Deep-sea ultra-long-distance sound propagation processing method and system

Abstract

The invention belongs to the field of underwater acoustic physics, and particularly relates to a deep-sea ultra-long-distance sound propagation processing method and system. The method includes: acquiring submarine topography and sediment parameters of a sea area; acquiring a sound velocity profile at a sea area sound signal receiving position; in combination with the influence of the earth curvature on ultra-long distance sound propagation, obtaining a corrected medium refractive index, and obtaining a corrected sound velocity profile through the relationship between the medium refractive index and the sound velocity profile; and inputting the corrected sound velocity profile and related seabed parameters into a sound field calculation model, and outputting sound field data. According to the method, the influence of the earth curvature on ultra-long-distance sound propagation in the deep sea environment is comprehensively considered, the sound propagation processing precision is improved, and the model calculation precision and applicability are improved under the condition that a sound field calculation model is not changed.

Description

Technical Field

[0001] The present invention belongs to the field of underwater acoustic physics, and in particular relates to a deep-sea ultra-long-range sound propagation processing method and system. Background Art

[0002] Sound waves are the only form of energy that can effectively propagate over long distances in the ocean. Studies have shown that sound waves can propagate over thousands or even tens of thousands of kilometers. When calculating long-distance deep-sea sound propagation, changes in the Earth's curvature cannot be ignored. For long-distance deep-sea sound propagation, there may be large spans of Earth's latitude, and the sound propagation characteristics caused by changes in the hydrological environment with distance are attracting increasing attention from researchers. When there is no real-time measurement of the sound velocity profile that varies with distance during sound propagation, or when the measured sound velocity profile along the sound propagation path is relatively small, the effect of the Earth's curvature on long-range sound propagation needs to be considered to correct for changes in the sound velocity profile with distance, thereby obtaining more accurate sound propagation calculations.

[0003] In the current research on the above-mentioned issues, some scholars have taken the earth's curvature into account in deep-sea long-distance sound propagation and modified the sound field calculation model to obtain good results. This method can be found in reference [1] ("The influence of earth curvature on deep-sea long-distance sound propagation", published in "Acoustic Technology" Vol. 34, No. 6 in December 2015, starting from page 79). However, for the correction of the sound field calculation model, the model code needs to be modified. Generally speaking, it is relatively complex and labor-intensive, and it is difficult to promote. There is another variable parameter medium method, which corrects the sound propagation medium without changing the existing sound field calculation model. It is mainly reflected in the correction of the sound velocity profile of the propagation medium, that is, the correction of the input parameters of the calculation model. This method can be found in reference [2] ("The influence of earth curvature on long-distance sound propagation", published in "Acta Physica Sinica" Vol. 70, No. 11 in June 2021, starting from page 192). However, this method uses relatively complex coordinate mapping and transformation, and only corrects the depth value of the sound velocity profile, which is not intuitive enough to clearly demonstrate the impact of the Earth's curvature on the sound velocity profile. Therefore, there is an urgent need for an ultra-long-range sound propagation processing method in deep-sea environments that considers the influence of Earth curvature. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and propose a deep-sea ultra-long-range sound propagation processing method and system.

[0005] In view of this, the present invention proposes a deep-sea ultra-long-range sound propagation processing method, comprising:

[0006] Step 1) obtaining the seabed topography and bottom parameters of the sea area;

[0007] Step 2) obtaining a sound velocity profile at a receiving location of the sea area sound signal;

[0008] Step 3) combining the effect of the earth's curvature on ultra-long-range sound propagation to obtain a corrected medium refractive index, and obtaining a corrected sound velocity profile through the relationship between the medium refractive index and the sound velocity profile;

[0009] Step 4) Input the corrected sound velocity profile and seabed related parameters into the sound field calculation model and output the sound field data.

[0010] Preferably, the seabed topography and bottom sediment parameters in step 1) adopt a double-layer seabed model, including: the sound velocity, density, absorption coefficient and thickness of the upper sediment layer, and the sound velocity, density and absorption coefficient of the lower base layer.

[0011] Preferably, the step 2) includes: obtaining seawater sound velocity profiles at different distances using a temperature-salinity-depth meter.

[0012] Preferably, the refractive index n′ of the medium corrected in step 3) satisfies the following formula:

[0013]

[0014] Where n is the refractive index of the medium, R e is the radius of the earth, z is the depth, and r is the horizontal distance.

[0015] Preferably, the corrected sound velocity profile c in step 3) w ' satisfies the following formula:

[0016]

[0017] Among them, c w is the sound velocity profile when the horizontal distance r = 0, that is, the uncorrected sound velocity profile, c0 is the reference sound velocity, R e is the radius of the Earth.

