Single hydrophone orientation device and method based on acoustic metamaterial

Abstract

The invention discloses a single hydrophone orientation device and method based on an acoustic metamaterial, and relates to an underwater acoustic engineering technology. By designing a three-dimensional geometric structure and utilizing an acoustic metamaterial to construct an auxiliary device, the orientation of an incident sound wave is determined based on a single hydrophone; the device comprises a honeycomb-shaped cylindrical base and a wedge-shaped acoustic grating group which are distributed asymmetrically; the honeycomb-shaped cylindrical base is divided into N grids, the sound grids in the wedge-shaped sound grid set are fixed to the grids in a one-to-one correspondence mode, and the lengths of the internal coiling structures of the sound grids are arranged in a differentiated mode. The direct wave time and the acoustic grating wave time received by the scalar hydrophone are extracted, the time difference is calculated to reversely deduce the propagation distance increment, and the length of the acoustic grating coiling structure is matched to determine the sound source orientation. The device is simple in structure, low in cost and easy to manufacture and install, can be used for transformation of an existing scalar hydrophone, enables the scalar hydrophone to have an orientation function, improves the detection capability of a single hydrophone, and has important application value for a detection system and a mobile platform deployed in a large range.

Description

Technical Field

[0001] This invention relates to the field of underwater acoustic engineering technology, and in particular to a single hydrophone directional device and method based on acoustic metamaterials. Background Technology

[0002] Underwater sound source localization technology is a core component of sonar systems, possessing irreplaceable strategic value in fields such as marine resource exploration, underwater target detection and tracking, marine environmental monitoring, and national defense security. Traditional underwater sound source localization primarily relies on an array of multiple hydrophones. Beamforming is achieved by measuring the time difference of arrival (TDOA) or phase difference of sound waves at different array elements, thereby determining the location of the sound source. While this method is highly accurate and technologically mature, its inherent drawbacks are becoming increasingly apparent: the system is bulky, costly, complex to deploy, and consumes a lot of power, significantly limiting its deployment in applications requiring miniaturization, low cost, and high platform compatibility, such as micro underwater vehicles (AUV / UUV), acoustic buoys, and marine bio-acoustic tags.

[0003] Developing sound source localization technology based on a single hydrophone to achieve extreme miniaturization, low cost, and low power consumption has become a highly challenging and popular research topic in the field of underwater acoustics engineering. A single hydrophone is essentially a scalar sensor, capable only of measuring sound pressure—a non-directional physical quantity—and theoretically cannot directly determine the direction of sound wave propagation. However, through specialized hydrophone structure design, the use of complex signal processing algorithms, or the integration of artificial intelligence methods, researchers have explored various approaches to achieve single-hydrophone localization.

[0004] Directional technology based on acoustic vector sensing is currently the most mature and widely used single-point direction finding technology. Although an acoustic vector hydrophone is a "single" device in terms of physical structure, it integrates multiple sensing units, which can simultaneously measure the scalar information (sound pressure) and vector information (particle velocity) of the sound field at the same point. Early vector hydrophones were mainly based on piezoelectric ceramic technology, which used differential output to approximate the sound pressure gradient, thereby obtaining vibration velocity information. The design principle and performance test of a piezoelectric ceramic co-point orthogonal triaxial velocity hydrophone were verified to demonstrate its good directional capability in the low-frequency range (Smith, JA, et al. (2005). Design and performance of a triaxial vector hydrophone for underwater acoustics. Journal of the Acoustical Society of America, 118(4),2345–2355). MEMS-based vector hydrophones utilize microcantilever beam structures to sense underwater particle vibrations, offering advantages such as small size, low cost, and ease of integration (Wang, Y., et al. (2021). MEMS-based biomimeticciliary vector hydrophone for underwater sound localization. IEEE SensorsJournal, 21(12), 12345–12356). Fiber optic vector hydrophones, on the other hand, utilize the strain effect of fiber optic gratings (FBGs) to measure vibration velocity, exhibiting significant advantages such as resistance to electromagnetic interference and high sensitivity, demonstrating great potential in fields such as towed arrays (Li, X., et al. (2023). Flexible fiber Bragg grating vector hydrophone array for towed array applications. Optics Express, 31(8), 12345–12357).

[0005] Directional techniques based on acoustic baffles or asymmetric structures artificially disrupt the uniformity of the sound field by introducing asymmetric structures (acoustic baffles) around a scalar hydrophone. This causes the signal characteristics (such as amplitude and phase) received by the hydrophone to correlate with the incident angle of the sound wave, thereby achieving directionality. Researchers have designed baffles in various shapes, such as spheres, cylinders, and cones. Chen and Liu proposed a single hydrophone directionality method based on a parabolic reflector. By placing the hydrophone at the focus of the parabolic reflector, its focusing properties are utilized to enhance signal reception in a specific direction, achieving a function similar to an acoustic "antenna" (Chen, L., & Liu, Y. (2019). A parabolic reflector-based single hydrophone direction finding method. UACE (Underwater Acoustics Conference & Exhibition), 12–15). In addition, some studies have used bionic principles to simulate the structure of the lateral line of fish or the "acoustic brain" of dolphins, designing acoustic lenses or focusing structures with complex shapes to modulate incident sound waves, thereby enhancing the directional resolution of single hydrophones (Chen, L., & Liu, Y. (2019). A parabolic reflector-based singlehydrophone direction finding method. UACE (Underwater Acoustics Conference & Exhibition), 12–15).

