A method for sound field reconstruction under local aperture measurement conditions

Abstract

This invention provides a sound field reconstruction method under local aperture measurement conditions. The method includes: spatial domain zero-padding expansion of holographic complex sound pressure data obtained from ship measurements under local aperture conditions; transforming the expanded holographic complex sound pressure data from the spatial domain to the wavenumber domain using a two-dimensional Fourier transform to obtain holographic complex sound pressure data in the wavenumber domain; performing wavenumber domain extrapolation calculation on the holographic complex sound pressure data in the wavenumber domain followed by an inverse two-dimensional Fourier transform to obtain holographic complex sound pressure data within the expanded aperture; replacing the holographic complex sound pressure data at the corresponding position of the local aperture within the expanded aperture with the measured holographic complex sound pressure data to obtain the final holographic complex sound pressure data; and reconstructing the sound field using the final holographic complex sound pressure data based on a spatial sound field transformation method. This invention achieves holographic reconstruction of the radiated sound field of a large-size structural sound source such as a ship by approximately extrapolating and expanding the holographic complex sound pressure data.

Description

Technical Field

[0001] This invention relates to the field of near-field radiation underwater acoustic measurement technology for ships, and in particular to a method for sound field reconstruction under local aperture measurement conditions. Background Technology

[0002] Near-field acoustic holography (NAH) is an advanced acoustic technology for noise source identification, localization, and spatial sound field visualization. It measures the complex sound pressure field (amplitude and phase) on the holographic surface located in the near-field radiation region of the sound source, and then, based on the laws and characteristics of sound radiation, inverts and reconstructs or predicts the acoustic quantities (such as sound pressure, particle vector velocity, and three-dimensional vector sound intensity) in the entire three-dimensional space.

[0003] Near-field acoustic holography algorithms include NAH algorithms based on spatial sound field transformation (STSF), boundary element method (BEM), and equivalent source method (ESM). The theoretical derivation of acoustic holography based on spatial sound field transformation is based on an infinitely large planar model. However, in practice, sound pressure data can only be measured under finite apertures, resulting in a "window effect" that leads to significant errors in sound field reconstruction.

[0004] To reduce the impact of the "window effect" on sound field reconstruction, traditional acoustic holography requires the measurement aperture to be at least four times the size of the sound source. This is to minimize energy leakage caused by the "window effect" and to attenuate the sound pressure outside the holographic measurement aperture to a negligible level. However, for large-scale structural sound sources like ships, meeting these requirements inevitably incurs high instrument costs and a huge workload for testing. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a sound field reconstruction method under local aperture measurement conditions, realizing a local aperture acoustic holography method. That is, based on the measurement of a smaller array aperture, the complex sound pressure data of the holographic surface obtained within the smaller aperture is approximately extrapolated and extended through an effective numerical calculation method, so as to obtain complex sound pressure data outside the holographic measurement aperture, thereby "increasing" the holographic measurement aperture, and thus realizing the holographic reconstruction of the radiated sound field of a large-sized structural sound source such as a ship.

[0006] This invention provides a method for sound field reconstruction under local aperture measurement conditions, comprising:

[0007] Spatial domain zero-padding expansion is performed on the holographic surface complex acoustic pressure data obtained from local aperture measurements of ships;

[0008] The holographic complex sound pressure data after zero-padding and expansion in the spatial domain is transformed from the spatial domain to the wavenumber domain using a two-dimensional Fourier transform to obtain the holographic complex sound pressure data in the wavenumber domain.

[0009] The holographic complex sound pressure data in the wavenumber domain is extrapolated in the wavenumber domain, and the extrapolated holographic complex sound pressure data is subjected to a two-dimensional inverse Fourier transform to obtain the holographic complex sound pressure data in the extended aperture.

[0010] Replace the holographic complex acoustic pressure data at the corresponding position of the local aperture within the extended aperture with the measured holographic complex acoustic pressure data to obtain the final holographic complex acoustic pressure data.

[0011] A spatial sound field transformation-based method is adopted, and the final holographic complex sound pressure data is used to reconstruct the sound field.

