A vector hydrophone horizontal channel sensitivity calibration device, system and method

Abstract

This invention discloses a vector hydrophone horizontal channel sensitivity calibration device, system, and method, belonging to the field of underwater acoustic metrology and testing. The calibration device includes a front acoustic tube, a rear acoustic tube, and an end cap, sequentially sealed and connected to form a horizontal cylindrical closed acoustic tube. The front acoustic tube is fixed with an exciter and a standard hydrophone. The rear acoustic tube has multiple sets of screw holes for suspending the vector hydrophone under test. The inner side of the end cap is covered with an acoustic reflection layer. The calibration system consists of the above device, an electronic switch, a programmable filter, a lock-in amplifier, a power amplifier, and a host computer. This invention also provides a corresponding calibration method, achieving accurate calibration of the horizontal channel sound pressure sensitivity of the vector hydrophone under test based on the acoustic transmission line comparison method. This invention can directly calibrate the horizontal channel of a vector hydrophone in a real underwater environment, filling the technical gap in vector hydrophone horizontal channel sensitivity calibration, and has advantages such as high calibration accuracy, high degree of systematization and automation, and flexible operation.

Description

Technical Field

[0001] This invention relates to the field of underwater acoustic metrology and testing technology, and in particular to a vector hydrophone horizontal channel sensitivity calibration device, system, and method. Background Technology

[0002] A vector hydrophone is a multi-channel acoustic sensor capable of simultaneously measuring the scalar sound pressure and vector velocity (or acceleration) of particles in a sound field. It consists of three orthogonal vector channels: X, Y, and Z. Through the synchronous reception and processing of real-time acoustic signals from these three channels, the vector hydrophone can achieve applications such as underwater target location estimation, positioning, and tracking, and has been widely used in various fields of underwater acoustic engineering. With the increasing demand for vector hydrophones, accurate calibration of their sensitivity has become a crucial factor in ensuring the performance of underwater detection systems.

[0003] Currently, the sensitivity calibration of vector hydrophones is mainly accomplished using the standing wave tube comparison method. A standing wave tube is an upward-opening cylindrical cavity excited by a planar piston-type exciter at its bottom, generating a plane wave rising from below. When the plane wave propagates to the water surface, most of its energy is absorbed by the gas-liquid boundary (where the sound pressure is approximately zero), forming a stable standing wave field within the tube. Based on the acoustic transmission line equation, the sensitivity of the vertical channel (Z-channel) of the hydrophone under test can be calculated by measuring the installation depth of the test hydrophone and a standard hydrophone using a comparison method. This method can achieve automatic calibration of the sensitivity and directionality of vector hydrophones within the frequency range of 20Hz to 2kHz.

[0004] However, the standing wave tube comparison method has significant limitations in practical applications. Vector hydrophones must maintain a vertically suspended posture during operation, and their horizontal channels (X and Y channels) can only receive sound pressure signals propagating in the horizontal direction, unable to respond to plane waves incident in the vertical direction. Therefore, the traditional standing wave tube comparison method can only calibrate the sensitivity of the vertical channel Z of the vector hydrophone, and cannot effectively calibrate the horizontal channels X and Y.

[0005] To compensate for this deficiency, the current main approach is to use a simulated displacement method based on a resonant small-displacement synchronous system. This method uses a standard accelerometer to convert the vibration velocity and sound pressure of the vector hydrophone's test channel, indirectly achieving calibration of the horizontal channel X and Y. However, this method can only be performed in air, making it a simulated calibration method that cannot be used in real underwater environments. Besides this method, there are currently no other effective ways to solve the calibration problem of the horizontal channel of a vector hydrophone. Furthermore, with the advent of low-frequency, large-scale vector hydrophones, conventional standing wave tubes are also insufficient to meet calibration requirements due to size limitations.

[0006] In summary, existing vector hydrophone calibration techniques have the following shortcomings: (1) the standing wave tube comparison method can only calibrate the vertical channel Z, and cannot calibrate the horizontal channels X and Y; (2) the simulation calibration method for the horizontal channel is divorced from the actual underwater working environment, and the calibration results lack reliability; (3) there is a lack of a systematic device and method for directly calibrating the horizontal channel of a vector hydrophone in a real underwater environment. Therefore, it is urgent to design an effective vector hydrophone horizontal channel sensitivity calibration system and method to meet the growing production, metrology and inspection needs. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a vector hydrophone horizontal channel sensitivity calibration device, system, and method, aiming to directly calibrate the horizontal channel of the vector hydrophone in a real underwater environment and improve the reliability of the calibration results.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows: A vector hydrophone horizontal channel sensitivity calibration device, comprising: The device comprises a front acoustic tube, a rear acoustic tube, and an end cap, which are sequentially and sealed together to form a horizontal cylindrical closed acoustic tube. A flange is located at the rear end of the front acoustic tube, with evenly spaced bolt holes and a sealing groove on its end face for installing a rubber sealing ring. The front acoustic tube and the rear acoustic tube are sealed and fixedly connected through the flange, bolts, and rubber sealing ring. The end cap, located at the very end of the entire device, is a circular disc structure. It is bolted to the rear end of the rear acoustic tube via evenly spaced bolt holes on its side, and a rubber sealing ring is provided on the contact surface for sealing. The front end of the acoustic tube is fixed with an exciter to generate a plane wave that propagates in the horizontal direction; a standard hydrophone is fixed at the top to collect standard hydrophone signals. The inner wall of the rear acoustic tube is provided with multiple sets of screw holes along the axial direction. Each set of screw holes is used to suspend and fix the vector hydrophone under test by means of retaining screws and rubber strips, and the horizontal channel of the vector hydrophone under test is aligned with the axial direction of the closed acoustic tube. Each set of screw holes includes four screw holes, which are located at the upper, lower, front, and rear positions on the inner wall of the rear acoustic tube at the same cross section along the axial direction, and are evenly distributed. When calibrating the horizontal channel X of the vector hydrophone under test, the rubber strips on both sides of the tube wall are fixedly connected to the two retaining rings of the horizontal channel Y. When calibrating the horizontal channel Y, the rubber strips on both sides of the tube wall are fixedly connected to the two retaining rings of the horizontal channel X. The rear acoustic tube is equipped with a watertight plug for connecting the signal line of the vector hydrophone under test; a liquid column tube is provided on the upper rear side of the rear acoustic tube, and an inlet and outlet water valve is provided on the lower rear side. The inner surface of the end cap is covered with an acoustic reflective layer to form an absolutely hard boundary.

