Device and method for measuring water sound tube with oblique incidence acoustic characteristics

Abstract

The invention discloses a device and a method for measuring a water sound tube with oblique incidence acoustic characteristics. The device comprises a sound tube body, an adapter tube, a transmitting transducer, a hydrophone, a tested sample, pressurizing equipment, numerical control equipment and a signal acquisition and processing system, during measurement, a three-way pipe or a straight-through pipe suite is selected to assemble a water sound pipe device according to oblique incidence measurement requirements, and acoustic performance measurement of a sample under different sound wave incidence angles and different hydrostatic pressures is realized by utilizing a distributed hydrophone and pressurizing equipment through a digital display control and signal acquisition and processing integrated system. And acoustic performance characterization quantities such as reflection coefficients, transmission coefficients, sound absorption coefficients and propagation characteristics of sound waves in different media under various working conditions are obtained based on the signal amplitude and the phase information. According to the invention, the multi-angle and multi-hydrostatic pressure working condition can be measured, the device has the characteristics of rich functions and flexible assembly, has the advantages of efficient and convenient measurement and control and accurate data, and can obtain rich acoustic performance by obtaining more reflection and transmission signals through the distributed hydrophone.

Description

Technical Field

[0001] This invention belongs to the field of underwater acoustic measurement technology, and specifically relates to a device and method for measuring the acoustic characteristics of an underwater acoustic tube with oblique incidence. Background Technology

[0002] Acoustic performance measurement is a crucial step in acoustic materials research and acoustic equipment development. Its core lies in accurately obtaining parameters such as the material's reflection coefficient, transmission coefficient, absorption coefficient, and the propagation characteristics of sound waves in different media. These parameters not only provide important data for the design and optimization of acoustic materials but also have wide applications in underwater acoustic equipment, marine engineering, and architectural acoustics.

[0003] Driven by the demands of complex engineering applications, the complexity of acoustic materials and their structures is gradually increasing, placing higher demands on the accuracy of acoustic material parameter acquisition and acoustic performance evaluation. Numerical simulation methods are insufficient to replace experimental measurements, often relying on experimental methods for data acquisition. Underwater acoustic tubes are one of the important devices for measuring the acoustic performance of underwater acoustic materials and have wide applications in the field of underwater acoustic measurement.

[0004] Traditional underwater acoustic tube measurement devices can only measure acoustic performance under perpendicular incidence conditions, failing to meet the requirements for measurement under oblique incidence conditions. The propagation characteristics of obliquely incident sound waves differ significantly from those of perpendicularly incident waves, especially in complex media or non-homogeneous materials, where the reflection, transmission, and absorption behaviors of obliquely incident sound waves are even more complex. Currently, oblique incidence performance can only be measured using finite-size plate samples in the free-field environment of an underwater acoustic tank. However, large-sample measurement conditions are demanding, and the measurement results are significantly affected by the directivity of the transmitting transducer and scattering from the plate edge.

[0005] Furthermore, in underwater acoustic equipment or marine engineering applications, the acoustic performance of materials often needs to be tested under different hydrostatic pressure conditions to simulate real-world application environments. Pressurization is an essential capability of underwater acoustic tubes. Currently, free-field measurements under pressurized conditions can only be performed in large pressure tanks, but the measurement conditions, costs, and operational difficulties are far greater than those of underwater acoustic tubes. The pressure range, measurement errors, and result stability are also relatively limited, resulting in a certain distance between this measurement method and practical applications, thus restricting the performance evaluation and optimization of underwater acoustic materials.

[0006] Patent CN202011397285.9 discloses "a method for measuring the oblique incidence emission characteristics of underwater acoustic materials using a pulse tube." However, this method, based on traditional pulse tube measurements, modifies the sample shape to place its plane obliquely within the tube and proposes a method for calculating acoustic coefficients. Other aspects of the tube structure and measurement process remain largely unchanged. While this method provides a useful reference for measuring oblique incidence acoustic performance, it does not consider transmission performance or pressurized environments.

