阅读说明：本技术 用于特高压线路分裂导线内侧的立方体形声强测量装置与实现方法 (Cubic sound intensity measuring device for inner side of split conductor of extra-high voltage line and implementation method ) 是由 袁海文 赵鹏辉 吕建勋 刘颖异 李鑫 于 2021-07-14 设计创作，主要内容包括：本发明提出了一种用于测量特高压线路分裂导线内侧声强的装置。该装置采用立方体结构,通过合理的均压、屏蔽设计,可使之适用于特高压电磁环境。该装置可以并行采集特高压线路可听噪声源处的声压,使用光纤将原始数据快速传输至远端上位机,然后通过本发明提出的声强算法得到声源声强。本发明将声压传感器阵列布置于立方体结构的特定位置,通过有规则的成对匹配,基于匹配信号获取特定方向的声强,进一步通过信息余度设计,可靠、快速地实现了相应位置声强的有效测量。(The invention provides a device for measuring the sound intensity of the inner side of a split conductor of an extra-high voltage line. The device adopts the cube structure, through reasonable voltage-sharing, shielding design, can make it be applicable to extra-high voltage electromagnetic environment. The device can collect the sound pressure of the audible noise source of the extra-high voltage line in parallel, the original data is rapidly transmitted to a far-end upper computer by using the optical fiber, and then the sound intensity of the sound source is obtained by the sound intensity algorithm provided by the invention. The sound pressure sensor array is arranged at a specific position of the cubic structure, the sound intensity in a specific direction is obtained based on the matching signal through regular pairing matching, and further effective measurement of the sound intensity at the corresponding position is reliably and quickly realized through information redundancy design.)

1. A cubic sound intensity measuring device and an implementation method for the inner side of a split conductor of an extra-high voltage line are characterized in that:

the cube-shaped sound intensity measuring device is arranged in the middle of a split conductor of an extra-high voltage circuit, consists of a cube-shaped fixing structure, a sound pressure sensor array, a signal transmitting module, a signal conditioning module, a digital acquisition module, an electro-optic modulation module and a power supply module, and then transmits a signal to a far end through an optical fiber insulator and transmits the signal to an upper computer through the electro-optic modulation module;

the cuboidal fixing structure is arranged on the inner side of the split conductor, is used for fixing a sound pressure sensor array, a signal transmitting module, a signal conditioning module, a digital acquisition module, an electro-optical modulation module and a power supply module in the measuring device, and has electromagnetic shielding and voltage-sharing effects; the sound pressure sensor array is arranged with a specific number of sensors in a unique mode to measure sound pressure; the signal transmitting module isolates the electric signal output by the sensor and carries out impedance transformation; the signal conditioning module obtains a standardized electric signal through filtering and voltage amplification; the digital acquisition module converts the standardized voltage analog signal into a digital signal; the electro-optical modulation module converts the digital signal into an optical signal and transmits the optical signal to a far end; the power supply module uses a high-capacity battery to supply power for other modules of the cubic measuring device; the optical fiber insulator is used for realizing effective electrical insulation between an ultrahigh voltage and a safe potential; the photoelectric demodulation module demodulates the optical signal into an electric signal and transmits the electric signal to an upper computer, and then the sound intensity vector of the point to be measured is obtained according to the sound intensity algorithm provided by the invention.

2. Cube-shaped holding structure according to claim 1, wherein:

the cubic fixing structure is used for installing and fixing the sound intensity measuring device, a cubic frame structure is designed for avoiding the influence on sound intensity measurement, the top point and the edge are processed into round corners, the surface is covered by a metal net, and the structural dimension parameters of the cubic frame structure need to be designed according to the measurement requirements and the strong electromagnetic environment adaptive to the extra-high voltage line.

3. The feature size parameter of claim 2, wherein:

the parameters to be determined in the structural dimension parameters are the edge length, the edge and the radius of a top fillet, the installation requirement of a measuring position needs to be considered for determining the parameter size, the surface curvature of the measuring device is adjusted, and a surface electric field is controlled not to be dizzy, so that the effects of electromagnetic shielding and voltage sharing are achieved.