[0018] Preferably, the sound field calculation model in step 4) is a parabolic equation RAM-PE sound field calculation model.

[0019] On the other hand, the present invention provides a deep-sea ultra-long-range sound propagation processing system, comprising:

[0020] Seabed related parameter acquisition module, used to obtain the seabed topography and bottom parameters of the sea area;

[0021] A sound velocity profile acquisition module is used to obtain the sound velocity profile at the receiving point of the sea area sound signal;

[0022] The sound velocity profile correction module is used to obtain the corrected medium refractive index based on the influence of the earth's curvature on ultra-long-range sound propagation, and the corrected sound velocity profile is obtained through the relationship between the medium refractive index and the sound velocity profile;

[0023] The sound field output module is used to input the corrected sound velocity profile and seabed related parameters into the sound field calculation model and output the sound field data.

[0024] Compared with the prior art, the advantages of the present invention are:

[0025] The method of the present invention comprehensively considers the influence of the earth's curvature on ultra-long-range sound propagation in deep-sea environments, improves the accuracy of sound propagation calculations, and provides a powerful algorithmic model support for the prediction of ultra-long-range deep-sea sound fields. In addition, this method incorporates the influence of the earth's curvature into the modification of the sound velocity profile, and provides a simple expression for the corrected refractive index and sound velocity profile, which can intuitively reflect the influence of the earth's curvature. The sound field is calculated using the corrected sound velocity profile, improving the model's calculation accuracy and applicability without changing the sound field calculation model. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 These are the seabed parameters used in the actual measurement of seabed topography and simulation in the offshore experiment in Example 1 of the present invention;

[0027] FIG2( a ) is a diagram showing the measured sound velocity profile at 0 km from the sound source and the corrected sound velocity profile taking into account the influence of the earth's curvature in Example 1 of the present invention;

[0028] FIG2( b ) is a diagram showing the measured sound velocity profile at 300 km from the sound source and the corrected sound velocity profile taking into account the influence of the earth's curvature in Example 1 of the present invention;

[0029] FIG2( c ) is a diagram showing the measured sound velocity profile at 600 km from the sound source and the corrected sound velocity profile taking into account the influence of the earth's curvature in Example 1 of the present invention;

[0030] Figure 3 The figure is a comparison of the theoretical sound propagation losses calculated using the model using the measured sound velocity profile and the modified sound velocity profile at a receiving depth of 513 m in Example 1 of the present invention;

[0031] FIG4( a ) is a comparison of the theoretical propagation loss calculated using the modified sound velocity profile and the propagation loss calculated using experimental data at a receiving depth of 513 m in Example 1 of the present invention;

[0032] FIG4( b ) is a comparison of the theoretical propagation loss calculated using the modified sound velocity profile and the propagation loss calculated using experimental data at a receiving depth of 2886 m in Example 1 of the present invention;

[0033] Figure 5 Flowchart of the method of the present invention. DETAILED DESCRIPTION

[0034] The present invention proposes a method for processing deep-sea ultra-long-range sound propagation, which takes into account the ultra-long-range sound propagation influence of the earth's curvature in the calculation. First, the seabed topography and bottom parameters of the sea area are obtained through actual measurement or historical database to provide a seabed environment basis for the calculation of the ultra-long-range sound propagation model; then, the sound velocity profile at the receiving point of the sea area sound signal is obtained through actual measurement to provide an ocean environment basis for the calculation of the ultra-long-range sound propagation model; in the ultra-long-range sound propagation process, it is necessary to consider the influence of the earth's curvature on the ultra-long-range sound propagation. In this method, its influence is taken into account in the transformation of the wave equation, and then the corrected medium refractive index is obtained. The corrected sound velocity profile is obtained through the relationship between the refractive index and the sound velocity profile; finally, the corrected sound velocity profile and seabed related parameters are input into the parabolic equation RAM-PE sound field calculation model to output the sound field data.

[0035] The present invention comprehensively considers the influence of the earth's curvature on ultra-long-distance sound propagation in deep-sea environments, improves the accuracy of sound propagation calculations, and provides powerful algorithm model support for the prediction of ultra-long-distance deep-sea sound fields.

[0036] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0037] Example 1

[0038] Embodiment 1 of the present invention proposes a method for processing deep-sea ultra-long-range sound propagation, and the implementation process is divided into the following steps:

[0039] Step 1: Obtain the seabed topography and bottom parameters of the sea area through actual measurement or historical database.