[0007] Patent CN201711455921.7 discloses a "Measuring Device and Method for Measuring the Sound Absorption Coefficient and Sound Insulation of Materials with Oblique Incidence of Sound Waves," which proposes a three-way pipe fitting for measuring the sound absorption coefficient and sound insulation of oblique incidence. However, it is a sound tube for measuring acoustic materials in the air. The loudspeakers, sound tubes, and other equipment used in it are different from the transducers and hydrophones used in underwater sound tubes. The plastic material tube body and structural dimensions used in the air sound tube are also significantly different from those of steel underwater sound tubes. Furthermore, it does not consider the pressurized environment and only has the sound field of the incident and reflection sections, not the sound field of the transmission section. That is, it only considers the reflection and sound absorption performance and does not consider the transmission performance. Therefore, the measurement environment and factors to be considered in underwater sound tubes are much more complex.

[0008] Therefore, existing underwater acoustic material acoustic performance measurement technologies still have shortcomings in terms of oblique incidence sound wave measurement, hydrostatic pressure testing, and signal acquisition and processing. There is an urgent need for a convenient, low-cost, and accurate method for measuring the acoustic characteristics of samples under oblique incidence pressure.

[0009] This invention proposes a hydroacoustic tube device and method for measuring the acoustic properties of obliquely incident sound waves. It adopts a multi-segment detachable sound tube design, and the measurement of obliquely incident sound waves is achieved by adjusting the angle and length of the sound tube. A distributed hydrophone system is introduced to improve the measurement accuracy through multi-point signal acquisition. With the help of pressurization equipment, acoustic performance testing is simulated under different hydrostatic pressure conditions, providing a new solution for the development of acoustic measurement technology for underwater acoustic materials. Summary of the Invention

[0010] To overcome the shortcomings and gaps in the existing technology, this invention provides a hydroacoustic tube device and method for measuring the acoustic properties of oblique incidence. The device is assembled using a T-junction or straight tube kit according to the oblique incidence measurement requirements. Utilizing distributed hydrophones and pressurization equipment, and through an integrated digital display and control system for signal acquisition and processing, the acoustic performance of samples under different sound wave incident angles and hydrostatic pressures is measured. Based on signal amplitude and phase information, acoustic properties such as reflection coefficient, transmission coefficient, absorption coefficient, and sound wave propagation characteristics in different media are obtained under various operating conditions. The device features rich functionality, flexible assembly, and convenient measurement and operation.

[0011] The technical solution of the present invention is as follows:

[0012] A device for measuring the acoustic characteristics of an underwater acoustic tube under oblique incidence, characterized in that it includes:

[0013] The sound tube system consists of three sections: an incident tube, a reflector tube, and a transmission tube. Each section is detachably connected via an adapter. One end of the incident tube is equipped with a transmitting transducer, and the other end is connected to the reflector tube and the transmission tube via an adapter. Both the reflector tube and the transmission tube are equipped with sound-absorbing ends.

[0014] Hydrophones, with at least two installed on the walls of each of the incident tube, the reflecting tube, and the transmitting tube, are used to receive sound wave signals and acquire amplitude and phase information;

[0015] The pressurizing device simultaneously pressurizes the injection tube, reflection tube, and transmission tube through a water injection hole set on the transmission tube to simulate different hydrostatic pressure conditions.

[0016] Numerical control equipment is used to control the position and posture of the acoustic tube.

[0017] The signal acquisition and processing system is electrically connected to each hydrophone and is used for signal acquisition, processing and analysis.

[0018] Furthermore, the transfer tube includes:

[0019] A three-way tube kit for achieving measurements at different oblique incidences; or

[0020] A straight tube is used to achieve measurements with perpendicular incidence.

[0021] Each adapter tube is equipped with a positioning structure at its connection point with the incident tube, reflector tube, and transmission tube to ensure precise connection angles.