4. The acoustic pressure sensor array of claim 1, wherein:

the sound pressure sensor array is composed of 14 sensors with the same characteristics, and the sensors are respectively arranged in the normal direction of the face center of the 6 faces of the cubic device and the body diagonal direction of 8 vertexes according to a specific arrangement mode.

5. The specific arrangement of claim 4, wherein:

the specific arrangement mode is based on the characteristics of a cubic fixed structure according to orthogonal vectors of a space coordinate system, and two orthogonal systems are selected: the center connecting line of 3 pairs of parallel surfaces of the cube and 4 pairwise orthogonal body diagonals divide each two of 14 sensors into 7 groups, and the groups are respectively arranged at the center of the surface and the vertex along the 7 straight lines. Two sensor diaphragms on the same straight line point to the outside sound field in parallel so as to measure the sound intensity of 7 specific directions.

6. The digital acquisition module of claim 1, wherein:

the digital acquisition module uses 14 parallel high-precision AD acquisition channels, the sampling frequency is adjustable within the range of 50 k-200 kHz, and the proper sampling frequency can be selected according to the signal analysis requirement and the environmental condition so as to meet the requirements of high-precision and high-speed sampling.

7. The fiber optic insulator of claim 1, wherein:

the optical fiber insulator uses a resin suspension type high-voltage insulator, the insulator is fixed on a transmission conductor, and an optical fiber transmission medium is sealed in the insulator and used for transmitting 14 paths of sound pressure signals collected in parallel, so that large-scale, rapid and safe signal transmission can be ensured.

8. The sound intensity algorithm of claim 1, wherein:

the sound intensity algorithm is to calculate and obtain the sound intensity value of each specific single direction according to the arrangement rule and the matching mode of the sensor array on the cubic structure, then establish an over-determined linear equation set comprising 3 unknowns and 7 equations, and obtain the optimal solution formula of the sound intensity vector under the condition by solving the pseudo-inverse of the coefficient matrix of the over-determined equation set.

9. The system of over-determined linear equations of claim 8, wherein:

the over-determined system of linear equations is described as

In the formula I_x、I_y、I_zThe component of the sound intensity vector of the position to be measured under the three-dimensional rectangular coordinate system;I_EC、I_HB、I_AG、I_DFis a sound intensity measurement for 7 specific directions; lambda [ alpha ]₁、λ₂、λ₃、λ₄Is a correction factor, is related to the distance between two mutually matched sensors, and is further determined according to a theoretical derivation and a test calibration method.

10. The optimal solution formula according to claim 8, wherein:

the optimal solution formula is a solution method for minimizing the error of the over-determined linear equation set, and the linear equation set is described in a matrix formTherein is provided with

According to matrix theory, the optimal solution is equal to the pseudo-inverse of the coefficient matrix multiplied by the vectorFind the optimal solution as

Technical Field

The invention belongs to the field of detection technology and automation devices, and particularly relates to a cubic sound intensity measuring device and an implementation method thereof.

Background

In an ultra-high voltage transmission system, the electric field intensity on the surface of a transmission line is increased along with the increase of the voltage grade, and air can be punctured to generate corona discharge when the field intensity reaches a critical point. Corona discharge not only causes a loss of electrical energy resources, but also is accompanied by a variety of corona effects, including audible noise, radio interference, ground electric fields, and ion currents. The audible noise is taken as environmental noise interference, can seriously affect the physical and mental health of local residents, and is one of the factors which need to be considered in the construction of the ultra-high voltage transmission line.

In order to optimize the design of an ultra-high voltage transmission line, reduce the level of ambient audible noise and create a good sound environment, the time domain and frequency domain characteristics and the change rule of the noise need to be analyzed, and the acquisition and measurement of the noise are important links and key steps of research. In the traditional research, the noise is acquired by scalar quantities such as sound pressure or sound power, and the like, only the intensity of the noise or sound energy can be reflected, the position, the propagation form and the propagation direction of the noise source cannot be exactly reflected, and the expressive force on a sound field is insufficient. The sound intensity is used as a vector, and the energy, flow and propagation state of the noise source can be better reflected.

