A method for measuring key parameters of a laser-piston sound generator sound pressure calculation model

Abstract

The application discloses a kind of key parameters of laser piston sound generator sound pressure calculation model determination method, belong to laser piston sound generator technical field, it is by the same one to be measured infrasound sensor and the acoustic coupling of three different lengths of piston cavity of piston sound generator, the response voltage of infrasound sensor is successively collected when different piston cavity length, the ratio of the response voltage of infrasound sensor when different piston cavity length is calculated, and the experimental data of the sound pressure ratio of piston sound generator when different piston cavity length is obtained;According to experimental data, the parameters to be determined in the sound pressure calculation model of piston sound generator are fitted using genetic algorithm, and the key parameters to be determined in the sound pressure calculation model of piston sound generator are obtained.The method can solve the problem of accurate determination of the change of piston cavity volume and additional acoustic impedance introduced by the acoustic coupling of infrasound sensor and piston sound generator, and improve the calculation accuracy of the sound pressure calculation model of laser piston sound generator.

Description

Technical Field

[0001] This invention belongs to the field of laser piston sound generator technology, specifically relating to a method for determining key parameters of a laser piston sound generator sound pressure calculation model. Background Technology

[0002] Infrasound typically refers to sound waves with frequencies below 20Hz. It is ubiquitous in nature, industrial production, and transportation, such as natural phenomena like earthquakes and volcanic eruptions, the operation of large machinery, transportation, rocket and missile launches, and supersonic aircraft flights.

[0003] Due to the strong penetrating power and long propagation distance of infrasound, monitoring technology using infrasound sensor arrays for infrasound source localization and identification is widely used in fields such as national defense security, geological disaster prevention and control, and geophysical research. Applications include nuclear explosion detection, prediction of natural disasters such as earthquakes, volcanoes, and debris flows, rocket and missile trajectory monitoring, and natural gas pipeline leak monitoring. Infrasound sensors are the data source for monitoring systems. The accuracy of their sound pressure measurements and the quality of the target sound source radiation signals they acquire determine the accuracy of nuclear explosion yield estimation, target sound source localization, and feature identification. This directly affects the effectiveness and reliability of infrasound monitoring data and reconnaissance results; therefore, metrological assurance is necessary.

[0004] Considering the signal characteristics of infrasound in different application scenarios, the calibration frequency range of infrasound sensors should cover at least 0.01Hz to 20Hz. The laser piston generator is the standard infrasound source for primary calibration of the infrasound sensor and the main standard for infrasound frequency airborne sound pressure reference. It consists of a piston generator and a laser interferometer. The piston generator is the sound-generating device, producing the standard infrasound wave used for sensor calibration. The laser interferometer is the assignment device; by measuring the displacement of the piston's reciprocating motion and combining theoretical formulas, it assigns a value to the sound pressure (unit: Pa) of the radiated infrasound wave within the piston generator. Then, based on the response voltage (unit: V) of the infrasound sensor, it achieves the calibration test of the sound pressure sensitivity (unit: mV / Pa).

[0005] The basic principle of a piston generator is as follows: a plane wave is excited by the reciprocating motion of a piston within a sealed cavity whose size is much smaller than the wavelength of the sound wave in the medium (at least 1 / 20 of the wavelength). The radiated sound pressure inside the laser piston generator is a calculated sound pressure. The accuracy of the calculation result is closely related to the values ​​of the parameters in the calculation formula and the sound pressure error correction model. In other words, the accuracy of the key parameters in the sound pressure calculation model directly affects the accuracy of the sound pressure value assigned inside the piston generator.