[0012] According to the sound field reconstruction method under local aperture measurement conditions provided by the present invention, the wavenumber domain extrapolation calculation is performed on the holographic complex sound pressure data in the wavenumber domain, including:

[0013] Wavenumber domain extrapolation calculations were performed on the holographic complex sound pressure data in the wavenumber domain using an improved Tikhonov regularization filter.

[0014] According to the acoustic field reconstruction method under local aperture measurement conditions provided by the present invention, the formula for the improved Tikhonov regularization filter is as follows:

[0015]

[0016]

[0017]

[0018] in, This is an improved Tikhonov regularization filter. For filter factors, To analyze wavenumbers, For the density of the medium, k is the speed of sound wave propagation. x Let k be the wavenumber component along the x-direction. y Let be the wavenumber component along the y-direction, j be the imaginary unit, and z be the wavenumber component along the y-direction. h The distance z is the holographic measurement surface. s The distance to the holographic reconstruction surface.

[0019] According to the present invention, a sound field reconstruction method under local aperture measurement conditions is provided, and the filter factor of the improved Tikhonov regularized filter is provided. The following steps were used to optimize the process:

[0020] Calculate the signal-to-noise ratio of the complex acoustic pressure data of the holographic surface after wavenumber domain extrapolation;

[0021] Two-dimensional wavelet analysis was performed on the holographic complex sound pressure data after zero-padding expansion in the spatial domain to obtain the wavelet-reconstructed holographic complex sound pressure data, and the signal-to-noise ratio of the wavelet-reconstructed holographic complex sound pressure data was calculated.

[0022] The difference between the signal-to-noise ratio (SNR) of the holographic complex sound pressure data extrapolated in the wavenumber domain and the SNR of the holographic complex sound pressure data reconstructed by wavelet is used as the objective function for the filter factor. Optimize the process so that the difference is zero.

[0023] According to the sound field reconstruction method under local aperture measurement conditions provided by the present invention, the signal-to-noise ratio of the holographic complex sound pressure data after wavenumber domain extrapolation is calculated using the following formula:

[0024]

[0025] in, The signal-to-noise ratio of the complex acoustic pressure data of the holographic surface after wavenumber domain extrapolation is given. This is the holographic complex sound pressure data calculated by extrapolation in the wavenumber domain. For holographic complex sound pressure data in the wavenumber domain, k x Let k be the wavenumber component along the x-direction. y Let z be the wavenumber component along the y-direction. h The distance to the holographic measurement surface.

[0026] According to the sound field reconstruction method under local aperture measurement conditions provided by the present invention, two-dimensional wavelet analysis is performed on the holographic complex sound pressure data after zero-padding expansion in the spatial domain to obtain wavelet-reconstructed holographic complex sound pressure data, and the signal-to-noise ratio of the wavelet-reconstructed holographic complex sound pressure data is calculated, including:

[0027] Based on the selected wavelet function and decomposition series, the holographic complex sound pressure data after zero-padded expansion in the spatial domain is decomposed.

[0028] Threshold denoising is performed on the wavelet coefficients of each level after decomposition;

[0029] The wavelet coefficients after threshold denoising are reconstructed to obtain the wavelet-reconstructed holographic complex sound pressure data.

[0030] The signal-to-noise ratio of the wavelet-reconstructed holographic complex acoustic pressure data is calculated based on the spatial domain zero-padded extended holographic complex acoustic pressure data and the wavelet-reconstructed holographic complex acoustic pressure data.

[0031] According to the present invention, a sound field reconstruction method under local aperture measurement conditions is provided for the filter factor. Optimization to make the difference zero includes:

[0032] For the filter factor within any interval The value of is calculated iteratively using the bisection method to obtain the optimal filter factor, making the objective function zero.

[0033] The present invention also provides a sound field reconstruction system under local aperture measurement conditions, comprising:

[0034] The extension module is used to perform spatial domain zero-padding extension on the holographic surface complex acoustic pressure data obtained from ship measurements at local apertures;

[0035] The transformation module is used to transform the zero-padded and extended holographic surface complex sound pressure data in the spatial domain to the wavenumber domain using a two-dimensional Fourier transform, so as to obtain the holographic surface complex sound pressure data in the wavenumber domain.