Since the noise source is near the power transmission line with extremely high potential, the generated audible noise is diffused and attenuated when the noise source propagates to the ground, and the audible noise is reflected by objects such as the earth and buildings to some extent. In addition, the environmental noise on the ground and the audible noise are greatly overlapped on the frequency band, and the ground measurement far away from the sound source is generally difficult to filter the background noise. The existing research shows that the closer the measuring point is to the audible noise source, the more remarkable the superiority of the obtained noise measurement result in the aspects of accuracy, integrity and background noise suppression capability is.

However, the prior art means lacks a device and a method suitable for measuring the sound intensity of the sound source at the split conductor under the extra-high voltage environment. Due to complex electromagnetic environments such as high electric potential, strong electric field, etc., various factors must be considered in the design of the measuring device, such as shape selection, layout, size calculation, system design, etc.

Disclosure of Invention

Aiming at the problems, the invention designs a cubic sound intensity measuring device for the inner side of the split conductor of the extra-high voltage line, provides a sound intensity algorithm based on the device, and solves the problem of safe and accurate measurement of a sound intensity vector at a sound source under the environment of an extra-high voltage complex electromagnetic field.

The invention specifically adopts the following technical scheme.

A cubic sound intensity measuring device and an implementation method for a split conductor of an extra-high voltage line are disclosed. The measuring system comprises a cubic fixing structure, a sound pressure sensor array, a signal transmitting module, a signal conditioning module, a digital acquisition module, an electro-optic modulation module, a power supply module, an optical fiber insulator, an electro-optic demodulation module and an upper computer; the corresponding sound intensity algorithm is to obtain specific sound intensity values in different linear directions according to the arrangement rule and the matching mode of the sensors on the cubic structure, and then obtain the sound intensity vector at the sensor array according to a sound intensity vector conversion method. The method is characterized in that:

the cubic fixing structure is arranged at the inner side of the split conductor and used for fixing and installing the sound intensity measuring device at the extra-high voltage potential. To avoid the influence on the sound intensity measurement, the structure is designed as a cubic frame, the surface of which is covered with a metal mesh, the size of which is limited by the polygonal space in the middle of the split conductor and the total volume of the modules that can be accommodated. In order to adapt to the strong electromagnetic environment of an extra-high voltage line, 8 vertexes and 12 edges of a cube are processed into round corners tangent to two adjacent side surfaces, the radius of each round corner should meet the measurement requirement of a sound intensity vector, the structure surface is enabled not to be dizzy, and each measurement module can stably work and is not broken down.

The sound pressure sensor array is used for measuring sound pressure signals of the sound source at different positions. The sensor selects an electret capacitance type sound pressure sensor with high precision, good accuracy and convenient use. By means of the characteristics of the cubic structure, two orthogonal systems of the cubic structure are selected: the connecting line of centers of 3 pairs of parallel surfaces of the cube and 4 body diagonals which are orthogonal pairwise are arranged. Every two sound pressure sensors with the same characteristics are divided into 7 groups, and the two groups are respectively arranged on the center of a face and the vertex along the 7 linear directions of the orthogonal system. The two sound pressure sensor diaphragms in each direction point outwards and are parallel to each other to measure the vibration of the sound waves.

The signal transmission module converts a high-impedance voltage signal output by the sensor into a low-impedance voltage signal through the preamplifier and simultaneously realizes signal isolation; the signal conditioning module completes signal filtering and amplification to obtain standard-5V- +5V voltage signals. The digital acquisition module realizes synchronous sampling on 14 channels, the quantization precision of the AD chip is required to reach 16 bits, and the sampling frequency can be dynamically adjusted within the range of 50 k-200 kHz according to the signal analysis requirement and the environmental condition; in addition, an oversampling technology is used to improve the signal-to-noise ratio of the system, improve the resolution of the AD, and reduce the design requirements for subsequent filtering.

The electro-optical modulation module modulates the sound pressure digital signal output by sampling into an optical signal. The power supply module uses a large-capacity battery to ensure that each module of the cubic device can be supplied with power for a long time.

The optical fiber insulator can transmit sound pressure optical signals collected by the system to a far end instantly and quickly, the optical fiber can effectively avoid signal interference of a complex electromagnetic field environment, and meanwhile, the resin suspension type high-voltage insulator is used for effective insulation of ultrahigh-voltage high potential and safe potential. The photoelectric demodulation module is positioned at the far end of the high potential position of the extra-high voltage line, and can resolve optical signals transmitted by the optical fibers into electric signals and transmit the electric signals to an upper computer. The upper computer solves the sound intensity vector of the point to be measured through the sound intensity algorithm provided by the patent and displays the change curve of the sound intensity in real time.

