Signal modeling method coupling a ray acoustic propagation model with a circular array transfer function

Abstract

The application relates to a signal modeling method coupling a ray sound propagation model and a circular ring array transfer function, which comprises the following steps: calculation of water sound field multi-path information, calculation of the circular ring array transfer function, coupling of the water sound field multi-path arrival information and the circular ring array transfer function and the like. The method has the beneficial effect that the coupling of sound propagation and infinite long cylindrical shell scattering effect is considered, the arrival information of the multi-path sound line at the center of the circular ring array is obtained by using the ray sound propagation model BELLHOP, and then the circular ring array element signal is obtained by combining the transfer function of the circular ring array.

Description

Technical Field

[0001] This invention relates to a signal modeling technique for underwater scattering sound field array elements, which is a method for modeling signals of an infinitely long rigid cylindrical surface ring array under a ray sound propagation model. Background Technology

[0002] The ray model is a type of sound propagation model with a clear physical concept, and it was one of the earliest methods applied to underwater sound field calculations. In ray acoustics, it is assumed that the received sound field consists of sound rays emitted from a sound source with certain amplitudes and grazing angles, and the propagation direction of the sound rays is perpendicular to the wavefront. The sound rays connecting the sound source and receiver are called eigenrays, and the superposition of all eigenrays at the receiving point constitutes the sound field at that point. The study of ray theory not only helps to understand the characteristics of sound ray paths but also helps to interpret the results of other sound propagation models.

[0003] The cylindrical shell can increase the time difference, intensity difference, and spectral difference between hydrophones. This information can serve as location clues to enhance detection capabilities. The physical process of sound waves from the sound source to the hydrophone reception can be described by a transfer function, which characterizes the effects of sound propagation and the sound scattering characteristics of the shell. This transfer function includes both the sound propagation transfer function and the shell's transfer function. Furthermore, the transfer function of the ring array requires the arrival elevation angles of the multipath sound rays provided by the ray model. In actual physical processes, the shell's scattering characteristics couple with the underwater acoustic field to form the hydrophone's observation signal. Therefore, modeling the element signals of a ring array considering sound propagation and shell scattering has certain application value. Summary of the Invention

[0004] To model the signal of an infinitely long rigid cylindrical surface ring array of a hydrophone, it is necessary to consider both the sound propagation effect and the scattering effect of the shell.

[0005] This invention proposes a signal modeling method that couples a ray acoustic propagation model with a circular array transfer function, comprising the following steps:

[0006] S1 Acquires multipath arrival information of underwater acoustic field: Input the sound source receiving parameters and environmental parameters into the ray calculation model BELLHOP to calculate the underwater acoustic field, read the calculation results, and obtain the multipath arrival information at the center of the circular array;

[0007] S2 Calculate the transfer function of the circular array: Based on the size of the circular array, the coordinates of the array elements, and the multipath arrival information obtained in step S1, the transfer function of the circular array is calculated.

[0008] S3 Coupling of multipath arrival information of underwater acoustic field with the transfer function of circular array: Multiply the sound pressure of the multipath sound ray obtained in step S1 with the transfer function of the circular array obtained in step S2, and then add the results of the multiplication of the multipath sound ray to obtain the circular array element signal of a single sound source.

[0009] S4 Superposition of Multiple Sound Source Signals: For the superposition of multiple sound source signals from different horizontal incoming wave directions, repeat steps S1, S2, and S3, and then add the corresponding array element signals to obtain the array element received signal after the superposition of multiple sound sources.

[0010] Step S1 specifically involves inputting the set environmental parameters and sound source receiving parameters into the Bellhop ray calculation model to calculate the underwater acoustic field, obtaining information such as the amplitude, propagation time, exit angle, incident angle, number of reflections at the water surface, number of reflections at the bottom, and the total number of sound rays reaching the receiving point. The incident angle information of the multipath sound rays is then sent to S2 for calculating the circular array transfer function. The amplitude and propagation time of the multipath sound rays are used to reconstruct the complex sound pressure of the multipath sound rays at the receiving point.