[0006] Currently, the structural parameters of the piston cavity are mainly given by the design drawings, failing to consider the actual assembly process and the volume changes introduced by the acoustic coupling interface adapter. The acoustic impedance of the infrasound sensor under test is generally considered infinite, but the additional acoustic impedance introduced by its internal cavity and the air path connection with the piston cavity cannot be ignored. Because its structural parameters are unknown, the additional acoustic impedance of the infrasound sensor under test cannot be accurately calculated. For these reasons, only infrasound sensors and their acoustic coupling methods that do not significantly alter the piston cavity volume can be calibrated using a laser piston generator, limiting the applicability of the laser piston generator calibration technique. Summary of the Invention

[0007] The purpose of this invention is to provide a method for determining key parameters of a laser piston generator sound pressure calculation model, solving the problem of accurately measuring the piston cavity volume change and additional acoustic impedance introduced by the acoustic coupling between the infrasound sensor and the piston generator, improving the calculation accuracy of the laser piston generator sound pressure calculation model, directly improving the uncertainty level of the sound pressure sensitivity calibration of the laser piston generator method infrasound sensor, and expanding the applicability of the laser piston generator method calibration technology to infrasound sensors of different types and with different interfaces.

[0008] The technical solution adopted in this invention is as follows:

[0009] A method for determining key parameters of a laser piston sound generator sound pressure calculation model includes the following steps:

[0010] (1) Based on the connection structure relationship between the laser piston generator and the infrasound sensor to be tested, a sound pressure calculation model of the laser piston generator is constructed. The connection structure between the laser piston generator and the infrasound sensor to be tested includes a piston cavity. A piston is installed at one end of the piston cavity, and the infrasound sensor to be tested is connected to the other end of the piston cavity through an air passage.

[0011] (2) Based on the internal cavity of the infrasound sensor under test and the additional acoustic impedance introduced by the acoustic coupling of the infrasound sensor under test, a sound pressure error correction term is constructed, and the key parameters to be measured in the sound pressure calculation model of the laser piston generator are determined. The key parameters include the equivalent length of the piston cavity, the internal cavity of the infrasound sensor under test and the additional acoustic impedance introduced by the acoustic coupling of the infrasound sensor under test.

[0012] (3) Process three piston cavities with different cavity lengths. Except for the cavity length, the other structural parameters of the piston sound generator remain unchanged.

[0013] (4) The same infrasound sensor to be tested is acoustically coupled to three piston cavities of different lengths of the piston generator. The response voltage of the infrasound sensor is collected sequentially for different piston cavity lengths. The ratio of the response voltage of the infrasound sensor for different piston cavity lengths is calculated to obtain experimental data of the calculated sound pressure ratio of the piston generator for different piston cavity lengths.

[0014] (5) Based on the experimental data of the sound pressure ratio of the piston generator with different piston cavity lengths, the genetic algorithm is used to fit the parameters to be measured in the sound pressure calculation model of the piston generator to obtain the optimal solution of the key parameters to be measured in the sound pressure calculation model of the piston generator.

[0015] Furthermore, in step (1), the calculation formula for the sound pressure calculation model of the laser piston generator is as follows:

[0016]

[0017] Where p is the sound pressure amplitude inside the piston cavity, γ is the specific heat ratio of air, p0 is the static pressure, and r c Let x be the piston radius, x be the piston displacement, V0 be the volume of the piston cavity when the piston is in equilibrium, and Δp(H,L,W) be the error correction related to heat conduction, cavity leakage, and sound pressure fluctuation.

[0018] Furthermore, the sound pressure error correction term in step (2) can be expressed as:

[0019] Δp(H, L, W)=p WC ×p LHC (2);

[0020] Where: p WC For sound pressure fluctuation correction, p LHC Correction for the coupling between heat conduction and cavity leakage;

[0021] The correction formula for sound pressure fluctuation is:

[0022]

[0023] in, Let m be the m-th zero of the first-order Bessel function, i.e. L is the length of the piston cavity, with the piston center point at its equilibrium position as the origin; z is the axial distance of the piston cavity from the origin; r is the radial distance of the piston cavity from the origin; and a is the radius of the piston cavity. c Where ω is the piston radius, ω = 2πf is the angular frequency of the sound wave, f is the frequency of the sound wave, and c0 is the speed of sound in air.

