are respectively arranged on the tube wall of the acoustic tube. In S2, when the test sample is tested, two hydrophones are evenly arranged on both sides of the test sample respectively. When the new sample to be measured is tested, two hydrophones are also evenly arranged on both sides of the new sample to be measured respectively, and the end of the acoustic tube is an absorbing end.

[0022] Preferably, an internal acoustic structure is provided inside the acoustic covering layer.

[0023] Through the above technical solutions, compared with the prior art, the present invention discloses a sound tube test method for the decoupling performance of an acoustic covering layer, which has the following beneficial effects:

[0024] 1. The present invention uses the insertion loss of the radiated sound pressure to measure the decoupling performance of the acoustic covering layer. Compared with the sound insulation measurement method that only examines the suppression of sound propagation by the acoustic covering layer without considering the suppression of the vibration of the structure itself after the covering layer is attached, the present invention further considers the suppression of the surface vibration of the structure and the suppression of sound propagation, which is more in line with the essence of the decoupling performance of the acoustic covering layer, and thus has better test accuracy;

[0025] 2. The present invention can directly carry out relevant tests using an underwater sound tube. Compared with the test method using a sound tube - exciter excitation, the complex exciter installation operation can be omitted, and at the same time, the test results under pressurized conditions can be conveniently obtained using the existing underwater sound tube;

[0026] 3. The present invention is simpler and easier to implement than the large - sample test method, has a short test cycle and low cost, can significantly improve the test efficiency, shorten the experimental period, and accelerate the iterative design of the decoupling performance of the acoustic covering layer. Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0028] Figure 1 It is a flowchart of the sound tube test method for the decoupling performance of an acoustic covering layer provided by the present invention;

[0029] Figure 2 It is a schematic diagram of the vibration and sound radiation of an infinite - large flat plate with a point - force excitation and an acoustic covering layer laid according to the existing test method provided by the embodiments of the present invention;

[0030] Figure 3 It is a schematic diagram of the structure of the cylindrical test sample to be measured provided by the embodiments of the present invention;

[0031] Figure 4 It is a schematic diagram of the principle of the underwater sound tube test provided by the embodiments of the present invention; where 1 - transmitting transducer; 2 - sound tube wall; 3 - first hydrophone; 4 - second hydrophone; 5 - test piece to be tested; 6 - third hydrophone; 7 - fourth hydrophone; 8 - sound - absorbing end;

[0032] Figure 5 It is a schematic diagram of the structure of the cylindrical acoustic covering layer bonded to a steel block provided by the embodiments of the present invention;

[0033] Among them, 9 - cylindrical acoustic covering layer sample; 10 - cylindrical steel block;

[0034] Figure 6 It is a comparison diagram of the decoupling performance experimental test and theoretical prediction structure of a cavity-type acoustic covering layer measured in an embodiment of the present invention. Specific embodiments

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with 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. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0036] The present invention provides a sound tube test method for the decoupling performance of an acoustic covering layer, as Figure 1 shown, including the following steps:

[0037] S1. Prepare a sample to be tested; the sample to be tested includes: a test sample and an acoustic covering layer sample, where the outer diameters of the test sample and the acoustic covering layer sample are the same and are adapted to the inner diameter of the underwater sound tube;

[0038] S2. Lay the acoustic covering layer sample on one side surface of the test sample to form a new sample to be tested, respectively set the test sample and the new sample to be tested in the underwater sound tube, and respectively test and obtain the complex reflection coefficient and complex transmission coefficient of the test sample and the new test sample under incident sound waves of different frequencies;

[0039] S3. Respectively obtain the radiation sound pressure transfer coefficients of the test sample and the new sample to be tested, where the specific calculation method of the radiation sound pressure transfer coefficient is:

[0040] ,

[0041] In the formula, is the radiation sound pressure transfer coefficient, and are the complex transmission coefficient and the complex reflection coefficient respectively;

[0042] S4. Calculate the radiation sound pressure insertion loss according to the ratio of the radiation sound pressure transfer coefficients of the new sample to be tested and the test sample, and characterize the decoupling performance of the acoustic covering layer through the radiation sound pressure insertion loss.

