A material acoustic impedance test tube with sound sources at both ends and a test method thereof
By setting a sound source at both ends of the planar acoustic wave guide, emitting sound waves of different phases, and calculating the acoustic impedance of the material, the problem of large errors and long time consumption in the middle and low frequency bands in the prior art is solved, and efficient and accurate acoustic impedance testing of acoustic materials is achieved.
Patent Information
- Application Number
- CN202310655538.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-05
- Publication Date
- 2025-08-12
- Estimated Expiration
- 2043-06-05
AI Technical Summary
When testing the acoustic performance of underwater vehicle materials, the prior art has problems such as large errors in the medium and low frequency bands, long test time, and multiple measurements of the disassembly device or material are required, and it is impossible to conduct effective testing under pressure conditions.
The material acoustic impedance test tube and method are used for the sound source at both ends. By setting a sound source at both ends of the plane acoustic wave guide, sound waves of the same frequency and different phases are emitted. The data is collected by four hydrophones to calculate the input and transfer of the material, avoiding the backing and disassembly process, and directly performing measurements in the closed space.
It improves the test accuracy of the medium and low frequency bands, simplifies the measurement process, reduces the test error, and improves the measurement efficiency. It is suitable for acoustic impedance testing of acoustic materials in the frequency range of 200Hz to 2kHz.
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Figure CN116559291B_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of underwater acoustic testing, and in particular relates to a material acoustic impedance testing tube with sound sources at both ends and a testing method. Background Art
[0002] The stealthiness of underwater vehicles depends on the development of acoustic materials' sound insulation performance. Material acoustic performance testing is a very important part of the development of acoustic coatings. For testing the low-frequency acoustic performance of small underwater sample materials, the standing wave method can only test the sound absorption coefficient when the material is laid on a rigid wall (Li Shui et al., Standing wave tube measurement of low-frequency acoustic performance of underwater acoustic materials, Acta Metrologica Sinica, 2003(03): 221-224). The test frequency of the pulse method is limited by the length of the pipe. The traveling wave method has the disadvantages of long control time, complex sound elimination process, and poor sound absorption effect when testing transmission and reflection performance (Li Shui et al., Traveling wave tube measurement of low-frequency acoustic performance of underwater acoustic materials [J]. Acta Acoustics, 2007(04): 349-355). Furthermore, all of the above methods directly evaluate the acoustic performance of the material, and the test results are often not objective enough when applied to actual structures. To predict the acoustic properties of materials, an acoustic impedance test method has been proposed. This method, based on the end-blocking method (Yu Xiaoli, "Acoustic Impedance Measurement Method for Acoustic Coatings and Prediction of Acoustic Reflection from Composite Structures," Harbin Engineering University, 2006), can determine material impedance information. The key concept is to apply a steel backing to the back of the acoustic material to create impedance blockage, thereby satisfying the impedance test conditions. However, steel backings often have limited stiffness, and the impedance blockage conditions cannot be met at low and medium frequencies, leading to errors. Furthermore, this test method requires applying a rigid backing to both sides of the acoustic coating and then performing two measurements, which is time-consuming. Another method, backing-free acoustic impedance testing (Yu Xiaoli, "A Backing-Independent Acoustic Coating Acoustic Impedance Testing Method," Proceedings of the 17th Symposium on Underwater Noise of Ships," 2019: 635-641), lacks the ability to pressurize the sample. Currently, there is no convenient test method that does not require disassembly of the device or material to complete two measurements to obtain material impedance parameters under pressure. Summary of the Invention
[0003] In order to solve the problems existing in the prior art, the present invention provides a material acoustic impedance test tube with sound sources at both ends and a test method. The specific technical solution to this problem is as follows:
[0004] A material acoustic impedance test tube with sound sources at both ends comprises a first sound source, a first hydrophone, a second hydrophone, a third hydrophone, a fourth hydrophone, a test material, a second sound source and a planar acoustic waveguide. The second sound source and the first sound source are respectively arranged at the upper and lower ends of the planar acoustic waveguide and emit sound waves simultaneously to form a planar standing wave field in the planar acoustic waveguide.