[0024] The coupling correction formula for heat conduction and cavity leakage is:

[0025]

[0026] Where j is the imaginary unit, T L Y is the leakage time constant of the piston generator. r The equivalent admittance introduced by the internal cavity of the infrasound sensor under test and its air passage connection with the piston generator, ρ0 is the air density in the cavity at the piston's equilibrium position, c0 is the air velocity, and α t x is the thermal diffusivity of the enclosed gas. m Let J0(x) be the m-th zero of the 0th-order Bessel function. m ) = 0.

[0027] Further, step (3) specifically involves processing three piston cavities. Except for the cavity length, all other structural parameters of the piston sound generator are the same. The equivalent lengths of the piston cavities are marked as L, L+ΔL1, and L+ΔL2, respectively. ΔL1 and ΔL2 are the changes in the physical length of the piston cavity, which have been set during processing.

[0028] Furthermore, the specific steps of step (4) are as follows:

[0029] (4.1) The same infrasound sensor to be tested is sequentially acoustically coupled to the three piston chambers of the piston generator, and its electrical signal output is recorded by data acquisition, analysis and recording of its response voltage.

[0030] For a piston cavity with an equivalent length of L, the response voltage sequence of the infrasound sensor at the calibration frequency point is recorded as U0;

[0031] For a piston cavity with an equivalent length of L+ΔL1, the response voltage sequence of the infrasound sensor at the calibration frequency point is recorded as U1;

[0032] For a piston cavity with an equivalent length of L+ΔL2, the response voltage sequence of the infrasound sensor at the calibration frequency point is recorded as U2;

[0033] (4.2) Let S be the sensitivity sequence of the infrasound sensor at the calibration frequency. Then the measurement results of the sound pressure generated in the piston cavity with equivalent lengths L, L+ΔL1, and L+ΔL2 are respectively expressed as follows:

[0034]

[0035] By combining formulas (9) to (11) in pairs, the sensitivity of the infrasound sensor can be eliminated, resulting in:

[0036]

[0037] Among them, the sound pressure p generated in the piston cavity with equivalent lengths of L, L+ΔL1, and L+ΔL2 are respectively. a0p a1 p a2 The theoretical model is given by formulas (1) and (2), where the parameters to be measured are the equivalent length L of the piston cavity and the equivalent acoustic impedance (a+jb) of the infrasound sensor to be measured, i.e., the equivalent admittance Y. r The reciprocals of , where a, j, and b are the real, imaginary, and imaginary units of the equivalent acoustic impedance, respectively.

[0038] Furthermore, the specific steps of step (6) are as follows:

[0039] The range of values ​​for the equivalent length L is derived from the physical length of the piston cavity, and ΔL1 and ΔL2 are the changes in the physical length of the piston cavity.

[0040] Based on the structural parameters of the infrasound sensor under test and the air circuit connection between the infrasound sensor under test and the piston generator, the range of values ​​for the corresponding equivalent acoustic impedance is obtained.

[0041] Based on the determined value range and the experimental data of the sound pressure ratio of the piston generator for different piston cavity lengths, a genetic algorithm is used to fit the key parameters to be measured in the sound pressure calculation model of the laser piston generator, and the optimal solutions for the equivalent length L and the equivalent acoustic impedance of the infrasound sensor to be measured are obtained.

[0042] Furthermore, the specific steps for fitting the equivalent length L of the piston cavity and the equivalent acoustic impedance of the infrasound sensor under test in the sound pressure calculation model of the laser piston generator using a genetic algorithm are as follows:

[0043] Experimental data for calculating the sound pressure ratio of the piston generator were obtained based on the response voltages U0, U1, and U2 of the infrasound sensor for different piston cavity lengths. By substituting the experimental environment parameters into empirical formulas for parameters such as air density, thermal diffusivity, sound velocity, and specific heat ratio, input parameters are provided for the sound pressure calculation models of formulas (1) and (2). By substituting the known parameters in the model, model data for calculating the sound pressure ratio of the piston generator are obtained.