[0011] a l (f)=A l ×exp(i2πft)

[0012] Among them, a l (f) is the complex sound pressure of the l-th multipath ray, A l denoted as the amplitude of the multipath sound ray, f as the signal frequency, c as the speed of sound, and t as the propagation time of the multipath sound ray.

[0013] The calculated complex sound pressure of the multipath sound ray is sent to S3 for related calculations.

[0014] In step S1, the environmental parameters and sound source receiving parameters include sound source depth, sound source distance, sound source signal frequency, receiving depth, water depth, sound velocity profile, and bottom sediment parameters.

[0015] Step S2 specifically involves: expressing the transfer function of the circular array as:

[0016]

[0017] Where, k l Represented as φ g Let g be the horizontal angle of the direction of the g-th incoming wave. Let be the elevation angle of the l-th ray from the g-th incoming wave direction, * denotes complex conjugation, jn(klr) is the n-th order cylindrical Bessel function, hn(2)(klr) is the second-order Hankel function, and φ q Let r be the horizontal angle represented by the q-th element of the circular array in the circular array coordinate system, and r be the radius of the circular array. a The radius of the rigid cylinder;

[0018] The radius r of the circular array and the coordinates φ of each element of the circular array are set. q The frequency f of the sound source signal and the multipath angle of arrival φ obtained in step S1 g , Substituting these values ​​into the formula for the transfer function of a circular array, we obtain the transfer function s of the circular array.

[0019] Step S3 specifically involves: each multipath ray has a corresponding circular array transfer function; the sound pressure level of the l-th multipath ray in the direction of the g-th horizontal incoming wave is calculated based on step S1. The transfer function of the acoustic ray relative to the q-th element of the circular array, calculated according to step S2, is as follows: For the direction of the incoming wave φ g The sound pressure of the q-th element of the circular array is:

[0020]

[0021] Step S4 specifically involves repeating steps S1, S2, and S3 to obtain the received signals of the circular array elements from multiple sound sources. The corresponding element signals are then added together to obtain the superimposed element received signal from the multiple sound sources.

[0022]

[0023] The method provided by this invention considers the coupling effect between sound propagation and scattering from an infinitely long cylindrical shell. It is a method for modeling array element signals by coupling a ray sound propagation model with the transfer function of a circular array on the cylindrical shell surface. Specifically, it uses the Bellhop ray sound propagation model to obtain the arrival information of multiple sound rays at the center of the circular array, and then combines it with the transfer function of the circular array to obtain the array element signals of an infinitely long rigid cylindrical surface. This invention provides model and methodological support for modeling array element signals of an infinitely long rigid cylindrical surface circular array considering sound propagation. Attached Figure Description

[0024] Figure 1 This is a flowchart of the signal modeling method for coupling the ray acoustic propagation model with the circular array transfer function of the present invention.

[0025] Figure 2 This refers to the multipath eigenline map of the arrival point on the depth-distance plane obtained by calculating the BELLHOP ray model in step S1 of the present invention.

[0026] Figure 3 The horizontal angle φ of the g-th incoming wave direction in the circular array coordinate system in step S2 of this invention is... g And the pitch angle θ of the lth sound ray gl and array element coordinates φ q picture. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] This invention utilizes a ray sound propagation model and the transfer function of a ring array on a rigid cylindrical surface to simulate and obtain the array element signal considering the coupling of sound propagation and shell scattering. The process includes: 1) calculating multipath information on the depth-range plane using the BELLHOP ray model; 2) inputting shell parameters and signal arrival information into the ring array transfer function formula to obtain the ring array transfer function; 3) multiplying the sound pressure of the multipath sound rays arriving at the center of the ring array with the corresponding ring array transfer function, and then summing the results of the multiplication to obtain the ring array element signal considering the coupling of sound propagation and shell scattering.