[0043] It should be noted that:

[0044] Figure 2 is a schematic diagram of the vibration and sound radiation of an infinite flat plate with a point force excitation laying an acoustic covering layer in an existing test method. Considering the cylindrical symmetry of the infinite flat plate, a cylindrical coordinate system is taken, and let the plane coincide with the middle plane of the plate with a thickness of , and a harmonic point force acts at the coordinate origin .

[0045] Before laying the acoustic covering layer, the radiated sound pressure of an infinite plate under point excitation is:

[0046] (1)

[0047] where is the imaginary unit, is the angular frequency, is the pi, is the excitation frequency, is the density of water, is the amplitude of the excitation force, is the natural constant, is the wave number of sound wave in water, is the sound speed in water, is the observation point to the distance from the excitation point on the plate surface ; is the mechanical impedance of the plate, that is, the impedance without fluid loading, and are the density and thickness of the thin plate respectively, , is the angle between the line connecting the observation point and the excitation point and the normal direction of the plate, is the bending wave number of the plate in vacuum, satisfying , is the bending stiffness of the plate, and are the Young's modulus and Poisson's ratio of the plate material respectively; is the radiation acoustic impedance of the plate.

[0048] The infinite plate with an acoustic covering layer is called a clad plate. The radiated sound pressure of the clad plate under point force excitation is obtained as:

[0049] (2)

[0050] where and are the elements of the sound pressure and vibration velocity transfer matrices at the front and rear interfaces of the acoustic covering layer. At this time is the observation point to the distance from the point on the surface of the covering layer corresponding to the excitation point on the plate. Under far-field conditions, it can be taken as the distance from the observation point to the excitation point on the plate surface, that is .

[0051] From equations (1) and (2), the ratio of the radiated sound pressure in water of the clad plate and the bare plate when the excitation forces are the same is:

[0052] (3)

[0053] Define the decibel value of the above ratio as the insertion loss of the acoustic covering layer for the radiated sound pressure of an infinite flat plate:

[0054] (4)

[0055] Since the radiated sound pressure has a directivity distribution that varies with and the directivity is different for different frequencies. It is also a quantity that varies with frequency and and is usually measured by i.e., the value in the vertical direction of the plate.

[0056] When , there is , , for the case of a single-layer acoustic covering layer on a flat plate, the insertion loss of the radiated sound pressure in the vertical direction is:

[0057] (5)

[0058] It can be seen from the above formula that the insertion loss of the radiated sound pressure of the acoustic covering layer in the vertical direction is a relative quantity, and its value is independent of the magnitude of the excitation force. As long as the values of the four elements and of the transfer matrix of the acoustic covering layer can be obtained, the decoupling performance of the acoustic covering layer can be characterized by formula (5). Further derivation will show that the insertion loss of the radiated sound pressure of the acoustic covering layer in the vertical direction can also be obtained through tests under uniform surface force excitation.

[0059] Under the excitation of a uniformly distributed surface force, only longitudinal waves can be excited in a multi-layer homogeneous medium. The transfer relationship between the particle velocity and stress at the front and rear interfaces of each layer of the medium can be described by a one-dimensional transfer matrix:

[0060] (6)

[0061] Among them, and are the normal stress and normal vibration velocity at the front interface of the -th layer of the medium, and are the normal stress and normal vibration velocity at the rear interface of the -th layer of the medium; is the transfer matrix of the -th layer of the medium, where , and are the wave number, thickness and impedance of the -th layer of the medium respectively, and are the The density and longitudinal wave speed of the layer medium. The full transfer matrix of the multi-layer system can be obtained by multiplying the sub-matrices, and satisfies:

[0062] (7)

[0063] and are the normal stress and normal vibration velocity at the front interface of the first layer medium, are respectively the transfer matrices of the layer medium, is the total number of layers of the multi-layer system, and are the transfer matrix of the multi-layer system of the four elements, and are the layer medium at the rear interface of the normal stress and normal vibration velocity.