[0022] Furthermore, the acoustic tube system also has:

[0023] Vibration and noise reduction devices are installed at the contact points between the pipe body and the ground.

[0024] Drainage holes are installed on each pipe section to replace the water inside the pipe.

[0025] The sample fixing mechanism includes a watertight flat-head screw for fixing the sample to be tested from the outside of the tube wall.

[0026] Furthermore, the signal acquisition and processing system includes:

[0027] The acoustic tube configuration module is used to set the incident angle, tube diameter, and hydrophone position parameters;

[0028] The transmitting module controls the operating parameters of the transmitting transducer;

[0029] The acquisition module allows you to set signal acquisition parameters.

[0030] The signal processing and analysis module is used to calculate acoustic performance parameters;

[0031] The digital display module shows the measurement results in real time.

[0032] The present invention also provides a method for measuring the acoustic characteristics of an underwater acoustic tube under oblique incidence, using the above-mentioned device, characterized by comprising the following steps:

[0033] Choose either a T-pipe or a straight pipe as the adapter pipe according to the measurement requirements;

[0034] Connect the incident tube, reflector tube, and transmission tube using an adapter tube;

[0035] The sample to be tested is installed in the sample fixing position inside the transmission tube, and the sample is fixed from the outside of the tube wall using a watertight flat-head screw.

[0036] Deionized water is injected through the water inlet, and the defoaming program is activated to eliminate air bubbles in the water.

[0037] The pressure is gradually increased to the set value using pressurization equipment, and the pressure consistency of each pipe section is monitored in real time.

[0038] It emits sound waves and collects signals from each hydrophone, then calculates acoustic parameters through a signal processing and analysis module.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] (1) Through the three-section detachable underwater acoustic tube device, combined with the flexible design of the three-way pipe and the straight pipe, the multi-angle adjustment of the oblique incident angle of the sound wave is realized, which can accurately measure the acoustic performance under different incident angles and expand the applicability of the device.

[0041] (2) Through a high-sensitivity hydrophone and a real-time signal processing system, it is possible to comprehensively obtain the reflection coefficient, transmission coefficient, sound absorption coefficient and the propagation characteristics of sound waves in different media, providing rich data support for the research of acoustic materials;

[0042] (3) The sound tube adopts an inverted design, which not only simplifies the sample installation and fixing process, but also ensures the stability of the sample under pressure conditions through watertight flat-head screws, thus improving the convenience and safety of operation.

[0043] (4) The pressure-resistant design of the device of the present invention enables it to perform acoustic performance measurements under different hydrostatic pressure conditions. Through the coordinated work of the pressurizing equipment and the digital display equipment, the pressure of each pipe section is kept consistent, and the experimental safety is ensured by the pressure alarm device.

[0044] (5) An acoustic performance signal processing method is proposed, including algorithms such as filtering, Fourier transform and phase estimation, which can process and analyze the acquired signals in real time and provide high-precision acoustic performance parameter calculation results.

[0045] (6) The device integrates numerical control and digital display functions, realizing integrated operation of data acquisition, processing and display. It can monitor the experimental process in real time and export data, which greatly improves the testing efficiency and data processing convenience. Attached Figure Description

[0046] Figure 1 A schematic diagram of a hydroacoustic tube device for measuring oblique incident acoustic characteristics provided in an embodiment of the present invention;

[0047] Figure 2 The following are schematic diagrams of tee adapters with different incident angles provided in the embodiments of the present invention: (a) incident angle 30°, (b) incident angle 45°, (c) incident angle 60°.

[0048] Figure 3 This is a schematic diagram of a pressurization device provided in an embodiment of the present invention;

[0049] Figure 4 The flowchart of the signal processing method provided in the embodiment of the present invention is shown in (a) oblique incidence model and (b) vertical incidence mode.

