Method and system for rapidly calibrating sensitivity of hydrophone in air based on knocking

Abstract

The invention provides a method and a system for rapidly calibrating the sensitivity of a hydrophone in air based on knocking, and belongs to the technical field of underwater acoustic measurement and test. According to the calibration method, a to-be-tested hydrophone is knocked by a standard hydrophone in a normal-temperature and normal-pressure air environment, and calibration calculation is carried out through amplitude and absolute value integration of an output signal. According to the invention, rapid calibration of the low-frequency sensitivity of the hydrophone in the air can be realized, and effective supplementation is carried out on a traditional method and system for calibrating the low-frequency sensitivity of the hydrophone; experimental measurement shows that the sensitivity of the spherical hydrophone and the sensitivity of the circular tube type hydrophone can be rapidly and effectively calibrated, the calibration frequency ranges from 200 Hz to 800 Hz, the measurement expansion uncertainty of the spherical hydrophone is about 1.3 dB, and the measurement expansion uncertainty of the circular tube type hydrophone is about 2 dB.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater acoustic measurement and testing, and in particular to a method and system for rapid calibration of hydrophone sensitivity in air based on tapping. Background Art

[0002] As my country's marine research continues to deepen, hydrophones are playing an important role in marine resource exploration, marine communications, and other fields. To ensure the consistency and accuracy of hydrophone underwater measurement results, their receiving sensitivity must be calibrated regularly.

[0003] Commonly used sensitivity calibration methods for low-frequency calibration of hydrophones include the hydrostatic pressure excitation method, the vibrating liquid column method, and the standing wave tube comparison method. The hydrostatic pressure excitation method is suitable for most types of hydrophones, the vibrating liquid column method is relatively simple to operate and has low measurement error, and the standing wave tube comparison method offers high repeatability and reliable results. All of these methods are effective in calibrating the receiving sensitivity of hydrophones and are relatively mature and widely used. However, due to the complex and ever-changing underwater calibration environment and the fact that most traditional calibration methods require the construction of a suitable low-frequency sound source, their calibration systems are relatively complex and require high measurement conditions and operational requirements. Therefore, it is necessary to develop methods for rapid hydrophone calibration in air and portable calibration systems to meet the needs of practical hydrophone sensitivity calibration. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and system for rapid calibration of hydrophone sensitivity in air based on tapping, which effectively supplements the traditional hydrophone low-frequency sensitivity calibration method.

[0005] The present invention is achieved through the following technical solutions:

[0006] A tapping-based rapid calibration method and system for hydrophone sensitivity in air. In an air environment of normal temperature and pressure, a standard hydrophone is tapped on the hydrophone to be tested. Calibration calculations are performed through the amplitude and absolute value integration of the output signal, and the calibration sensitivity results are displayed, thereby achieving rapid low-frequency sensitivity calibration of spherical and cylindrical hydrophones in air.

[0007] Further:

[0008] The method described comprises the following steps:

[0009] (1) The sound center of the standard hydrophone strikes the sound center of the hydrophone to be tested;

[0010] (2) Collect and record the output signal of the hydrophone after the tapping;

[0011] (3) preprocessing the stored signal and determining the signal-to-noise ratio;

[0012] (4) Identify the absolute value of the amplitude of the processed signal or calculate the absolute value integral of the signal interval;

[0013] (5) Calculate the sensitivity of the hydrophone to be tested.

[0014] Further:

[0015] The step (1) comprises:

[0016] (1.1) The acoustic centers of the standard hydrophone and the hydrophone under test are the geometric centers of the spherical hydrophone and the circular hydrophone;

[0017] (1.2) For spherical hydrophones, the standard hydrophone strikes the hydrophone under test with the ball head facing the ball head; for cylindrical hydrophones, the standard hydrophone strikes the hydrophone under test vertically.

[0018] Further:

[0019] The step (2) comprises:

[0020] (2.1) The output signal of the hydrophone is collected by the main control module 1 under the control of the acquisition module 2, and is saved and recorded by the storage module 3.

[0021] Further:

[0022] Said (2.1) includes: said acquisition module 2 has a sampling frequency of 20 kHz, and said storage module 3 stores 480 kb of data in a single calibration.

[0023] Further:

[0024] The step (3) comprises:

[0025] (3.1) Calculate the mean of the signal;

[0026] (3.2) Subtract the mean value from each sampling point of the signal to filter out the DC component;

[0027] (3.3) Read the absolute value of the peak value U f , calculate the signal-to-noise ratio S N Is it greater than 20dB?

[0028] U n =20mV is the maximum background noise of the calibration system

[0029] Further:

[0030] The step (4) comprises:

[0031] (4.1) For the spherical hydrophone, identify the absolute value of the processed signal amplitude, and extract the peak absolute value U1 of the standard hydrophone and the peak absolute value U2 of the hydrophone to be tested;

[0032] (4.2) For the circular tube hydrophone, perform absolute value integration on the signal interval with a length of approximately 11 ms.