[0040] This example uses an ultra-long-range acoustic propagation survey line from a sea trial in the eastern Indian Ocean as an example. The survey line is 803 km long and uses a hydrophone with a sampling rate of 16 kHz to receive acoustic signals. In the experiment, the 10,000-meter single-beam bathymetric system or nautical charts are combined with historical databases to obtain information such as seawater depth and seabed topography parameters. The results are as follows: Figure 1 As shown, the seabed acoustic parameters are for a double-layer seabed model: the upper sediment layer has a sound velocity of 1560 m / s and a density of 1.60 g / cm 3 , absorption coefficient 0.10dB / λ, sediment thickness 20m; lower substrate sound velocity 1650m / s, density 1.80g / cm 3 , the absorption coefficient is 0.10dB / λ.

[0041] Step 2: Obtain the sound speed profile at the receiving point of the sea area sound signal through actual measurement.

[0042] During the experiment, the sound velocity profiles of seawater at different distances were obtained using a temperature-salinity-depth meter. The sound velocity profiles at 0 km, 300 km, and 600 km from the sound source are taken as an example, as shown by the black solid line, blue solid line, and red solid line in Figure 2(a), Figure 2(b), and Figure 2(c).

[0043] Step 3: Consider the influence of the earth's curvature on ultra-long-range sound propagation and incorporate its influence into the transformation of the wave equation to obtain the corrected medium refractive index. The corrected sound velocity profile is obtained through the relationship between the refractive index and the sound velocity profile.

[0044] The two-dimensional coordinate Helmholtz equation without considering the influence of the earth's curvature is:

[0045]

[0046] Where P is the sound pressure amplitude, r is the horizontal distance, z is the vertical depth, and k is the wave number. For the long-distance sound field, the variable substitution is used. Ignoring the far-field terms and the quadratic differential terms that vary with distance, we can obtain the equation for p:

[0047]

[0048] Where p is the complex sound pressure, k0 is the horizontal beam, and i represents the imaginary part.

[0049] When considering the problem of long-distance sound propagation in the deep sea, the influence of the earth's curvature must be considered. In this case, the plane z = 0 is not the sea surface. If the radius of the earth is R e , at a horizontal distance of r, the actual water depth calculated from the sea surface should be z–z s , through geometric relations we can get:

[0050]

[0051] where z s is the receiving depth, R e is the radius of the Earth. Now select a set of new variables and slave variables:

[0052] r′=r

[0053]

[0054] Substituting the coordinate transformation into the equation for p, we can obtain the equation for p′ in the new coordinate system:

[0055]

[0056] Where n is the refractive index of the medium. From the above formula, we can see that the effect of the earth's curvature on sound propagation can be equivalent to the earth's curvature changing the refractive index of the sound wave propagation medium. For long-distance sound propagation, the refractive index after the earth's curvature correction satisfies:

[0057]

[0058] Where n' is the corrected refractive index. Based on the relationship between the refractive index and the sound velocity profile, the corrected sound velocity profile can be obtained:

[0059]

[0060] where c w ′ is the corrected sound velocity profile, c w is the sound velocity profile at horizontal distance r = 0, that is, the uncorrected sound velocity profile, which changes with the depth and is a function of the depth z. c0 is the reference sound velocity set to 1500 m / s, R e The radius of the earth is taken as 6356.9 km.

[0061] The above-mentioned modified sound velocity profile expression takes the influence of the earth's curvature on sound propagation into account, and the measured sound velocity profile is corrected by this formula, as follows: Figure 2(a)-Figure 2(c) As shown by the black dotted line, blue dotted line and red dotted line, it can be seen that the sound velocity profile correction result is not obvious above the sound channel axis. Below the sound channel axis, the sound velocity profile correction value increases with the increase of depth, and the sound velocity gradient of the deep sea isothermal layer becomes larger.

[0062] Step 4: Input the corrected sound velocity profile and seabed related parameters into the acoustic field calculation model and output acoustic field data. In one embodiment, a parabolic equation RAM-PE acoustic field calculation model is used.

[0063] The seabed topography and bottom parameters in step 1 and the corrected sound velocity profile c in step 3 are used to calculate the seabed topography and bottom parameters in step 1 and step 3. w ′ is input into the parabolic equation RAM-PE sound field calculation model, and given other sound source parameters (sound source depth, sound source frequency) and receiving parameters (receiving distance, receiving depth), the sound field data is output through the model.

