A method for exciting the plane wave sound field in a local area of the shallow sea

Abstract

The present invention relates to a method for exciting a planar wave sound field in a local area of the shallow sea, and the specific steps are as follows: Step 1: Deploy M transmitting transducers at the transmitting end, and place N hydrophones in the target test area. The N hydrophones receive M×N signals; Step 2: Analyze the amplitude and phase of each signal, and represent them in complex form to obtain an M×N matrix, denoted as A; Step 3: Under the action of the complex weighting factor q, the M transducers can make the test area a planar wave field. Then, the amplitude and phase of the sound wave received by each hydrophone are equal, denoted as a 1×N matrix B composed of elements 1, and the 1×M matrix parameter q is calculated by solving the formula q×A = B; Step 4: Modify the excitation signal of the transmitting transducer with the complex weighting factor q to generate a planar wave sound field in the test area; It can form a planar wave sound field in the local area of the shallow sea, thus ensuring the planar wave incidence condition in the target echo test, and can play a role in reducing the measurement error in the target echo test.

Description

Technical Field

[0001] The present invention belongs to the field of underwater acoustic testing and metrology, and particularly relates to a method for exciting a plane wave sound field in a local area of the shallow sea. Background Art

[0002] Underwater acoustic measurement has always been a very important research direction. The development of underwater acoustic metrology and testing technology is closely related to underwater acoustic equipment technology. The accuracy of underwater acoustic quantity parameters is not only related to the performance and quality of underwater acoustic equipment, but also related to the accuracy of underwater acoustic scientific research.

[0003] Since most of our sea areas are shallow seas, when conducting echo tests on large targets, it is often only possible to carry out the tests in shallow seas. In shallow seas, the reflection and scattering effects of the sea surface and the seabed exist, resulting in a complex incident sound signal of the target, which is not a plane wave signal, bringing great errors to the target echo test. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for exciting a plane wave sound field in a local area of the shallow sea, so as to ensure the plane wave incident condition in the target echo test, and can play a role in reducing the metrology error in the target echo test.

[0005] To solve the above technical problem, the technical solution of the present invention is: a method for exciting a plane wave sound field in a local area of the shallow sea, and its innovation lies in: using a weighted correction method to make a specific area meet the plane wave sound field condition, and the specific steps are as follows:

[0006] Step 1: Deploy M transmitting transducers at the transmitting end, place N hydrophones in the target test area, and each transmitting transducer emits a test signal separately. A total of M×N signals can be received by the N hydrophones;

[0007] Step 2: Analyze the amplitude and phase of each of the M×N signals received in Step 1, and represent them in complex form to obtain an M×N matrix, denoted as A;

[0008] Step 3: Under the action of the complex weighting factor q, the M transducers can make the test area a plane wave field, so that the amplitude and phase of the sound wave received by each hydrophone are equal. Let it be a 1×N matrix B composed of elements 1, and solve the 1×M matrix parameter q from the formula q×A = B;

[0009] Step 4: Correct the excitation signal of the transmitting transducer with the complex weighting factor q to generate a plane wave sound field in the test area.

[0010] Further, in the above Step 1, the distance between any two transducers is greater than the coherence radius of the acoustic channel propagation, and the N hydrophones cover the entire target test area.

[0011] Further, in the step 4, the excitation signal of the transmitting transducer is corrected with a complex weighting factor q. Specifically, q is a complex number, the modulus of q corrects the amplitude of the transmitted signal, and the phase of q corrects the phase of the transmitted signal.

[0012] The advantages of the present invention are as follows: The method for exciting a plane wave sound field in a local area of the shallow sea of the present invention is not affected by the shallow sea interface and is not restricted by the near-field conditions. Compared with the existing target incident sound technology in target echo measurement, by using multiple transducers to form a plane wave field in the target area, it can greatly improve the incident sound field conditions in target echo testing and obtain accurate test results. Description of the Drawings

[0013] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0014] Figure 1 It is a flowchart of exciting a plane wave sound field in a local area of the shallow sea of the present invention.

[0015] Figure 2 It is a layout schematic diagram of the transmitting transducer and receiving hydrophone of the present invention.

[0016] Figure 3 It is the sound field calculation setting of the present invention.

[0017] Figures 4a - 4l It is the sound field generated by the test signals of each transducer of the present invention.

[0018] Figure 5 It is the time-domain signal received by each hydrophone of the present invention.

[0019] Figure 6 It is the amplitude of the signal received by each hydrophone of the present invention.

[0020] Figure 7 It is the phase of the signal received by each hydrophone of the present invention.

[0021] Figure 8 It is the time-domain signal of the signal received by each hydrophone after correction of the present invention.