[0033] Further:

[0034] Said (4.2) includes: the length of said signal interval is 1ms before the absolute value of the peak value of the entire signal and 10ms after it.

[0035] Further:

[0036] The step (5) comprises:

[0037] (5.1) Spherical hydrophone sensitivity calibration formula:

[0038]

[0039] Where, U1 and U2 are the absolute values ​​of the signal peaks of the hydrophone to be tested and the standard hydrophone respectively; M S is the sensitivity of a standard hydrophone.

[0040] (5.2) Circular tube hydrophone sensitivity calibration formula:

[0041]

[0042] Where U a 、U b are the absolute values ​​of the amplitudes in the signal integration intervals of the hydrophone under test and the standard hydrophone, respectively.

[0043] Further:

[0044] The sensitivity calibration result is displayed by the display module 4.

[0045] Further:

[0046] Said (3.3) includes: said signal-to-noise ratio is less than 20dB, said display module 4 displays: this calibration result is invalid.

[0047] The advantages of the present invention are:

[0048] 1. The present invention can quickly calibrate the sensitivity of the hydrophone in air;

[0049] 2. Compared with the traditional calibration method, the present invention is simpler to operate;

[0050] 3. The calibration system of the present invention is more compact and portable. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A schematic diagram of the system of the present invention;

[0052] Figure 2 Schematic diagram of the tapping of a spherical hydrophone;

[0053] Figure 3 Schematic diagram of the tapping of a circular tube hydrophone;

[0054] Figure 4 Graph of the tap output signal for the hydrophone. DETAILED DESCRIPTION

[0055] The present invention will be described in detail below with reference to the accompanying drawings:

[0056] A tapping-based rapid air sensitivity calibration method and system for hydrophones uses a standard hydrophone to tap the hydrophone under test in an air environment at normal temperature and pressure. Calibration calculations are performed using the amplitude and absolute value integral of the output signal, and the calibration sensitivity results are displayed. This method enables rapid low-frequency sensitivity calibration of spherical and tubular hydrophones in air. Experimental measurements have shown that this method can quickly and effectively calibrate the sensitivity of spherical and tubular hydrophones at calibration frequencies between 200Hz and 800Hz. The expanded measurement uncertainty for spherical hydrophones is approximately 1.3dB, and for tubular hydrophones is approximately 2dB.

[0057] The method described comprises the following steps:

[0058] (1) The sound center of the standard hydrophone strikes the sound center of the hydrophone to be tested;

[0059] (2) Collect and record the output signal of the hydrophone after the tapping;

[0060] (3) preprocessing the stored signal and determining the signal-to-noise ratio;

[0061] (4) Identify the absolute value of the amplitude of the processed signal or calculate the absolute value integral of the signal interval;

[0062] (5) Calculate the sensitivity of the hydrophone to be tested.

[0063] The step (1) comprises:

[0064] (1.1) The acoustic centers of the standard hydrophone and the hydrophone under test are the geometric centers of the spherical hydrophone and the circular hydrophone;

[0065] (1.2) For spherical hydrophones, the standard hydrophone strikes the hydrophone under test in the following manner: Figure 2 For the round tube hydrophone, the standard hydrophone strikes the hydrophone to be tested in the following way: Figure 3 vertical tap as indicated.

[0066] As attached Figure 1 As shown:

[0067] The step (2) comprises:

[0068] (2.1) The output signal of the hydrophone is collected by the main control module 1 under the control of the acquisition module 2, and is saved and recorded by the storage module 3.

[0069] Said (2.1) includes: said acquisition module 2 has a sampling frequency of 20 kHz:

[0070] f s >20*f N

[0071] Where, f s is the sampling frequency of acquisition module 2; f N is the output signal of the hydrophone, f N <1kHz.

[0072] The storage module 3 stores 480kb of data in a single calibration.

[0073]

[0074] Where N S =16bit is the resolution of acquisition module 2; C is the number of acquisition channels, which is 2; t=6s is the time for main control module 1 to control a single storage.

[0075] The step (3) comprises:

[0076] (3.1) Calculate the mean of the signal;

[0077] (3.2) As attached Figure 4 As shown, the mean value of each sampling point of the signal is subtracted to filter out the DC component;

[0078] (3.3) Read the absolute value of the peak value U f , calculate the signal-to-noise ratio S N Is it greater than 20dB?

[0079] U n =20mV is the maximum background noise of the calibration system

[0080] The step (4) comprises:

[0081] (4.1) For the spherical hydrophone, identify the absolute value of the processed signal amplitude, and extract the peak absolute value U1 of the standard hydrophone and the peak absolute value U2 of the hydrophone to be tested;

[0082] (4.2) For the circular tube hydrophone, perform absolute value integration on the signal interval with a length of approximately 11 ms.

[0083] Said (4.2) includes: the length of said signal interval is 1ms before the absolute value of the peak value of the entire signal and 10ms after it.

