Vibration liquid column hydrophone calibration device and method based on laser interference measurement

Abstract

The invention relates to the technical field of measurement of mechanical vibration or ultrasonic waves, water sound waves or infrasonic waves, in particular to a vibration liquid column hydrophone calibration device and method based on laser interferometry, and the device comprises a laser vibration meter, a hydrophone to be measured, a liquid column cavity for suspending the hydrophone to be measured, and a vibration table connected with the liquid column cavity. The to-be-measured hydrophone is detachably connected with an adjusting and positioning mechanism, the adjusting and positioning mechanism is connected with a laser vibration measuring instrument for executing vibration measurement, the adjusting and positioning mechanism and the laser vibration measuring instrument are introduced, the problem that accurate calibration of the low-frequency hydrophone cannot be achieved in the prior art is solved, and through sound field modeling calculation and correction, accurate calibration of the low-frequency hydrophone is achieved. The technical problem that the uncertainty and deviation of a hydrophone sensitivity calibration result caused by a non-uniform sound field cannot be effectively reduced in the prior art is solved.

Description

Technical Field

[0001] The present application relates to the technical field of measuring mechanical vibration or ultrasonic wave, hydroacoustic wave or infrasonic wave, and in particular to a vibrating liquid column hydrophone calibration device based on laser interferometry, and also to a calibration method. Background Art

[0002] The hydrophone is the most basic and commonly used sensor for picking up and measuring underwater acoustic signals. Its sensitivity needs to be calibrated regularly to ensure the accuracy of the measured underwater acoustic signals. It is widely used in underwater target detection, positioning navigation, ocean noise measurement and other fields. The vibrating liquid column method is an important and commonly used method for low-frequency calibration of hydrophones. The hydrophone is suspended in a liquid column cavity driven sinusoidally by a vibrating table. The vibration acceleration is measured by an acceleration sensor (accelerometer). The sensitivity of the hydrophone at different frequency points is calculated based on transmission line theory using parameter information such as vibration frequency, sound speed in water, cavity size, and hydrophone immersion depth, and the calibration is completed. However, in the existing vibrating liquid column hydrophone calibration scheme, the sensitivity of the acceleration sensor is calibrated by the laser method or the comparison method, which introduces a large measurement uncertainty component, and long-term measurement may cause the connection between the acceleration sensor and the liquid column cavity to loosen, affecting the measurement results; on the other hand, when calibrating a larger hydrophone in a liquid column cavity, the hydrophone itself will affect the sound field distribution in the liquid column cavity, especially when the calibration frequency increases, the wavelength of the sound wave is not much larger than the cavity size or the hydrophone size, which will cause uneven sound field acting on the hydrophone sensitive element, resulting in obvious deviations in the calibration results, and will also affect the improvement of the measurement uncertainty level.

[0003] In the prior art, the publication date is November 26, 2021, the publication number is CN214893653U, and the name is a Chinese patent for a low-frequency hydrophone calibration device based on the vibrating liquid column method. It discloses a four-party vertical bracket, and a vertical connector is fixed on the side surface of the upper end of the four-party vertical bracket. A cross-shaped connector is arranged above the four-party vertical bracket, and the cross-shaped connector is provided with a cross-shaped jack. The cross-shaped connector is provided with three, and the vertical connector is provided with a vertical jack between the vertical connector and the cross-shaped connector; the four-party vertical bracket can fix the hydrophone to be tested very stably so that it always remains vertically downward, and the position of the hydrophone is adjustable, and the height can be accurately adjusted according to the scale of the hollow tube wall. After adjustment, the cross connector can be locked to start the next step of the experiment. It is convenient and easy to operate, the vibration cavity has good airtightness, and it is easy to fix to the vibration table, easy to install, and the vibration is stable. It adopts a three-stage design, which greatly facilitates the installation of the accelerometer.