The sound intensity algorithm firstly selects the edge length of a cube as a standardized distance of two matched microphones according to a specific sensor layout mode on the cube structure, and deduces a unidirectional sound intensity conversion method based on sound pressures of two adjacent points when the distance is obtained. Then, 3 coordinate components of the sound intensity vector are mapped in 7 linear directions by utilizing the special geometric relationship between the 7 specific directions and three coordinate axes in a rectangular coordinate system, thereby establishing an equation set in the specific arrangement mode provided by the invention. As shown below, the system of equations contains 3 unknowns and 7 equations, belonging to an overdetermined system of linear equations.

In the formula I_x、I_y、I_zThe component of the sound intensity vector of the position to be measured under the three-dimensional rectangular coordinate system;I_EC、I_HB、I_AG、I_DFis a sound intensity measurement for 7 specific directions, as shown in fig. 6; lambda [ alpha ]₁、λ₂、λ₃、λ₄Is a correction factor that is related to the distance between two sensors that are matched to each other. Since the distance between the diagonal direction matching sensors is not the normalized distance defined in the derivation of this patent, the correction factor must be further determined based on error theory analysis and experimental calibration.

In general, the above-mentioned overdetermined linear equations have no mathematically exact solution, and therefore the measurement data should be fully utilized to find the engineering optimum solution. The patent abandons the traditional method of selecting partial equations to solve, and describes the linear equation set as a matrix form in order to minimize the error of the equation setTherein is provided with

According to the matrix theory, the pseudo inverse of the coefficient matrix Q is obtainedLet the optimal solution beThe optimal solution is equal to the pseudo-inverse P of the coefficient matrix multiplied by the vectorIs provided with3-dimensional vectorThe optimal solution of the sound intensity vector of the position to be measured is obtained.

Compared with the prior art, the invention has the beneficial effects that:

firstly, the cubic structure provided by the invention is easy to process and install, sensors can be arranged at a plurality of point positions, the geometric relationship between the point positions is clear and definite, and the synthesis and the decomposition of a vector field are convenient; the cubic structure adopts various voltage-sharing designs, so that the overhigh electric field intensity on the surface of the device can be avoided, and the safe and stable operation of the device in an extra-high voltage environment is ensured.

Secondly, the multi-redundancy array type sound intensity acquisition system can improve vector measurement accuracy and reduce random errors. Meanwhile, the measuring system has higher information redundancy, and even if a single sensor fails, the measuring function of the sound intensity vector can be completed by using partial sensors, so that the robustness of the system is improved.

Finally, the digital optical fiber transmission system has the advantages of wide frequency band, less attenuation and large effective distance, can meet the requirement of large-scale data quick transmission during 14-path parallel acquisition, and can transmit the original data to a far-end upper computer in real time for sound intensity calculation and analysis. The optical fiber insulator can effectively isolate the external environment, protect the data transmission in the optical fiber from being influenced by an extra-high voltage strong electric field and ensure the safe transmission of the originally acquired sound pressure data.

Drawings

FIG. 1 is a schematic diagram of the system architecture of the present invention;

FIG. 2 is a schematic diagram of a cube-shaped structure of the present invention;

FIG. 3 is a diagram of a sound pressure sensor structure;

FIG. 4 is a schematic view of a fiber optic insulator connection;

FIG. 5 is a schematic diagram of a unidirectional matching sensor;