[0044] Define a fitness function to quantify the error between the model data and experimental data for calculating the sound pressure ratio of the piston generator, determine the optimization objective, and ensure the global optimality of parameter fitting through the joint constraints of the three sets of data;

[0045] The genetic algorithm configuration and evolution execution begins. Based on the determined value range, the real and imaginary parts of the equivalent cavity length and the equivalent acoustic impedance of the infrasound sensor are encoded. Genetic operators such as crossover, mutation, and selection are configured. Hybrid crossover maintains diversity, Gaussian perturbation avoids local optima, tournament selection retains high-quality individuals, and then evolution is executed. The number of individuals and the number of generations are initialized to balance the global search and convergence speed.

[0046] The genetic algorithm extracts the optimal individual to obtain the optimal solution for the equivalent length L of the piston cavity and the equivalent acoustic impedance of the infrasound sensor to be measured in the sound pressure calculation model of the piston generator.

[0047] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0048] 1. This invention extracts the parameters to be measured in the piston generator sound pressure calculation model, including the equivalent length of the piston cavity, the internal cavity of the infrasound sensor, and the additional acoustic impedance introduced by its acoustic coupling with the piston generator. In actual calibration, the additional acoustic impedance introduced by acoustic coupling of different types of infrasound sensors and the change in the volume of the piston generator cavity can be quantitatively measured experimentally. This improves the accuracy of the piston generator sound pressure calculation results, thereby reducing the measurement uncertainty of the laser piston generator method for infrasound sensor calibration results. It expands the applicability of the laser piston generator method calibration technology, no longer limiting it to infrasound sensors without obvious internal cavities and whose acoustic coupling method does not significantly change the volume of the piston generator cavity, such as standard-sized laboratory standard microphones and working standard microphones, thus meeting the primary calibration requirements of different types of infrasound sensors. Attached Figure Description

[0049] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort, wherein:

[0050] Figure 1 This is a schematic diagram of the connection structure between the laser piston sound generator and the infrasound sensor to be tested in this invention;

[0051] Figure 2 This is a schematic diagram illustrating the measurement of key parameters in this invention. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0053] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0054] Refer to the instruction manual. Figure 1-2 ;

[0055] Among them, the typical structure of the laser piston sound generator and its connection relationship with the infrasound sensor are as follows: Figure 1 As shown, the formula for calculating the radiated sound pressure of a piston generator is:

[0056]

[0057] Where p is the sound pressure amplitude inside the piston cavity, γ is the specific heat ratio of air, p0 is the static pressure, and r c Let x be the piston radius, x be the piston displacement, V0 be the volume of the piston cavity when the piston is in equilibrium, and Δp(H,L,W) be the error correction related to heat conduction, cavity leakage, and sound pressure fluctuation.

[0058] The sound pressure error correction effect of the piston generator includes heat conduction, cavity leakage, and sound pressure fluctuation. At higher frequencies, sound pressure fluctuation correction dominates; at lower frequencies, heat conduction and cavity leakage correction dominate. Heat conduction and cavity leakage are strongly coupled and require coupled correction, while their coupling with sound pressure fluctuation is weak and can be corrected independently. The sound pressure error correction term in formula (1) can be expressed as:

[0059] Δp(H, L, W)=p WC ×p LHC (2)

[0060] Where: p WC For sound pressure fluctuation correction, p LHC Correction for the coupling between heat conduction and cavity leakage.

[0061] The correction formula for sound pressure fluctuation is:

[0062]

[0063]

[0064] in: Let m be the m-th zero of the first-order Bessel function, i.e. L is the length of the piston cavity, with the piston center point at its equilibrium position as the origin; z is the axial distance of the piston cavity from the origin; r is the radial distance of the piston cavity from the origin; and a is the radius of the piston cavity. cLet ω be the piston radius, ω = 2πf be the angular frequency of the sound wave, f be the frequency of the sound wave, and c0 be the speed of sound in air.

