Aerial sound low-frequency sensitivity calibration device

Abstract

The invention belongs to the technical field of acoustic measurement testing, and particularly discloses an airborne sound low-frequency sensitivity calibration device. The device comprises a piston structure, an air cylinder structure, a bottom tool structure, a static pressure control unit and a signal acquisition unit. The static pressure control unit controls the piston structure to vertically move at a certain speed; the piston structure controls air static pressure with certain frequency and size to act in a cavity of the air cylinder structure; a low-frequency sound signal is simulated and generated by applying periodically changing air static pressure in the air cylinder structure, and is received by a standard hydrophone needing to be calibrated; the bottom tool structure transmits the output electric signal to the signal acquisition unit; and the signal acquisition unit acquires and analyzes the signal after passing through the pre-amplification circuit, thereby realizing effective calibration of the sensitivity of the low-frequency hydrophone. According to the invention, the working frequency range is between 2Hz and 20Hz, and the low-frequency sensitivity calibration of the air sound can be realized simply, conveniently and quickly.

Description

Technical Field

[0001] The invention belongs to the technical field of acoustic measurement and testing, and particularly relates to a low-frequency sensitivity calibration device for airborne sound. Background Art

[0002] With my country's in-depth research in marine science, hydrophones are playing a key role in marine resource exploration, communications, monitoring, and other areas. The widespread application of underwater acoustic technology has placed higher demands on underwater target detection and early warning capabilities, especially in the field of low-frequency detection.

[0003] During the low-frequency calibration of hydrophones, commonly used sensitivity calibration methods include the hydrostatic pressure excitation method, the vibrating liquid column method, and the standing wave tube comparison method. Although the hydrostatic pressure excitation method is applicable to a variety of hydrophone types, its accuracy is easily affected by environmental factors such as water temperature and flow. The vibrating liquid column method is simple to operate and has high accuracy, but it is limited by the cavity volume and is difficult to apply to large hydrophones. The standing wave tube comparison method, while highly repeatable and reliable, has diverse sources of error and is also limited by the size of the hydrophone. Furthermore, the calibration equipment required for these methods is bulky, difficult to carry, complex to operate, and difficult to replicate.

[0004] Therefore, to meet the needs of hydrophone calibration, it is necessary to explore more efficient, portable, and accurate calibration methods. This will help improve the technical level of my country's marine scientific research, resource exploration, communication, and monitoring, and provide strong support for the development of the marine industry. Summary of the Invention

[0005] To address the above shortcomings of known technologies, the present invention provides an airborne low-frequency sensitivity calibration device with an operating frequency range of 2Hz-20Hz. This device avoids the complex and variable underwater environment that affects low-frequency hydrophone calibration, simplifies the operation process, and enhances the simplicity and reproducibility of the calibration device. Using this airborne low-frequency sensitivity calibration device, the sensitivity of low-frequency hydrophones can be effectively calibrated quickly and easily.

[0006] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0007] An airborne sound low-frequency sensitivity calibration device comprises a piston structure, a cylinder structure, a bottom tooling structure, a static pressure control unit and a signal acquisition unit;

[0008] The cylinder structure has a total length of 163 mm, an inner diameter of 50 mm, and a thickness of 2.4 mm. The piston structure includes two grooves for nesting sealing rings, a groove for nesting wear-resistant belts, and a threaded hole.

[0009] The bottom tooling structure includes two threaded holes, two grooves for nested sealing rings, and an outlet;

[0010] The static pressure control unit includes a telescopic guide rod, a metal plate, a rotating plate, a servo motor, and a speed regulating power supply;

[0011] The signal acquisition unit includes a preamplifier, an oscilloscope, and a computer;

[0012] One end of the cylinder structure is connected to the bottom tooling structure by screws through the threaded hole, and the other end is an open container with a scale marked on the inner wall;

[0013] The piston structure is placed in the cylinder structure, the groove is nested with a sealing ring with an inner diameter of 43.7 mm and a wire diameter of 3.55 mm, and the groove is nested with a wear-resistant belt with an inner diameter of 44 mm;

[0014] The piston structure is driven by the static pressure control unit to perform periodic vertical movement up and down;

[0015] The telescopic guide rod is connected to the metal plate via screws and is connected to the piston structure via threaded holes;

[0016] The servo motor is provided with ±12V power by the speed regulating power supply, driving the rotating plate to rotate, so that the telescopic guide rod moves vertically periodically;

[0017] The speed regulating power supply can adjust the speed of the servo motor, and is powered by a 220V external power supply.