[0050] Figure 5 This is a schematic diagram of a signal acquisition and processing system provided in an embodiment of the present invention, (a) a signal acquisition and processing module, and (b) a digital display module;

[0051] Figure 6 The numerical calculation results of the sound field distribution inside the sound tube provided in the embodiments of the present invention are as follows: (a) oblique incidence at 30°, (b) oblique incidence at 45°, and (c) oblique incidence at 60°.

[0052] Figure 7 The numerical calculation results of the acoustic performance of the underwater acoustic tube provided in the embodiments of the present invention are: (a) sound pressure reflection coefficient, (b) sound pressure transmission coefficient.

[0053] The diagram is labeled as follows: 1. Acoustic tube body; 2. Adaptor tube; 3. Transmitter transducer; 4. Hydrophone; 5. Sample under test; 6. Pressurization equipment; 7. CNC equipment; 8. Signal acquisition and processing system; 9. Inlet tube; 10. Reflector tube; 11. Transmitter tube; 12. Watertight connector; 13. Sound-absorbing end; 14. Sealing ring; 15. Watertight end cap; 16. Water inlet hole; 17. Vibration reduction and noise reduction device; 18. Acoustic tube configuration module; 19. Transmitter module; 20. Acquisition module; 21. Signal processing and analysis module; 22. Digital display module; 23. Filter water tank; 24. Defoaming water tank. Detailed Implementation

[0054] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] Please see Figure 1This invention relates to a hydroacoustic tube device for measuring the acoustic properties of oblique incidence. It is a three-section detachable hydroacoustic tube with pressurization capabilities. It can be used to measure the acoustic properties of samples under different incident angles of sound waves and different hydrostatic pressures, such as reflection coefficient, transmission coefficient, sound absorption coefficient, and propagation characteristics of sound waves in different media.

[0056] The structure and working principle of the device are as follows:

[0057] The acoustic tube system consists of a three-section tube body 1, made of metal with a smooth inner wall to reduce sound wave scattering and loss. The length is designed according to the measurement frequency and testing requirements, typically an integer multiple of the sound wave wavelength, to form standing waves or meet specific measurement conditions. The tube thickness should be able to withstand the maximum hydrostatic pressure while ensuring no other unnecessary acoustic modes are introduced that could affect measurement accuracy. The tube diameter is selected at 60mm to match the measurement frequency band of 1kHz to 5kHz, using a transmission tube as a reference. This is consistent with the requirements for the diameter and measurement frequency band of standard underwater acoustic tubes, typically with a diameter smaller than the sound wave wavelength to avoid interference from higher-order acoustic modes. The acoustic tube body 1 includes an incident tube 9, a reflecting tube 10, and a transmission tube 11, connected by an adapter tube 2. The cable penetration points on the tube wall require waterproof joints for sealing. The diameters of the incident tube 9 and the reflecting tube 10 are the same, but can be different from the diameter of the transmission tube 11. The diameters of the incident tube 9 and the reflecting tube 10 can be the product of the diameter of the transmission tube 11 and the cosine of the incident angle, so as to ensure that the incident and reflected sound waves on the entire plane of the sample under test are in a mirror reflection relationship. Here, the incident angles are selected as 30°, 45° and 60° respectively.

[0058] The incident tube 9 is responsible for emitting sound waves and receiving corresponding signals. It has a built-in underwater acoustic transducer 3, two hydrophones 4, a watertight connector 12, a sound-absorbing end 13, a sealing ring 14, and a watertight end cap 15.

[0059] The reflector tube 10 is responsible for receiving reflected sound wave signals and has two built-in hydrophones 4, a watertight connector 12, a sound-absorbing end 13, a sealing ring 14, and a watertight end cap 15.

[0060] The transmission tube 11 is responsible for receiving transmitted sound wave signals and has a pressurization function. It is equipped with two hydrophones 4, a watertight connector 12, a water injection hole 16, a sound-absorbing end 13, a sealing ring 14, and a watertight end cap 15.

[0061] The ends of the reflector tube 10 and the transmitter tube 11 are sound-absorbing ends 13, which are used to absorb the sound waves at the ends and avoid interference with the measurement results from the end cap reflection.