[0009] A vector hydrophone horizontal channel sensitivity calibration system, comprising: The vector hydrophone horizontal channel sensitivity calibration device as described above; An electronic switch is connected to the standard hydrophone and the vector hydrophone under test, respectively, to switch the signal feedback channel; A programmable filter, connected to the electronic switch, is used to filter the returned acoustic signal; A lock-in amplifier, whose signal output terminal is connected to the exciter via a power amplifier, and whose receiving terminal is connected to the programmable filter, is used to emit an acoustic signal and process the received acoustic signal. A power amplifier is connected between the lock-in amplifier and the exciter to amplify the acoustic signal emitted by the lock-in amplifier before inputting it to the exciter. The host computer is connected to the lock-in amplifier, the programmable filter, and the electronic switch, respectively, and is used to control the working status of each device and read the output data of the lock-in amplifier.

[0010] In the above scheme, the acoustic signal emitted by the lock-in amplifier is amplified by the power amplifier and then input to the exciter. The exciter generates a plane wave that propagates along the horizontal axis in the horizontal cylindrical closed acoustic tube. The acoustic signals collected by the standard hydrophone and the vector hydrophone under test are switched by the electronic switch and then sequentially input to the programmable filter, and then processed by the lock-in amplifier. The processing result is then sent back to the host computer.

[0011] A method for calibrating the horizontal channel sensitivity of a vector hydrophone, employing the vector hydrophone horizontal channel sensitivity calibration system described above, includes the following steps: S1: Align the horizontal channel of the vector hydrophone under test with the axial direction of the sealed acoustic tube, suspend and fix the vector hydrophone under test in the rear acoustic tube using buckle screws and rubber strips, and connect the output end of the vector hydrophone under test to the watertight plug. S2: Seal and fix the front acoustic tube, rear acoustic tube and end cap in sequence to form a closed acoustic tube; S3: Add test liquid into the closed acoustic tube through the inlet and outlet water valves until the liquid level in the liquid column tube is stable and no bubbles emerge, then close the inlet and outlet water valves; S4: The host computer controls the lock-in amplifier to emit an acoustic signal, which, after being amplified by the power amplifier, drives the exciter to generate a plane wave propagating along the horizontal axis in the closed acoustic tube; the effective value of the output voltage of the horizontal channel of the vector hydrophone under test is collected by switching via an electronic switch. and the effective value of the output voltage of a standard hydrophone The acoustic pressure sensitivity of the horizontal channel of the vector hydrophone under test is calculated according to the following formula. : ; in, The sensitivity of a standard hydrophone at the measurement frequency. To measure the wave number at a given frequency, The distance between the vector hydrophone to be measured and the acoustic reflector layer. This is the distance between the standard hydrophone and the acoustic reflector layer. S5: After calibration, open the inlet and outlet water valves to drain the test liquid, adjust the other horizontal channels of the vector hydrophone under test to be in the same direction as the axis, and repeat steps S1 to S4, or remove the vector hydrophone under test.

[0012] In the above scheme, in step S1, a set of screw holes with axial positions are selected according to the calibration requirements. Four retaining screws are screwed into the corresponding screw holes and tightened. Each retaining screw uses a rubber strip, one end of which is fixed to the retaining screw and the other end is fixed to the retaining hole on the surface of the vector hydrophone to be tested.

[0013] In the above scheme, in step S4, a horizontal coordinate system is established with the position of the acoustic reflection layer of the end cap as the origin, and the direction is towards the exciter end; the acoustic reflection layer is an absolutely hard boundary, the vibration velocity is zero and the sound pressure is at its maximum value at the absolutely hard boundary, and the sound pressure and vibration velocity at any position in the closed acoustic tube satisfy the acoustic transmission line equation.

[0014] In the above scheme, the horizontal channels of the vector hydrophone under test include mutually orthogonal X channels and Y channels. The other horizontal channels mentioned in step S5 are another horizontal channel orthogonal to the current calibration channel. By adjusting the suspension direction of the vector hydrophone under test, the other horizontal channel is aligned with the axis of the closed acoustic tube, so as to complete the sensitivity calibration of the X channel and Y channel in sequence.

[0015] Through the above technical solutions, the vector hydrophone horizontal channel sensitivity calibration device, system, and method provided by the present invention have the following beneficial effects: (i) Direct calibration of the horizontal channel of the vector hydrophone in a real underwater environment was achieved. This invention employs a horizontal cylindrical sealed acoustic tube. By filling the tube with water and exciting plane waves propagating along the horizontal axis, and combining this with an acoustic reflection layer on the inner side of the end cap to construct an absolutely hard boundary, a stable horizontal standing wave field is formed. This allows the horizontal channels (X and Y channels) of the vector hydrophone to directly receive the horizontally propagating sound pressure signal. Compared to existing calibration methods that indirectly convert through simulated displacement in air, this invention can directly calibrate the horizontal channels in a real underwater environment. The calibration results are closer to the actual working state of the vector hydrophone, effectively improving the accuracy and reliability of the calibration results.

[0016] (ii) It fills the technical gap in the horizontal channel sensitivity calibration of vector hydrophones. Existing standing wave tube comparison methods, due to their vertically open structure, can only generate plane waves propagating in the vertical direction. Therefore, they can only calibrate the vertical channel Z of a vector hydrophone, and are powerless to calibrate the horizontal channels X and Y. This invention, by arranging the acoustic tube horizontally and adopting a closed structure, fundamentally changes the direction of sound wave propagation, and for the first time achieves direct calibration of the horizontal channel of a vector hydrophone in a standing wave tube system, filling a technological gap in this field.

[0017] (iii) High calibration accuracy and sufficient theoretical basis This invention establishes a one-dimensional acoustic transmission line waveguide model based on the acoustic transmission line equation. Using absolutely hard boundaries as boundary conditions, it derives a quantitative relationship between the sound pressure in the horizontal channel of a standard hydrophone and the hydrophone under test. During calibration, no approximate assumptions about the sound field distribution within the acoustic tube are required; only accurate measurements of the distances between the standard and the hydrophone under test relative to the acoustic reflection layer and their output voltages are needed to precisely calculate the sound pressure sensitivity of the channel under test. This method is theoretically rigorous, has clear physical meaning, and the calibration results have good traceability.

[0018] (iv) High degree of systematization and automation This invention integrates a sealed acoustic tube calibration device, exciter, standard hydrophone, electronic switch, programmable filter, lock-in amplifier, power amplifier, and host computer into a complete calibration system. The host computer software enables unified control and data acquisition of all devices. During calibration, the host computer automatically acquires voltage signals and calculates sensitivity based on the input measurement parameters, eliminating the need for manual intervention. This not only reduces human error but also significantly improves calibration efficiency.

[0019] (v) Flexible operation, suitable for sequential calibration of multiple channels. This invention features multiple sets of screw holes along the axial direction on the inner wall of the rear acoustic tube, allowing for the selection of different axial positions to suspend the vector hydrophone under test according to calibration needs, thus achieving calibration at different distances. Furthermore, the invention employs a suspension and fixing method using snap-on screws and rubber strips. Through the orthogonal snap-on layout of the horizontal channels X and Y, calibration of the X and Y channels can be completed sequentially simply by adjusting the suspension direction of the vector hydrophone under test, without the need to disassemble the device or replace the hydrophone, making operation convenient.