[0018] A standard hydrophone to be calibrated is placed in the bottom tooling structure. The standard hydrophone 4 includes two grooves for nested sealing rings.

[0019] The output signal is transmitted to the signal acquisition unit by the outlet, and the signal is displayed by the oscilloscope through the preamplifier and then transmitted to the computer; the preamplifier is powered by a ±5V DC source.

[0020] As can be seen from the above, in this airborne low-frequency sensitivity calibration device, the static pressure control unit controls the piston structure to perform periodic vertical movement, thereby controlling the magnitude and frequency of the air static pressure applied to the calibration cavity, and then generating a periodically alternating air static pressure in the cavity, simulating the generation of a low-frequency sound signal which is received by the standard hydrophone to be calibrated, and the output signal is collected and analyzed by the signal acquisition unit, ultimately achieving airborne low-frequency sensitivity calibration in the operating frequency range of 2Hz-20Hz. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

[0022] Figure 1 This is a schematic diagram of a low-frequency sensitivity calibration device for airborne sound according to an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the internal structure of the airborne sound low-frequency sensitivity calibration device according to an embodiment of the present invention;

[0024] Figure 3 Schematic diagram of air static pressure changes in the airborne sound low-frequency sensitivity calibration device according to an embodiment of the present invention;

[0025] Figure 4 This is a sensitivity calibration flow chart of the low-frequency sensitivity calibration device for airborne sound according to an embodiment of the present invention;

[0026] In the figure, 1. Cylinder structure; 2. Piston structure sealing ring groove; 3. Piston structure wear-resistant belt groove; 4. Standard hydrophone; 5. Bottom tooling structure sealing ring groove; 6. M5 threaded hole; 7. Bottom tooling structure; 8. Piston structure; 9. Standard hydrophone sealing ring groove; 10. Inlet port; 11. Telescopic rod; 12. Metal plate; 13. Rotating plate; 14. Servo motor; 15. Speed ​​control power supply; 16. Preamplifier; 17. Oscilloscope; 18. Computer; 19. M6 threaded hole. DETAILED DESCRIPTION

[0027] In order to better explain the present invention and facilitate understanding, preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings through specific implementation methods.

[0028] Embodiment Airborne sound low frequency sensitivity calibration device

[0029] The specific technical solutions, objectives and advantages of the present invention, as well as the working principle and calibration method of the airborne sound low-frequency sensitivity calibration device will be explained below with reference to the accompanying drawings.

[0030] This embodiment provides an airborne low-frequency sensitivity calibration device for simple and rapid calibration of the sensitivity of low-frequency hydrophones, primarily in the 2Hz-20Hz frequency range. This device primarily controls the rate and displacement of the piston's periodic vertical motion, thereby applying a static air pressure of a certain frequency and magnitude to the calibration chamber. This pressure, in turn, generates a periodically alternating static air pressure within the calibration chamber, simulating a low-frequency acoustic signal received by the hydrophone to be calibrated. The output signal is then collected and analyzed, ultimately achieving effective calibration of the low-frequency sensitivity of the airborne hydrophone.

[0031] To achieve the above object, the present invention provides a low-frequency sensitivity calibration device for airborne sound, such as Figures 1 to 4 As shown, a low-frequency sensitivity calibration device for airborne sound comprises:

[0032] The piston structure, cylinder structure, bottom tooling structure, static pressure control unit and signal acquisition unit are characterized in that: the cylinder structure 1 has a total length of 163 mm, an inner diameter of 50 mm and a thickness of 2.4 mm; the piston structure 8 includes two nested sealing ring grooves 2, a nested wear-resistant belt groove 3 and a threaded hole 18; the bottom tooling structure 7 includes two M5 threaded holes 6, two nested sealing ring grooves 5 and an outlet 10; the static pressure control unit includes a telescopic guide rod 11, a metal plate 12, a rotating plate 13, a servo motor 14, and a speed regulating power supply 15; the signal acquisition unit includes a preamplifier 15, an oscilloscope 16 and a computer 17.