[0062] The adapter tube 2 consists of either a tee tube or a straight tube with different angles. When a tee tube is used, the incident tube and the reflecting tube are at a certain angle, forming a three-way junction together with the transmission tube. When a straight tube is used, the incident tube serves both incident and reflection purposes and is connected in a straight line to the transmission tube. These can be used to measure acoustic performance at different oblique and perpendicular incident angles. The tee tube is a series of tee tube kits with different fixed angles. Tee tubes with angles of 60°, 90°, and 120° are selected according to the oblique incident angle measurement requirements. Please refer to the schematic diagram of the tee tube structure. Figure 2 Both the T-joint and straight-through pipes have watertight inlets with male and female connectors. They are watertightly connected to the incident pipe 9, reflector pipe 10, and transmission pipe 11 via a sealing ring 14, screw holes, and clamps to ensure watertightness under pressure. The sample to be tested is installed inside the transmission pipe end of both the T-joint and straight-through pipes, its shape conforming to the pipe wall to ensure no gaps between the sample and the pipe wall and to prevent sound wave leakage. It is circumferentially fixed by watertight flat-head screws screwed in from the outside of the pipe wall.

[0063] The tested sample 5 is cylindrical with a thickness of 0.05 μm. The end faces are ensured to be flat, and the cylindrical surface is uniformly fitted to the tube wall. The sample material is rubber with a density of 1100 kg / m³. 3 Young's modulus is 1.4E8 Pa, and Poisson's ratio is 0.49.

[0064] Transmitting transducer 3 is installed at one end of the incident tube to generate sound waves of a specific frequency and intensity. A suitable transmitting transducer is selected according to the signal transmission requirements. Transmitting transducer 3 fits into the wall of the incident tube 9 to ensure water tightness and prevent sound wave leakage.

[0065] Hydrophone 4 should have good sensitivity in the measurement frequency band from 1kHz to 5kHz. When measuring oblique incidence performance, the hydrophones in the incident tube 9, the reflecting tube 10, and the transmitting tube 11 respectively receive the emitted, reflected, and transmitted sound wave signals. When measuring perpendicular incidence performance, the incident tube has both incident and reflection conditions, and the hydrophone 4 in the incident tube receives the emitted and reflected sound wave signals. Two hydrophones 4 are installed on the wall of each section of the tube, and the distance between them is determined to be 0.2m according to the signal frequency to obtain the sound wave amplitude and phase information. Thus, the reflection, transmission, and absorption performance, as well as the propagation characteristics such as insertion loss, equivalent sound velocity, and phase change are obtained according to the signal processing method. The cable penetration part of the tube wall needs to be sealed with a waterproof joint.

[0066] The connection end between the sound tube body 1 and the ground is designed with a vibration reduction and noise reduction device 17 to isolate the interference caused by ground vibration;

[0067] CNC equipment 7 is used for digital control of the position and posture of each section of the pipe;

[0068] The pressurizing device 6 synchronously pressurizes the water through the pressurizing ports of the injection pipe 9, reflection pipe 10, and transmission pipe 11, and monitors the pressure in real time through a digital display device to ensure that the water pressure in each section remains consistent at all times. It includes a pressure alarm device. Please refer to the schematic diagram of the pressurizing device. Figure 3 ;

[0069] The signal acquisition and processing system 8 includes a sound tube configuration module 18, a transmission module 19, an acquisition module 20, a signal processing and analysis module 21, and a digital display module 22. For the specific display interface of the system, please refer to [link / reference needed]. Figure 5 ;

[0070] The sound tube configuration module is used to set parameters such as the incident angle, tube diameter, frequency band, hydrophone position, and pressure value of the sound tube;

[0071] The transmitting module 19 is used to set parameters such as the sampling rate, signal frequency, period, and amplitude of the transmitted signal;

[0072] The acquisition module 20 is used to set parameters such as sampling rate and number of acquisition cycles;

[0073] The signal processing and analysis module 21 and the digital display module 22, by inputting parameters such as the position of the hydrophone and combining them with the transmitted signal design, perform filtering, Fourier transform, envelope energy, and phase estimation on the acquired signal to obtain propagation characteristics such as reflection, transmission, and absorption performance, insertion loss, equivalent sound velocity, and phase change. For the measurement results in this embodiment, please refer to [link to relevant documentation]. Figure 7 .