[0065] The coupling correction formula for heat conduction and cavity leakage is:

[0066]

[0067] Where: j is the imaginary unit, T L Y is the leakage time constant of the piston generator. r The equivalent admittance introduced by the internal cavity of the infrasound sensor under test and its air passage connection with the piston generator, ρ0 is the air density in the cavity at the piston's equilibrium position, and α t x is the thermal diffusivity of the enclosed gas. m Let J0(x) be the m-th zero of the 0th-order Bessel function. m ) = 0.

[0068] In the calculation formulas for the radiated sound pressure of the piston generator described in formulas (1) and (2): static pressure, piston radius and piston displacement can be accurately measured, and the specific heat ratio of air can be calculated according to empirical formulas; ideally, the cavity volume of the piston generator can be calculated as a standard cylindrical cavity, and the calculation parameters include the radius and length of the piston cavity. The radius of the piston cavity can be accurately measured, and its length is related to the sealing structure of the piston and the cavity, such as membrane seal, gap seal, etc., which makes the cavity volume calculation more complicated. If the cavity volume is still calculated as a cylindrical cavity, it is more appropriate to express its cavity length as an equivalent length to characterize the correction of the cavity volume by the irregular structure of the piston cavity; in addition, the internal cavity of the infrasound sensor to be measured and the additional cavity volume introduced by the air path interface of the piston generator are not easy to be directly measured. In the calculation process of formula (2), the internal cavity of the infrasound sensor to be measured and the additional acoustic impedance introduced by acoustic coupling are described by equivalent acoustic impedance. Therefore, the key parameters that are difficult to measure accurately in the calculation formula of the radiated sound pressure of the piston generator can be summarized as the equivalent length of the piston cavity and the equivalent acoustic impedance of the infrasound sensor to be measured.

[0069] like Figure 2 As shown, the key parameters of the laser piston generator sound pressure calculation model were determined:

[0070] Three piston cavities are machined. Except for the cavity length, all other structural parameters of the piston sound generator are the same. The equivalent lengths of the piston cavities are marked as L, L+ΔL1, and L+ΔL2, respectively. Among them, ΔL1 and ΔL2 are the changes in the physical length of the piston cavity, which are set during machining and are known quantities.

[0071] The same infrasound sensor under test is sequentially acoustically coupled to the three cavities of the piston generator, and its electrical signal output is analyzed and recorded by data acquisition.

[0072] For a piston cavity with an equivalent length of L, the response voltage sequence of the infrasound sensor at the calibration frequency point is recorded as U0;

[0073] For a piston cavity with an equivalent length of L+ΔL1, the response voltage sequence of the infrasound sensor at the calibration frequency point is recorded as U1;

[0074] For a piston cavity with an equivalent length of L+ΔL2, the response voltage sequence of the infrasound sensor at the calibration frequency point is recorded as U2;

[0075] Assuming the sensitivity sequence of the infrasound sensor at the calibration frequency is recorded as S, the measurement results of the sound pressure generated in the piston cavity with equivalent lengths L, L+ΔL1, and L+ΔL2 are respectively expressed as:

[0076]

[0077] By combining formulas (9) to (11) in pairs, the sensitivity of the infrasound sensor can be eliminated, resulting in:

[0078]

[0079] Among them, the sound pressure p generated in the piston cavity with equivalent lengths of L, L+ΔL1, and L+ΔL2 are respectively. a0 p a1 p a2 The theoretical model is given by formulas (1) and (2), where the parameters to be measured are the equivalent length L of the piston cavity and the equivalent acoustic impedance (a+jb) of the infrasound sensor to be measured, i.e., the equivalent admittance Y. r The reciprocal of , a, j and b are the real part, imaginary unit and imaginary part of the equivalent acoustic impedance respectively. Based on the test data of formula (12) to formula (14), the three undetermined parameters in the laser piston generator sound pressure calculation model are obtained by fitting with a genetic algorithm.