[0029] Specifically, a signal modeling method coupling a ray acoustic propagation model with a circular array transfer function is proposed, including the following steps:

[0030] Acquisition of multipath arrival information in the S1 underwater acoustic field. Target and environmental parameters such as sound source depth, sound source distance, sound source signal frequency, receiving depth, water depth, sound velocity profile, and seabed composition are input into the Bellhop ray calculation model to calculate the underwater acoustic field, obtaining the multipath eigenlines at the receiving point, such as... Figure 2 As shown, this includes information such as the arrival angle, amplitude, and phase of the multipath sound rays. BELLHOP packages the calculated multipath information into a "*.arr" file. Reading this file yields the amplitude, propagation time, exit angle, incident angle, number of reflections at the water surface, number of reflections at the bottom of the water, and the total number of sound rays reaching the receiving point. The incident angle information of the multipath sound rays is sent to S2 for calculating the circular array transfer function. The amplitude and propagation time of the multipath sound rays are used to reconstruct the complex sound pressure level of the multipath sound rays at the receiving point.

[0031] a l (f)=A l ×exp(i2πft)

[0032] Among them, a l (f) is the complex sound pressure of the l-th multipath ray, A l denoted as the amplitude of the multipath sound ray, f as the signal frequency, c as the speed of sound, and t as the propagation time of the multipath sound ray.

[0033] The calculated complex sound pressure of the multipath sound ray is sent to S3 for related calculations.

[0034] S2. Calculation of the transfer function of the circular array. Based on the size of the circular array, the positions of the array elements, and the multipath arrival angles obtained in step S1, the transfer function of the circular array is calculated. The transfer function of the circular array is expressed as:

[0035]

[0036] Where, k l Represented as φ gLet g be the horizontal angle of the direction of the g-th incoming wave. Let j be the elevation angle of the l-th ray from the g-th incoming wave direction, * denotes complex conjugate, and j n (k l r) is an nth-order cylindrical Bessel function, h n (2) (k l r) is the Hankel function of the second kind, φ q Let r be the horizontal angle represented by the q-th element of the circular array in the circular array coordinate system, and r be the radius of the circular array. a Let be the radius of the rigid cylinder.

[0037] Some parameters are represented in a ring matrix as follows: Figure 3 As shown, based on actual needs, the radius r of the circular array and the coordinates φ of each element of the circular array are set. q The frequency f and multipath angle of arrival φ of the sound source signal g θ gl (The result of the calculation in S1 is read from BEELHOP) Substituting it into the formula for the transfer function of the circular array, we can obtain the transfer function s of the circular array.

[0038] S3 Coupling of Multipath Arrival Information and Circular Array Transfer Function in Underwater Acoustic Field: The array element signals are obtained by combining the multipath arrival information and the circular array transfer function. Each multipath ray has a corresponding circular array transfer function. Based on the calculation results of steps S1 and S2, the sound pressure of the l-th multipath ray in the direction of the g-th horizontal incoming wave is a. gl (f) The transfer function of the sound ray relative to the q-th element of the circular array is s(f,r,φ). q ,θ gl ,φ g If the direction of the incoming wave is φ, then... g The sound pressure of the q-th element of the circular array is:

[0039]

[0040] S4. Superposition of multiple sound source signals. Repeat steps S1, S2, and S3 to obtain the received signals of the circular array elements from multiple sound sources. Add the corresponding array element signals to obtain the superimposed array element received signal from the multiple sound sources:

[0041]

[0042] It should be noted that the above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Equivalent modifications made based on the above embodiments are all within the scope of protection of the present invention.