[0005] A method for testing the acoustic impedance of a material using a two-end sound source, the method comprising the following steps:
[0006] Step 1: Using the above-mentioned material acoustic impedance test tube, place the test material in the middle position of a planar acoustic waveguide, with sound sources provided at both ends of the tube cavity of the planar acoustic waveguide, a first hydrophone and a second hydrophone provided in the liquid column on the lower surface of the test material, and a third hydrophone and a fourth hydrophone provided in the liquid column on the upper surface of the test material, wherein the distance between the first hydrophone and the lower surface of the test material is greater than the distance between the second hydrophone and the lower surface of the test material, and the distance between the fourth hydrophone and the upper surface of the test material is greater than the distance between the third hydrophone and the upper surface of the test material, each hydrophone is connected to a data acquisition device of the system, and the data acquisition device is connected to a measurement control computer;
[0007] Step 2: driving the first sound source and the second sound source to emit single-frequency signals with the same amplitude and phase;
[0008] Step 3: The data collector simultaneously collects the sound pressure p of the first hydrophone, the second hydrophone, the third hydrophone and the fourth hydrophone. x1 、p x2 、p x3 、p x4 , save as data file;
[0009] Step 4: Read the sound pressure data file and separate the plane waves in the plane acoustic waveguide according to the following formula:
[0010]
[0011] In the above formula, p Aa 、p Ba 、p Ca 、p Da are the sound pressures of the four plane acoustic waves A, B, C, and D in the plane acoustic waveguide, x1, x2, x3, and x4 are the position coordinates of the first, second, third, and fourth hydrophones in the plane acoustic waveguide, respectively, and k1 and k2 are the wave numbers of the liquid columns on both sides of the test material, respectively;
[0012] Step 5. After separating the sound waves, calculate the sound pressure and vibration velocity on the lower and upper surfaces of the test material according to the following formula:
[0013]
[0014] In the above formula, p1 represents the sound pressure on the lower surface of the test material, u1 represents the vibration velocity on the lower surface of the test material, l1 represents the position of the lower surface of the test material, p2 represents the sound pressure on the upper surface of the test material, u2 represents the vibration velocity on the upper surface of the test material, and l2 represents the position of the upper surface of the test material;
[0015] Step 6. Consider the test material as a dual-input, dual-output acoustic unit. The input parameters are the sound pressure p1 and vibration velocity u1 on the lower surface of the test material, and the output parameters are the sound pressure p2 and vibration velocity u2 on the upper surface of the test material. Take the acoustic impedance matrix of the test material as the unknown quantity, and obtain two equations about the acoustic impedance matrix:
[0016]
[0017] Where z 11 、z 22 is the input impedance of the material, defined as
[0018]
[0019] z 12 、z 21 is the transfer impedance of the material, defined as
[0020]
[0021] Step 7: Change the phase of the sound wave emitted by the second sound source so that it emits sound waves with the same frequency and opposite phase as the first sound source. Repeat steps 4 to 6 to obtain the other two equations about the acoustic impedance matrix:
[0022]
[0023] Step 8. Combine equations (3) and (4) to obtain a solvable system of equations for the acoustic impedance matrix:
[0024]
[0025] Get the acoustic impedance matrix of the test material
[0026]
[0027] That is, the test of the acoustic impedance of the material at the end of changing the acoustic source impedance is completed.
