Dynamic mirror image boundary acoustical holography testing device and method

Abstract

The invention discloses a dynamic mirror boundary acoustical holography testing device and method, and belongs to the technical field of near-field acoustical holography test.The dynamic mirror boundary acoustical holography testing device comprises a translation track, a first driving mechanism is arranged on one side of the translation track, a testing mechanism is arranged on the other side of the translation track, the first driving mechanism is connected with a first base, and a second driving mechanism is installed on the first base; the second driving mechanism is connected with the second base. The top of the second base is connected with the rigid plate. According to the dynamic mirror image boundary acoustical holography test device and method, under the condition that the number of sensors is not increased, the test information amount is increased, and the sound field reconstruction precision is improved; fixed measuring points are combined with rigid boundary movement, the number of all sensors is increased according to rigid surface single-time movement sound pressure data, and the measuring time is shortened compared with point-by-point movement of the sensors; the synchronization and calibration difficulty of multiple sensors is reduced by depending on a small number of fixed sound pressure sensors and controllable rigid boundaries; a position-adjustable mirror image source point is introduced by using a mirror image principle, and is not limited by a holographic aperture requirement.

Description

Technical Field

[0001] The present invention relates to the technical field of near-field acoustic holography testing, and in particular to a dynamic mirror boundary acoustic holography testing device and method. Background Art

[0002] As an important means for sound source identification and sound field reconstruction, acoustic holography technology has important value in the fields of noise localization, vibration analysis, and acoustic imaging. Although near-field acoustic holography (NAH) is theoretically more accurate than other methods due to its near-field measurement characteristics, the cost of achieving high-precision sound field reconstruction is high. According to different algorithms, NAH can be divided into branches such as Fourier transform (FFT)-based, boundary element method (BEM)-based, and equivalent source method (ESM)-based, but these methods are all restricted by two major hard constraints: insufficient number of measurement points and limited measurement aperture. For example, FFT-based NAH requires the measurement point spacing to be less than half of the wavelength of the highest-frequency sound wave (Nyquist criterion). In actual engineering, due to the cost and deployment difficulty of sensors, the measurement point density often fails to meet the requirements, resulting in the loss of high-frequency sound field information or aliasing errors. In addition, the physical size of the measurement aperture directly limits the spatial resolution. To alleviate the above problems, researchers often use regularization methods (such as Tikhonov regularization) to solve the underdetermined inverse problem, or introduce sparse sampling strategies to reduce the number of measurement points. However, these improvement schemes often fall into the contradiction between computational efficiency and accuracy: regularization requires manual adjustment of the penalty factor, and over-regularization will lead to the loss of sound field details, while sparse sampling may cause distortion in the reconstruction of the low-frequency sound field due to information loss. Although the dynamic NAH technology based on measurement point scanning can expand the aperture by moving the sensor, it will introduce Doppler effect errors and sensor positioning deviations. Summary of the Invention

[0003] The purpose of the present invention is to provide a dynamic mirror boundary acoustic holography testing device and method, which can increase the test information volume and improve the accuracy of sound field reconstruction without increasing the number of sensors; by combining fixed measurement points with the movement of a rigid boundary, the sound pressure data obtained from a single movement of the rigid surface increases to the total number of sensors, reducing the measurement time compared with moving the sensor point by point; relying on a small number of fixed sound pressure sensors and a controllable rigid boundary, it reduces the difficulty of multi-sensor synchronization and calibration; by introducing a position-adjustable mirror source point using the mirror principle, it is not restricted by the holographic aperture requirements.

[0004] To achieve the above purpose, the present invention provides a dynamic mirror boundary acoustic holography testing device, including a translation track, a first driving mechanism is arranged on one side of the translation track, a testing mechanism is arranged on the other side, the first driving mechanism is connected to a first base, a second driving mechanism is installed on the first base, the second driving mechanism is connected to a second base, and the top of the second base is connected to a rigid plate.

[0005] Preferably, the first driving mechanism includes a first motor, the first motor is installed on one side of the translation track, the first motor is connected to the lead screw, and the bottom of the first base is connected to the lead screw.

[0006] Preferably, the second driving mechanism includes a second motor, the second motor is installed on the first base, the second motor is connected to the rotating assembly, and the rotating assembly is connected to the second base.

[0007] Preferably, sliders are provided at both ends of the bottom of the first base, and chutes cooperating with the sliders are provided on the translation track.