Claims

1. A signal modeling method coupling a ray acoustic propagation model with a circular array transfer function, characterized in that, Includes the following steps: S1 Acquires multipath arrival information of underwater acoustic field: Input the sound source receiving parameters and environmental parameters into the ray calculation model BELLHOP to calculate the underwater acoustic field, read the calculation results, and obtain the multipath arrival information at the center of the circular array; S2 Calculate the transfer function of the circular array: Based on the size of the circular array, the coordinates of the array elements, and the multipath arrival information obtained in step S1, the transfer function of the circular array is calculated. S3 Coupling of multipath arrival information of underwater acoustic field with the transfer function of circular array: Multiply the sound pressure of the multipath sound ray obtained in step S1 with the transfer function of the circular array obtained in step S2, and then add the results of the multiplication of the multipath sound ray to obtain the circular array element signal of a single sound source. S4 Superposition of Multiple Sound Source Signals: For the superposition of multiple sound source signals from different horizontal incoming wave directions, repeat steps S1, S2, and S3, and then add the corresponding array element signals to obtain the array element received signal after the superposition of multiple sound sources.

2. The signal modeling method coupling the ray acoustic propagation model with the circular array transfer function according to claim 1, characterized in that, Step S1 specifically involves inputting the set environmental parameters and sound source receiving parameters into the Bellhop ray calculation model to calculate the underwater acoustic field, obtaining information such as the amplitude, propagation time, exit angle, incident angle, number of reflections at the water surface, number of reflections at the bottom, and the total number of sound rays reaching the receiving point. The incident angle information of the multipath sound rays is then sent to S2 for calculating the circular array transfer function. The amplitude and propagation time of the multipath sound rays are used to reconstruct the complex sound pressure of the multipath sound rays at the receiving point. a l (f)=A l ×exp(i2πft) Among them, a l (f) is the complex sound pressure of the l-th multipath ray, A l denoted as the amplitude of the multipath sound ray, f as the signal frequency, c as the speed of sound, and t as the propagation time of the multipath sound ray. The calculated complex sound pressure of the multipath sound ray is sent to S3 for related calculations.

3. The signal modeling method coupling the ray acoustic propagation model with the circular array transfer function according to claim 2, characterized in that: In step S1, the environmental parameters and sound source receiving parameters include sound source depth, sound source distance, sound source signal frequency, receiving depth, water depth, sound velocity profile, and bottom sediment parameters.

4. The signal modeling method coupling the ray acoustic propagation model with the circular array transfer function according to claim 1, characterized in that, Step S2 specifically involves: expressing the transfer function of the circular array as: Where, k l Represented as φ g Let g be the horizontal angle of the direction of the g-th incoming wave. Let j be the elevation angle of the l-th ray from the g-th incoming wave direction, * denotes complex conjugate, and j n (k l r) is an nth-order cylindrical Bessel function, h n (2) (k l r) is the Hankel function of the second kind, φ q Let r be the horizontal angle represented by the q-th element of the circular array in the circular array coordinate system, and r be the radius of the circular array. a The radius of the rigid cylinder; The radius r of the circular array and the coordinates φ of each element of the circular array are set. q The frequency f of the sound source signal and the multipath angle of arrival φ obtained in step S1 g , Substituting these values ​​into the formula for the transfer function of a circular array, we obtain the transfer function s of the circular array.

5. The signal modeling method coupling the ray acoustic propagation model with the circular array transfer function according to claim 1, characterized in that, Step S3 specifically involves: each multipath ray has a corresponding circular array transfer function; the sound pressure level of the l-th multipath ray in the direction of the g-th horizontal incoming wave is calculated based on step S1. The transfer function of the acoustic ray relative to the q-th element of the circular array, calculated according to step S2, is as follows: For the direction of the incoming wave φ g The sound pressure of the q-th element of the circular array is:

6. The signal modeling method coupling the ray acoustic propagation model with the circular array transfer function according to claim 1, characterized in that, Step S4 specifically involves repeating steps S1, S2, and S3 to obtain the received signals of the circular array elements from multiple sound sources. The corresponding element signals are then added together to obtain the superimposed element received signal from the multiple sound sources.

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