[0028] The present invention provides a material acoustic impedance test tube and test method with two-terminal sound sources. Compared with existing technologies, the advantages include: 1. Conventional impedance parameter measurement methods. The impedance parameter measurement method uses the end-blocking method, which utilizes a steel backing applied to the back of an acoustic cover layer to create impedance blockage, thereby meeting impedance measurement requirements. However, steel backings often have limited thickness and rigidity, and cannot meet the impedance blockage requirements in the mid- and low-frequency bands, resulting in measurement errors. The present invention does not rely on a backing, ensuring the accuracy of medium and low frequency testing. Second, the end-blocking measurement method requires applying a steel backing to the front and back of the acoustic cover layer and then performing two measurements. The test application is time-consuming. The test method of the present invention does not require a second application of the sample, simplifying the measurement process. The material impedance test under pressurized conditions needs to be carried out in a closed space. Other end-load methods such as changing the end load material or changing the output end pipe wall length require disassembling the watertight pipe wall. By adding a second sound source to change the end load, there is no need to disassemble the pipe wall, and only the emitted sound wave can be changed, thereby improving measurement efficiency. Third, the change in the end load between the two tests will interfere with the impact of the test error on the test results. By changing the sound wave phase, the output end sound source emits sound waves of opposite phases during the two measurements. At this time, the change in the end load is more obvious, effectively reducing the impact of the test error on the test results, and making the test results more accurate. It is suitable for testing the acoustic impedance of acoustic materials in the frequency range of 200Hz to 2kHz. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 is a schematic structural diagram of the test tube of the present invention, Figure 2 yes Figure 1 The model diagram using finite element software, Figure 3 is a schematic diagram of the material impedance characteristics. Figure 4 This is a schematic diagram of the change of various impedance parameters with frequency. Figure 5 This diagram shows how the sound pressure transmission coefficient and sound pressure reflection coefficient vary with frequency, as measured using the acoustic impedance method using an end-source acoustic source. In the figure, 5-1 and 5-2 represent the medium. DETAILED DESCRIPTION
[0030] like Figure 1 As shown, a material acoustic impedance test tube with two sound sources in this embodiment comprises a first sound source 1-1, a first hydrophone 2-1, a second hydrophone 2-2, a third hydrophone 2-3, a fourth hydrophone 2-4, a test material 3, the second sound source 1-2, and a planar acoustic waveguide 4. The second sound source 1-2 and the first sound source 1-1 are respectively disposed at the upper and lower ends of the planar acoustic waveguide 4 and simultaneously emit sound waves to form a plane wave field within the planar acoustic waveguide 4. The first sound source 1-1 is disposed at the lower end of the test material 3, and the second sound source 1-2 is disposed at the upper end of the test material 3.
[0031] The steps of a material acoustic impedance testing method of a two-end sound source in this embodiment are as follows:
[0032] Step 1: Press Figure 2 As shown in the figure, a cylindrical plane acoustic waveguide model with a diameter of 0.3m and a height of 3m is constructed using finite element software. The sample to be tested is set at the center of the plane acoustic waveguide as test material 3. The material of the sample to be tested is rubber, with a Young's modulus of 6.1×106Pa and a density of 1080kg / m 3 , Poisson's ratio 0.47, loss factor 0.30, and thickness 0.04m. Water is used as the acoustic medium on both sides. A first sound source 1-1 and a second sound source 1-2 are respectively set at the upper and lower ends of the planar acoustic waveguide 4. Sound pressure monitoring points are set on both sides of the sample to be tested at intervals of 0.3m, serving as the first hydrophone 2-1, the second hydrophone 2-2, the third hydrophone 2-3, and the fourth hydrophone 2-4 from top to bottom.