FIG. 6 is a model of the geometric layout of a sensor array of the present invention (only a portion of the sensors are shown);

wherein, 1-cube fixed structure, 2-sound pressure sensor array, 3-signal transmission module, 4-signal conditioning module, 5-central processing module, 6-electro-optical modulation module, 7-power supply module, 8-optical fiber insulator, 9-photoelectric demodulation module, 10-upper computer, 11-sound pressure sensor 1, 12-sound pressure sensor 2, 13-sound pressure sensor 3, 14-sound pressure sensor 4, 15-sound pressure sensor 5, 16-sound pressure sensor 6, 17-sound pressure sensor 7, 18-sound pressure sensor 8, 19-sound pressure sensor 9, 20-sound pressure sensor 10, 21-sound pressure sensor 11, 22-sound pressure sensor 12, 23-sound pressure sensor 13, 24-sound pressure sensor 14, 25-sensor shell, 26-vibrating diaphragm, 27-damping hole, 28-back plate, 29-inner cavity, 30-insulator, 31-low-voltage end connecting hardware, 32-low-voltage measuring end optical fiber adapter box, 33-optical fiber insulator extension hardware, 34-high-voltage measuring end optical fiber adapter box, 35-optical fiber insulator fixing expansion spring, 36-optical fiber insulator and outdoor optical fiber connecting interface, 37-optical fiber insulator and measuring system optical fiber connecting interface, 38-equalizing ring and 39-insulator.

Detailed Description

The technical scheme of the invention is further explained in detail by combining the drawings in the specification.

The invention relates to a cubic sound intensity measuring device and an implementation method for the inner side of a split conductor of an extra-high voltage line. As shown in fig. 1, the measurement system is composed of the following parts: the device comprises a 1-cubic fixed structure, a 2-sound pressure sensor array, a 3-signal transmitting module, a 4-signal conditioning module, a 5-data acquisition module, a 6-electro-optic modulation module, a 7-power supply module, an 8-optical fiber insulator, a 9-photoelectric demodulation module and a 10-upper computer. In the process of measuring the sound intensity vector, firstly, measuring sound pressure in 7 specific directions by a sound pressure sensor array at a sound source of an extra-high voltage circuit, realizing impedance transformation and signal isolation by a signal transmission module, and conditioning an electric signal into standard voltage of-5V to +5V by a signal conditioning module; the digital acquisition module obtains high-precision digital signals through a 16-bit 14-channel AD acquisition device, the electro-optical modulation module modulates the digital signals of sound pressure into optical signals, the optical signals are transmitted to a far end through optical fibers and optical fiber insulators, finally, the electro-optical demodulation module resolves the transmitted optical signals, and through the sound intensity algorithm provided by the patent, the sound intensity vector of a point to be measured is resolved by the upper computer and the change curve of the sound intensity is displayed in real time.

The cuboidal fixing structure is arranged on the inner side of the split conductor and used for fixing and installing the measuring device. To ensure effective measurement of sound intensity vectors at the split conductor sound source of an extra-high voltage line, the design and processing aspects of the cubic fixed structure need to meet the high potential constraint of a strong electric field, namely, the physical structure needs to ensure no corona, so that the measuring device is prevented from electric breakdown, and the measuring device can work safely and reliably under the voltage of +/-1100 kV. Preferably, the cubic structure uses aluminum metal material. The surface of the cubic structure is covered by a metal mesh, and the top point and the edge are processed into round corners, so that the intensity of a surface distortion electric field of the device can be reduced, and the pressure-equalizing performance is improved. The main parameters comprise the edge length, the radius of an edge and a vertex fillet, the size of the parameters needs to consider the installation requirement of a measuring position and the limitation of surface electric field intensity, and the parameters are determined through simulation and experimental tests. And finally, carrying out an ultraviolet discharge test in an ultra-high voltage environment of +/-1100 kV to ensure that the surface of the cubic structure does not generate corona, so that each measuring module can stably work in the ultra-high voltage environment.

The arrangement of the acoustic pressure sensor array on a cube-shaped structure is shown in fig. 2. The central connecting line of the parallel surfaces of the cubic structure 3 and 4 pairwise orthogonal body diagonals are selected, every two of 14 sound pressure sensors with the same characteristics are divided into 7 groups, and the groups are respectively arranged on the center of a plane and the vertex along the directions of the 7 straight lines. The two sound pressure sensor vibrating diaphragms in each direction point to the outer side and are parallel to each other, the sound pressure at two specific positions on the same straight line can be measured, and then the sound intensity vector of the position to be measured is obtained through the algorithm provided by the patent.