[0004] The calibration results of the aforementioned technical solutions need to be improved, and at the same time, the uncertainty and deviation of the hydrophone sensitivity calibration results caused by the non-uniform sound field cannot be effectively reduced. Summary of the invention

[0005] Through research, the inventors found that laser interferometry, as a new technology for vibration and acoustic measurement, can achieve non-contact measurement compared to traditional acceleration sensors, and has higher measurement accuracy and resolution, especially when measuring small vibrations. It can achieve accurate measurement of nanometer-level displacement changes, while acceleration sensors may be limited by their own noise and sensitivity in measuring such tiny vibrations. In particular, acceleration sensors are generally calibrated by laser interferometry, and the acceleration information of a vibrating liquid column cavity is measured using an acceleration sensor, which has a longer transmission path and greater measurement uncertainty.

[0006] The purpose of the present application is to provide a vibrating liquid column hydrophone calibration device and method based on laser interferometry, specifically to provide a vibrating liquid column low-frequency hydrophone calibration device and method based on laser interferometry, by introducing an adjustment positioning mechanism and a laser vibrometer based on an existing publicly available calibration device, to solve the problem that the low-frequency hydrophone cannot be accurately calibrated in the prior art; on the other hand, by sound field modeling calculation and correction, to solve the technical problem that the prior art cannot effectively reduce the uncertainty and deviation of the hydrophone sensitivity calibration result caused by the non-uniform sound field.

[0007] According to one aspect of the present application, a vibrating liquid column hydrophone calibration device based on laser interferometry is provided, comprising a hydrophone to be measured, a liquid column chamber for suspending the hydrophone to be measured, and a vibration table connected to the liquid column chamber, wherein the hydrophone to be measured is detachably connected to an adjustment and positioning mechanism, and the adjustment and positioning mechanism is connected to a laser vibrometer for performing vibration measurement.

[0008] In some embodiments, the laser vibrometer signal is connected to a vibration velocity signal demodulator.

[0009] In some embodiments, the vibration velocity signal demodulator is connected to an oscilloscope via a channel.

[0010] In some embodiments, the hydrophone signal to be measured is connected to a preamplifier.

[0011] In some embodiments, the preamplifier is connected to an oscilloscope via a channel.

[0012] In some embodiments, the oscilloscope data is connected to a host computer.

[0013] In some embodiments, the host computer signal is connected to a signal source.

[0014] In some embodiments, the signal source is signally connected to a power amplifier.

[0015] In some embodiments, the power amplifier is signally connected to the vibration table.

[0016] According to another aspect of the present application, a vibrating liquid column hydrophone calibration method based on laser interferometry is provided, comprising:

[0017] Determining the size parameters of the target liquid column cavity (2), and removing bubbles in the liquid in the target liquid column cavity (2);

[0018] Installing target hydrophone (3);

[0019] Performing gain calibration on the preamplifier (7) to set signal parameters and power amplifier gain;

[0020] The laser vibrometer (4) measures the vibration velocity u(f) of the target liquid column chamber (2);

[0021] Calculate the surface sound pressure p of the target hydrophone (3) in the target liquid column cavity (2) h (f);

[0022] Simulation modeling to correct sound pressure Δp h (f);

[0023] Measure the output open circuit voltage U of the target hydrophone (3) H (f);

[0024] Calculate the sensitivity M of the target hydrophone (3) H (f);

[0025] It is determined whether calibration needs to be continued. If so, the upper computer (10) program controls to automatically change the signal frequency f; if not, the calibration ends.

[0026] Compared with the prior art, the present application utilizes a laser vibrometer instead of a traditional acceleration sensor to directly and contactlessly measure the vibration velocity of the liquid column cavity, thereby avoiding possible loose connections, shortening the transmission path of the hydrophone sensitivity value, and improving the calibration level of low-frequency hydrophones. At the same time, the present application obtains correction values ​​for the effects of hydrophones of different frequencies and sizes on the sound field distribution through sound field modeling and simulation calculations, thereby improving the accuracy of the calibration results and increasing the applicability of the entire device to hydrophones. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 It is a schematic diagram of the composition of the calibration device of the present application;

[0029] Figure 2 is a schematic diagram of the calibration device of the present application;

[0030] Figure 3 It is a flow chart of the calibration method of this application.