[0064] For the case of a single-layer acoustic covering layer laid behind an infinite flat plate, the two form a double-layer system, and there is:

[0065] (8)

[0066] Among them, and are the normal stress and normal vibration velocity at the front interface of the flat plate, and are the normal stress and normal vibration velocity at the rear interface of the acoustic covering layer, and are the longitudinal wave number of the thin plate, and the longitudinal wave characteristic impedance, is the density and longitudinal wave speed of the plate, and are the elements of the sound pressure and vibration velocity transfer matrix at the front and rear interfaces of the acoustic covering layer.

[0067] Assume that the flat plate structure is uniformly distributed along the direction and is excited by a harmonic surface force, and the excitation amplitude is . Considering that the medium behind the plate is air, and the front side is water medium, the forward radiation plane waves and the backward propagation wave are generated in the media on both sides of the plate, is the wave number of the sound wave in the air, is the sound wave speed in the air, and there is:

[0068] (9)

[0069] Among them, and are the densities of air and water respectively.

[0070] Combining the system of equations (9) and the formula (7), the acoustic pressure of the radiation wave can be solved as follows:

[0071] (10)

[0072] where and are the acoustic characteristic impedances of air and water respectively. Considering , the above formula can be further simplified as:

[0073] (11)

[0074] Substituting the elements of the total transfer matrix of the light plate and the cladding plate into the formula (11) respectively, the ratio of the radiation acoustic pressure of the plate with the cladding layer and the light plate in water under the same excitation force can be obtained:

[0075] (12)

[0076] Define the decibel value of this ratio as the insertion loss of the acoustic cladding layer on the radiation acoustic pressure of the flat plate:

[0077] (13)

[0078] It can be seen that the formula (13) is consistent with the expression (5) of the insertion loss of the radiation acoustic pressure in the vertical direction under point excitation for the same structure, that is, the insertion loss of the radiation acoustic pressure under surface force excitation can be used as a brief characterization of the insertion loss under point excitation conditions.

[0079] So far, the insertion loss of the radiation acoustic pressure of the acoustic cladding layer can be transformed into the insertion loss of the radiation acoustic pressure of the small-sized sample before and after applying the acoustic cladding layer under the condition of uniform surface force excitation for simple characterization. However, although the implementation of the uniform surface force excitation condition can be achieved by exciting the small-sized sample with a vibrator, the problem that the vibrator needs to be pressure-resistant and sealed under pressure conditions still cannot be solved. Observing the formula (11), this problem can be further solved by the relationship between the complex reflection coefficient and the complex transmission coefficient and the transfer matrix of the sample to be measured during the in-tube sound insulation test in the underwater sound tube.

[0080] The relationship between the complex reflection and complex transmission coefficients measured in the underwater sound insulation test and the total transfer matrix is:

[0081] (14)

[0082] It is not difficult to obtain:

[0083] (15)

[0084] Comparing the formula (11) and the formula (15), the radiation acoustic pressure transfer coefficient satisfies:

[0085] (16)

[0086] This expression indicates the radiation sound pressure transfer coefficient of the pressure hull under the excitation of unit surface force. It can be obtained by converting the complex reflection and complex transmission coefficient obtained from its sound insulation test in water. Calculated and obtained.

[0087] Therefore, through the above theoretical derivation process, the radiation sound pressure insertion loss of the acoustic coating can be calculated by measuring the complex reflection coefficient and complex transmission coefficient of the small-size sound tube sample. The specific method is as follows: First, calculate the radiation sound pressure transfer coefficient of the steel plate through theoretical calculation or underwater sound tube test ; Then, paste an acoustic coating with the same diameter on the surface of the steel plate and measure the radiation sound pressure transfer coefficient of the coated plate ; Finally, take the logarithm of the ratio of the radiation sound pressure transfer coefficients under the two working conditions according to formula (17) to obtain the radiation sound pressure insertion loss value of the acoustic coating:

[0088] (17)

[0089] By obtaining the complex reflection and complex transmission coefficients under different pressure conditions through the in-tube test environment of the underwater sound tube, the radiation sound pressure insertion loss of the acoustic coating under different hydrostatic pressure conditions can be obtained, thereby characterizing its decoupling performance under different pressures.