[0084] The step (5) comprises:

[0085] (5.1) Spherical hydrophone sensitivity calibration formula:

[0086]

[0087] Where, U1 and U2 are the absolute values ​​of the signal peaks of the hydrophone to be tested and the standard hydrophone respectively; M S is the sensitivity of a standard hydrophone.

[0088] (5.2) Circular tube hydrophone sensitivity calibration formula:

[0089]

[0090] Where U a 、U b are the absolute values ​​of the amplitudes of the signals of the hydrophone to be tested and the standard hydrophone within the signal integration interval, respectively. The sensitivity calibration result is displayed by the display module 4.

[0091] Said (3.3) includes: said signal-to-noise ratio is less than 20dB, said display module 4 displays: this calibration result is invalid.

[0092] It is understandable that for those skilled in the art, any equivalent replacement or modification of the technical solution and inventive concept of the present invention should be included in the protection scope defined by the claims of the present invention.

Claims

1. A method and system for rapid calibration of hydrophone sensitivity in air based on tapping, characterized by: In an air environment of normal temperature and pressure, a standard hydrophone is used to strike the hydrophone to be tested. The amplitude and absolute value integral of the output signal are used for calibration calculation and the calibration sensitivity results are displayed, thereby realizing rapid calibration of the low-frequency sensitivity of spherical and cylindrical hydrophones in air.

2. The method and system for rapid calibration of hydrophone sensitivity in air based on tapping according to claim 1, characterized in that: The method described comprises the following steps: (1) The sound center of the standard hydrophone strikes the sound center of the hydrophone to be tested; (2) Collect and record the output signal of the hydrophone after the tapping; (3) preprocessing the stored signal and determining the signal-to-noise ratio; (4) Identify the absolute value of the amplitude of the processed signal or calculate the absolute value integral of the signal interval; (5) Calculate the sensitivity of the hydrophone to be tested.

3. The method and system for rapid calibration of hydrophone sensitivity in air based on tapping according to claim 2, characterized in that: The step (1) comprises: (1.1) The acoustic centers of the standard hydrophone and the hydrophone under test are the geometric centers of the spherical hydrophone and the circular hydrophone; (1.2) For spherical hydrophones, the standard hydrophone strikes the hydrophone under test with the ball head facing the ball head; for cylindrical hydrophones, the standard hydrophone strikes the hydrophone under test vertically.

4. The method and system for rapid calibration of hydrophone sensitivity in air based on tapping according to claim 2, characterized in that: The step (2) comprises: (2.1) The output signal of the hydrophone is collected by the main control module 1 under the control of the acquisition module 2, and is saved and recorded by the storage module 3.

5. The method and system for rapid calibration of hydrophone sensitivity in air based on tapping according to claim 4, characterized in that: Said (2.1) includes: said acquisition module 2 has a sampling frequency of 20 kHz, and said storage module 3 stores 480 kb of data in a single calibration.

6. The method and system for rapid calibration of hydrophone sensitivity in air based on tapping according to claim 2, characterized in that: The step (3) comprises: (3.1) Calculate the mean of the signal; (3.2) Subtract the mean value from each sampling point of the signal to filter out the DC component; (3.3) Read the absolute value of the peak value U f , calculate the signal-to-noise ratio S N Is it greater than 20dB? U n =20mV is the maximum background noise of the calibration system.

7. The method and system for rapid calibration of hydrophone sensitivity in air based on tapping according to claim 2, characterized in that: The step (4) comprises: (4.1) For the spherical hydrophone, identify the absolute value of the processed signal amplitude, and extract the peak absolute value U1 of the standard hydrophone and the peak absolute value U2 of the hydrophone to be tested; (4.2) For the circular tube hydrophone, perform absolute value integration on the signal interval with a length of approximately 11 ms.

8. The method and system for rapid calibration of hydrophone sensitivity in air based on tapping according to claim 7, characterized in that: Said (4.2) includes: the length of said signal interval is 1ms before the absolute value of the peak value of the entire signal and 10ms after it.

9. The method and system for rapid calibration of hydrophone sensitivity in air based on tapping according to claim 2, characterized in that: The step (5) comprises: (5.1) Spherical hydrophone sensitivity calibration formula: Where, U1 and U2 are the absolute values ​​of the signal peaks of the hydrophone to be tested and the standard hydrophone respectively; M S is the sensitivity of a standard hydrophone. (5.2) Circular tube hydrophone sensitivity calibration formula: Where U a 、U b are the absolute values ​​of the amplitudes in the signal integration intervals of the hydrophone under test and the standard hydrophone, respectively.

10. The method and system for rapid calibration of hydrophone sensitivity in air based on tapping according to claim 9, characterized in that: The sensitivity calibration result is displayed by the display module 4.

11. The method and system for rapid calibration of hydrophone sensitivity in air based on tapping according to claim 6, characterized in that: Said (3.3) includes: said signal-to-noise ratio is less than 20dB, said display module 4 displays: this calibration result is invalid.

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