[0033] Step 2: The first sound source 1-1 and the second sound source 1-2 are configured to simultaneously emit plane sound waves of the same amplitude and phase;
[0034] Step 3: Simultaneously record the sound pressures p of the four sound pressure detection points corresponding to the first hydrophone 2-1, the second hydrophone 2-2, the third hydrophone 2-3 and the fourth hydrophone 2-4 from bottom to top. x1 、p x2 、p x3 、p x4 , save as data file;
[0035] Step 4: Read the sound pressure data file and separate the plane waves in the plane acoustic waveguide according to the following formula:
[0036]
[0037] In the above formula, p Aa 、p Ba 、p Ca 、p Da They are Figure 2 The sound pressures of the four plane acoustic waves A, B, C, and D in the plane acoustic waveguide 4 are shown as follows: x1, x2, x3, and x4 are respectively Figure 2 The coordinates of the four sound pressure monitoring points from bottom to top in the plane acoustic waveguide shown, k1 and k2 are the wave numbers of the acoustic media on both sides of the sample to be tested;
[0038] Step 5. After separating the plane acoustic wave, calculate the sound pressure and vibration velocity on the lower and upper surfaces of the sample to be tested according to the following formula:
[0039]
[0040] In the above formula, p1 represents the sound pressure on the lower surface of the sample to be tested, u1 represents the vibration velocity on the lower surface of the sample to be tested, l1 represents the position of the lower surface of the sample to be tested, p2 represents the sound pressure on the upper surface of the sample to be tested, u2 represents the vibration velocity on the upper surface of the sample to be tested, and l2 represents the position of the upper surface of the sample to be tested;
[0041] Step 6: Figure 3 As shown in the figure, the sample to be tested is regarded as an acoustic unit with dual input and dual output. The input parameters are the sound pressure p1 and vibration velocity u1 on the lower surface of the sample to be tested, and the output parameters are the sound pressure p2 and vibration velocity u2 on the upper surface of the sample to be tested. The acoustic impedance matrix of the sample to be tested is used as the unknown quantity, and two equations about the acoustic impedance matrix are obtained:
[0042]
[0043] Where z 11 、z 22 is the input impedance of the material, defined as
[0044]
[0045] z 12 、z 21 is the transfer impedance of the material, defined as
[0046]
[0047] Step 7: Change the phase of the sound wave emitted by the second sound source 1-2 so that it emits sound waves with the same frequency and opposite phase as the first sound source 1-1. Repeat steps 4 to 6 to obtain two other equations about the acoustic impedance matrix:
[0048]
[0049] Step 8. Combine equations (3) and (4) to obtain a solvable system of equations for the acoustic impedance matrix:
[0050]
[0051] Get the acoustic impedance matrix of the sample to be tested
[0052]
[0053] The input impedance and transfer impedance of the acoustic impedance matrix are obtained, and the results are as follows: Figure 4 As shown, from Figure 4 It can be seen that its input impedance z 11 、z 22 The amplitudes are equal and the phases are opposite. The opposite phases are caused by the fact that the directions of the sound waves on both sides are marked as upward and positive. The transfer impedance z 12 、z 21Maintaining the same characteristics, its impedance matrix is a symmetrical matrix, which conforms to the characteristics of the symmetrical material itself;
[0054] The acoustic impedance matrix of the material can be used to predict the acoustic properties of the material, including the sound pressure transmission coefficient T and the sound pressure reflection coefficient R. The results of the material acoustic performance prediction using the impedance matrix are compared with the theoretical calculation results of the material acoustic performance. Figure 5 As shown,
[0055]
[0056] The acoustic impedance testing method of materials in a planar acoustic waveguide using a terminal sound source to change the impedance can accurately test the material impedance information and accurately predict the acoustic performance of the material.
[0057] Sound sources are provided at both ends of the planar acoustic waveguide. The two sound sources can simultaneously emit plane acoustic waves of the same frequency with arbitrary phase difference. By changing the phase difference of the sound waves emitted by the two sound sources, the boundary impedance at the end of the planar acoustic waveguide can be changed, thereby realizing the test of the material input acoustic impedance and transmission acoustic impedance.
[0058] The testing method can test the input acoustic impedance and transfer acoustic impedance of the material, and can also predict the transmission coefficient and reflection coefficient acoustic parameters of the tested material.
[0059] The above embodiments are merely exemplary and do not limit the present invention. It should be pointed out that for those skilled in the art, other equivalent changes, modifications, substitutions and variations made under the inspiration of the technical solution provided by the present invention should all be regarded as within the scope of protection of the present invention.