[0090] In this embodiment, the material of the test sample can be selected according to actual needs, such as steel, titanium alloy, aluminum alloy, and hard composite material plate, etc. The shape of the test sample is designed according to the shape of the underwater sound tube. For example, if the current underwater sound tube is cylindrical, the test sample in this embodiment is set to be cylindrical.

[0091] To further implement the above technical solution, the specific content of the complex reflection coefficient and complex transmission coefficient of the test sample obtained by testing under different frequency incident sound waves in S2 includes:

[0092] Place the test sample in the underwater sound tube, and the axis direction of the test sample is consistent with that of the underwater sound tube, so that both ends of the test sample are water, and the complex reflection coefficient of the test sample under different frequency incident sound waves is measured and complex transmission coefficient .

[0093] To further implement the above technical solution, the specific content of the complex reflection coefficient and complex transmission coefficient of the new test sample obtained by testing under different frequency incident sound waves in S2 includes:

[0094] Lay the acoustic covering sample on one side surface of the test sample to form a new test sample to be measured. Place the new test sample to be measured in the underwater sound tube, and the axis direction of the test sample is consistent with that of the underwater sound tube, so that both ends of the test sample to be measured are water, and measure the complex reflection coefficient of the new test sample to be measured under incident sound waves of different frequencies. and the complex transmission coefficient .

[0095] To further implement the above technical solution, the specific calculation method of the radiation sound pressure insertion loss in S4 is as follows:

[0096] ,

[0097] In the formula, radiation sound pressure insertion loss, and are respectively the radiation sound pressure transfer coefficients of the new test sample to be measured and the test sample.

[0098] To further implement the above technical solution, a transmitting transducer is set at the opening of the underwater sound tube, and hydrophones are respectively set on the tube wall of the underwater sound tube. In S2, when the test sample is tested, two hydrophones are evenly set on both sides of the test sample respectively. When the new test sample to be measured is tested, two hydrophones are also evenly set on both sides of the new test sample to be measured respectively. The end of the underwater sound tube is an acoustic absorption end.

[0099] To further implement the above technical solution, an internal acoustic structure is provided inside the acoustic covering layer.

[0100] It should be noted that:

[0101] The internal acoustic structure can be a simple air cavity, a heavy material or other structures with specific acoustic functions through special design. That is, the inside of the acoustic covering layer can be a cavity capable of setting an acoustic structure, or other solid or porous structures, and can be specifically set according to actual test requirements when specifically implementing the test method disclosed by the present invention.

[0102] In this embodiment, as Figure 3 shown in the structural schematic diagram, test samples for underwater sound tube testing are respectively prepared. Among them, the test sample is a cylindrical steel block, and the new test sample to be measured is a cylindrical acoustic covering layer sample laid with a cylindrical acoustic covering layer, and the acoustic covering layer sample contains a uniformly distributed internal cavity structure. In this embodiment, a cylindrical underwater sound tube with an inner diameter of 120 mm is selected for test. The outer diameter of the selected cylindrical sample is 118 mm, the thickness of the cylindrical steel block is 30 mm, the thickness of the cylindrical acoustic covering layer sample is 36.5 mm, and it contains 13 A cylindrical cavity with a size of 16×12.5 mm.

[0103] Referring to Figure 4 the test principle shown, place the cylindrical steel block sample to be measured in the acoustic waveguide. When placing, align the axis direction of the steel block with the acoustic waveguide. Both ends of the sample to be measured are in water. Using the four-hydrophone transfer function method, measure the complex reflection coefficient of the sample to be measured under incident sound waves of different frequencies and the complex transmission coefficient , and calculate its radiation sound pressure transfer coefficient . Among them, the four hydrophones are the first hydrophone, the second hydrophone, the third hydrophone, and the fourth hydrophone;

[0104] Referring to Figure 4 the test principle shown, apply the cylindrical acoustic coating on one side surface of the cylindrical steel block by pasting (as Figure 5 shown, the pasting direction is consistent with the actual application of the acoustic coating). Place the pasted sample to be measured in the acoustic waveguide, and make the surface that is in contact with the external seawater during actual application face the transmitting transducer in the acoustic waveguide. Both ends of the sample to be measured are in water. Using the four-hydrophone transfer function method, measure the complex reflection coefficient of the sample to be measured under incident sound waves of different frequencies and the complex transmission coefficient , and further calculate its radiation sound pressure transfer coefficient . In Figure 4 , is the incident wave, is the reflected wave, and the lengths of each and are not shown for the distances.