[0031] Legend:

[0032] 1-vibration table; 2-liquid column chamber; 3-hydrophone to be tested; 4-laser vibrometer; 5-adjustment and positioning mechanism; 6-vibration velocity signal demodulator; 7-preamplifier; 8-power amplifier; 9-oscilloscope; 10-host computer; 11-signal source; In order to avoid interference with technical features, Figure 1 Some guide lines in the figure are dotted. DETAILED DESCRIPTION

[0033] The following will be combined with the attached examples of the present application Figure 1-3 The technical solutions in the embodiments of the present application are described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0034] Explanation of some terms in this application:

[0035] Channel 1: CH1;

[0036] Channel 2: CH2.

[0037] Application Overview

[0038] The existing vibrating liquid column hydrophone calibration system uses an accelerometer to measure the acceleration values ​​of the vibration table 1 and the cavity, but the performance of the accelerometer itself depends on the mechanical sensor element, and the measurement accuracy is low. In order to obtain the sensitivity value of the accelerometer, the accelerometer must first be calibrated using the reciprocity method or laser interferometry. The uncertainty introduced by the calibration exceeds 0.2dB, which in turn causes the synthetic uncertainty of the hydrophone calibration to exceed 0.6dB, increasing the traceability path of the hydrophone sensitivity value. In addition, when measuring higher-frequency vibrations, the accelerometer is limited by its sensitive materials and structure, and the frequency response range is limited. Finally, the accelerometer needs to be in physical contact with the object to be measured (liquid column cavity 2). Factors such as the fixing method and position during the installation process may affect the measurement results and increase many uncertainties. For example, the accelerometer may become loose if it follows the vibration of the liquid column cavity 2 for a long time, affecting the acceleration measurement and hydrophone calibration results.

[0039] At the same time, when the size of the hydrophone 3 to be tested is large, the hydrophone itself will affect the sound pressure distribution of the sound field in the liquid column cavity. Especially when the calibration frequency increases, the wavelength of the sound wave is not far greater than the cavity size or the hydrophone size, which will cause the sound field acting on the hydrophone sensitive element to be uneven, causing a significant deviation in the calibration result and a significant increase in measurement uncertainty. The existing scheme does not take this situation into consideration, resulting in the vibrating liquid column method hydrophone calibration system being only suitable for hydrophones with a small size and negligible impact on the sound field, and the scope of application is limited. Alternatively, the cavity size can be increased to accommodate the calibration of large-sized hydrophones, but this will also reduce the upper limit of the operating frequency of the vibrating liquid column method hydrophone calibration system.

[0040] Example 1

[0041] The present embodiment provides a vibrating liquid column hydrophone calibration device based on laser interferometry, the device comprising a hydrophone to be measured 3, a liquid column chamber 2 for suspending the hydrophone to be measured, and a vibration table 1 connected to the liquid column chamber, the hydrophone to be measured 3 is detachably connected to an adjustment and positioning mechanism 5, and the adjustment and positioning mechanism 5 is connected to a laser vibrometer 4 for performing vibration measurement.

[0042] It should be noted that the present embodiment is provided with an adjustment and positioning mechanism 5 and a laser vibrometer 4, and the adjustment and positioning mechanism 5 is provided to realize a detachable connection with the laser vibrometer 4, so that timely adjustments can be made according to actual use conditions, and the device can be easily disassembled, installed, repaired and maintained, thereby improving the convenience of the entire device during use. The acceleration sensor used in the prior art may become loose due to long-term vibration, and its sensitivity needs to be calibrated each time it is used, which is not only troublesome to operate, but also easy to loosen and produce errors, which ultimately affects the error of the measurement of the entire device. The present embodiment is provided with a laser vibrometer 4. The laser interferometer measurement technology of the laser vibrometer 4 is directly introduced into the calibration of the low-frequency hydrophone for vibration measurement. Compared with the acceleration sensor used in the prior art, the laser vibrometer 4 used in the present embodiment can not only be more direct in calculating the sound pressure in the cavity, but also can save the calibration link of the acceleration sensor sensitivity, thereby effectively eliminating the measurement uncertainty introduced by the acceleration sensor calibration, shortening the value transfer chain, achieving the effect of further reducing the measurement uncertainty of the existing calibration device, reducing the measurement error of the entire calibration device, improving the accuracy of the measurement result, and thus improving the calibration level of the entire vibrating liquid column method low-frequency hydrophone.