[0008] The present invention provides a dynamic mirror boundary acoustic holography test method, which specifically includes the following steps:

[0009] S1. Determine the number of equivalent sources of the vibrating structure and the position between the sound source surface and the holographic measurement surface;

[0010] S2. Set and adjust the translation amount and rotation angle of the rigid surface to obtain the position coordinates of the sound source and the mirror image source;

[0011] S3. Determine the number and position coordinates of the sound pressure sensors on the holographic measurement surface, and calculate the distances between the sound source points, the mirror image source points and the measurement points;

[0012] S4. Perform sound pressure measurement on the measurement points determined in S3;

[0013] S5. Adjust the translation amount and rotation angle of the rigid surface alone or in combination to obtain the adjusted position coordinates of the mirror image source, repeat S3 and S4, obtain the measurement results, and perform multiple measurements until the measured sound pressure on the holographic surface and the source strength vector acoustic transfer matrix are full rank or the change in the condition number of the acoustic transfer matrix after additional testing is small;

[0014] S6. Use the measurement results obtained in S4, and calculate the sound source strength vector by combining the least squares method or the regularization method.

[0015] Preferably, the coordinate origin in S2 is set on the sound source surface, then the coordinates of the sound source point i in the rectangular coordinate system can be expressed as (x si , y si , z si ). When the rigid surface is parallel to the oyz plane and the distance from the origin o in the x direction is D, the coordinates of the mirror image source point can be expressed as (2D - x si , y si , z si ). When the rigid surface rotates by an angle θ around the (D, 0) axis, the formula for determining the position coordinates of the mirror image source is as follows:

[0016] (2Dcos 2 θ - x si cos2θ + y si sin2θ, (x si-D)sin2θ + y si cos2θ, z si );

[0017] Preferably, the distance between the sound source point determined according to S1 and S2 and the measurement point and the position of the mirror source in S3 can be used to obtain the distance r between the sound source point (x si , y si , z si ) and the measurement point (x hj , y hj , z hj ), and the distance r ij ' between the mirror source point (x' si , y' si , z' si ) and the measurement point (x hj , y hj , z hj ), ij ',

[0018]

[0019] Preferably, in S5, when the number of measurement points is P, the number of sound source points is M, and P < M, N×P sound pressure data are generated after N measurements, forming the following formula:

[0020] (G + G')q = p;

[0021] where G is the transfer matrix between the sound source and the sound pressure at the measurement point, G' is the transfer matrix between the mirror source point and the sound pressure at the measurement point, q is the sound source strength vector, and p is the sound pressure vector;

[0022] Or directly establish the relationship between the sound pressure and the sound source intensity based on the measured sound pressure difference with and without a rigid boundary:

[0023] G'q = p 刚性 -p 自由场 ;

[0024] where p 刚性 is the sound pressure measurement result with a dynamic rigid boundary, and p 自由场 is the sound pressure test result at the measurement point without a dynamic boundary;

[0025] The matrix element G ij of the transfer matrix G between the sound source and the sound pressure at the measurement point can be expressed as:

[0026]

[0027] where j is the imaginary part, c is the speed of sound, ρ is the density of the sound propagation medium, k is the wave number, k = 2πf / c, and f is the frequency;

[0028] The matrix element G of the transfer matrix G' between the mirror source point and the sound pressure at the measurement point i ' j can be expressed as:

[0029]

[0030] Preferably, the sound source strength vector q obtained by the least squares method in S6 is:

[0031]

[0032] The sound source strength vector q obtained by the Tikhonov regularization method is:

[0033]

[0034] After obtaining the sound source strength vector q, the sound pressure information at any position in the sound field is reconstructed by p = Gq, and the sound field reconstruction is completed.

[0035] Therefore, the present invention adopts the above-mentioned dynamic mirror boundary acoustic holography test device and method, and has the following beneficial effects:

[0036] (1) Without increasing the number of sensors, the test information amount is increased, and the sound field reconstruction accuracy is improved;

[0037] (2) The fixed measurement points are combined with the movement of the rigid boundary. The sound pressure data increased by the single movement of the rigid surface is the total number of sensors, which reduces the measurement time compared with moving the sensors point by point;

[0038] (3) Relying on a small number of fixed sound pressure sensors and a controllable rigid boundary, the difficulty of multi-sensor synchronization and calibration is reduced;

[0039] (4) By using the mirror principle to introduce a position-adjustable mirror source point, it is not limited by the holographic aperture requirement.

[0040] Next, through the drawings and embodiments, the technical solutions of the present invention will be further described in detail. Description of the Drawings

[0041] Figure 1 is a three-dimensional structural schematic diagram of a dynamic mirror boundary acoustic holography test device of the present invention;

[0042] Figure 2 is a schematic diagram of sound field superposition after the rigid surface translation of a dynamic mirror boundary acoustic holography test method of the present invention;

[0043] Figure 3 is a schematic diagram of sound field superposition after the rigid surface rotation of a dynamic mirror boundary acoustic holography test method of the present invention;

[0044] Figure 4It is the result of comparing the sound field reconstruction accuracy between the dynamic mirror boundary acoustic holography test method and the equivalent source acoustic holography method with Tikhonov regularization.