[0074] The application method of the above-mentioned underwater acoustic tube device for measuring oblique incident acoustic characteristics includes the following steps:

[0075] (1) Design and manufacture the sample 5 to be measured according to the measurement requirements. Its geometry is usually cylindrical, and the end face must be flat. The cylindrical surface and the tube wall should fit evenly to ensure that there is no leakage when the sound wave propagates.

[0076] (2) Select the appropriate transmitting transducer model according to the measurement frequency and sound wave intensity requirements, install the transmitting transducer 3 at one end of the incident tube 9, ensure that it fits the tube wall to avoid sound wave leakage, check the contact surface between the transducer 3 and the tube wall to ensure water tightness, and use sealant or sealing ring to seal if necessary.

[0077] (3) Select a hydrophone 4 with high sensitivity in the measurement frequency band, and install two hydrophones 4 on the walls of the incident tube 9, the reflector tube 10 and the transmission tube 11. The positions are determined according to the measurement frequency and the sound wave propagation characteristics to obtain sound wave amplitude and phase information; check the hydrophone to receive the sound wave signal; check the connection between the hydrophone and the tube wall to ensure water tightness and use a waterproof joint to seal it.

[0078] (4) Install the sample 5 to be tested inside the transmission section of the adapter pipe 2 to ensure that there is no gap between the sample and the pipe wall to avoid sound leakage; use a watertight flat-head screw to screw in from the outside of the pipe wall to fix the sample in a circular manner to ensure that the sample will not be displaced under pressure; according to the measurement requirements, select a tee pipe or straight pipe with a suitable included angle and adjust the angle of the sample to measure the acoustic performance of different oblique incident angles.

[0079] (5) Use the filter tank 23 to remove impurities from the water, or inject deionized water or distilled water into the sound tube; use the defoaming tank 24 to remove air bubbles from the water. The defoaming tank can be used by letting the water stand still, and if necessary, adjust the water temperature to reduce the generation of air bubbles, so as to ensure that there are no air bubbles in the water and avoid the interference of air bubbles on the propagation of sound waves.

[0080] (6) Confirm that the positions of the transmitting transducer 3, hydrophone 4 and the sample 5 are correct, and make adjustments if necessary; check the installation positions of each pipe section connection, transducer, hydrophone and sample to ensure there are no leaks;

[0081] (7) Check the operating status of the pressurizing equipment 6, the CNC equipment 7 and the signal acquisition and processing system 8 to ensure that the equipment is safe and reliable;

[0082] (8) Simultaneously pressurize the incident tube 9, the reflector tube 10 and the transmission tube 11, and gradually increase the static water pressure to the set value; use the CNC equipment 7 to monitor the pressure of each pipe section in real time to ensure that the water pressure of each section is consistent; observe the pressure alarm device to ensure that the pressure is within the safe range and avoid overpressure damage to the equipment;

[0083] (9) Measure the background noise level inside the tube without emitting sound waves; assess the impact of background noise on the measurement results; if the noise level is too high, measures should be taken to reduce the noise.

[0084] (10) The frequency, period, pulse width and amplitude of the transmitted signal are set by the transmitting module 19 to transmit sound waves of a specific frequency and intensity; the incident, reflected and transmitted sound wave signals are received by the hydrophone 4 respectively, and sound pressure data is collected; the transmitted signal and the signal waveforms of each hydrophone channel are observed in the digital display module 22 to ensure signal quality;

[0085] (11) The signal is processed by the signal processing and analysis module 21, which performs filtering, Fourier transform, envelope energy and phase estimation on the collected signal. Based on the processed data, acoustic performance parameters such as reflection coefficient, transmission coefficient and sound absorption coefficient are calculated. The propagation characteristics of sound waves in different media, such as insertion loss, equivalent sound velocity and phase change, are analyzed. The processing results are exported as data files to facilitate subsequent analysis and report writing.