[0043] In detail, the vibrating liquid column hydrophone calibration device provided in this embodiment measures the vibration velocity of the liquid column cavity 2 by the laser interferometry of the laser vibrometer 4, and then calculates the sound pressure value of the hydrophone receiving surface by the relationship between the vibration velocity and the sound pressure, and finally uses the preamplifier 7 and the oscilloscope 9 to measure the hydrophone output voltage.

[0044] It should be noted that when designing the liquid column cavity 2, it is preferred to use a rust-proof metal material with acoustic rigidity, and its size should meet the following requirements: the cavity diameter 2r is much smaller than the wavelength of the sound wave in water corresponding to the highest operating frequency, the height L of the liquid column formed in the cavity during the test should be greater than the cavity diameter 2r, and the total mass of the cavity and the liquid column should not exceed the maximum load of the vibration table 1 to prevent signal distortion; the liquid column height L should also be less than 1 / 4 of the wavelength of the sound wave in water corresponding to the measured (highest) frequency to avoid liquid column resonance. The upper end of the cavity should be smoothed and polished to allow good reflection of the laser. Preferably, a reflective material can be attached to the laser measurement area on the upper surface of the cavity.

[0045] Furthermore, the laser vibrometer 4 is signal-connected to a vibration velocity signal demodulator 6. The connected vibration velocity signal demodulator 6 converts the laser interference signal into a vibration velocity signal.

[0046] In some embodiments, the vibration velocity signal demodulator is connected to the oscilloscope 9 through a channel. The preamplifier 7 is connected to the oscilloscope 9 through a channel. The oscilloscope 9 is configured to convert the invisible electrical signal into a visible image.

[0047] Furthermore, the hydrophone signal to be measured is connected to a preamplifier 7. Through the connected gain-calibrated preamplifier 7, it is combined with an oscilloscope 9 to measure the voltage output by the hydrophone.

[0048] Further, the oscilloscope data is connected to the host computer 10. The control command is directly issued through the connected host computer 10, which can be a PC or a host computer or a master computer or an upper computer, which has a display screen, and various signal changes such as sound pressure, voltage, temperature, etc. are displayed on the screen.

[0049] Further, the host computer signal is connected to a signal source 11. The signal source 11 is connected to a power amplifier 8. The power amplifier 8 is connected to the vibration table 1. The connected signal source 11 and the power amplifier 8 are used to drive the vibration table 1 to drive the liquid column cavity 2 and the internal liquid to perform sinusoidal motion at a certain set frequency in the vertical direction.

[0050] Example 2

[0051] In order to better understand the present application, this embodiment provides an exemplary method, refer to Figure 3 , a vibrating liquid column hydrophone calibration method based on laser interferometry, comprising:

[0052] Determining the size parameters of the target liquid column cavity (2), and removing bubbles in the liquid in the target liquid column cavity (2);

[0053] Installing target hydrophone (3);

[0054] Performing gain calibration on the preamplifier (7) to set signal parameters and power amplifier gain;

[0055] The laser vibrometer (4) measures the vibration velocity u(f) of the target liquid column chamber (2);

[0056] Calculate the surface sound pressure p of the target hydrophone (3) in the target liquid column cavity (2) h (f);

[0057] Simulation modeling to correct sound pressure Δp h (f);

[0058] Measure the output open circuit voltage U of the target hydrophone (3) H (f);

[0059] Calculate the sensitivity M of the target hydrophone (3) H (f);

[0060] It is determined whether calibration needs to be continued. If so, the upper computer (10) program controls to automatically change the signal frequency f; if not, the calibration ends.

[0061] It should be noted that, for hydrophones with larger sensitive element sizes, when it is difficult to obtain an accurate analytical expression for the sound field after the hydrophone is immersed in liquid, a sound field simulation analysis model is established based on the vibrating liquid column low-frequency hydrophone calibration device provided in this embodiment, and the load (cavity size and liquid column height) suitable for the vibration table 1 is determined through numerical simulation. The influence of hydrophones of different sizes at different frequencies on the sound field distribution is calculated, and the hydrophone sensitivity correction factor is given, which effectively reduces the uncertainty and deviation of the hydrophone sensitivity calibration result caused by the non-uniform sound field, improves the accuracy of the low-frequency hydrophone calibration, and can reduce the uncertainty from 0.6dB to within 0.4dB.