[0020] (vi) It has good prospects for industrial application. This invention can be widely applied to the production inspection, factory calibration, metrological verification, and performance evaluation of underwater acoustic detection systems of vector hydrophones. It is of great significance for improving the product quality of vector hydrophones and ensuring the reliability of underwater detection systems, and has broad market application prospects. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0022] Figure 1 This is a schematic diagram of a vector hydrophone horizontal channel sensitivity calibration device disclosed in an embodiment of the present invention; Figure 2 This is a schematic diagram of the installation method of the vector hydrophone under test; Figure 3 This is a schematic diagram of a vector hydrophone horizontal channel sensitivity calibration system disclosed in an embodiment of the present invention; Figure 4 This is a schematic diagram of the coordinate axes of the calibration system of the present invention.

[0023] In the diagram, 1. Front acoustic tube; 2. Rear acoustic tube; 3. End cap; 4. Exciter; 5. Standard hydrophone; 6. Vector hydrophone under test; 7. Buckle screw; 8. Screw hole; 9. Rubber strip; 10. Watertight plug; 11. Liquid column tube; 12. Rubber sealing ring; 13. Inlet and outlet water valves; 14. Sound reflection layer; 15. Bolt hole. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0025] This invention provides a vector hydrophone horizontal channel sensitivity calibration device, system, and method, with specific embodiments as follows: I. Vector Hydrophone Horizontal Channel Sensitivity Calibration Device (I) Overall Structure like Figure 1As shown, the vector hydrophone horizontal channel sensitivity calibration device has an overall horizontal cylindrical tubular structure, made of stainless steel. The device mainly consists of three parts: a front acoustic tube 1, a rear acoustic tube 2, and an end cap 3. The front acoustic tube 1, rear acoustic tube 2, and end cap 3 are arranged sequentially along the horizontal axis and are sealed and fixedly connected by flanges and bolts, together forming a horizontal cylindrical closed acoustic tube.

[0026] The horizontal arrangement of the device is one of the core structural features of this invention. Its purpose is to enable the plane wave generated in the sound tube to propagate in the horizontal direction, so that the horizontal channels (X channel and Y channel) of the vector hydrophone can directly receive the sound pressure signal from the horizontal direction. This is a key structural improvement that distinguishes it from the existing vertical standing wave tube comparison method.

[0027] The inner diameter and total length of the sealed acoustic tube are determined based on the calibration frequency range. In a preferred embodiment, the inner diameter of the acoustic tube is not less than the maximum external dimensions of the vector hydrophone 6 under test, to ensure that the hydrophone can suspend freely inside the tube without contacting the tube wall. The total length of the acoustic tube should ensure that at least one complete standing wave field distribution can be formed inside the acoustic tube at the lowest calibration frequency, and is generally designed according to the wavelength corresponding to the lower limit of the calibration frequency.

[0028] (ii) Front-end sound tube The front-end acoustic tube 1 is located at the very front of the entire device (i.e., the transmitting end), and is responsible for generating horizontally propagating plane waves and collecting signals from the standard hydrophone 5.

[0029] A vibrator 4 is fixedly mounted on the front end face of the front acoustic tube 1. The vibrator 4 is the driving source for generating sound waves. Its vibration is coupled into the test liquid inside the acoustic tube through the end structure of the front acoustic tube 1, exciting a plane wave that propagates along the horizontal axis from the end of the vibrator 4 towards the end cap 3. As a preferred embodiment, the vibrator 4 is an electric vibrator 4 or a piezoelectric vibrator 4, and the specific selection is determined according to the required calibration frequency range and sound pressure level requirements. The connection between the vibrator 4 and the front acoustic tube 1 is a rigid fixed connection to ensure that the vibration energy can be efficiently transferred to the inside of the acoustic tube.

[0030] A standard hydrophone 5 is fixedly mounted on the top of the front-end acoustic tube 1. The standard hydrophone 5 is a reference hydrophone that has been calibrated and has a known sensitivity value; its installation position is fixed in the axial direction of the acoustic tube. The signal output line of the standard hydrophone 5 is led out through a sealed interface at the top of the front-end acoustic tube 1 to the outside of the acoustic tube for connection to subsequent signal acquisition and processing equipment. The type of standard hydrophone 5 can be a piezoelectric hydrophone or other acoustic pressure hydrophones that meet metrological requirements, depending on the calibration frequency range.

[0031] A flange is provided at the rear end of the front acoustic tube 1. Bolt holes 15 are evenly distributed on the flange, and a sealing groove is provided on the end face of the flange for installing a rubber sealing ring 12. Through the cooperation of the flange, bolts and rubber sealing ring 12, the front acoustic tube 1 and the rear acoustic tube 2 are sealed and fixedly connected.

[0032] (III) Rear end sound tube The rear acoustic tube 2 is located in the middle of the device and is the receiving end of the entire device. It is responsible for fixing the vector hydrophone 6 under test and acquiring signals, as well as the liquid injection, drainage and venting functions of the acoustic tube.

[0033] Hydrophone suspension and fixing structure: Multiple sets of screw holes 8 are provided axially on the inner side of the tube wall of the rear acoustic tube 2. In a preferred embodiment, three sets of screw holes 8 are provided axially, located at different axial positions, for selecting different axial positions to suspend the vector hydrophone 6 under test, thereby achieving calibration at different distances to verify the consistency of calibration results.

[0034] like Figure 2 As shown, each group of screw holes 8 contains four screw holes 8, located at four positions (upper, lower, front, and rear) on the inner side of the tube wall at the same cross-section along the rear acoustic tube 2, evenly distributed (i.e., circumferentially spaced at 90° intervals). The four screw holes 8 penetrate the tube wall radially and are used to screw in the retaining screws 7. After being screwed in, the retaining screws 7 protrude from the inner surface of the tube wall. Each retaining screw 7 is connected to a rubber strip 9. One end of the rubber strip 9 is fixed to the retaining screw 7 by a knot, and the other end is used to connect to the retaining hole on the surface of the vector hydrophone 6 under test.

[0035] The surface of the vector hydrophone 6 under test is provided with fixing rings. The vector hydrophone has a spherical or near-spherical structure, with a fixing ring at the top and bottom (for vertical fixation), a fixing ring at each end of the horizontal channel X, and a fixing ring at each end of the horizontal channel Y. Since the horizontal channels X and Y are orthogonal to each other, the line connecting the two fixing rings corresponding to the horizontal channel X is also orthogonal to the line connecting the two fixing rings corresponding to the horizontal channel Y in the horizontal direction.