[0036] The extrapolation module is used to perform wavenumber domain extrapolation calculation on the holographic complex sound pressure data in the wavenumber domain, and to perform a two-dimensional inverse Fourier transform on the holographic complex sound pressure data after the wavenumber domain extrapolation calculation to obtain the holographic complex sound pressure data in the extended aperture.

[0037] The replacement module is used to replace the holographic complex acoustic pressure data at the corresponding position of the local aperture within the extended aperture with the measured holographic complex acoustic pressure data, so as to obtain the final holographic complex acoustic pressure data.

[0038] The reconstruction module is used to reconstruct the sound field using the final holographic complex sound pressure data, based on a spatial sound field transformation method.

[0039] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the sound field reconstruction method under local aperture measurement conditions as described above.

[0040] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the sound field reconstruction method under local aperture measurement conditions as described above.

[0041] The present invention also provides a computer program product, including a computer program that, when executed by a processor, implements the sound field reconstruction method under local aperture measurement conditions as described above.

[0042] This invention provides a sound field reconstruction method under local aperture measurement conditions. By proposing a local aperture acoustic holography method, based on a smaller array aperture measurement, the complex sound pressure data of the holographic surface obtained within the smaller aperture is approximately extrapolated and extended through an effective numerical calculation method to obtain complex sound pressure data outside the holographic measurement aperture, thereby "increasing" the holographic measurement aperture and thus realizing the holographic reconstruction of the radiated sound field of a large-sized structural sound source such as a ship. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0044] Figure 1 This is a schematic flowchart of the sound field reconstruction method under local aperture measurement conditions provided by the present invention;

[0045] Figure 2 This is a schematic diagram of the spatial domain expansion of the holographic surface complex sound pressure under local aperture in the sound field reconstruction method under local aperture measurement conditions provided by the present invention;

[0046] Figure 3 This is a schematic diagram of the signal-to-noise ratio calculation process for holographic complex sound pressure data reconstructed by wavelet in the sound field reconstruction method under local aperture measurement conditions provided by the present invention;

[0047] Figure 4 This is a schematic diagram of the process of expanding the holographic complex sound pressure spatial domain under local aperture in the sound field reconstruction method under local aperture measurement conditions provided by the present invention;

[0048] Figure 5 This is one of the schematic diagrams showing the comparison of sound pressure amplitude distribution on the reconstruction surface (f=381Hz) in the sound field reconstruction method under local aperture measurement conditions provided by the present invention;

[0049] Figure 6 This is one of the schematic diagrams comparing the acoustic pressure amplitude distribution of the reconstruction surface (f=858Hz) in the acoustic field reconstruction method under local aperture measurement conditions provided by the present invention;

[0050] Figure 7 This is the second schematic diagram comparing the acoustic pressure amplitude distribution of the reconstruction surface (f=381Hz) in the acoustic field reconstruction method under local aperture measurement conditions provided by this invention.

[0051] Figure 8 This is the second schematic diagram comparing the acoustic pressure amplitude distribution of the reconstruction surface (f=858Hz) in the acoustic field reconstruction method under local aperture measurement conditions provided by the present invention.

[0052] Figure 9 This is a schematic diagram of the acoustic field reconstruction system under local aperture measurement conditions provided by the present invention. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0054] The following is combined Figure 1 A method for sound field reconstruction under local aperture measurement conditions according to the present invention includes:

[0055] Step 101: Spatial domain zero-padding expansion is performed on the holographic surface complex acoustic pressure data obtained from the local aperture of the ship.

[0056] Step 102: Use two-dimensional Fourier transform to transform the zero-padded holographic complex sound pressure data in the spatial domain to the wavenumber domain, and obtain the holographic complex sound pressure data in the wavenumber domain.

[0057] Step 103: Perform wavenumber domain extrapolation calculation on the holographic complex sound pressure data in the wavenumber domain, and perform two-dimensional inverse Fourier transform on the holographic complex sound pressure data after wavenumber domain extrapolation calculation to obtain the holographic complex sound pressure data in the extended aperture.

[0058] Step 104: Replace the holographic complex acoustic pressure data at the corresponding position of the local aperture within the extended aperture with the measured holographic complex acoustic pressure data to obtain the final holographic complex acoustic pressure data.

[0059] Step 105: Using a spatial sound field transformation-based method, the final holographic complex sound pressure data is used to reconstruct the sound field.