[0045] Reference numerals

[0046] 1. Translation track; 2. Testing mechanism; 3. First motor; 4. Lead screw; 5. First base; 6. Slide block; 7. Slide groove; 8. Second motor; 9. Rotating assembly; 10. Second base; 11. Rigid plate. Detailed implementation manners

[0047] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0048] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention belongs. The "first", "second" and similar terms used in the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. The terms such as "including" or "comprising" mean that the elements or objects appearing before the term cover the elements or objects listed after the term and their equivalents, without excluding other elements or objects. The terms such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms such as "upper", "lower", "left" and "right" are only used to represent relative position relationships, and when the absolute position of the object being described changes, the relative position relationships may also change accordingly.

[0049] Embodiment 1

[0050] As Figure 1 shown, the present invention provides a dynamic mirror boundary acoustic holography test device, including a translation track 1. A first driving mechanism is arranged on one side of the translation track 1. The first driving mechanism is connected to a first base 5, and the first driving mechanism can drive the first base 5 to slide along the translation track 1. The first driving mechanism includes a first motor 3. The first motor 3 is installed on one side of the translation track 1, and the first motor 3 provides power for the first driving mechanism. The first motor 3 is connected to a lead screw 4. The bottom of the first base 5 is connected to the lead screw 4. A threaded hole matching the lead screw 4 is provided at the bottom of the first base 5. The first motor 3 can drive the lead screw 4 to rotate, and the rotation of the lead screw 4 can make the first base 5 move along the lead screw 4. Slide blocks 6 are provided at both ends of the bottom of the first base 5. Slide grooves 7 matching the slide blocks 6 are provided on the translation track 1. When the first base 5 moves along the lead screw 4, it can drive the slide blocks 6 to slide along the slide grooves 7, so as to keep the first base 5 stable. A testing mechanism 2 is arranged on the other side of the translation track 1. A sound pressure sensor is installed on the testing mechanism 2. The sound pressure sensor, as a sensitive element, can convert the sound pressure change in the sound field into an electrical signal, so as to obtain the sound pressure information in the sound field.

[0051] A second drive mechanism is installed on the first base 5. The second drive mechanism is connected to the second base 10. The top of the second base 10 is connected to the rigid plate 11. The second drive mechanism can drive the second base 10 to rotate, so that the rigid plate 11 rotates. The second drive mechanism includes a second motor 8, and the second motor 8 provides power for the second drive mechanism. The second motor 8 is installed on the first base 5, and the first base 5 provides support for the second motor 8. The second motor 8 is connected to the rotating assembly 9, and the rotating assembly 9 is connected to the second base 10. The second motor 8 can drive the second base 10 to rotate through the rotating assembly 9.

[0052] The present invention provides a dynamic mirror boundary acoustic holographic testing method, which specifically includes the following steps:

[0053] S1. Determine the number of equivalent sources of the vibrating structure and the position between the sound source surface and the holographic measurement surface;

[0054] S2. Set and adjust the translation amount and rotation angle of the rigid surface to obtain the position coordinates of the sound source and the mirror source;

[0055] If the coordinate origin is set on the sound source surface, the coordinates of the sound source point i in the rectangular coordinate system can be expressed as (x si , y si , z si ). When the rigid surface is parallel to the oyz plane and the distance from the origin o in the x direction is D, the coordinates of the mirror source point can be expressed as (2D - x si , y si , z si ). When the rigid surface rotates by an angle θ around the (D, 0) axis, the formula for determining the position coordinates of the mirror source is as follows:

[0056] (2Dcos 2 θ - x si cos2θ + y si sin2θ, (x si -D)sin2θ + y si cos2θ, z si );

[0057] S3. Determine the number and position coordinates of the sound pressure sensors on the holographic measurement surface, and calculate the distances between the sound source point and the mirror source point and the measurement point;

[0058] According to the distance between the sound source point and the measurement point and the position of the mirror source determined by S1 and S2, the distance r between the sound source point (x si , y si , z si ) and the measurement point (x hj , y hj , z hj ) can be obtained as follows:ij and the distance r si ' between the mirror source point (x' si , y' si , z' hj ) and the measurement point (x hj , y hj , z ij ';

[0059]

[0060] S4. Perform sound pressure measurement on the measurement points determined in S3;