[0036] During suspension, different buckle connection methods are selected according to the horizontal channel to be calibrated: when calibrating horizontal channel X, the rubber strips 9 on both sides of the tube wall are fixedly connected to the two buckles of the horizontal channel Y of the vector hydrophone 6 under test; when calibrating horizontal channel Y, the rubber strips 9 on both sides of the tube wall are fixedly connected to the two buckles of the horizontal channel X of the vector hydrophone 6 under test. The upper and lower rubber strips 9 are fixedly connected to the buckles at the top and bottom of the vector hydrophone 6 under test, respectively. With this suspension method, the vector hydrophone 6 under test is stably suspended inside the acoustic tube, its horizontal channel under test is precisely aligned with the axis of the acoustic tube, and the hydrophone body does not contact the tube wall.

[0037] It should be noted that the core purpose of the above-mentioned fixing method is to ensure that the horizontal channel under test is aligned with the axial direction of the acoustic tube. Because the rubber strip 9 applies tension in a direction orthogonal to the horizontal channel, it can keep the hydrophone in a stable position in the horizontal plane, thereby ensuring that the horizontal channel under test is accurately pointed in the axial direction of the acoustic tube.

[0038] Signal extraction structure: A watertight plug 10 is installed on the wall of the rear acoustic tube 2. The watertight plug 10 is a sealed electrical connector that penetrates the tube wall. Its inner interface is located on the inner surface of the tube wall and is used to connect to the signal output connector of the vector hydrophone 6 under test; its outer interface is located on the outer surface of the tube wall and is used to connect to the signal acquisition device via a cable. The watertight plug 10 has a sealing structure at the penetration point of the tube wall to ensure that no leakage occurs when the acoustic tube is filled with test liquid.

[0039] Exhaust and injection structure: A liquid column tube 11 is provided on the upper rear side of the rear acoustic tube 2. The liquid column tube 11 is a vertically arranged transparent tube, with its lower end connected to the interior of the rear acoustic tube 2 and its upper end open to the atmosphere. The functions of the liquid column tube 11 are threefold: first, to expel air from the acoustic tube during water injection, preventing residual air bubbles from affecting the sound field distribution; second, to balance the air pressure inside and outside the acoustic tube after it is filled with liquid; and third, to monitor the water level inside the acoustic tube through the transparent tube wall, ensuring that the acoustic tube is completely filled with test liquid and that there is no residual air.

[0040] A water inlet / outlet valve 13 is provided on the lower rear side of the rear acoustic tube 2. The water inlet / outlet valve 13 is a valve that can be opened and closed. One end of it is connected to the inside of the rear acoustic tube 2, and the other end is connected to an external water source or drainage pipe for injecting water into the acoustic tube and draining water from the acoustic tube.

[0041] (iv) End cap End cap 3 is located at the very end of the entire device and is the termination point of the horizontally propagating plane wave inside the acoustic tube. End cap 3 has a circular disc-shaped structure and is bolted to the rear end of the acoustic tube 2 through evenly distributed bolt holes 15 on its side. A rubber sealing ring 12 is provided on the contact surface for sealing.

[0042] The inner surface of the end cap 3 is covered with an acoustic reflection layer 14. The acoustic reflection layer 14 is made of a rigid material with an acoustic impedance much greater than that of the test liquid, thus forming an absolutely hard boundary. At this absolutely hard boundary, the sound wave velocity is zero, the sound pressure reaches its maximum, and the incident wave undergoes total internal reflection. The acoustic reflection layer 14 is one of the key structures of this invention. Its function is to ensure that the plane wave inside the acoustic tube is completely reflected at this boundary, superimposed with the incident wave to form a stable standing wave field. This ensures that the sound field distribution inside the acoustic tube strictly satisfies the acoustic transmission line equation, providing an accurate theoretical basis for the comparison method calibration.

[0043] (v) Connection and sealing methods of each component The front acoustic tube 1 and the rear acoustic tube 2 are connected by flanges. Each of the two flanges has a flange at its rear end and a flange at its front end, with evenly distributed bolt holes 15 on each flange. During connection, the two flanges are butted together, aligning the bolt holes 15, and bolts are inserted and tightened evenly. A rubber sealing ring 12 is provided between the contact surfaces of the two flanges. The rubber sealing ring 12 is embedded in the sealing groove on the end face of the flange and undergoes elastic deformation under the tightening force of the bolts, achieving a watertight seal at the contact surfaces.

[0044] The end cap 3 is fixedly connected to the rear acoustic tube 2 by bolts. The rear side of the rear acoustic tube 2 and the side of the end cap 3 are provided with evenly distributed bolt holes 15. During connection, the end cap 3 is placed over the rear opening of the rear acoustic tube 2, aligning the bolt holes 15, and the bolts are inserted and tightened evenly. A rubber sealing ring 12 is provided between the contact surfaces of the end cap 3 and the rear acoustic tube 2 to achieve a watertight seal.

[0045] The above connection method ensures the water tightness of the entire sound tube in a sealed state. After sealing, the closed sound tube is only connected to the outside through the liquid column tube 11 at the upper rear side.

[0046] (vi) Preferred embodiments of the device structure As a preferred embodiment, the inner wall surface of the sound tube is precision machined, with an inner wall roughness of not less than Ra 1.6, in order to reduce the scattering and attenuation of sound waves at the tube wall and ensure the propagation quality of plane waves.

[0047] As a preferred embodiment, the acoustic reflector layer 14 is made of stainless steel or hard alloy material, and its surface is mirror polished to maximize the acoustic reflection coefficient and make it close to the ideal absolute hard boundary.

[0048] As a preferred embodiment, each rubber sealing ring 12 is made of water-resistant, oil-resistant, and aging-resistant nitrile rubber or fluororubber. The cross-sectional shape of the sealing ring is O-shaped or rectangular, and its compression ratio is controlled between 15% and 25% to ensure that it can maintain good sealing performance after repeated disassembly and assembly.

[0049] In a preferred embodiment, a scale is provided on the liquid column tube 11 for accurate reading of the liquid level. During the injection process, the change in the liquid level in the liquid column tube 11 is used to determine whether the inside of the acoustic tube is completely filled with liquid. When the liquid level in the liquid column tube 11 is stable and no bubbles emerge, it indicates that the air inside the acoustic tube has been completely expelled.

[0050] II. Vector Hydrophone Horizontal Channel Sensitivity Calibration System (I) Overall System Composition like Figure 3As shown, the vector hydrophone horizontal channel sensitivity calibration system consists of the following main components: the aforementioned vector hydrophone horizontal channel sensitivity calibration device (sealed acoustic tube), electronic switch, programmable filter, lock-in amplifier, power amplifier, and host computer. The calibration device includes the installation and signal output structure for the exciter 4, standard hydrophone 5, and the vector hydrophone under test 6. The aforementioned external electronic devices are connected to the corresponding interfaces in the calibration device via signal lines, forming a complete closed-loop calibration system. The functions and connection methods of each electronic device are described below.

[0051] (ii) Electronic switch An electronic switch is installed outside the calibration device. Its input channels are connected to the signal output lines of the standard hydrophone 5 and the vector hydrophone under test 6 (leading out through the watertight plug 10) on the calibration device, respectively. Its common output terminal is connected to the input terminal of the programmable filter. The function of the electronic switch is to selectively connect the output signals of the standard hydrophone 5 or the vector hydrophone under test 6 to the subsequent signal processing link under the control of the host computer.