[0062] In detail, before calibration begins, add degassed water to the target liquid column cavity 2, and hang the target hydrophone 3 in the target liquid column cavity 2, coinciding with the central axis of the liquid column, and the target hydrophone 3 and its cable are completely isolated from the vibration table and the liquid column cavity without direct coupling; preferably, the acoustic center of the target hydrophone 3 is placed at the center height of the liquid column. Accurately measure the height h of the acoustic center of the target hydrophone 3 from the liquid surface and the height L from the bottom of the cavity to the liquid surface, and perform gain calibration on the preamplifier 7 at the output end of the target hydrophone 3 to obtain the actual gain value at different frequencies. It is also necessary to check whether the excitation signal amplitude of the signal source 11 and the gain of the power amplifier 8 are appropriate. The specific method is: when the target hydrophone 3 is moved into and out of the liquid column respectively under the actual working state, the signal-to-noise ratio of the output open circuit voltage of the target hydrophone 3 is measured, and its value should be not less than 30dB, and the output waveform of the target hydrophone 3 has no obvious distortion in the entire working frequency range.

[0063] Furthermore, during calibration, the signal source is set to emit a sinusoidal signal with a frequency of f, and the power amplifier 8 drives the vibration table 1 to vibrate, wherein the amplitude of the sinusoidal signal and the gain setting of the power amplifier 8 should meet the above conditions. Since the height L of the liquid column is greater than the inner diameter 2r of the cavity, the cavity can be regarded as only plane waves propagating; and the sound pressure at the interface between the liquid column and the air is 0. Using the sound propagation theory and boundary conditions, the sound pressure at the depth h can be calculated:

[0064]

[0065] Where p L represents the sound pressure at the depth L (i.e. the bottom of the liquid column chamber 2), is the wave number, ω=2πf is the vibration angular frequency, and c is the speed of sound in the liquid. The sound pressure at the bottom of the liquid column cavity 2 and the vibration speed u(f) satisfy the following relationship:

[0066] p L (f) = ρcu(f)tan(kL)

[0067] Where ρ is the liquid density. Combining the above two equations, the sound pressure at the depth h where the hydrophone is located is:

[0068]

[0069] Except for the vibration velocity u(f), all other quantities in the above formula are known. The vibration velocity of the cavity can be directly measured by a laser vibrometer 4 and obtained by demodulating the vibration velocity signal.

[0070] Furthermore, the output open circuit voltage U of the hydrophone when it is placed in the liquid column chamber 5 is measured using the preamplifier 7 and the oscilloscope 9. H (f), obtain the acoustic pressure sensitivity of the hydrophone:

[0071]

[0072] From the above process, it can be seen that compared with the traditional method of using acceleration sensors, the measurement uncertainty introduced by directly measuring the vibration velocity through laser interferometer is higher in accuracy, so it will be smaller and can improve the overall uncertainty level of the calibration device.

[0073] Furthermore, the above hydrophone sensitivity calculation process does not take into account the impact of the hydrophone immersed in the liquid column cavity 2 on the sound pressure distribution of the sound field, especially when the size of the hydrophone is larger than the wavelength of the sound wave, this impact cannot be ignored. Using the sound field modeling simulation software, according to the parameters such as the vibration speed and frequency of the liquid column cavity 2, the size of the liquid column cavity 2 (inner diameter and height), the liquid density and sound speed, the height of the liquid column, the size of the hydrophone and the depth of the sound center of the hydrophone into the water, the sound field distribution model in the cavity is established, and the average sound pressure acting on the surface of the hydrophone sensitive element when the vibration frequency is f is obtained by simulation calculation. The sound pressure on the hydrophone surface calculated by the above formula is p h (f), then for a hydrophone of a certain model or size, the sound pressure correction value when calibrated in the vibrating liquid column chamber 2 is:

[0074]

[0075] It can be obtained that, considering the influence of the hydrophone on the sound field distribution, the actual sound pressure sensitivity of the corrected hydrophone is

[0076]