[0086] Among them, 1) the method for calculating the reflection coefficient is as follows:

[0087]

[0088] Where R is the complex reflection coefficient, and |R| is the magnitude of the reflection coefficient. For the phase of the reflection coefficient, He jθ =p1 / p2 is the transfer function between the two hydrophones, l1 is the distance between the hydrophone closer to the test piece and the test piece, and s1 is the distance between the two test hydrophones.

[0089] 2) The method for calculating the transmission coefficient is as follows:

[0090]

[0091] Among them, t p Let T be the complex transmittance coefficient, and T be the modulus of the transmittance coefficient. L1 represents the phase of the transmission coefficient, L2 represents the distance between the hydrophone closer to the test piece inside the incident reflection tube and the test piece, and L3 represents the distance between the hydrophone closer to the test piece inside the transmission tube and the test piece. S1 and S2 represent the distances between the two receiving hydrophones in the incident reflection tube and the transmission tube, respectively.

[0092] 3) The method for calculating the sound absorption coefficient is as follows:

[0093] α = 1 - |R| 2 -|t p | 2 (3)

[0094] Where α is the sound absorption coefficient, |R| is the modulus of the reflection coefficient, and |t p | represents the modulus of the transmission coefficient.

[0095] 4) The method for calculating insertion loss is as follows:

[0096]

[0097] Where IL is the insertion loss and T is the sound pressure transmission coefficient.

[0098] 5) The equivalent sound velocity is calculated as follows: the surface impedance Z at the incident end of the test piece is obtained from the complex reflection coefficient R. in ,Right now

[0099]

[0100] Where ρ0 and c0 are the density of water and the speed of sound, respectively. For a waveguide propagating in the thickness direction, the surface impedance is used as the waveguide boundary condition. The matrix equation for the equivalent P-wave number is constructed using the spectral method, and the equivalent P-wave number is obtained by solving it, thus yielding the equivalent wave velocity.

[0101] 6) The phase change calculation method is as follows:

[0102] Δφ=arg[FFT(p i )]-arg[FFT(p j (6)

[0103] Where Δφ is the phase difference between the two hydrophones, p i and p j The two hydrophones, numbered i and j, represent the time-domain sound pressure signals measured by the two hydrophones. FFT represents the Fourier transform of the acquired time-domain sound pressure signals, and arg represents the phase calculation.

[0104] (12) Gradually reduce the hydrostatic pressure inside the tube to ensure safe operation; loosen the fixing screws and carefully disassemble the sample to avoid damaging the sample or the tube wall; clean the inside of the acoustic tube to remove residual moisture and impurities to ensure the cleanliness of the equipment and its reliability for the next use.

[0105] Experiments show that the underwater acoustic tube device for measuring oblique incident acoustic properties of the present invention has the following advantages: (1) Through the three-section detachable underwater acoustic tube device, combined with the flexible design of the three-way pipe and the straight pipe, the multi-angle adjustment of the oblique incident angle of the sound wave is realized, which can accurately measure the acoustic performance under different incident angles and expand the applicability of the device. (2) Through the high-sensitivity hydrophone and the real-time signal processing system, the reflection coefficient, transmission coefficient, sound absorption coefficient and the propagation characteristics of sound waves in different media can be fully obtained, providing rich data support for the research of acoustic materials. (3) The acoustic tube adopts an inverted design, which not only simplifies the sample installation and fixing process, but also ensures the stability of the sample under pressure conditions through watertight flat-head screws, improving the convenience and safety of operation. (4) The pressure-resistant design of the device of the present invention enables it to measure acoustic performance under different hydrostatic pressure conditions. Through the coordinated work of the pressurization equipment and the digital display equipment, the pressure of each pipe section is consistent, and the experimental safety is guaranteed by the pressure alarm device. (5) A real-time acoustic performance signal processing method is proposed, including algorithms such as filtering, Fourier transform, and phase estimation, which can process and analyze the acquired signals in real time and provide high-precision acoustic performance parameter calculation results. (6) The device integrates numerical control and digital display functions, realizing integrated operation of data acquisition, processing and display, and can monitor the experimental process and export data in real time, which greatly improves experimental efficiency and data processing convenience.