[0080] The range of values ​​for the equivalent length L is given based on the physical length of the piston cavity. ΔL1 and ΔL2 are the changes in the physical length of the piston cavity, which are known quantities.

[0081] Based on the structural parameters of the infrasound sensor to be tested and its connection with the piston generator air circuit, the range of values ​​for their equivalent acoustic impedance can be estimated, and the range can be appropriately expanded.

[0082] Based on the aforementioned value range, and using experimental data on the sound pressure ratio of the piston generator for different piston cavity lengths, a genetic algorithm was used to fit the key parameters to be measured in the sound pressure calculation model of the laser piston generator.

[0083] Specifically, the steps for fitting key parameters in the sound pressure calculation model of the laser piston generator using a genetic algorithm are as follows:

[0084] Experimental data for calculating the sound pressure ratio of the piston generator were obtained based on the response voltages U0, U1, and U2 of the infrasound sensor for different piston cavity lengths.

[0085] Substituting the experimental environmental parameters (temperature, air pressure, humidity) into empirical formulas for parameters such as air density, thermal diffusivity, sound velocity, and specific heat ratio, we provide input parameters for the sound pressure calculation models of formulas (1) and (2). Substituting the known parameters in the model, we obtain model data for calculating the sound pressure ratio of the piston generator.

[0086] Define a fitness function to quantify the error between the model data and experimental data for calculating the sound pressure ratio of the piston generator, determine the optimization objective, and ensure the global optimality of parameter fitting through the joint constraints of the three sets of data;

[0087] The genetic algorithm configuration and evolution execution begins. Individuals (equivalent cavity length, real and imaginary parts of the additional acoustic impedance of the infrasound sensor) are encoded according to the previously determined value range. Genetic operators crossover, mutation and selection are configured. Hybrid crossover maintains diversity, Gaussian perturbation avoids local optima, tournament selection retains high-quality individuals, and then evolution is executed. The number of individuals and the number of generations must be balanced between global search and convergence speed.

[0088] The genetic algorithm extracts the optimal individual to obtain the optimal solution for the equivalent length L of the piston cavity and the equivalent acoustic impedance of the infrasound sensor to be measured in the sound pressure calculation model of the piston generator.

[0089] In addition, when determining the key parameters of the sound pressure calculation model of the laser piston generator, the number of piston cavities used is not limited to three, but at least two. The number of piston cavities only affects the available data and fitting accuracy of the fitting algorithm. The parameter fitting method based on experimental data is not limited to the genetic algorithm, and other algorithms and models that can achieve the same function can be used. The sound pressure calculation model of the piston generator is not limited to the formula given in this patent, especially the coupling correction of heat conduction and cavity leakage, and the sound pressure fluctuation correction model.

[0090] The above description constitutes an embodiment of the present invention. The foregoing descriptions are preferred embodiments of the present invention. Unless there is a clear contradiction or a prerequisite for a particular preferred embodiment, the preferred embodiments can be arbitrarily combined and used. The embodiments and specific parameters described are merely for clearly illustrating the verification process of the invention and are not intended to limit the scope of patent protection of the present invention. The scope of patent protection of the present invention is still determined by its claims. Similarly, any equivalent structural changes made based on the description and drawings of the present invention should also be included within the scope of protection of the present invention.