[0052] The electronic switch has at least two input channels and one common output channel. Channel switching is achieved by a host computer sending control commands through a communication interface. As a preferred embodiment, the electronic switch uses a low-distortion, high-isolation relay switch or analog switch to avoid crosstalk and signal distortion between channels.

[0053] (III) Programmable Filter The input terminal of the programmable filter is connected to the common output terminal of the electronic switch, and its output terminal is connected to the receiving terminal of the lock-in amplifier. The function of the programmable filter is to filter the electrical signal output by the hydrophone, remove out-of-band noise and interference signals, and improve the signal-to-noise ratio.

[0054] A programmable filter (PBB) is an active filter whose filtering parameters can be adjusted via external control commands. In a preferred embodiment, the PBB uses a bandpass filter, whose center frequency and bandwidth are automatically set by the host computer based on the current calibration frequency. The filter type can be Butterworth or Chebyshev, with a second or fourth order to ensure sufficient out-of-band rejection. The PBB connects to the host computer via a communication interface, receiving filtering parameter setting commands from the host computer.

[0055] (iv) Lock-in amplifier The lock-in amplifier has a dual function in the system: first, it acts as a signal source to emit a sinusoidal electrical signal at the calibrated frequency; second, it acts as a receiver to perform phase-sensitive detection and amplitude measurement on the acoustic signal returned by the hydrophone.

[0056] The lock-in amplifier's signal output is connected to the power amplifier's input to emit a sinusoidal electrical signal with a set frequency and amplitude. The lock-in amplifier's receiving end is connected to the output of a programmable filter to receive the filtered hydrophone signal. Using its own emitted reference signal (in phase and frequency with the transmitted signal) as a reference, the lock-in amplifier performs phase-sensitive detection and integration on the received signal, extracting the weak signal component with the same frequency as the reference signal from the noise, and outputting the effective value of the received signal's amplitude.

[0057] In a preferred embodiment, the lock-in amplifier employs a dual-channel lock-in amplifier, which can simultaneously output a reference signal and a measurement reception signal, further improving the accuracy of phase and amplitude measurements. The lock-in amplifier is connected to the host computer via a communication interface, receiving parameter setting commands such as frequency, amplitude, and integration time sent by the host computer, and transmitting the measured data back to the host computer.

[0058] (v) Power Amplifier The input terminal of the power amplifier is connected to the signal output terminal of the lock-in amplifier, and its output terminal is connected to the drive terminal of the exciter 4 on the calibration device. The function of the power amplifier is to linearly amplify the low-power sinusoidal electrical signal output from the lock-in amplifier, and output an electrical signal with sufficient driving power to drive the exciter 4 to work normally.

[0059] The power amplifier's operating frequency range should cover the lock-in amplifier's output frequency range (20Hz to 2kHz), and its output power should meet the drive power requirements of exciter 4 across the entire frequency band. The power amplifier's gain should be continuously adjustable to accommodate different requirements for the drive amplitude of exciter 4 at different calibration frequencies.

[0060] (vi) Host computer The host computer is the control core of the entire calibration system, and it connects to the lock-in amplifier, programmable filter, and electronic switch via communication interfaces. As a preferred implementation, the communication interface uses any one of GPIB, USB, RS232 serial interface, or Ethernet interface. The host computer's functions include the following three aspects: First, parameter setting and equipment control. The host computer sends parameter setting commands such as frequency, amplitude, and integration time to the lock-in amplifier via the communication link; sends parameter setting commands such as filter type, center frequency, and bandwidth to the programmable filter; and sends channel switching commands to the electronic switch to control the hydrophone channel connected to the subsequent signal processing link.

[0061] Second, data acquisition and processing. The host computer receives the measurement data returned by the lock-in amplifier, including the effective values ​​of the output voltages of the standard hydrophone 5 and the vector hydrophone under test 6. The host computer software automatically calculates the sound pressure sensitivity of the horizontal channel of the vector hydrophone under test 6 based on the preset calibration algorithm, using the acquired voltage values ​​and the input measurement parameters.

[0062] Third, data display and storage. The host computer displays the measurement and calculation results in real time on the operation interface, and automatically saves complete calibration data records according to the set data storage path, including calibration date and time, ambient temperature, calibration frequency, standard hydrophone 5 sensitivity, standard hydrophone 5 output voltage, output voltage of the channel under test, and sensitivity calculation results of the channel under test, etc.

[0063] As a preferred implementation, the host computer software is developed using programming languages ​​such as LabVIEW or C++, has a graphical user interface, and can complete the entire process of parameter input, device control, data acquisition, automatic calculation, data storage, and report generation.

[0064] (vii) A brief description of the overall working process of the system After system startup, the host computer first initializes and configures the lock-in amplifier, programmable filter, and electronic switch. The lock-in amplifier outputs a sinusoidal electrical signal at the calibration frequency, which, after being amplified by the power amplifier, drives the exciter 4 on the calibration device to establish a stable horizontal standing wave field in the closed acoustic tube. The standard hydrophone 5 and the vector hydrophone under test 6 on the calibration device sense the sound pressure signal at their respective locations and output electrical signals. The host computer controls the electronic switch to sequentially switch to the standard hydrophone 5 channel and the vector hydrophone under test 6 channel. The signals from the two channels are filtered by the programmable filter and then input into the lock-in amplifier for amplitude measurement. The host computer acquires the effective voltage values ​​of the two channels, substitutes them into the calibration formula to calculate the sound pressure sensitivity of the horizontal channel under test, and saves and displays the results.

[0065] III. Vector Hydrophone Horizontal Channel Sensitivity Calibration Method Step S1: Pre-calibration inspection Check that the entire system hardware is in normal working order. Inspect the rubber sealing rings 12 between the front and rear acoustic tubes 1 and 2, and between the rear acoustic tube 2 and the end cap 3, for damage, aging, or deformation. Ensure the sealing ring surface is smooth and free of cracks to guarantee a good seal. Check that the standard hydrophone 5 is intact and that its signal output line is undamaged. Ensure the standard hydrophone 5 is securely and reliably installed. Check that the internal and external interfaces of the watertight plug 10 are clean and free of rust, and that the signal contact is good. Check that the power connections and signal cable connections of all electronic devices are normal.

[0066] Step S2: Suspend the vector hydrophone to be tested 6 Select one set of screw holes 8 axially arranged on the inner side of the rear acoustic tube 2 as the suspension position for this calibration, according to the calibration requirements. Screw the four retaining screws 7 into the four screw holes 8 at the corresponding positions (one each at the top, bottom, front, and back) and tighten them appropriately. Each retaining screw 7 is connected to a rubber strip 9, and one end of the rubber strip 9 is fixed to the retaining screw 7 by a knot.