Preferably, the sound pressure sensor is an electret condenser microphone of model 4189 from B & K company. As shown in fig. 3, the electret condenser microphone is composed of a metal case, a delicate and highly elastic diaphragm, a damping hole located behind the diaphragm, a back plate, an inner cavity, and an insulator. The measuring frequency range of the microphone is 6.3-20 kHz, the audible noise frequency range of human ears is met, the measuring sound pressure range is 14.6-146 dB, and the sensitivity is higher and reaches 50 mV/Pa. In addition, the microphone is insensitive to temperature and humidity changes, does not need 200V polarization voltage, and is very suitable for sound pressure measurement of a free field on the inner side of a split conductor in an open air environment.

The signal transmitting module converts high-impedance voltage signals output by the 14 paths of sound pressure sensors into low-impedance signals and meanwhile realizes signal isolation. The signal conditioning module amplifies the signal into a standard voltage signal of-5V- +5V for AD acquisition.

Preferably, the digital acquisition module uses an AD7606 chip, the chip uses 5V power supply, 16-bit precision 8-path synchronous sampling, the voltage input range can be selected from-5V to +5V, and the resolution reaches 152 μ V. When the sampling rate reaches 200kSPS, the chip has 40dB anti-aliasing inhibition characteristic, and the requirement of the system on the sampling rate is met. The chip may be selected to be an oversampling mode to avoid aliasing, improve resolution, and reduce noise. Since the measuring device is provided with 14 paths of sound pressure signals, 2 AD7606 chips are needed to complete synchronous sampling.

The electro-optical signal modulation module modulates the sound pressure electric signal output by the digital acquisition module into an optical signal by utilizing the change of the electric refractive index of the crystal and transmits the optical signal to a far end. The power module uses high capacity batteries to ensure that each module of the cube-shaped device can be powered for a longer period of time.

The optical fiber insulator is mainly used for rapid data transmission between an extra-high voltage potential and a far end. Due to the influence of extra-high voltage special electromagnetic environment, the optical fiber transmission medium can be damaged, and the stability of transmission is influenced. Therefore, in practical engineering, firstly, the optical signal sent at the extra-high voltage potential is effectively isolated at high voltage through the special optical fiber communication insulator, and then the signal is transmitted to a safe position through the outdoor optical fiber. And according to the installation design requirement, hanging the communication insulator at the extra-high voltage potential position on the pole tower of the extra-high voltage transmission line.

Fig. 4 shows a schematic of the fiber-optic insulator connection. The optical fiber insulator is specially processed, and the optical fiber transmission medium is sealed in the common insulator, so that the safety and stability of the optical fiber data transmission and testing device are effectively protected. The optical fiber insulator comprises a 31-low-voltage end connecting hardware fitting, a 32-low-voltage measuring end optical fiber adapter, a 33-optical fiber insulator extension hardware fitting, a 34-high-voltage measuring end optical fiber adapter, a 35-optical fiber insulator fixing expansion spring, a 36-optical fiber insulator and outdoor optical fiber connecting interface, a 37-optical fiber insulator and measuring system optical fiber connecting interface, a 38-equalizing ring and a 39-insulator. The optical fiber insulator is connected through the optical fiber adapter box and the connecting hardware fitting and is fixed between the high-voltage side and the low-voltage side of the test line. The fixed telescopic spring has certain elasticity, and the connection distance can be adjusted in a small range.

According to the cubic structure arranged in 7 specific directions in an array manner, the sound intensity algorithm provided by the patent comprises two steps: firstly, unidirectional sound intensity conversion is carried out, namely a sound intensity value in the direction is obtained through two sound pressure sensors matched in pairs on a specific single straight line; and then, three-dimensional sound intensity vector conversion is carried out, namely an equation set is established according to a special geometric mapping relation in 7 straight line directions, the solving error is minimized through the pseudo-inverse of a coefficient matrix, and the optimal solution of the sound intensity vector is obtained through calculation.

The sensor that arranges on the cube device measures the sound pressure signal, therefore this patent proposes one-way sound intensity conversion, turns into the sound intensity with two sound pressures that match the sensor and measure on the collinear. Assuming that the edge length of the cubic device is d, the length is taken as the standard distance between two matched sensors, and the arrangement is shown in fig. 5, wherein reference points 1 and 2 are two adjacent points of the point 0 to be measured, and the distances from the two adjacent points to the point 0 are equal. The sound intensity at the central point 0 can be obtained by the sound pressure approximation at the two points 1 and 2.