[0022] Figure 9 It is the amplitude of the signal received by each hydrophone after correction of the present invention.

[0023] Figure 10 It is the phase of the signal received by each hydrophone after correction of the present invention. Specific Embodiments

[0024] The following embodiments can enable those skilled in the art to understand the present invention more comprehensively, but do not limit the present invention to the scope of the described embodiments.

[0025] Embodiment

[0026] The method for exciting the plane wave sound field in a local area of the shallow sea in this embodiment is as follows Figure 1 shown. Taking the shallow sea sound field as the detection object, the implementation process is as follows

[0027] Step 1: As shown Figure 2 in the figure, 12 transmitting transducers are arranged at equal intervals from top to bottom at the center below the measurement ship. The distance between any two transducers is greater than the coherent radius of the sound channel propagation. 10 hydrophones are placed at equal intervals from top to bottom at the center below the target suspension ship, and the 10 hydrophones cover the entire target test area

[0028] Step 2: The Pekeries model of the shallow sea sound field was proposed by Pekeries in 1944 to explain the propagation of explosion pulses in the shallow sea. Establish the Pekeries shallow water waveguide model as shown Figure 3 in the figure. The upper half-infinite space is air with a density ρ = 1.293 kg / m 3 , and the sound speed c = 340 m / s; the lower half-infinite space is silt with a density ρ = 1850 kg / m 3 , and the sound speed c = 3000 m / s; the middle is water with a density ρ = 1000 kg / m 3 , and the sound speed c = 1500 m / s. Calculate the sound fields of the 200 Hz sound signals emitted by each transmitting transducer, as shown Figures 4a to 4l in the figure; use the adaptive technology to obtain the amplitude and phase of the signals in the area where the hydrophones are located, which are represented by complex numbers, and form a 12×10 matrix A

[0029] Step 3: Before the weighted adjustment of each transmitting transducer, the time-domain signal of the sound field in the hydrophone area is as shown Figure 5 in the figure, and the curves of the amplitude and phase changing with the vertical depth are as shown Figure 6 and Figure 7 in the figure. It can be seen that the amplitude and phase of the signal change violently and do not meet the plane wave field condition

[0030] Step 4: Let B be a 1×10 matrix with all elements being 1; substitute the parameters A and B into the formula q×A = B, solve the parameter q, and obtain q = -0.0158 + 0.4080i, 0.1154 - 0.1633i, -0.2496 + 0.3901i, 0.2418 + 1.4329i, -0.3710 + 1.6695i, -0.3986 + 2.2630i, 0.0641 + 1.0877i, -0.5868 + 0.3269i, -0.1867 + 0.3531i, -0.1845 + 0.1459i, -0.4385 + 0.5538i, -0.2300 + 0.4439i

[0031] Step 5: Modify the excitation signal of the transducer with a weighting factor, and the time-domain sound field signal in the test area is as Figure 8 shown. The 16th - 25th curves in the middle are hydrophones; the curves of amplitude and phase varying with the vertical depth are as Figure 9 and Figure 10 shown. The middle horizontal line area in the figure is the hydrophone placement area. It can be seen that the amplitude and phase change amplitudes of the signal in this area are small, basically meeting the plane wave field condition.

[0032] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A method for exciting a plane wave sound field in a local area of the shallow sea, characterized in that: The weighted correction method is used to make a specific area meet the plane wave sound field condition, and the specific steps are as follows: Step 1: Arrange M transmitting transducers at the transmitting end, and place N hydrophones in the target test area. Each transmitting transducer emits a test signal separately, and a total of M×N signals can be received by the N hydrophones; Step 2: Analyze the amplitude and phase of each of the M×N signals received in Step 1, and represent them in complex form to obtain an M×N matrix, denoted as A; Step 3: Under the action of the complex weighting factor q of the M transducers, the test area can be made into a plane wave field, so that the amplitude and phase of the sound wave received by each hydrophone are equal. Let it be a 1×N matrix B composed of elements 1, and the 1×M matrix parameter q is calculated by the formula q×A = B; Step 4: Correct the excitation signal of the transmitting transducer with the complex weighting factor q to generate a plane wave sound field in the test area; Arrange M transmitting transducers at equal intervals from top to bottom at the center below the measurement ship, and place N hydrophones at equal intervals from top to bottom at the center below the target suspension ship, and the N hydrophones cover the entire target test area; In Step 1, the distance between any two transducers is greater than the coherence radius of the acoustic channel propagation, and the N hydrophones cover the entire target test area; In Step 4, correcting the excitation signal of the transmitting transducer with the complex weighting factor q specifically means that q is a complex number, the modulus of q corrects the amplitude of the transmitted signal, and the phase of q corrects the phase of the transmitted signal.

Images