Underwater sound field rapid reconstruction method based on semi-analytical ray acoustic model

Abstract

The invention discloses an underwater sound field rapid reconstruction method based on a semi-analytical ray acoustic model, which aims at the influence of a distance-dependent waveguide formed by non-uniform sound velocity and an uneven seabed surface on underwater sound field distribution, disperses a medium in a ray advancing process, and dynamically adjusts a stepping distance calculated by a sound velocity gradient so as to realize rapid reconstruction of an underwater sound field. The number of ray segments used for calculating the whole ray trajectory is remarkably reduced, the calculation efficiency of ray tracing is improved, and rapid sound field forecasting closer to the actual marine environment can be achieved.

Description

Technical Field

[0001] The present invention relates to a technology in the field of underwater testing, in particular to a method for rapid reconstruction of underwater sound fields based on a semi-analytical ray acoustic model. Background Art

[0002] Methods for predicting underwater acoustic fields include wavenumber integrals, simple normal waves, parabolic equations, and ray acoustic models. The wavenumber integral model cannot handle sound propagation in distance-dependent waveguides. The simple normal wave model struggles to balance computational efficiency and accuracy. The parabolic equation model struggles to calculate the acoustic field in environments with varying waveguide boundaries. Summary of the Invention

[0003] In response to the above-mentioned shortcomings of the existing technology, the present invention proposes a method for rapid reconstruction of underwater sound fields based on a semi-analytical ray acoustic model. In view of the influence of non-uniform sound speed and distance-dependent waveguides composed of uneven seabed surfaces on the distribution of underwater sound fields, the discrete medium is used during the ray travel process. By dynamically adjusting the step distance of sound speed gradient calculation, the number of ray segments used to calculate the entire ray trajectory is significantly reduced, the computational efficiency of ray tracing is improved, and a rapid prediction of the sound field that is closer to the actual ocean environment can be achieved.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention relates to a method for rapid reconstruction of an underwater sound field based on a semi-analytical ray acoustic model, comprising:

[0006] Step 1: Aiming at the problem of calculating the sound field in inhomogeneous media, an analytical expression of the ray trajectory and the sound pressure amplitude is established when the sound speed varies linearly with the spatial coordinates.

[0007] The ray trajectory is ,in: is the coordinate of any point on the current ray segment, is the coordinate of the starting point of the current ray segment, The speed of sound at The ray trajectory is The slowness vector at and Slowness vector exist Axis and The component in the axial direction, The sound velocity gradient at and The sound velocity gradient exist Axis and The component in the axial direction, It is the radius of the current arc ray segment.

[0008] The analytical expression of the sound pressure amplitude includes:

[0009] ① Sound pressure amplitude at any point on the ray trajectory ,in: is the sound pressure amplitude, The ray propagation distance is The speed of sound at the location, is the propagation distance of the ray, which can be calculated based on the geometric properties of the arc , is the speed of sound at the sound source, is the emission angle of the ray at the sound source, is the horizontal distance coordinate at the position, , is the ray propagation distance corresponding to the starting point of the current ray segment, is the radius of the current arc ray segment, are the coordinates of the center of the arc ray segment, are the coordinates of the starting point of the arc ray segment, and They are Sound velocity gradient exist Axis and The component in the axial direction, at value;

[0010] ② For the sound pressure amplitude outside the ray trajectory, the geometric properties of the arc are used to calculate the distance from the receiving point to the ray, so as to obtain the sound pressure contribution value of the ray to the receiving point. Then, the sound pressure contribution values ​​of all rays at this point are superimposed to obtain the sound pressure value of the point outside the ray trajectory. Specifically, the center of the arc ray trajectory is obtained by a semi-analytical fast algorithm. The coordinates of the receiving point are calculated To the center distance , and further obtain the radius of the arc ray trajectory by a semi-analytical fast algorithm , then the receiving point Distance to ray , all pairs of receiving points The sound pressure of the beam that contributes to the sound pressure at this point is superimposed to obtain the receiving point The sound pressure at .

[0011] Step 2: According to the sound velocity gradient at the current position of the ray, the size of the adaptive rectangular cell is calculated in real time during the ray's travel, and the discretization processing of the inhomogeneous medium is realized, that is, the sound velocity in the adaptive rectangular cell is considered to change linearly with the spatial coordinates.

[0012] The sonic velocity gradient is: The sound velocity gradient at The axis components are , The sound velocity gradient at The component in the axial direction is .

[0013] The adaptive rectangular cell is: the coordinates of the current position of the ray , with coordinates 、 、 、 A rectangular region constructed for the node where: , , is an adaptive parameter.

[0014] The linear change of the sound velocity in the adaptive cell with the spatial coordinates refers to: .