[0060] Figure 2 (a) is a schematic diagram of the spatial expansion of the complex acoustic pressure domain of the holographic surface within a local aperture, where and These represent the holographic measurement surface within the local aperture and the holographic measurement surface after spatial domain expansion, i.e., the holographic measurement surface within the expanded aperture. The expanded region is denoted as... ; and These represent the reconstructed sound source surface and the sound source surface after spatial domain expansion, respectively. The expanded region is denoted as... .

[0061] Figure 2 (b) in the diagram is a schematic diagram of zero-padding of the complex sound pressure on the holographic surface. The basic steps of the local aperture acoustic holography method based on spatial sound field transformation consist of 5 steps, which are described in detail below:

[0062] (1) Spatial domain extension of complex acoustic pressure of holographic surface under local aperture, that is, complex acoustic pressure data of holographic measurement surface Spatial domain zero-padding extension is performed to obtain ,in:

[0063] (1)

[0064] (2) Perform a two-dimensional Fourier transform to transform from the spatial domain to the wavenumber domain to obtain complex sound pressure data in the wavenumber domain. And perform wavenumber domain extrapolation calculations on it.

[0065] (3) Extrapolation calculation of wavenumber domain A two-dimensional inverse Fourier transform is performed to obtain the complex sound pressure level of the holographic surface within the extended aperture. The complex acoustic pressure data located within the local aperture was compared with the actual measured complex acoustic pressure data. Replace, thus obtaining ,Right now:

[0066] (2)

[0067] (4) Transfer the complex sound pressure data As input, steps (2) and (3) are used for iterative calculation to reduce the error between the complex sound pressure data in the expanded aperture and the actual complex sound pressure data.

[0068] (5) If the iteration process ends, then the complex acoustic pressure of the holographic surface within the extended aperture is used. Perform holographic reconstruction of the sound field.

[0069] This embodiment proposes a local aperture acoustic holography method, which, based on a smaller array aperture measurement, uses an effective numerical calculation method to approximately extrapolate and extend the complex sound pressure data of the holographic surface obtained within the smaller aperture, so as to obtain complex sound pressure data outside the holographic measurement aperture, thereby "increasing" the holographic measurement aperture, and thus realizing the holographic reconstruction of the radiated sound field of a large-sized structure such as a ship.

[0070] Based on the above embodiments, this embodiment performs wavenumber domain extrapolation calculations on the holographic complex sound pressure data in the wavenumber domain, including:

[0071] Wavenumber domain extrapolation calculations were performed on the holographic complex sound pressure data in the wavenumber domain using an improved Tikhonov regularization filter.

[0072] The wavenumber domain extrapolation calculation of the holographic complex sound pressure data in the wavenumber domain is performed according to the following formula:

[0073] (3)

[0074] in, This is an improved Tikhonov regularization filter. This is the filter factor.

[0075] Based on the above embodiments, the formula for the improved Tikhonov regularization filter in this embodiment is:

[0076] (4)

[0077] (5)

[0078] (6)

[0079] in, This is an improved Tikhonov regularization filter. For filter factors, To analyze wavenumbers, For the density of the medium, k is the speed of sound wave propagation. x Let k be the wavenumber component along the x-direction. y Let be the wavenumber component along the y-direction, j be the imaginary unit, and z be the wavenumber component along the y-direction. h The distance z is the holographic measurement surface. s The distance to the holographic reconstruction surface.

[0080] Based on the above embodiments, the filter factor of the improved Tikhonov regularization filter in this embodiment is... The following steps were used to optimize the process:

[0081] Calculate the signal-to-noise ratio of the complex acoustic pressure data of the holographic surface after wavenumber domain extrapolation;

[0082] Two-dimensional wavelet analysis was performed on the holographic complex sound pressure data after zero-padding expansion in the spatial domain to obtain the wavelet-reconstructed holographic complex sound pressure data, and the signal-to-noise ratio of the wavelet-reconstructed holographic complex sound pressure data was calculated.

[0083] The difference between the signal-to-noise ratio (SNR) of the holographic complex sound pressure data extrapolated in the wavenumber domain and the SNR of the holographic complex sound pressure data reconstructed by wavelet is used as the objective function for the filter factor. Optimize the process so that the difference is zero.