[0067] Place the vector hydrophone 6 to be tested inside the rear acoustic tube 2, and adjust its posture so that the horizontal channel to be tested is aligned with the axis of the acoustic tube. Select the suspension method according to the horizontal channel to be tested: When calibrating the horizontal channel X, fix the rubber strips 9 on the front and rear sides of the tube wall to the two buckles of the horizontal channel Y of the vector hydrophone 6 to be tested (cross fixation), and fix the upper and lower rubber strips 9 to the top and bottom buckles of the vector hydrophone 6 to be tested; when calibrating the horizontal channel Y, fix the rubber strips 9 on the front and rear sides of the tube wall to the two buckles of the horizontal channel X of the vector hydrophone 6 to be tested, and fix the upper and lower rubber strips 9 to the top and bottom buckles of the vector hydrophone 6 to be tested.

[0068] Using the above suspension method, the vector hydrophone 6 under test is stably suspended on the horizontal axis inside the acoustic tube, with its horizontal channel precisely aligned with the axial direction of the acoustic tube, and the hydrophone body not in contact with the tube wall. Connect and tighten the output connector of the vector hydrophone 6 to the inner interface of the watertight plug 10.

[0069] Step S3: Seal the device Connect the end cap 3 to the rear acoustic tube 2, aligning the bolt holes 15 on the side of the end cap 3 with the corresponding bolt holes 15 on the rear acoustic tube 2. Insert the bolts and tighten them evenly. A rubber sealing ring 12 is installed between the contact surfaces of the end cap 3 and the rear acoustic tube 2 to achieve a seal.

[0070] Connect the front acoustic tube 1 and the rear acoustic tube 2, align the bolt holes 15 on their flanges, insert the bolts and tighten them evenly, and set a rubber sealing ring 12 between the flange contact surfaces to achieve a seal.

[0071] After sealing, the entire sealed acoustic tube is connected to the outside world only through the liquid column tube 11 at the upper rear side of the rear acoustic tube 2.

[0072] Step S4: Add test liquid Open the inlet / outlet water valve 13 at the lower rear side of the rear acoustic tube 2, and slowly add the test liquid into the closed acoustic tube through the valve. The test liquid is usually clean fresh water that has been degassed or other liquid media that meets the test requirements. In the degasing process, vacuum degasing or heating to boiling and then cooling can be used to remove dissolved gases from the liquid to prevent the formation of bubbles in the acoustic tube that would affect the sound field distribution.

[0073] The top of the liquid column tube 11 is a transparent glass tube, which allows real-time observation of the liquid level during the filling process. When a small amount of liquid flows out of the liquid column tube 11 and the liquid level stabilizes and no longer changes, it indicates that the sealed acoustic tube is completely filled with test liquid and all air has been expelled through the liquid column tube 11.

[0074] Close the inlet and outlet water valves 13 and let it stand for a period of time (usually 10 to 30 minutes). When the liquid level in the liquid column tube 11 is completely stable and no bubbles emerge from the liquid column tube 11, it indicates that the gas inside the sound tube has been completely expelled and the temperature of the test liquid has reached equilibrium, and the calibration operation can begin.

[0075] Step S5: System Connection Connect the wire exiting the watertight plug 10 from the outer wall of the acoustic tube to the first input channel of the electronic switch, and connect the wire exiting the standard hydrophone 5 from the outer wall of the acoustic tube to the second input channel of the electronic switch. Connect the output terminal of the electronic switch to the input terminal of the programmable filter, and connect the output terminal of the programmable filter to the receiving terminal of the lock-in amplifier. Connect the signal output terminal of the lock-in amplifier to the input terminal of the power amplifier, and connect the output terminal of the power amplifier to the driving terminal of the exciter 4.

[0076] The host computer establishes connections with the lock-in amplifier, programmable filter, and electronic switch via communication interfaces. After verifying the correctness and reliability of the connections between each device, power on each device sequentially.

[0077] Step S6: Communication self-test and parameter input After the host computer software starts, it first performs a communication self-test to confirm that the communication between the host computer and the lock-in amplifier, programmable filter, and electronic switch is normal. The host computer software is then used to set the operating parameters of the lock-in amplifier, including signal frequency, amplitude, and integration time; to set the filter type and cutoff frequency of the programmable filter; and to confirm that the operating status of each channel of the electronic switch is normal.

[0078] In the host computer software interface, enter the following measurement parameters as prompted: the sensitivity value of the standard hydrophone 5 at the calibration frequency (given by the calibration certificate of the standard hydrophone 5), the sound velocity of the test liquid at the current temperature (which can be obtained from a table based on the water temperature or measured by a sound velocity measuring instrument), the calibration frequency, the distance between the vector hydrophone 6 under test and the acoustic reflection layer 14, and the distance between the standard hydrophone 5 and the acoustic reflection layer 14.

[0079] The distance between the vector hydrophone 6 under test and the acoustic reflection layer 14, as well as the distance between the standard hydrophone 5 and the acoustic reflection layer 14, can be obtained directly from the installation position dimensions reserved during the manufacturing of the acoustic tube, or can be confirmed by actual measurement using a ranging tool during the assembly process.

[0080] Step S7: Establish a coordinate system like Figure 4 As shown, a horizontal coordinate system is established with the position of the acoustic reflection layer 14 inside the end cap 3 as the origin, and the coordinate axes point towards the exciter 4 (i.e., the direction from the end cap 3 to the exciter 4 is the positive direction). In this coordinate system, the coordinates of the position of the vector hydrophone 6 under test are its distance from the acoustic reflection layer 14. The coordinates of the standard hydrophone 5 are its distance from the sound-reflecting layer 14. .

[0081] Step S8: Transmit acoustic signals and establish a standing wave field The calibration program is initiated via the host computer software. The lock-in amplifier outputs a sinusoidal electrical signal with a set amplitude at a set frequency. This signal is amplified by the power amplifier and then input to the exciter 4. The exciter 4 generates mechanical vibration, which is coupled to the test liquid inside the acoustic tube through the end structure of the front acoustic tube 1. This generates a plane wave that propagates along the horizontal axis from the end of the exciter 4 to the end cap 3 within the horizontally closed acoustic tube.

[0082] When a plane wave propagates to the acoustic reflection layer 14 inside the end cap 3, the sound wave is completely reflected because the acoustic reflection layer 14 is an absolutely hard boundary, at which point the vibration velocity of the sound wave is zero and the sound pressure reaches its maximum value. The reflected wave and the incident wave superimpose within the closed acoustic tube, forming a stable standing wave field. The distribution of this standing wave field satisfies the acoustic transmission line equation, that is, the sound pressure at each position along the axial direction of the acoustic tube varies with distance in a cosine manner, and the vibration velocity varies with distance in a sine manner.