[0006] Orientation techniques based on artificial intelligence and machine learning treat the orientation problem as an end-to-end pattern recognition problem, utilizing neural networks to solve the single hydrophone orientation problem. Researchers first convert the received time-domain signal into a time-frequency graph, which serves as the input to the neural network. Then, in a controlled environment (such as an anechoic pool), sound source signals are played from various known directions and received by a single hydrophone, constructing a large-scale training set containing data pairs such as time-frequency graphs and azimuth angles. This dataset is used to train a deep neural network. After training, the network can estimate the orientation of signals from new, unknown directions (Zhang, K., et al. (2024). Deep learning-based direction finding with single hydrophone using spectrogram. Signal Processing, 200, 108–120).

[0007] Single-hydrophone directional technology, a cutting-edge topic in underwater acoustics, focuses on maximizing the directional information from a single measurement point within strict constraints of cost, size, and power consumption. From physics-based vector sensing and structure scattering to data-driven artificial intelligence methods, the technological approaches are becoming increasingly diverse and deeply integrated. Current single-hydrophone directional technologies primarily utilize vector hydrophones, while scalar hydrophone directional technology is more challenging. Methods using acoustic baffles rely on precise spatial structures and are suitable for narrowband signals. Machine learning methods lack high-quality samples, resulting in insufficient model accuracy and generalization ability. To date, although existing technologies have demonstrated feasibility in specific scenarios, a universally applicable solution that performs perfectly across all dimensions still exists. This indicates that significant room for innovation and potential technological breakthroughs remain in this field. Summary of the Invention

[0008] The purpose of this invention is to address the problems of high difficulty in locating scalar hydrophones, narrow applicability of acoustic baffle methods, and insufficient performance of machine learning models in existing technologies. This invention provides a single hydrophone locating device and method based on acoustic metamaterials, which realizes the sound source locating function of a single scalar hydrophone and improves its detection capability.

[0009] To achieve the above objectives, this project adopts the following technical solution:

[0010] A single hydrophone directional device based on acoustic metamaterials includes a honeycomb cylindrical base and a wedge-shaped acoustic grating assembly;

[0011] The honeycomb-shaped cylindrical base is used to fix the wedge-shaped acoustic grating assembly; the minimum diameter of the honeycomb-shaped cylindrical base is the same as the diameter of the scalar hydrophone, and the height of the cylinder is 1 / 2 of the height of the scalar hydrophone; the honeycomb-shaped cylindrical base is divided along the circumference into... One grid, Number each grid. Each number corresponds to a horizontal azimuth angle. The horizontal azimuth angle is taken as... ;

[0012] The wedge-shaped acoustic grating assembly is used to prolong the arrival time of acoustic signals; the wedge-shaped acoustic grating assembly consists of multiple individual acoustic gratings, each of which has a wedge-shaped structure; the number of acoustic gratings in the wedge-shaped acoustic grating assembly is related to the number of grids on the surface of the honeycomb cylindrical base. The acoustic gratings are consistent, with each grating fixed to a grid on a honeycomb cylindrical base in a one-to-one correspondence; all wedge-shaped acoustic gratings have the same external length, which is 2 to 10 times the diameter of the honeycomb cylindrical base; each wedge-shaped acoustic grating has an internal coiled structure, and each base grid is numbered. The length of the corresponding internal coiled structure of the acoustic grating is , represented as:

[0013]

[0014]

[0015]

[0016] in, When sound waves pass through the coiled structure inside the chord, the propagation distance of the sound signal will increase. The increase in propagation distance due to the chord is... , This is the propagation distance increment coefficient. By fabricating internal coiled structures within acoustic gratings with different tooth pitches, the incremental coefficient can be controlled. Adjustments.

[0017] Preferably, the honeycomb cylindrical base is made of resin.

[0018] Preferably, the material of the wedge-shaped acoustic grating is silicone rubber acoustic metamaterial.

[0019] Preferably, N=36, and the angular resolution is 10°.