[0084] Filter factor The choice of the filter cutoff wavenumber determines the accuracy of wavenumber domain extrapolation calculations. If... If the value is too low, an "under-filtering" situation will occur, resulting in too many iterations during the wavenumber domain extrapolation calculation; if... A high filter factor will result in a "filtered wave" situation, causing the useful sound pressure signal to be filtered out during wavenumber domain extrapolation calculations, leading to excessively large sound field reconstruction errors. Therefore, the filter factor... The selection of the filter factor is very important. In this embodiment, the filter factor is determined based on the holographic surface signal-to-noise ratio estimation. Perform parameter optimization selection.

[0085] Based on the above embodiments, according to formula (3) in this embodiment, if wavenumber domain filtering is performed using a filter, theoretically all noise signals can be filtered out, that is, at this time... If the hologram does not contain any noise signal, then the holographic surface noise signal in the wavenumber domain is... It can be represented as:

[0086] (7)

[0087] The signal-to-noise ratio of the holographic complex acoustic pressure data after wavenumber domain extrapolation is calculated using the following formula:

[0088] (8)

[0089] in, The signal-to-noise ratio of the complex acoustic pressure data of the holographic surface after wavenumber domain extrapolation is given. This is the holographic complex sound pressure data calculated by extrapolation in the wavenumber domain. For holographic complex sound pressure data in the wavenumber domain, k x For, k y For, z h For. k x Let k be the wavenumber component along the x-direction. y Let z be the wavenumber component along the y-direction. h The distance to the holographic measurement surface.

[0090] Based on the above embodiments, this embodiment performs two-dimensional wavelet analysis on the spatially zero-padded holographic complex sound pressure data to obtain wavelet-reconstructed holographic complex sound pressure data, and calculates the signal-to-noise ratio of the wavelet-reconstructed holographic complex sound pressure data, including:

[0091] Based on the selected wavelet function and decomposition series, the holographic complex sound pressure data after zero-padded expansion in the spatial domain is decomposed.

[0092] Threshold denoising is performed on the wavelet coefficients of each level after decomposition;

[0093] The wavelet coefficients after threshold denoising are reconstructed to obtain the wavelet-reconstructed holographic complex sound pressure data.

[0094] The signal-to-noise ratio of the wavelet-reconstructed holographic complex acoustic pressure data is calculated based on the spatial domain zero-padded extended holographic complex acoustic pressure data and the wavelet-reconstructed holographic complex acoustic pressure data.

[0095] like Figure 3 As shown, the signal-to-noise ratio of the holographic surface can be estimated by performing two-dimensional wavelet analysis on the complex sound pressure of the holographic surface after spatial domain expansion. The basic steps are as follows:

[0096] 1) Wavelet decomposition of two-dimensional signals, i.e., determining the two-dimensional wavelet function and decomposition level. Then the holographic sound pressure signal can be obtained. Intra-layer decomposition;

[0097] 2) Threshold quantization is performed on the wavelet coefficients, and different thresholds can be selected for different decomposition levels;

[0098] 3) Reconstruction of the effective sound pressure signal of the holographic surface, based on the wavelet decomposition of the first wavelet... The low-frequency coefficients of each layer and the high-frequency coefficients of each layer after threshold quantization are used to realize wavelet reconstruction of the effective sound pressure signal of the holographic surface;

[0099] 4) The holographic noise signal can be obtained from the original holographic surface sound pressure signal and the effective sound pressure signal reconstructed by the effective wavelet, thereby realizing the signal-to-noise ratio estimation.

[0100] By performing two-dimensional wavelet analysis on the complex sound pressure of the holographic surface after spatial domain extension, the signal-to-noise ratio of the holographic surface can be estimated. Therefore, the objective function can be established as follows:

[0101] (9)

[0102] when When the function value is zero, then the filter factor is... The optimal value is found at this value. The flowchart of a local aperture acoustic holography based on spatial sound field transformation is shown below. Figure 4 As shown.

[0103] Based on the above embodiments, this embodiment focuses on the filter factor. Optimization to make the difference zero includes:

[0104] For the filter factor within any interval The value of is calculated iteratively using the bisection method to obtain the optimal filter factor, making the objective function zero.