[0015] Step 3: Calculate the intersection of the arc's ray trajectory and the boundary of the rectangular cell by looping to get the starting point of the next arc , repeatedly discretizing the medium in real time during the ray travel process, and sequentially obtaining the sound pressure amplitude of each point on the ray through a semi-analytical fast algorithm, and realizing the stepping of the ray trajectory until it reaches the maximum horizontal distance or stops when the sound pressure amplitude is less than the threshold, thereby realizing underwater sound field reconstruction.

[0016] The reconstruction is to solve the sound pressure level SPL at different positions and convert it into the distribution of the underwater sound field, specifically: , where: underwater reference sound pressure .

[0017] Technical Effects

[0018] The present invention takes into account that the underwater sound speed varies with horizontal distance and depth, and according to the sound speed gradient of the current position of the ray, the size of the rectangular cell is dynamically calculated during the ray's travel, and circular arc ray trajectories are used in the rectangular area to form a semi-analytical sound field calculation method. Compared with the prior art, the present invention dynamically calculates the size of the rectangular cell according to the sound speed gradient of the current position of the ray, which not only reduces the number of ray segments used in ray tracing, but also avoids the early division of the grid discrete medium and the occupation of a large amount of computer memory. Secondly, the semi-analytical sound field calculation method using rectangular cells and circular arc ray trajectories is adopted, and the geometric properties of circular arc ray trajectories are utilized to improve the method disclosed in the existing paper, that is, the semi-analytical sound field calculation method using circular cells and parabolic ray trajectories, which faces the difficulty of large amount of calculation when solving the sound field in an environment where the sound speed varies with horizontal distance and depth. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Flowchart of the present invention;

[0020] Figure 2 Schematic diagram of the system of the present invention;

[0021] Figure 3 The curves of sound pressure level versus horizontal distance calculated for the embodiment and the Bellhop model at depths of (a) 1000 m and (b) 2000 m are shown;

[0022] Figure 4 The point sound source calculated for the embodiment is as follows Figure 2 The sound pressure level contours in the distance-dependent waveguide shown;

[0023] Figure 5 A comparison of the time taken to calculate the sound field between the embodiment and the Bellhop model is shown. DETAILED DESCRIPTION

[0024] like Figure 2 As shown, a system for rapid reconstruction of an underwater sound field based on a semi-analytical ray acoustic model involved in this embodiment includes: a configuration file reading unit, a sound field calculation unit, a calculation result display unit, and a progress display unit, wherein: the configuration file reading unit reads calculation parameters, sound velocity profile, seabed topography, and sound source information and outputs them to the sound field calculation unit; the sound field calculation unit calculates the underwater sound field based on the input, obtains the sound pressure level distribution result, and outputs it to the calculation result display unit; the calculation result display unit displays the underwater sound pressure level cloud map, sound velocity profile, and seabed topography cloud map; the progress display unit displays the current progress based on the progress information of the configuration file reading unit and the sound field calculation unit.

[0025] like Figure 1 The following is a fast underwater sound field reconstruction method based on the above system in this embodiment. In the hardware environment setting of CPU 13thGen Intel(R) Core(TM) i7-13700K and memory 32GB, the calculation parameters and Figure 3 The underwater sound field is quickly reconstructed from the sound velocity profile shown, including:

[0026] Step 1: Aiming at the problem of calculating the sound field in an inhomogeneous medium, an analytical expression of the ray trajectory and the sound pressure amplitude is established when the sound speed varies linearly with the three-dimensional space coordinates.

[0027] Step 2: Considering a distance-dependent waveguide in which both the sound velocity and seafloor topography vary with horizontal distance, a semi-analytical ray acoustics model based on the adaptive rectangular cell method is established. Based on the sound velocity gradient at the ray's current location, the rectangular cell size is calculated in real time as the ray travels, automatically discretizing the inhomogeneous medium. The sound velocity within the cell is assumed to vary linearly with the spatial coordinates, thus making the analytical solution derived above applicable.

[0028] Step 3: Using the Gaussian beam superposition method, according to the geometric properties of the arc ray trajectory, the distance from the receiving point to the ray trajectory can be accurately calculated, thus obtaining Figure 4 The sound field simulation results shown in the figure are compared with the sound pressure level versus horizontal distance curves at depths of 1000m and 2000m calculated by the present invention and the existing underwater acoustic calculation model Bellhop. The two are highly consistent, as shown in the figure. Figure 5 At the same time, the calculation time of the present invention is reduced from 5.6 seconds in the prior art to 0.63 seconds in the present invention, achieving a calculation acceleration of about 8 times.

[0029] Table 1 Calculation parameters

[0030] Compared with the prior art, the present invention significantly reduces the number of ray segments used in ray tracing while ensuring the accuracy of sound field calculation, thereby reducing the time used for sound field calculation.

[0031] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principles and purpose of the present invention. The scope of protection of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. All implementation schemes within its scope shall be subject to the constraints of the present invention.