[0083] Step S9: Acquire standard hydrophone 5 signal The host computer switches the electronic switch to the second input channel (standard hydrophone channel 5) via control commands, sending the voltage signal output from standard hydrophone 5 into a programmable filter. After out-of-band noise is filtered out by the programmable filter, the signal is input to a lock-in amplifier for phase-sensitive detection and amplitude measurement. The output of the lock-in amplifier is transmitted back to the host computer via the communication interface, where it is recorded and saved as the effective value of the output voltage of standard hydrophone 5. .

[0084] To ensure the stability of the measurement results, multiple consecutive samplings (usually 5 to 10 times) can be performed in the standard hydrophone 5-channel measurement, and the average value is taken as the final effective value of the output voltage of the channel.

[0085] Step S10: Acquire the horizontal channel signal of the 6th channel of the vector hydrophone under test. The host computer switches the electronic switch to the first input channel (channel 6 of the vector hydrophone under test) via control commands, sending the voltage signal output from the horizontal channel of the vector hydrophone under test to a programmable filter. After filtering by the programmable filter, the signal is input to a lock-in amplifier for phase-sensitive detection and amplitude measurement. The output of the lock-in amplifier is transmitted back to the host computer via the communication interface, where it is recorded and saved as the effective value of the output voltage of the horizontal channel under test. .

[0086] Similarly, multiple consecutive samples are taken during the measurement of the channel under test, and the average value is taken as the final effective value of the output voltage of the channel.

[0087] It should be noted that the order of steps S9 and S10 can be interchanged; that is, the channel under test can be sampled first, followed by the standard channel, without affecting the calibration results. To reduce the impact of system drift on the measurement results, multiple alternating samples can be taken between the two channels, and the average value can be calculated separately.

[0088] Step S11: Calculate the horizontal channel sound pressure sensitivity The host computer software, based on the principle of the acoustic transmission line comparison method, utilizes the acquired effective value of the output voltage of the channel under test. Standard hydrophone 5 output voltage RMS value Standard hydrophone 5 sensitivity , wave number ,distance and The sound pressure sensitivity of the horizontal channel of the vector hydrophone under test is calculated according to the following formula: ; Among them, wave number , To calibrate the frequency, To test the speed of sound in a liquid.

[0089] The derivation of this formula is based on the following: taking the sound reflection layer 14 as the origin, the coordinates inside the closed sound tube are... The sound pressure at that point can be expressed as ,in, This represents the sound pressure amplitude at sound reflection layer 14. From this, the sound pressure at the horizontal channel of the vector hydrophone 6 under test can be obtained. Sound pressure at point 5 of the standard hydrophone Simultaneously, according to the definition of hydrophone sound pressure sensitivity, the sensitivity of the channel under test... Standard hydrophone sensitivity 5 By combining the above relationships, we can obtain the aforementioned calculation formula.

[0090] Step S12: Display, store, and output calibration results After the host computer software completes the calculation, it will display the results. The data is displayed in the operation interface. Simultaneously, the host computer software automatically saves complete calibration data records according to the user-defined data storage path, including: calibration date and time, ambient temperature, relative humidity, calibration frequency, test liquid sound velocity, standard hydrophone 5 model and sensitivity value, vector hydrophone 6 model and serial number under test, under-test channel identifier (X or Y), standard hydrophone 5 output voltage RMS value, under-test channel output voltage RMS value, and under-test channel sound pressure sensitivity calculation results, etc.

[0091] If the host computer is equipped with a printer or report generation module, it can automatically generate a calibration report in a standard format.

[0092] Step S13: Drainage and disassembly When the vector hydrophone 6 under test needs to be calibrated simultaneously for two horizontal channels (X channel and Y channel), after the current channel calibration is completed, open the inlet and outlet water valves 13 to completely drain the test liquid in the sealed acoustic tube. Remove the flange connecting bolts between the front acoustic tube 1 and the rear acoustic tube 2 to separate the front acoustic tube 1 and the rear acoustic tube 2, exposing the vector hydrophone 6 under test.

[0093] Step S14: Adjust the suspension direction Loosen all retaining screws 7, but keep the four retaining screws 7 in their original positions on the tube wall. Remove the connection between each rubber strip 9 and the retaining ring of the vector hydrophone 6 under test. Rotate the vector hydrophone 6 under test 90° in the horizontal plane so that the other horizontal channel is aligned with the axial direction of the acoustic tube. Reuse the two retaining rings orthogonal to the current channel under test, and suspend and fix the vector hydrophone 6 under test using the rubber strips 9. The upper and lower rubber strips 9 are connected to the top and bottom retaining rings, respectively.

[0094] For example, if the first calibration is of the horizontal channel X, after calibration, rotate the hydrophone 90° so that the horizontal channel Y is aligned with the axial direction of the sound tube, and use the two buckles of the horizontal channel X for suspension and fixation. Then repeat steps S3 to S12 to complete the sensitivity calibration of the horizontal channel Y.

[0095] Step S15: Repeat the calibration operation Following steps S3 to S12, repeat the sealing, liquid injection, parameter input, signal acquisition, calculation, and storage steps to complete the sensitivity calibration of the second horizontal channel.

[0096] If the calibration task is only for a single horizontal channel, you can skip directly to step S16 after step S12 is completed and end the calibration operation.

[0097] Step S16: Draining and removing the hydrophone After all calibration tasks are completed, open the inlet and outlet water valves 13 to completely drain the test liquid from the sealed acoustic tube. Remove the flange connecting bolts between the front acoustic tube 1 and the rear acoustic tube 2, as well as the connecting bolts between the end cap 3 and the rear acoustic tube 2, to separate the various parts of the device. Take out the vector hydrophone 6 to be tested.

[0098] Step S17: Equipment Cleaning and Maintenance Clean any remaining water stains from inside the sealed acoustic tube and all sealing surfaces. Clean and dry the interfaces of the standard hydrophone 5 and the watertight plug 10. Inspect the condition of each sealing ring; replace any that are aged, deformed, or damaged. After cleaning all components of the device, store them properly for future calibration.

[0099] IV. Calibration Environmental Conditions According to the standard hydrophone verification conditions specified in GJB 3803A-2018 "Verification Procedure for Standard Hydrophones", the environmental conditions for the calibration method of this invention are as follows: Ambient temperature: 20℃ ± 10℃; relative humidity: not greater than 85%; power supply: voltage 220V ± 20V, frequency 50Hz ± 2Hz; the surrounding environment should be free from mechanical vibration and impact sources to ensure the stability of the measurement results.

[0100] The temperature of the test liquid inside the sound tube should remain stable after filling (the change should not exceed ±0.5℃). The sound velocity of the test liquid can be calculated based on the measured temperature using the empirical formula for sound velocity, or it can be directly measured by a sound velocity measuring instrument.

[0101] V. Calibration Frequency Range The applicable frequency range of the calibration device, system, and method described in this invention is 20Hz to 2kHz. The specific calibrable frequency point is determined by the following factors: the response characteristics of the exciter 4 at the corresponding frequency, the size and acoustic characteristics of the acoustic tube, the acoustic parameters of the test liquid, and the calibration coverage of the standard hydrophone 5.