Assume that the sound pressure of reference point 1 is p₁(t), the sound pressure of reference point 2 is p₂(t) of (d). According to the propagation equation of sound waves in an ideal flow medium, the correlation function of signals of 1 and 2 points is calculated, and the frequency distribution function of 0 sound intensity can be obtained:

in the formula, G₁₂Is a single-sided cross-spectral density function of the sound pressure at points 1 and 2, Im represents the imaginary part of the complex number, ω is the sound frequency, ρ₀Is the air density and d is the edge length of the cubic device。

As can be seen from equation (1), the average sound intensity at its center point at this normalized distance can be obtained by two matched sound pressure sensors at a distance d. Therefore, the sound intensity values in 7 specific directions can be obtained by this method. For the obtained sound intensity value in the body diagonal direction, because the distance between the sensors is not equal to the edge length d, a correction coefficient needs to be added to enable the calculation result to be more accurate.

The three-dimensional sound intensity vector conversion method can solve the sound intensity vector of the center position of the cube by establishing an equation set according to the specific geometric relationship of sound intensity values in 7 directions. The sensor geometry model is shown in fig. 6 (only a portion of the sensors are shown). Selecting the central point S of six faces of the cube₁、S₂、S₃、S₄、S₅、S₆Three sets of sound pressure sensors are arranged at the center of the face in the normal direction of the 6 faces. Then 8 vertexes are selected, and four groups of sensors are arranged along the diagonal direction of the body.

Recording the sound intensity components of the body center O point in the x, y and z orthogonal directions as I_x、I_y、I_zThe unit vectors in the three orthogonal directions are I, j and k, respectively, and the sound intensity I at the O point_O＝I_xi+I_yj+I_zk. The sound intensity value measured in each direction is actually I_OThe projection in this direction can also be regarded as the sound intensity components I of three orthogonal directions_x、I_y、I_zProjection in this direction. Taking the direction of the body diagonal DF as an example, the cosine values of the included angles between DF and the x-axis, y-axis and z-axis are known according to the mathematical relationship:

let I_OSound intensity value in DF direction is I_DFWith a correction factor of λ₄Then the sound intensity value is equal to I_xi+I_yj+I_zk the sum of the projections in this direction:

similarly, projection equations for other body diagonal directions and equations for the face center normal direction can be listed, and the following equation sets are established:

in the formula I_x、I_y、I_zThe component of the sound intensity vector of the body center O point at the position to be detected in the three-dimensional rectangular coordinate system; I_EC、I_HB、I_AG、I_DFis a sound intensity measurement for 7 specific directions; lambda [ alpha ]₁、λ₂、λ₃、λ₄Is a correction factor, is related to the distance between two mutually matched sensors, and is further determined according to a theoretical derivation and a test calibration method.

Since the sound intensity in a single direction is approximately obtained according to the finite difference principle, the left and right ends of the above equation set are approximately equal rather than strictly equal. The equation set comprises 3 unknowns and 7 equations, belongs to an overdetermined linear equation set, and cannot be solved accurately. In order to minimize the error of the equation set solution, the patent provides a three-dimensional sound intensity vector conversion method based on a matrix theory. The system of equations (4) is first written as a matrix of a system of linear equations:therein is provided with

For the above linear homogeneous system of equations without solution, letIs a solution that minimizes the error of the equation set, i.e., it can be a normA minimum value is reached. According to the matrix theory, it can be known thatWhere P is the pseudo-inverse of the coefficient matrix Q. Is calculated to The optimal solution of the system of linear equations under this condition is then

According to the formula (6), the optimal solution of the sound intensity vector at the point O can be obtained:

the embodiments of the present invention have been described in detail and illustrated in the accompanying drawings by the applicant of the present invention, but it should be understood by those skilled in the art that the above embodiments are only the preferred embodiments of the present invention, and the detailed description is only for the purpose of helping the reader to better understand the spirit of the present invention, and not for limiting the scope of the present invention, and on the contrary, any improvement or modification made based on the spirit of the present invention should fall within the scope of the present invention.