[0105] In the actual calculation process, it can be proven that... Function follows The value increases while monotonically decreasing. Therefore, for any interval... The value of can be obtained quickly by iterative calculation using the binary search method. The zero point is the point where the optimal filter factor is obtained.

[0106] To verify the effectiveness of the local aperture acoustic holography method based on spatial sound field transformation, a simply supported plate with infinitely large baffles on all four sides under harmonic excitation was used as the object, and its radiated sound field in the air was holographically reconstructed. During the sound field calculation and analysis, the holographic surface size was 0.25m × 0.25m, and the number of measurement points was 16 × 16. At this point, the aperture of the holographic measurement surface was only 1 / 4 of the simply supported plate surface, far below the aperture requirement for acoustic holography based on spatial sound field transformation. The distance between the holographic measurement surface and the four sides of the simply supported plate surface was 0.05m, and the reconstructed surface was the simply supported plate surface. The theoretical values ​​of the complex sound pressure on the holographic surface and the reconstructed surface were calculated using Rayleigh integrals, with white noise of 30dB signal-to-noise ratio added to the theoretically calculated complex sound pressure. Considering that when the harmonic excitation frequency is 381Hz and 858Hz, the four-sided simply supported plate mainly vibrates in the (2,2)th mode (natural frequency of 382Hz) and the (3,3)th mode (natural frequency of 857Hz), 381Hz and 858Hz are selected as the analysis frequencies.

[0107] Figure 5 and Figure 6 These represent the theoretical sound pressure level on the reconstructed surface and the amplitude distribution of the sound pressure level in the direct holographic reconstruction, respectively. Figure 5 In the diagram, (a) represents the theoretical sound pressure amplitude distribution of the reconstruction surface, and (b) represents the sound pressure amplitude distribution calculated by holographic reconstruction. Figure 6 In the diagram, (a) represents the theoretical sound pressure amplitude distribution at the sound source surface, and (b) represents the sound pressure amplitude distribution calculated by holographic reconstruction.

[0108] The comparison shows that, under local aperture measurement, if the acoustic holography method based on spatial sound field transformation is directly used, the energy leakage and aliasing caused by the "window effect" will result in a large error in the sound field reconstruction. At the same time, under local aperture measurement, the complex sound pressure at the edge of the holographic surface aperture may be much greater than zero. If the sound field is reconstructed directly after zeroing in the spatial domain, it will inevitably bring about a more serious "Gibbs effect", thus causing a large sound field reconstruction error.

[0109] Figure 7 and Figure 8 The calculations are as follows: the theoretical sound pressure of the reconstructed surface and the sound pressure amplitude distribution reconstructed using the Patch acoustic holography method based on fast Fourier transform. During the calculation, the spatial domain of the complex sound pressure of the holographic surface is expanded to twice the local aperture size, and the number of iterations is 2000.

[0110] Figure 7In the diagram, (a) represents the theoretical sound pressure amplitude distribution within the local aperture, (b) represents the reconstructed sound pressure amplitude distribution within the local aperture, (c) represents the theoretical sound pressure amplitude distribution within the reconstructed surface of the extended aperture, and (d) represents the reconstructed sound pressure amplitude distribution within the reconstructed surface of the extended aperture.

[0111] Figure 8 In the diagram, (a) represents the theoretical sound pressure amplitude distribution within the local aperture, (b) represents the reconstructed sound pressure amplitude distribution within the local aperture, (c) represents the theoretical sound pressure amplitude distribution within the extended aperture, and (d) represents the reconstructed sound pressure amplitude distribution within the extended aperture.

[0112] The comparison shows that:

[0113] (1) Under local aperture measurement, the Patch acoustic holography method based on fast Fourier transform is used to reconstruct the sound field, which can effectively reduce the error caused by the "window effect" and effectively overcome the edge "Gibbs effect" in the sound field reconstruction process.

[0114] (2) There is a certain error between the reconstructed sound pressure and the theoretical sound pressure amplitude distribution within the local aperture, and this error often occurs at the edge of the local aperture. This is mainly due to the approximation in the extrapolation process of the holographic surface pressure data. Nevertheless, the maximum amplitude error in the simulation analysis process does not exceed 22%, which can fully meet the engineering needs.