Claims

1. A method for determining key parameters of a laser piston sound generator sound pressure calculation model, characterized in that, Includes the following steps: (1) Based on the connection structure relationship between the laser piston generator and the infrasound sensor to be tested, a sound pressure calculation model of the laser piston generator is constructed. The connection structure between the laser piston generator and the infrasound sensor to be tested includes a piston cavity. A piston is installed at one end of the piston cavity, and the infrasound sensor to be tested is connected to the other end of the piston cavity through an air passage. (2) Based on the internal cavity of the infrasound sensor under test and the additional acoustic impedance introduced by the acoustic coupling of the infrasound sensor under test, construct the sound pressure error correction term and determine the key parameters to be measured in the sound pressure calculation model of the laser piston generator. The key parameters include the equivalent length of the piston cavity, the internal cavity of the infrasound sensor under test and the additional acoustic impedance introduced by the acoustic coupling of the infrasound sensor under test. (3) Process three piston cavities with different lengths. Except for the cavity length, the other structural parameters of the piston sound generator remain unchanged. (4) The same infrasound sensor to be tested is acoustically coupled to three piston cavities of different lengths of the piston generator. The response voltage of the infrasound sensor is collected sequentially for different piston cavity lengths. The ratio of the response voltage of the infrasound sensor for different piston cavity lengths is calculated to obtain experimental data of the calculated sound pressure ratio of the piston generator for different piston cavity lengths. (5) Based on the experimental data of the sound pressure ratio of the piston generator with different piston cavity lengths, the genetic algorithm is used to fit the parameters to be measured in the sound pressure calculation model of the piston generator to obtain the optimal solution of the key parameters to be measured in the sound pressure calculation model of the piston generator.

2. The method for determining key parameters of the sound pressure calculation model of a laser piston generator according to claim 1, characterized in that, In step (1), the calculation formula for the sound pressure calculation model of the laser piston generator is as follows: （1）； in, p This represents the sound pressure amplitude within the piston cavity. γ It is the specific heat ratio of air. p 0 represents static pressure. r c Where is the piston radius. x For piston displacement, V 0 represents the volume of the piston cavity when the piston is in its equilibrium position, Δ p ( H , L , W This is an error correction related to heat conduction, cavity leakage, and sound pressure fluctuations.

3. The method for determining key parameters of the sound pressure calculation model of a laser piston generator according to claim 2, characterized in that, The sound pressure error correction term in step (2) can be expressed as: （2）； in: Correction for sound pressure fluctuations Correction for the coupling between heat conduction and cavity leakage; The correction formula for sound pressure fluctuation is: （3）； （4）； （5）； （6）； in, The first-order Bessel function m One zero point, that is , L Let be the length of the piston cavity, with the piston's center point at its equilibrium position as the origin. z This represents the axial distance of the piston cavity from the origin. r This is the radial distance of the piston cavity from the origin. a Where is the radius of the piston cavity. r c Where is the piston radius. The angular frequency of the sound wave f For sound wave frequency, c 0 represents the speed of sound in air; The coupling correction formula for heat conduction and cavity leakage is: （7）； （8）； Where j is the imaginary unit, T L The leakage time constant of the piston sound generator. Y r The equivalent admittance is introduced for the internal cavity of the infrasound sensor under test and its air path connection with the piston generator. ρ 0 represents the air density inside the piston cavity at its equilibrium position. c 0 represents the speed of sound in air. α t The thermal diffusivity of the enclosed gas. The 0th order Bessel function m One zero point, that is .