[0033] One end of the cylinder structure 1 is connected to the bottom tooling structure 2 by screws through the M5 threaded hole 6, and the other end is an open container with scales marked on the inner wall.

[0034] The piston structure 8 is placed in the cylinder structure 1, the groove 2 is nested with a sealing ring with an inner diameter of 43.7 mm and a wire diameter of 3.55 mm, and the groove 3 is nested with a wear-resistant belt with an inner diameter of 44 mm.

[0035] The piston structure 8 is driven by the static pressure control unit to perform periodic vertical movement up and down;

[0036] The telescopic guide rod 11 is connected to the metal plate 12 by screws and is connected to the piston structure 8 by a threaded hole 18. The servo motor 14 is powered by the speed regulating power supply 15 with a power supply of ±12V and drives the rotating plate 13 to rotate.

[0037] The speed regulating power supply 15 can adjust the speed of the servo motor 15, and is powered by a 220V external power supply.

[0038] A standard hydrophone 4 to be calibrated is placed in the bottom tooling structure 7 , and the standard hydrophone 4 includes two grooves 9 for nesting sealing rings.

[0039] The outlet 10 transmits the output signal to the signal acquisition unit, and the signal is displayed by the oscilloscope 16 through the preamplifier 15 and then transmitted to the computer 17; the preamplifier 15 is powered by a ±5V DC source.

[0040] The operating principle and calibration process of the present invention are as follows: During the calibration process, the static pressure control unit drives the piston in periodic motion, thereby applying a static air pressure of a certain frequency and magnitude to the calibration device. The static pressure value can be calculated and analyzed from the piston's downward displacement. To achieve this, a scale is simply calibrated on the inner wall of the cylinder to read the piston's downward displacement during each cycle of its periodic up and down vertical motion. In other words, by reading the piston's downward displacement during each cycle, the static pressure applied to the cylinder cavity during the calibration process can be calculated.

[0041] Under the condition of good air tightness of the device, the relationship between the piston drop displacement and the static pressure is analyzed as follows:

[0042] The state of a gas can usually be represented by its three state parameters, namely pressure P, specific heat v, and temperature T. Regardless of the type of gas, these three parameters are interrelated and can be expressed as:

[0043] F(P,v,T)=0 (1)

[0044] For this device, during the periodic motion of the piston, it can be approximately considered to be in a sealed state, and the gas inside the device can be considered to reach dynamic equilibrium when the piston is pressed to the target scale. Without considering the intermolecular forces and the volume of gas molecules, the ideal gas state equation (2) can be used to represent it.

[0045] PV=nRT(2)

[0046] Where V is the volume of the gas in the device, n is the amount of substance in the gas, R is the molar gas constant, and T is the absolute temperature. At this point, the molar constant for air, R, is 8.31 J / mol·k. At room temperature, the absolute temperature, T, is 298.15 K. Before the piston is pressed, the initial gas volume in the device's cylinder is V0, approximately 0.245 L. At standard atmospheric pressure, the molar mass of gas in the cylinder is:

[0047]

[0048] Therefore, from formula (2), we can know that the pressure in the cylinder before the piston is pressed is:

[0049]

[0050] When using this device to calibrate the sensitivity of the hydrophone, the piston on the device moves vertically up and down periodically. The piston's drop displacement in one cycle is Δh. The volume of gas in the cylinder of the device at this time can be expressed as πr 2 (h0-Δh). Therefore, during the calibration process, the static air pressure ΔP applied inside the cylinder cavity is proportional to the piston's falling displacement.