[0115] (3) The Patch acoustic holography method based on fast Fourier transform can not only effectively ensure the accuracy of the sound field reconstruction of the sound source surface within the local aperture, but also approximate the sound pressure amplitude distribution outside the local measurement aperture. Especially at the analysis frequency of 381Hz, the sound pressure reconstructed within the entire extended aperture has little error compared with the theoretical value.

[0116] Therefore, under local aperture measurement, it is accurate, effective and feasible to reconstruct the sound field by using a local aperture acoustic holography method based on spatial sound field transformation.

[0117] The sound field reconstruction system under local aperture measurement conditions provided by the present invention is described below. The sound field reconstruction system under local aperture measurement conditions described below can be referred to in correspondence with the sound field reconstruction method under local aperture measurement conditions described above.

[0118] like Figure 9 As shown, the system includes an expansion module 901, a transformation module 902, an extrapolation module 903, a replacement module 904, and a reconstruction module 905, wherein:

[0119] The extension module 901 is used to perform spatial domain zero-padding expansion on the holographic surface complex acoustic pressure data under the local aperture obtained from ship measurements;

[0120] The transformation module 902 is used to transform the zero-padded and extended holographic surface complex sound pressure data in the spatial domain to the wavenumber domain using a two-dimensional Fourier transform, so as to obtain the holographic surface complex sound pressure data in the wavenumber domain.

[0121] Extrapolation module 903 is used to perform wavenumber domain extrapolation calculation on the holographic complex sound pressure data in the wavenumber domain, and to perform two-dimensional inverse Fourier transform on the holographic complex sound pressure data after wavenumber domain extrapolation calculation to obtain the holographic complex sound pressure data in the extended aperture.

[0122] The replacement module 904 is used to replace the holographic complex acoustic pressure data at the corresponding position of the local aperture within the extended aperture with the measured holographic complex acoustic pressure data, so as to obtain the final holographic complex acoustic pressure data.

[0123] The reconstruction module 905 is used to reconstruct the sound field using the final holographic complex sound pressure data, based on a spatial sound field transformation method.

[0124] This embodiment proposes a local aperture acoustic holography method, which, based on a smaller array aperture measurement, uses an effective numerical calculation method to approximately extrapolate and extend the complex sound pressure data of the holographic surface obtained within the smaller aperture, so as to obtain complex sound pressure data outside the holographic measurement aperture, thereby "increasing" the holographic measurement aperture, and thus realizing the holographic reconstruction of the radiated sound field of a large-sized structure such as a ship.

[0125] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for sound field reconstruction under local aperture measurement conditions, characterized in that, include: Spatial domain zero-padding expansion is performed on the holographic surface complex acoustic pressure data obtained from local aperture measurements of ships; The holographic complex sound pressure data after zero-padding and expansion in the spatial domain is transformed from the spatial domain to the wavenumber domain using a two-dimensional Fourier transform to obtain the holographic complex sound pressure data in the wavenumber domain. The holographic complex sound pressure data in the wavenumber domain is extrapolated in the wavenumber domain, and the extrapolated holographic complex sound pressure data is subjected to a two-dimensional inverse Fourier transform to obtain the holographic complex sound pressure data in the extended aperture. Replace the holographic complex acoustic pressure data at the corresponding position of the local aperture within the extended aperture with the measured holographic complex acoustic pressure data to obtain the final holographic complex acoustic pressure data. A spatial sound field transformation-based method is adopted, and the final holographic complex sound pressure data is used to reconstruct the sound field.

2. The sound field reconstruction method under local aperture measurement conditions according to claim 1, characterized in that, The wavenumber domain extrapolation calculation of the holographic complex sound pressure data in the wavenumber domain includes: Wavenumber domain extrapolation calculations were performed on the holographic complex sound pressure data in the wavenumber domain using an improved Tikhonov regularization filter.

3. The method for processing near-field radiated noise of ships based on fiber optic hydrophone array measurement according to claim 1, characterized in that, The formula for the improved Tikhonov regularization filter is: ； ； ； in, This is an improved Tikhonov regularization filter. For filter factors, To analyze wavenumbers, For the density of the medium, k is the speed of sound wave propagation. x Let k be the wavenumber component along the x-direction. y Let be the wavenumber component along the y-direction, j be the imaginary unit, and z be the wavenumber component along the y-direction. h The distance z is the holographic measurement surface. s The distance to the holographic reconstruction surface.