[0102] Within this frequency range, the sound field inside the acoustic tube can be considered as a one-dimensional plane wave sound field, satisfying the description conditions of the acoustic transmission line equation. The calibration frequency should be selected within the range of one-dimensional plane wave propagation conditions of the acoustic tube, that is, the upper limit of the operating frequency of the acoustic tube should be lower than the cutoff frequency of the acoustic tube to ensure that no higher-order mode waves are generated inside the tube.

[0103] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A device for calibrating the sensitivity of a horizontal channel of a vector hydrophone, characterized in that, include: The front acoustic tube, the rear acoustic tube, and the end cap are sequentially and sealed together to form a horizontal cylindrical closed acoustic tube. A flange is provided at the rear end of the front acoustic tube. Bolt holes are evenly distributed on the flange, and a sealing groove is provided on the end face of the flange for installing a rubber sealing ring. The front acoustic tube and the rear acoustic tube are sealed and fixedly connected through the cooperation of the flange, bolts and rubber sealing ring. The end cap is located at the rear end of the entire device. The end cap is a circular disc structure. It is fixedly connected to the rear end of the rear acoustic tube with bolts through evenly distributed bolt holes on its side. A rubber sealing ring is provided on the contact surface for sealing. The front end of the front acoustic tube is fixed with an exciter for generating a plane wave that propagates in the horizontal direction; a standard hydrophone is fixed at the top for collecting standard hydrophone signals. The inner wall of the rear acoustic tube is provided with multiple sets of screw holes along the axial direction. Each set of screw holes is used to suspend and fix the vector hydrophone under test by means of retaining screws and rubber strips, and the horizontal channel of the vector hydrophone under test is aligned with the axial direction of the closed acoustic tube. Each set of screw holes includes four screw holes, which are located at the upper, lower, front, and rear positions on the inner wall of the rear acoustic tube at the same cross section along the axial direction, and are evenly distributed. When calibrating the horizontal channel X of the vector hydrophone under test, the rubber strips on both sides of the tube wall are fixedly connected to the two retaining rings of the horizontal channel Y. When calibrating the horizontal channel Y, the rubber strips on both sides of the tube wall are fixedly connected to the two retaining rings of the horizontal channel X. The rear acoustic tube is equipped with a watertight plug for connecting the signal line of the vector hydrophone under test; a liquid column tube is provided on the upper rear side of the rear acoustic tube, and an inlet and outlet water valve is provided on the lower rear side. The inner surface of the end cap is covered with an acoustic reflective layer to form an absolutely hard boundary.

2. A vector hydrophone horizontal channel sensitivity calibration system, characterized by, include: The vector hydrophone horizontal channel sensitivity calibration device as described in claim 1; An electronic switch is connected to the standard hydrophone and the vector hydrophone under test, respectively, to switch the signal feedback channel; A programmable filter, connected to the electronic switch, is used to filter the returned acoustic signal; A lock-in amplifier, whose signal output terminal is connected to the exciter via a power amplifier, and whose receiving terminal is connected to the programmable filter, is used to emit sound signals and process the received sound signals. A power amplifier is connected between the lock-in amplifier and the exciter to amplify the acoustic signal emitted by the lock-in amplifier before inputting it into the exciter. The host computer is connected to the lock-in amplifier, the programmable filter, and the electronic switch, respectively, and is used to control the working status of each device and read the output data of the lock-in amplifier.

3. The vector hydrophone horizontal channel sensitivity calibration system of claim 2, wherein, The acoustic signal emitted by the lock-in amplifier is amplified by the power amplifier and then input to the exciter. The exciter generates a plane wave that propagates along the horizontal axis in the horizontal cylindrical closed acoustic tube. The acoustic signals collected by the standard hydrophone and the vector hydrophone under test are switched by the electronic switch and then input to the programmable filter in sequence. They are then processed by the lock-in amplifier, and the processing result is sent back to the host computer.

4. A method for calibrating the horizontal channel sensitivity of a vector hydrophone using the vector hydrophone horizontal channel sensitivity calibration system of claim 2, wherein, Includes the following steps: S1: Align the horizontal channel of the vector hydrophone under test with the axial direction of the sealed acoustic tube, suspend and fix the vector hydrophone under test in the rear acoustic tube using buckle screws and rubber strips, and connect the output end of the vector hydrophone under test to the watertight plug. S2: Seal and fix the front acoustic tube, rear acoustic tube and end cap in sequence to form a closed acoustic tube; S3: Add test liquid into the closed acoustic tube through the inlet and outlet water valves until the liquid level in the liquid column tube is stable and no bubbles emerge, then close the inlet and outlet water valves; S4: the host computer controls the phase-locked amplifier to send an acoustic signal, which is amplified by a power amplifier and then drives the exciter to generate a plane wave along the horizontal axis in the closed sound tube; through electronic switch switching, the output voltage effective value of the horizontal channel of the vector hydrophone to be measured and the output voltage effective value of the standard hydrophone are collected respectively ; and the output voltage effective value of the standard hydrophone ; the sound pressure sensitivity of the horizontal channel of the vector hydrophone to be measured is calculated according to the following formula : ； wherein, is the sensitivity of the standard hydrophone at the measurement frequency, is the wave number at the measurement frequency, is the distance between the vector hydrophone under test and the sound-reflecting layer, is the distance between the standard hydrophone and the sound-reflecting layer; S5: After calibration, open the inlet and outlet water valves to drain the test liquid, adjust the other horizontal channels of the vector hydrophone under test to be in the same direction as the axis, and repeat steps S1 to S4, or remove the vector hydrophone under test.

5. The vector hydrophone horizontal channel sensitivity calibration method according to claim 4, characterized in that, In step S1, select a set of screw holes in the axial position according to the calibration requirements, screw four retaining screws into the corresponding screw holes and tighten them. Each retaining screw uses a rubber strip, one end of which is fixed to the retaining screw and the other end is fixed to the retaining hole on the surface of the vector hydrophone to be tested.

6. The vector hydrophone horizontal channel sensitivity calibration method according to claim 4, characterized in that, In step S4, a horizontal coordinate system is established with the position of the acoustic reflection layer of the end cap as the origin, and the direction is towards the exciter end; the acoustic reflection layer is an absolutely hard boundary, the vibration velocity is zero and the sound pressure is at its maximum value at the absolutely hard boundary, and the sound pressure and vibration velocity at any position inside the closed acoustic tube satisfy the acoustic transmission line equation.

7. The vector hydrophone horizontal channel sensitivity calibration method according to claim 4, characterized in that, The horizontal channels of the vector hydrophone under test include mutually orthogonal X and Y channels. The other horizontal channel mentioned in step S5 is another horizontal channel orthogonal to the current calibration channel. By adjusting the suspension direction of the vector hydrophone under test, this other horizontal channel is aligned with the axis of the closed acoustic tube to complete the sensitivity calibration of the X and Y channels in sequence.

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