4. The method for determining key parameters of the sound pressure calculation model of a laser piston generator according to claim 1, characterized in that, Step (3) specifically involves: machining three piston cavities. Except for the cavity length, all other structural parameters of the piston-generator are identical. The equivalent lengths of the piston cavities are marked as follows: L , L+ Δ L 1. L+ Δ L 2, where Δ L 1 and Δ L 2 represents the change in the physical length of the piston cavity, which is set during manufacturing. 。 5. The method for determining key parameters of the sound pressure calculation model of a laser piston generator according to claim 4, characterized in that, The specific steps of step (4) are as follows: (4.1) The same infrasound sensor to be tested is sequentially acoustically coupled to the three piston chambers of the piston generator, and its electrical signal output is recorded by data acquisition, analysis and recording of its response voltage. For equivalent length of L The piston cavity, the response voltage sequence of the infrasound sensor at the calibration frequency point, is recorded as follows: U 0; For equivalent length of L+ Δ L The response voltage sequence of the infrasound sensor at the calibration frequency point of the piston cavity is recorded as follows: U 1; For equivalent length of L+ Δ L The response voltage sequence of the infrasound sensor at the calibration frequency point of the piston chamber 2 is recorded as follows: U 2; (4.2) Let the sensitivity sequence of the infrasound sensor used at the calibration frequency be recorded as follows: S The equivalent lengths are respectively L , L +Δ L 1. L+ Δ L The measurement results of the sound pressure generated in the piston cavity of 2 are expressed as follows: （9）； （10）； （11）； Formula (9) ~ By combining formulas (11) in pairs, the sensitivity of the infrasound sensor can be eliminated, resulting in: （12）； （13）； （14）； Among them, the equivalent lengths are respectively L , L +Δ L 1. L+ Δ L Sound pressure is generated inside the piston chamber of 2. p a0 , p a1 , p a2 The theoretical model is given by formulas (1) and (2), where the parameter to be determined is the equivalent length of the piston cavity. L The equivalent acoustic impedance, i.e., the equivalent admittance, of the infrasound sensor under test Y r The reciprocal of.

6. The method for determining key parameters of the sound pressure calculation model of a laser piston generator according to claim 5, characterized in that, The specific steps of step (6) are as follows: The equivalent length is derived from the physical length of the piston cavity. L The range of values ​​for Δ L 1 and Δ L 2 represents the change in the physical length of the piston cavity; Based on the structural parameters of the infrasound sensor under test and the air circuit connection between the infrasound sensor under test and the piston generator, the range of values ​​for the corresponding equivalent acoustic impedance is obtained. Based on the determined value range and experimental data on the sound pressure ratio of the piston generator for different piston cavity lengths, a genetic algorithm was used to fit the key parameters to be measured in the sound pressure calculation model of the laser piston generator, thus obtaining the equivalent length. L The optimal solution for the equivalent acoustic impedance of the infrasound sensor under test.

7. The method for determining key parameters of the sound pressure calculation model of a laser piston generator according to claim 6, characterized in that, The equivalent length of the piston cavity in the sound pressure calculation model of the laser piston generator is fitted using a genetic algorithm. L The specific steps for determining the equivalent acoustic impedance of the infrasound sensor under test are as follows: The response voltage of the infrasound sensor varies depending on the piston cavity length. U 0、 U 1. U 2. Obtain experimental data for calculating the sound pressure ratio of the piston-generator. , 、 ; Substituting the experimental environment parameters into the empirical formulas for air density, thermal diffusivity, sound velocity, and specific heat ratio, we provide input parameters for the sound pressure calculation models of formulas (1) and (2). Substituting the known parameters in the model, we obtain the model data for calculating the sound pressure ratio of the piston generator. , 、 ; Define a fitness function to quantify the error between the model data and experimental data for calculating the sound pressure ratio of the piston generator, determine the optimization objective, and ensure the global optimality of parameter fitting through the joint constraints of the three sets of data; The genetic algorithm configuration and evolution execution begins. Based on the determined value range, the real and imaginary parts of the equivalent cavity length and the additional acoustic impedance of the infrasound sensor are encoded. Genetic operators such as crossover, mutation, and selection are configured. Hybrid crossover maintains diversity, Gaussian perturbation avoids local optima, tournament selection retains high-quality individuals, and then evolution is executed. The number of individuals and the number of generations are initialized to balance the global search and convergence speed. The genetic algorithm extracts the optimal individual to obtain the optimal solution for the equivalent length L of the piston cavity and the equivalent acoustic impedance of the infrasound sensor to be measured in the sound pressure calculation model of the piston generator.

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