4. The method for processing near-field radiated noise of ships based on fiber optic hydrophone array measurement according to claim 2, characterized in that, Filter factor of the improved Tikhonov regularized filter The following steps were used to optimize the process: Calculate the signal-to-noise ratio of the complex acoustic pressure data of the holographic surface after wavenumber domain extrapolation; Two-dimensional wavelet analysis was performed on the holographic complex sound pressure data after zero-padding expansion in the spatial domain to obtain the wavelet-reconstructed holographic complex sound pressure data, and the signal-to-noise ratio of the wavelet-reconstructed holographic complex sound pressure data was calculated. The difference between the signal-to-noise ratio (SNR) of the holographic complex sound pressure data extrapolated in the wavenumber domain and the SNR of the holographic complex sound pressure data reconstructed by wavelet is used as the objective function for the filter factor. Optimize the process so that the difference is zero.

5. The method for processing near-field radiated noise of ships based on fiber optic hydrophone array measurement according to claim 4, characterized in that, The signal-to-noise ratio of the holographic complex acoustic pressure data after wavenumber domain extrapolation is calculated using the following formula: ； in, The signal-to-noise ratio of the complex acoustic pressure data of the holographic surface after wavenumber domain extrapolation is given. This is the holographic complex sound pressure data calculated by extrapolation in the wavenumber domain. For holographic complex sound pressure data in the wavenumber domain, k x Let k be the wavenumber component along the x-direction. y Let z be the wavenumber component along the y-direction. h The distance to the holographic measurement surface.

6. The method for processing near-field radiated noise of ships based on fiber optic hydrophone array measurement according to claim 4, characterized in that, Two-dimensional wavelet analysis is performed on the spatially zero-padded extended holographic surface complex sound pressure data to obtain wavelet-reconstructed holographic surface complex sound pressure data. The signal-to-noise ratio of the wavelet-reconstructed holographic surface complex sound pressure data is calculated, including: Based on the selected wavelet function and decomposition series, the holographic complex sound pressure data after zero-padded expansion in the spatial domain is decomposed. Threshold denoising is performed on the wavelet coefficients of each level after decomposition; The wavelet coefficients after threshold denoising are reconstructed to obtain the wavelet-reconstructed holographic complex sound pressure data. The signal-to-noise ratio of the wavelet-reconstructed holographic complex acoustic pressure data is calculated based on the spatial domain zero-padded extended holographic complex acoustic pressure data and the wavelet-reconstructed holographic complex acoustic pressure data.

7. The method for processing near-field radiated noise of ships based on fiber optic hydrophone array measurement according to claim 4, characterized in that, For the filter factor Optimization to make the difference zero includes: For the filter factor within any interval The value of is calculated iteratively using the bisection method to obtain the optimal filter factor, making the objective function zero.

8. A sound field reconstruction system under local aperture measurement conditions, characterized in that, include: The extension module is used to perform spatial domain zero-padding extension on the holographic surface complex acoustic pressure data obtained from ship measurements at local apertures; The transformation module is used to transform the zero-padded and extended holographic surface complex sound pressure data in the spatial domain to the wavenumber domain using a two-dimensional Fourier transform, so as to obtain the holographic surface complex sound pressure data in the wavenumber domain. The extrapolation module is used to perform wavenumber domain extrapolation calculation on the holographic complex sound pressure data in the wavenumber domain, and to perform a two-dimensional inverse Fourier transform on the holographic complex sound pressure data after the wavenumber domain extrapolation calculation to obtain the holographic complex sound pressure data in the extended aperture. The replacement module is used to replace the holographic complex acoustic pressure data at the corresponding position of the local aperture within the extended aperture with the measured holographic complex acoustic pressure data, so as to obtain the final holographic complex acoustic pressure data. The reconstruction module is used to reconstruct the sound field using the final holographic complex sound pressure data, based on a spatial sound field transformation method.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the sound field reconstruction method under local aperture measurement conditions as described in any one of claims 1 to 7.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the sound field reconstruction method under local aperture measurement conditions as described in any one of claims 1 to 7.

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