[0105] According to the measured and , calculate the radiation sound pressure insertion loss of the cylindrical steel block before and after applying the acoustic coating .

[0106] Figure 6 Give a comparison chart of the decoupling performance experimental test and theoretical prediction structure of a cavity-type acoustic coating measured in this embodiment. The theoretical prediction results are in good agreement with the experimental test results, which proves the effectiveness of the method of the present invention.

[0107] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A method for testing the acoustic tube decoupling performance of an acoustic cover layer, characterized in that: The following steps are involved: S1. Prepare the sample to be tested; the sample to be tested includes: a test sample and an acoustic cover layer sample, wherein the outer diameter of the test sample is the same as that of the acoustic cover layer sample and is compatible with the inner diameter of the hydroacoustic tube; S2. Lay the acoustic covering layer sample on one side of the test sample to form a new test sample, respectively place the test sample and the new test sample in the underwater acoustic tube, and respectively test and obtain the complex reflection coefficient and complex transmission coefficient of the test sample and the new test sample under different frequency incident sound waves; S3. Obtain the radiation sound pressure transfer coefficient of the test sample and the new sample to be tested respectively, wherein the specific calculation method of the radiation sound pressure transfer coefficient is: ， In the formula, is the radiation sound pressure transfer coefficient, and are the complex transmission coefficient and complex reflection coefficient respectively; S4. Calculate the radiation sound pressure insertion loss based on the ratio of the radiation sound pressure transfer coefficient of the new sample to be tested and the radiation sound pressure insertion loss to characterize the decoupling performance of the acoustic covering layer.

2. The acoustic tube testing method for acoustic cover decoupling performance according to claim 1, characterized in that: The specific contents of the complex reflection coefficient and complex transmission coefficient of the test sample under different frequency incident sound waves tested in S2 include: The test sample is placed in the hydroacoustic tube and between two groups of hydrophones. The axis direction of the test sample is consistent with the hydroacoustic tube. Both ends of the test sample are filled with water. The complex reflection coefficient of the test sample under different frequency incident sound waves is obtained. and the complex transmission coefficient .

3. The acoustic tube testing method for acoustic cover decoupling performance according to claim 1, characterized in that: The specific contents of the complex reflection coefficient and complex transmission coefficient of the new test sample under different frequency incident sound waves tested in S2 include: The acoustic coating layer sample is laid on the surface of one side of the test sample to form a new test sample. The new test sample is placed in the hydroacoustic sound tube and located between two groups of hydrophones. The axial direction of the test sample is consistent with the hydroacoustic sound tube. The side where the acoustic coating layer sample is laid faces the position of the transducer in the hydroacoustic sound tube and contacts the external seawater. The complex reflection coefficient of the new test sample under different frequency incident sound waves is tested. and the complex transmission coefficient .

4. The acoustic tube testing method for acoustic cover decoupling performance according to claim 1, characterized in that: The specific calculation method of the radiation sound pressure insertion loss in S4 is: ， In the formula, Radiated sound pressure insertion loss, and are the radiation sound pressure transfer coefficients of the new sample to be tested and the test sample respectively.

5. The acoustic tube testing method for acoustic cover decoupling performance according to claim 1, characterized in that: A transmitting transducer is arranged at the opening of the hydroacoustic sound tube, and hydrophones are respectively arranged on the walls of the hydroacoustic sound tube. In S2, when the test sample is tested, two hydrophones are respectively evenly arranged on both sides of the test sample. When a new sample to be tested is tested, two hydrophones are also respectively evenly arranged on both sides of the new sample to be tested. The end of the hydroacoustic sound tube is a sound absorbing end.

6. The acoustic tube testing method for acoustic cover decoupling performance according to claim 1, characterized in that: An internal acoustic structure is provided inside the acoustic cover.

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