[0051] Δh has the following relationship:

[0052]

[0053] Where r represents the radius of the device cylinder. h0 represents the initial height of the gas-filled portion of the device cylinder before the piston is pressed. This height is calculated by subtracting the volume occupied by the bottom fixture structure and the hydrophone to be calibrated from the total volume of the cylinder. A more accurate estimate is approximately 125 mm. If the volume occupied by the bottom fixture structure and the hydrophone to be calibrated in this device cylinder is V1 = 7.4575 * 10 -5 m 3 , the volume of the cylinder V2=3.198875*10 -4 m 3 , then there is the following relationship among V0, V1, V2, and h0:

[0054]

[0055] From formula (5), we can know that when the piston starts to fall from the zero initial position of the cylinder, the static pressure of the air exerted by the piston from 0 to 5 cm is as follows:

[0056]

[0057] According to the sensitivity calibration formula:

[0058]

[0059] Among them, M P To measure the sensitivity of the hydrophone; U oc To measure the open circuit voltage across the hydrophone.

[0060] Combining formula (5) we can get:

[0061]

[0062] According to formula (9), the sound pressure sensitivity of the hydrophone to be tested can be calculated. oc To measure the open-circuit voltage across the hydrophone, h is the displacement of the falling piston; V0 is the initial volume of the gas in the cavity before the piston is pressed; n is the amount of gas in the device; R is the molar gas constant; T is the absolute temperature; and M is the low-frequency sensitivity value of the hydrophone to be measured.

[0063] Finally, it should be noted that the above is only the preferred embodiment of the present invention and does not limit the present invention. Although the preferred embodiment of the present invention has been explained in detail, relevant technical personnel in this profession and field can still refer to this embodiment to modify or improve the solution, or make equivalent replacements for certain components. The preferred embodiment of the present invention is only for the detailed explanation of the technical solution design of the present invention, and does not limit the present invention itself. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An airborne low-frequency sensitivity calibration device, comprising a piston structure, a cylinder structure, a bottom tooling structure, a static pressure control unit, and a signal acquisition unit, characterized in that: The cylinder structure 1 has a total length of 163 mm, an inner diameter of 50 mm, and a thickness of 2.4 mm. The piston structure 8 includes two nested sealing ring grooves 2, a nested wear-resistant belt groove 3, and a threaded hole 18. The bottom tooling structure 7 includes two threaded holes 6, two nested sealing ring grooves 5, and an outlet 10. The static pressure control unit includes a telescopic guide rod 11, a metal plate 12, a rotating plate 13, a servo motor 14, and a speed control power supply 15. The signal acquisition unit includes a preamplifier 15, an oscilloscope 16, and a computer 17.

2. The airborne sound low-frequency sensitivity calibration device according to claim 1, characterized in that: One end of the cylinder structure 1 is connected to the bottom tooling structure 2 by screws through the threaded hole 6, and the other end is an open container with scales marked on the inner wall.

3. The airborne sound low-frequency sensitivity calibration device according to claim 2, characterized in that: The piston structure 8 is placed in the cylinder structure 1, the groove 2 is nested with a sealing ring with an inner diameter of 43.7 mm and a wire diameter of 3.55 mm, and the groove 3 is nested with a wear-resistant belt with an inner diameter of 44 mm.

4. The airborne sound low-frequency sensitivity calibration device according to claim 3, characterized in that: The piston structure 8 is driven by the static pressure control unit to perform periodic vertical movement up and down; The telescopic guide rod 11 is connected to the metal plate 12 by screws and is connected to the piston structure 8 by a threaded hole 18. The servo motor 14 is powered by the speed regulating power supply 15 with a power supply of ±12V and drives the rotating plate 13 to rotate. The speed regulating power supply 15 can adjust the speed of the servo motor 15, and is powered by a 220V external power supply.

5. The airborne sound low-frequency sensitivity calibration device according to claim 1, characterized in that: A standard hydrophone 4 to be calibrated is placed in the bottom tooling structure 7 , and the standard hydrophone 4 includes two grooves 9 for nesting sealing rings.

6. The airborne sound low-frequency sensitivity calibration device according to claim 1, characterized in that: The outlet 10 transmits the output signal to the signal acquisition unit, and the signal is displayed by the oscilloscope 16 through the preamplifier 15 and then transmitted to the computer 17; the preamplifier 15 is powered by a ±5V DC source.

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