Claims
1. A method for testing acoustic impedance using a material acoustic impedance test tube with two sound sources at both ends, wherein the material acoustic impedance test tube with two sound sources at both ends comprises a first sound source, a first hydrophone, a second hydrophone, a third hydrophone, a fourth hydrophone, a test material, and a second sound source; wherein: The second sound source and the first sound source are respectively arranged at the upper and lower ends of the planar acoustic waveguide, and emit sound waves simultaneously to form a plane wave field in the planar acoustic waveguide; The method is characterized in that the steps are as follows: Step 1: Using the above-mentioned material acoustic impedance test tube, place the test material in the middle position of a planar acoustic waveguide, with sound sources provided at both ends of the tube cavity of the planar acoustic waveguide, a first hydrophone and a second hydrophone provided in the liquid column on the lower surface of the test material, and a third hydrophone and a fourth hydrophone provided in the liquid column between the upper surface of the test material and the transmitting transducer, wherein the distance between the first hydrophone and the lower surface of the test material is greater than the distance between the second hydrophone and the lower surface of the test material, and the distance between the fourth hydrophone and the upper surface of the test material is greater than the distance between the third hydrophone and the upper surface of the test material, each hydrophone is connected to a data acquisition device of the system, and the data acquisition device is connected to a measurement control computer; Step 2: driving the first sound source and the second sound source to emit single-frequency signals with the same amplitude and phase; Step 3: The data collector simultaneously collects the sound pressure of the first hydrophone, the second hydrophone, the third hydrophone and the fourth hydrophone , save as data file; Step 4: Read the sound pressure data file and separate the plane waves in the plane acoustic waveguide according to the following formula: （1） In the above formula, are the sound pressures of the four plane acoustic waves A, B, C, and D in the plane acoustic waveguide, are the position coordinates of the first, second, third and fourth hydrophones in the planar acoustic waveguide, are the wave numbers of the liquid columns on both sides of the test material; Step 5. After separating the sound waves, calculate the sound pressure and vibration velocity on the lower and upper surfaces of the test material according to the following formula: （2） In the above formula, Indicates the sound pressure on the lower surface of the test material, Indicates the vibration velocity of the lower surface of the test material, Indicates the location of the lower surface of the test material, Indicates the sound pressure on the upper surface of the test material, Indicates the vibration velocity of the upper surface of the test material, Indicates the position of the upper surface of the test material; Step 6: Treat the test material as a dual-input dual-output acoustic unit, where the input parameter is the sound pressure on the lower surface of the test material. and vibration speed , the output parameter is the sound pressure on the upper surface of the test material and vibration speed , taking the acoustic impedance matrix of the test material as the unknown quantity, two equations about the acoustic impedance matrix are obtained: （3） Where, is the material input impedance, defined as , is the transfer impedance of the material, defined as ; Step 7: Change the phase of the sound wave emitted by the second sound source so that it emits sound waves with the same frequency and opposite phase as the first sound source. Repeat steps 4 to 6 to obtain the other two equations about the acoustic impedance matrix: （4） Step 8. Combine equations (3) and (4) to obtain a solvable system of equations for the acoustic impedance matrix: （5） Get the acoustic impedance matrix of the test material (6) That is, the test of the acoustic impedance of the material at the end of changing the acoustic source impedance is completed.
2. The method for testing the acoustic impedance of a material with two-terminal sound sources according to claim 1, characterized in that: Sound sources are provided at both ends of the planar acoustic waveguide. The two sound sources can simultaneously emit plane acoustic waves of the same frequency with arbitrary phase difference. By changing the phase difference of the sound waves emitted by the two sound sources, the boundary impedance at the end of the planar acoustic waveguide can be changed, thereby realizing the test of the material input acoustic impedance and transmission acoustic impedance.
3. The method for testing the acoustic impedance of a material with two-terminal sound sources according to claim 1, wherein: The testing method can test the input acoustic impedance and transfer acoustic impedance of the material, and can also predict the transmission coefficient and reflection coefficient acoustic parameters of the tested material.