[0106] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for measuring the acoustic characteristics of a hydrophone under oblique incidence, characterized in that, include: The sound tube system consists of three sections: an incident tube, a reflector tube, and a transmission tube. Each section is detachably connected via a connector (2). One end of the incident tube is equipped with a transmitting transducer, and the other end is connected to the reflector tube (10) and the transmission tube (11) via the connector (2). Both the reflector tube (10) and the transmission tube (11) are equipped with sound-absorbing ends (13). Hydrophone (4), at least two of which are installed on the walls of the incident tube (9), the reflector tube (10) and the transmission tube (11), are used to receive sound wave signals and obtain amplitude and phase information; The pressurizing device (6) pressurizes the incident tube, the reflector tube and the transmission tube simultaneously through the water injection hole (16) set on the transmission tube (11) to simulate different hydrostatic pressure conditions; Numerical control equipment (7) is used to control the position and posture of the acoustic tube body (1); The signal acquisition and processing system (8) is electrically connected to each hydrophone (4) and is used for signal acquisition, processing and analysis.

2. The underwater acoustic tube measuring device for oblique incidence acoustic characteristics according to claim 1, characterized in that, The transfer tube (2) includes: A three-way tube kit for achieving measurements at different oblique incidences; or A straight tube is used to achieve measurements with perpendicular incidence. Each adapter tube (2) is equipped with a positioning structure at the connection point with the incident tube (9), the reflector tube (10), and the transmission tube (11) to ensure accurate connection angle.

3. The underwater acoustic tube measuring device for oblique incidence acoustic characteristics according to claim 1, characterized in that, The acoustic tube system also has: Vibration reduction and noise reduction device (17) is installed at the contact point between the pipe body and the ground; Drainage holes are installed on each pipe section to replace the water inside the pipe. The sample fixing mechanism includes a watertight flat-head screw for fixing the sample to be tested from the outside of the tube wall (5).

4. The underwater acoustic tube measuring device for oblique incidence acoustic characteristics according to claim 1, characterized in that, The signal acquisition and processing system (8) includes: The acoustic tube configuration module (18) is used to set the incident angle, tube diameter, and hydrophone position parameters; The transmitting module (19) controls the operating parameters of the transmitting transducer (3); Acquisition module (20), setting signal acquisition parameters; The signal processing and analysis module (21) is used to calculate acoustic performance parameters; The digital display module (22) displays the measurement results in real time.

5. A method for measuring the acoustic characteristics of an underwater acoustic tube under oblique incidence, using the apparatus described in any one of claims 1-4, characterized in that, The following steps are involved: Choose either a T-pipe or a straight pipe as the adapter pipe according to the measurement requirements (2); Connect the incident tube (9), the reflector tube (10) and the transmission tube (11) through the adapter tube (2); The sample to be tested (5) is installed in the sample fixing position inside the transmission tube (11), and the sample is fixed from the outside of the tube wall using a watertight flat-head screw; Deionized water is injected through the water injection hole (16), and the defoaming program is started to eliminate air bubbles in the water; The pressure is gradually increased to the set value using the pressurizing device (6), and the pressure consistency of each pipe section is monitored in real time. The sound waves are emitted and the signals from each hydrophone (4) are collected. The acoustic parameters are calculated by the signal processing and analysis module (21).

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