[0077] When it is impossible to obtain an accurate analytical expression for the sound field after the hydrophone is immersed in liquid, a sound field simulation analysis model is established based on the developed vibrating liquid column calibration device. The influence of hydrophones of different sizes on the sound field distribution at different frequencies is obtained through numerical calculation, and the hydrophone sensitivity correction factor is given. This can effectively reduce the calibration uncertainty and deviation of the sensitivity of large-sized hydrophones caused by non-uniform sound fields, improve the absolute calibration level of hydrophones in the frequency range of 10Hz to 2kHz, and help to better ensure the performance and role of hydrophones in applications such as ocean detection, noise measurement, and resource exploration.

[0078] It should be noted that the vibrating liquid column hydrophone calibration method provided in this embodiment obtains correction values ​​for the effects of hydrophones of different frequencies and sizes on the sound field distribution through sound field modeling and simulation calculation, thereby improving the accuracy of the calibration results and being applicable to a wider range of hydrophones.

[0079] It should be noted that, in the vibrating liquid column hydrophone calibration method provided in this embodiment, the calculation process of the sensitivity of the hydrophone 3 to be measured takes the common piezoelectric hydrophone as an example, and calculates the sound pressure sensitivity of the hydrophone through its output open-circuit voltage. However, as long as the measurement frequency is in the range of 10 Hz to 2 kHz, this method is also applicable to optical fiber hydrophones, vector hydrophones, etc., and it is only necessary to change its output open-circuit voltage to the output phase shift (optical fiber hydrophone), output vibration velocity or acceleration (vector hydrophone), respectively, to calibrate and obtain the phase shift sensitivity of the optical fiber hydrophone, the vibration velocity sensitivity or acceleration sensitivity of the vector hydrophone.

[0080] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. For those skilled in the art, it is obvious that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the spirit or basic features of the present application. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present application is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present application. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0081] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A vibrating liquid column hydrophone calibration device based on laser interferometry, comprising a hydrophone to be measured (3), a liquid column chamber (2) for suspending the hydrophone to be measured (3), and a vibration table (1) connected to the liquid column chamber (2), characterized in that: The hydrophone to be tested (3) is detachably connected to an adjustment and positioning mechanism (5), and the adjustment and positioning mechanism (5) is connected to a laser vibrometer (4) for performing vibration measurement.

2. The calibration device according to claim 1, characterized in that: The laser vibrometer (4) is signal-connected to a vibration velocity signal demodulator (6).

3. The calibration device according to claim 2, characterized in that: The vibration velocity signal demodulator (6) is connected to an oscilloscope (9) via a channel 2.

4. The calibration device according to claim 1, characterized in that: The signal of the hydrophone (3) to be tested is connected to a preamplifier (7).

5. The calibration device according to claim 4, characterized in that: The preamplifier (7) is connected to an oscilloscope (9) via channel 1.

6. The calibration device according to any one of claims 3 or 5, characterized in that: The oscilloscope (9) is data-connected to a host computer (10).

7. The calibration device according to claim 6, characterized in that: The host computer (10) is signal-connected to a signal source (11).

8. The calibration device according to claim 7, characterized in that: The signal source (11) is signal-connected to a power amplifier (8).

9. The calibration device according to claim 8, characterized in that: The power amplifier (8) is signal-connected to the vibration table (1).

10. A method for calibrating a vibrating liquid column hydrophone based on laser interferometry, characterized in that: include: Determining the size parameters of the target liquid column cavity (2), and removing bubbles in the liquid in the target liquid column cavity (2); Installing target hydrophone (3); Performing gain calibration on the preamplifier (7) to set signal parameters and power amplifier gain; The laser vibrometer (4) measures the vibration velocity u(f) of the target liquid column chamber (2); Calculate the surface sound pressure p of the target hydrophone (3) in the target liquid column cavity (2) h (f); Simulation modeling to correct sound pressure Δp h (f); Measure the output open circuit voltage U of the target hydrophone (3) H (f); Calculate the sensitivity M of the target hydrophone (3) H (f); It is determined whether calibration needs to be continued. If so, the upper computer (10) program controls to automatically change the signal frequency f; if not, the calibration ends.

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