Claims

1. A method for rapid reconstruction of underwater sound fields based on a semi-analytical ray acoustic model, characterized in that: include: Step 1: For the acoustic field calculation problem in inhomogeneous media, an analytical expression for the ray trajectory and sound pressure amplitude is established when the sound speed varies linearly with the spatial coordinates; Step 2: Based on the sound velocity gradient at the current position of the ray, the size of the adaptive rectangular cell is calculated in real time during the ray's travel, and the discretization of the inhomogeneous medium is realized. That is, the sound velocity in the adaptive rectangular cell is assumed to change linearly with the spatial coordinates. Step 3: Calculate the intersection of the arc's ray trajectory and the boundary of the rectangular cell by looping to get the starting point of the next arc , repeatedly discretizing the medium in real time during the ray travel process, and sequentially obtaining the sound pressure amplitude of each point on the ray through a semi-analytical fast algorithm, and realizing the stepping of the ray trajectory until it reaches the maximum horizontal distance or stops when the sound pressure amplitude is less than the threshold, thereby realizing underwater sound field reconstruction.

2. The method for rapid underwater sound field reconstruction based on a semi-analytical ray acoustic model according to claim 1 is characterized in that: The ray trajectory is ,in: is the coordinate of any point on the current ray segment, is the coordinate of the starting point of the current ray segment, The speed of sound at The ray trajectory is The slowness vector at and Slowness vector exist Axis and The component in the axial direction, The sound velocity gradient at and The sound velocity gradient exist Axis and The component in the axial direction, It is the radius of the current arc ray segment.

3. The method for rapid underwater sound field reconstruction based on a semi-analytical ray acoustic model according to claim 1 is characterized in that: The analytical expression of the sound pressure amplitude includes: ① Sound pressure amplitude at any point on the ray trajectory ,in: is the sound pressure amplitude, The ray propagation distance is The speed of sound at the location, is the propagation distance of the ray, which is calculated based on the geometric properties of the arc , is the speed of sound at the sound source, is the emission angle of the ray at the sound source, is the horizontal distance coordinate at the position, , is the ray propagation distance corresponding to the starting point of the current ray segment, is the radius of the current arc ray segment, are the coordinates of the center of the arc ray segment, are the coordinates of the starting point of the arc ray segment, and They are Sound velocity gradient exist Axis and The component in the axial direction, at value; ② For the sound pressure amplitude outside the ray trajectory, the geometric properties of the arc are used to calculate the distance from the receiving point to the ray, so as to obtain the sound pressure contribution value of the ray to the receiving point. Then, the sound pressure contribution values ​​of all rays at this point are superimposed to obtain the sound pressure value of the point outside the ray trajectory. Specifically, the center of the arc ray trajectory is obtained by a semi-analytical fast algorithm. The coordinates of the receiving point are calculated To the center distance , and further obtain the radius of the arc ray trajectory by a semi-analytical fast algorithm , then the receiving point Distance to ray , all pairs of receiving points The sound pressure of the beam that contributes to the sound pressure at this point is superimposed to obtain the receiving point The sound pressure at .

4. The method for rapid underwater sound field reconstruction based on a semi-analytical ray acoustic model according to claim 1 is characterized in that: The sonic velocity gradient is: The sound velocity gradient at The axis components are , The sound velocity gradient at The component in the axial direction is .

5. The method for rapid reconstruction of underwater sound fields based on a semi-analytical ray acoustic model according to claim 1 is characterized in that: The adaptive rectangular cell is: the coordinates of the current position of the ray , with coordinates 、 、 、 A rectangular region constructed for the node where: , , is an adaptive parameter.

6. The method for rapid underwater sound field reconstruction based on a semi-analytical ray acoustic model according to claim 1 is characterized in that: The linear change of the sound velocity in the adaptive cell with the spatial coordinates refers to: .

7. The method for rapid underwater sound field reconstruction based on a semi-analytical ray acoustic model according to claim 1 is characterized in that: The reconstruction is to solve the sound pressure level SPL at different positions and convert it into the distribution of the underwater sound field, specifically: , where: underwater reference sound pressure .

8. A system for rapidly reconstructing an underwater sound field for implementing the method according to any one of claims 1 to 7, characterized in that: include: A configuration file reading unit, a sound field calculation unit, a calculation result display unit, and a process display unit, wherein: the configuration file reading unit reads the calculation parameters, sound velocity profile, seabed topography, and sound source information and outputs them to the sound field calculation unit; the sound field calculation unit calculates the underwater sound field according to the input, obtains the sound pressure level distribution result, and outputs it to the calculation result display unit; the calculation result display unit displays the underwater sound pressure level cloud map, sound velocity profile, and seabed topography cloud map; the process display unit displays the current process according to the process information of the configuration file reading unit and the sound field calculation unit.

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