[0064] In this experiment, the sound source is an explosion sound source at a calibrated depth of 200m. To verify the accuracy of the calculated propagation loss, the propagation loss of the sound signal at a frequency of 200Hz was analyzed, and the hydrophone reception data at depths of 513m and 2886m were used for verification. When simulating the propagation loss using the RAM-PE model, the sound field calculation is performed by swapping the depth positions of the sound source and receiver according to the reciprocity principle. Figure 3The calculation results of the theoretical propagation loss at a receiving depth of 513m before and after the sound velocity profile correction are shown. It can be seen that due to the influence of the earth's curvature, the position of the convergence zone moves to a long distance. At 700km, the convergence zone moves by about 7-8km. The difference in propagation loss is mainly reflected at the convergence zone distance due to the offset of the convergence zone, and the difference in local propagation loss results can reach 10dB.

[0065] The acoustic signal received by the hydrophone in the experiment was Fourier transformed to obtain its spectrum, and then the propagation loss was calculated on average within the 1 / 3 octave of the center frequency of 200 Hz, as shown by the blue circles in Figures 4(a) and 4(b), where the red solid line is the theoretical propagation loss calculated using the corrected sound velocity profile. It can be seen that the experimental data and the theoretical calculation data are in good agreement, which can better reflect the convergence zone structure at ultra-long distances, indicating the accuracy of the sound field calculation results of this method, and that the calculation of ultra-long-distance sound propagation in the deep sea can be realized. Based on the above analysis, the process of the present invention is as follows: Figure 5 shown.

[0066] Example 2

[0067] Embodiment 2 of the present invention provides a deep-sea ultra-long-range sound propagation processing system, which is implemented based on the method of embodiment 1 and includes:

[0068] Seabed related parameter acquisition module, used to obtain the seabed topography and bottom parameters of the sea area;

[0069] A sound velocity profile acquisition module is used to obtain the sound velocity profile at the receiving point of the sea area sound signal;

[0070] The sound velocity profile correction module is used to obtain the corrected medium refractive index based on the influence of the earth's curvature on ultra-long-range sound propagation, and the corrected sound velocity profile is obtained through the relationship between the medium refractive index and the sound velocity profile;

[0071] The sound field output module is used to input the corrected sound velocity profile and seabed related parameters into the sound field calculation model and output the sound field data.

[0072] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention and are intended to be encompassed by the claims of the present invention.

Claims

1. A method for processing deep-sea ultra-long-range sound propagation, comprising: Step 1) obtaining the seabed topography and bottom quality parameters of the sea area; Step 2) obtaining the sound velocity profile at the receiving point of the sea area sound signal; Step 3) combining the influence of the earth curvature on ultra-long-distance sound propagation, obtaining a corrected medium refractive index, and obtaining a corrected sound velocity profile through the relationship between the medium refractive index and the sound velocity profile; Step 4) input the corrected sound velocity profile and seabed related parameters into the sound field calculation model and output the sound field data.

2. The deep sea ultra-long-range sound propagation processing method according to claim 1, characterized in that: The seafloor topography and bottom parameters of step 1) adopt a double-layer seafloor model, including: the sound velocity, density, absorption coefficient and thickness of the upper sediment layer, and the sound velocity, density and absorption coefficient of the lower basement.

3. The deep sea ultra-long-range sound propagation processing method according to claim 1, characterized in that: The step 2) includes: obtaining seawater sound velocity profiles at different distances by using a temperature-salinity-depth measuring instrument.

4. The deep sea ultra-long-range sound propagation processing method according to claim 1, characterized in that: The refractive index n′ of the medium corrected in step 3) satisfies the following formula: Where n is the refractive index of the medium, R e is the radius of the earth, z is the depth, and r is the horizontal distance.

5. The deep sea ultra-long-range sound propagation processing method according to claim 4, characterized in that: The corrected sound velocity profile c in step 3) w ' satisfies the following formula: Among them, c w is the sound velocity profile when the horizontal distance r = 0, that is, the uncorrected sound velocity profile, c0 is the reference sound velocity, R e is the radius of the Earth.

6. The deep sea ultra-long-range sound propagation processing method according to claim 1, characterized in that: The sound field calculation model in step 4) is a parabolic equation RAM-PE sound field calculation model.

7. A deep-sea ultra-long-range sound propagation processing system, characterized in that: include: The seabed related parameter acquisition module is used to obtain the seabed topography and bottom quality parameters of the sea area; A sound velocity profile acquisition module is used to acquire the sound velocity profile at the receiving point of the sea area sound signal; The sound velocity profile correction module is used to obtain the corrected medium refractive index by combining the influence of the earth's curvature on ultra-long-distance sound propagation, and obtain the corrected sound velocity profile through the relationship between the medium refractive index and the sound velocity profile; and The sound field output module is used to input the corrected sound velocity profile and seabed related parameters into the sound field calculation model and output the sound field data.

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