[0061] S5. As shown in Figure 2 and Figure 3 , adjust the rigid surface translation amount and rotation angle separately or in combination to obtain the adjusted mirror source position coordinates, repeat S3 and S4, obtain the measurement results, and perform multiple measurements until the sound pressure measured on the holographic surface and the source strength vector sound transfer matrix are full rank or the change in the condition number of the sound transfer matrix after additional tests is small;

[0062] When the number of measurement points is P, the number of sound source points is M, and P < M, after N measurements, N×P sound pressure data are generated, forming the following formula:

[0063] (G + G')q = p;

[0064] where G is the transfer matrix between the sound source and the sound pressure of the measurement point, G' is the transfer matrix between the mirror source point and the sound pressure of the measurement point, q is the sound source strength vector, and p is the sound pressure vector;

[0065] Or directly establish the relationship between the sound pressure and the sound source intensity based on the measured sound pressure difference with and without the rigid boundary:

[0066] G'q = p 刚性 -p 自由场 ;

[0067] where p 刚性 is the sound pressure measurement result with the dynamic rigid boundary, and p 自由场 is the sound pressure test result of the measurement point without the dynamic boundary;

[0068] The matrix element G ij of the transfer matrix G between the sound source and the sound pressure of the measurement point can be expressed as:

[0069]

[0070] where j is the imaginary part, c is the sound speed, ρ is the density of the sound propagation medium, k is the wave number, k = 2πf / c, and f is the frequency;

[0071] The matrix element Gi ' j It can be expressed as:

[0072]

[0073] Here, G' is the case of an ideal rigid surface. In actual use, G' can be adjusted according to the measured or simulated results to adapt to non-ideal situations such as surface sound absorption caused by boundary sound diffraction and wall impedance caused by finite-size rigid surfaces. Each time the position of the rigid surface is adjusted, r ij ' changes, resulting in a non-linear change in G'. Therefore, the newly generated equation is linearly independent of the original equation.

[0074] S6. Using the measurement results obtained in S4, the sound source intensity vector is calculated by combining the least squares method or the regularization method;

[0075] The sound source intensity vector q calculated by the least squares method is:

[0076]

[0077] The sound source intensity vector q calculated by the Tikhonov regularization method is:

[0078]

[0079] After obtaining the sound source intensity vector q, the sound pressure information at any position in the sound field is reconstructed by p = Gq, completing the sound field reconstruction.

[0080] Comparing the sound field reconstruction accuracy of the dynamic mirror boundary acoustic holography test method and the equivalent source acoustic holography method with Tikhonov regularization, as Figure 4 shown, it can be known the variation of the sound reconstruction error of the dynamic rigid surface acoustic holography test method with frequency and the variation of the sound reconstruction error of the Tikhonov regularization equivalent source acoustic holography method with frequency. The sound reconstruction error of the dynamic rigid surface acoustic holography test method is relatively stable throughout the frequency range, and the reconstruction error always remains at a low level, fluctuating slightly around 2%. This indicates that this method is less affected by frequency changes and the sound reconstruction accuracy is relatively stable. The sound reconstruction error of the Tikhonov regularization equivalent source acoustic holography method shows an obvious upward trend as the frequency gradually increases from 200 Hz to 2000 Hz, rising from about 8.5% to nearly 17%. This shows that the sound reconstruction accuracy of this method is greatly affected by frequency, and the reconstruction error increases significantly when the frequency increases. In the tested frequency range, the sound field reconstruction accuracy of the dynamic mirror boundary acoustic holography test method is significantly better than that of the Tikhonov regularization equivalent source acoustic holography method, especially in the high-frequency region, where the advantage of the dynamic rigid surface acoustic holography is more prominent, and the reconstruction error of the Tikhonov regularization method increases significantly at high frequencies.

[0081] Therefore, the present invention adopts the above-mentioned dynamic mirror boundary acoustic holography test device and method. Without increasing the number of sensors, the amount of test information is increased, and the accuracy of sound field reconstruction is improved. The combination of fixed measurement points and the movement of the rigid boundary increases the sound pressure data of the rigid surface during a single movement to the total number of sensors. Compared with moving the sensors point by point, the measurement time is reduced. Relying on a small number of fixed sound pressure sensors and a controllable rigid boundary reduces the difficulty of multi-sensor synchronization and calibration. The position-adjustable mirror source point is introduced using the mirror principle, which is not restricted by the holographic aperture requirements.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A dynamic mirror boundary acoustic holography test device, characterized in that: It includes a translation track. A first driving mechanism is arranged on one side of the translation track, and a testing mechanism is arranged on the other side. The first driving mechanism is connected to a first base. A second driving mechanism is installed on the first base, and the second driving mechanism is connected to a second base. The top of the second base is connected to a rigid plate.

2. The dynamic mirror boundary acoustic holographic testing device according to claim 1, wherein: The first driving mechanism includes a first motor. The first motor is installed on one side of the translation track. The first motor is connected to a lead screw, and the bottom of the first base is connected to the lead screw.

3. The dynamic mirror boundary acoustic holography test device according to claim 1, characterized in that: The second driving mechanism includes a second motor. The second motor is installed on the first base. The second motor is connected to a rotating assembly, and the rotating assembly is connected to the second base.

4. The dynamic mirror boundary acoustic holographic testing device according to claim 1, characterized in that: Sliders are provided at both ends of the bottom of the first base, and sliding grooves matching the sliders are provided on the translation track.

5. A dynamic mirror boundary acoustic holographic testing method according to any one of claims 1-4, characterized in that: Specifically, it includes the following steps: S1. Determine the number of equivalent sources of the vibration structure and the position between the sound source surface and the holographic measurement surface; S2. Set and adjust the translation amount and rotation angle of the rigid surface to obtain the position coordinates of the sound source and the mirror image source; S3. Determine the number and position coordinates of the sound pressure sensors on the holographic measurement surface, and calculate the distances between the sound source points, the mirror image source points and the measurement points; S4. Measure the sound pressure at the measurement points determined in S3; S5. Adjust the translation amount and rotation angle of the rigid surface alone or in combination to obtain the adjusted position coordinates of the mirror image source. Repeat S3 and S4 to obtain the measurement results. Conduct multiple measurements until the sound pressure measured on the holographic surface and the source strength vector acoustic transfer matrix are full rank or the change in the condition number of the acoustic transfer matrix after additional testing is small; S6. Use the measurement results obtained in S4, and calculate the sound source strength vector by combining the least squares method or the regularization method.

6. The dynamic mirror boundary acoustic holographic testing method according to claim 5, characterized in that: In S2, the origin of coordinates is set on the sound source surface. Then the coordinates of the sound source point i in the rectangular coordinate system can be expressed as (x si , y si , z si ). When the rigid surface is parallel to the oyz plane and the distance from the origin o in the x direction is D, the coordinates of the mirror source point can be expressed as (2D - x si , y si , z si ). When the rigid surface rotates by an angle θ around the (D, 0) axis, the formula for determining the coordinates of the mirror source position is as follows: (2Dcos 2 θ - x si cos2θ + y si sin2θ, (x si -D)sin2θ + y si cos2θ, z si )。 7. A dynamic mirror boundary acoustic holography testing method according to claim 6, characterized in that: The distance between the sound source point and the measurement point and the position of the mirror source determined according to S1 and S2 in S3 can obtain the sound source point (x si , y si , z si ) and the distance r ij ) between the measurement point (x hj , y hj , z hj ) and the distance r ij ' between the mirror source point (x' si , y' si , z' si ) and the measurement point (x hj , y hj , z hj ), as shown below:

8. A dynamic mirror boundary acoustic holography test method according to claim 7, characterized in that: In S5, when the number of measurement points is P, the number of sound source points is M, and P < M, after N measurements, N×P sound pressure data are generated, forming the following formula: (G + G')q = p; where G is the transfer matrix between the sound source and the sound pressure at the measurement point, G' is the transfer matrix between the mirror image source point and the sound pressure at the measurement point, q is the sound source strength vector, and p is the sound pressure vector; Or directly establish the relationship between the sound pressure and the sound source intensity based on the measured sound pressure difference with or without a rigid boundary: G'q = p 刚性 -p 自由场 ; Among them, p 刚性 is the sound pressure measurement result when there is a dynamic rigid boundary, and p 自由场 is the measured sound pressure test result of the measurement point without a dynamic boundary; The matrix element G of the transfer matrix G between the sound source and the sound pressure at the measurement point ij can be expressed as: where j is the imaginary part, c is the sound speed, ρ is the density of the sound propagation medium, k is the wave number, k = 2πf / c, and f is the frequency; The matrix element G of the transfer matrix G' between the mirror source point and the sound pressure at the measurement point i ' j can be expressed as:

9. The dynamic mirror boundary acoustic holography testing method according to claim 8, wherein: The sound source strength vector q calculated by the least squares method in S6 is: The sound source strength vector q calculated by the Tikhonov regularization method is: After obtaining the sound source strength vector q, reconstruct the sound pressure information at any position in the sound field by p = Gq to complete the sound field reconstruction.

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