[0020] A method for directional mounting of a single hydrophone based on acoustic metamaterials, employing the aforementioned directional device, includes the following steps:

[0021] S1: Install the orientation device outside the scalar hydrophone so that the center of the scalar hydrophone is coaxial with the center of the honeycomb cylindrical base;

[0022] S2: When the sound source signal propagates to the directional device, the sound signal passes through the first... The time it takes for a chord to propagate to a scalar hydrophone for ;in, It is the time it takes for the sound source signal to travel directly to the scalar hydrophone. It is the sound wave after the first The increase in the propagation distance of each acoustic grating It is the speed of sound; For the sound wave to pass through the first The propagation distance increment of each acoustic grating;

[0023] S3: Extract the time from the signal recorded by the scalar hydrophone to when the sound source signal directly propagates to the scalar hydrophone. and the signal time to the hydrophone along the acoustic grating By calculating the time difference between the two This yields an estimate of the propagation distance increment. ;

[0024] S4: Calculate the estimated length of the internal coiled structure of the acoustic grating. ,in, This is the propagation distance increment coefficient; Length of the internal structure of the wedge-shaped acoustic grating assembly Comparison: When the absolute difference is minimized, the corresponding This refers to the number of the acoustic grating through which the sound signal propagates, i.e., the direction of the sound source incident is indicated by the number. corresponding azimuth angle .

[0025] In step S4, the propagation distance increment coefficient The range of values ​​for is 1≤ ≤3.

[0026] Compared with the prior art, the present invention has the following outstanding technical effects and advantages:

[0027] 1. Simple and compact structure: It adopts a combination structure of honeycomb cylindrical base and wedge-shaped acoustic grating assembly. The overall volume is small and can be directly installed on the outside of existing scalar hydrophones without modifying the hydrophone body. It has strong compatibility.

[0028] 2. Low cost: There is no need to build a multi-hydrophone array, nor to integrate complex sensing units or train a large neural network. Acoustic metamaterial structures are easy to fabricate and mass-produce, which significantly reduces the cost of directional systems.

[0029] 3. High directional accuracy: By designing differentiated winding structure lengths inside the wedge-shaped chord, directional recognition is achieved using the sound propagation time difference. The angular resolution can be flexibly set by adjusting the number of grids N to meet the accuracy requirements of different scenarios.

[0030] 4. Wide range of applications: It is not dependent on signal bandwidth characteristics, and is applicable to both broadband and narrowband signals. It is also unaffected by electromagnetic interference in complex underwater environments and has strong stability.

[0031] 5. Easy deployment: The device is lightweight and easy to install and operate, and can be quickly applied to mobile platforms such as micro underwater vehicles and acoustic buoys or large-scale detection systems, which has important engineering application value. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the honeycomb-shaped cylindrical base.

[0033] Figure 2 This is a schematic diagram of the structure of a wedge-shaped acoustic grating assembly.

[0034] Figure 3 An enlarged schematic diagram of the internal coiled structure of the wedge-shaped acoustic grating.

[0035] Figure 4 This is a schematic diagram of the assembly of the directional device and the scalar hydrophone.

[0036] Figure 5 This is a schematic diagram of the directional principle of a single hydrophone.

[0037] Figure 6 This is a schematic diagram of the time-domain waveform of the signal received by the hydrophone. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the following embodiments will be used in conjunction with the accompanying drawings to further illustrate the invention. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0039] Example 1

[0040] A single hydrophone directional device based on acoustic metamaterials includes a honeycomb cylindrical base and a wedge-shaped acoustic grating assembly. The honeycomb cylindrical base is used to fix the wedge-shaped acoustic grating assembly; the wedge-shaped acoustic grating assembly is used to extend the arrival time of the acoustic signal.

[0041] 1. Honeycomb-shaped cylindrical base

[0042] According to the specifications of a scalar hydrophone, its diameter As the minimum diameter of the honeycomb-shaped cylindrical base, the cylinder height Half the height of the hydrophone; based on the set angle resolution. The cylindrical base is divided along the circumference into One grid, Number each grid. Each number corresponds to a horizontal azimuth angle. The horizontal azimuth angle is taken as... ,like Figure 1 As shown.

[0043] 2. Wedge-shaped acoustic grating assembly

[0044] A wedge-shaped acoustic grating assembly consists of multiple individual acoustic gratings, each of which is wedge-shaped. The number of acoustic gratings in the wedge-shaped acoustic grating assembly is the same as the number of grids on the surface of the honeycomb cylindrical base, and each acoustic grating is fixed to its corresponding base grid. Figure 2 ), the outer length of all wedge-shaped acoustic gratings Consistent (for diameter) (2 to 10 times that of the previous type), each wedge-shaped acoustic grating has an internal coiled structure, such as... Figure 3 As shown. The number of each base grid. The length of the corresponding internal coiled structure of the acoustic grating is , represented as:

[0045]

[0046]

[0047]

[0048] in, When sound waves pass through the coiled structure inside the chord, the propagation distance of the sound signal will increase. Figure 3 The increment of propagation distance due to the grating is , The propagation distance increment coefficient (in general) Structures with different tooth pitches can be prefabricated. By adjusting the tooth pitch of the coiled structure inside the acoustic grating, the incremental coefficient can be adjusted. Adjustments.

[0049] Example 2

[0050] A single hydrophone orientation method based on acoustic metamaterials, the specific steps of which are as follows:

[0051] The wedge-shaped acoustic gratings correspond to different incident angles. Once the grating through which the sound wave passes is determined, the azimuth angle of the incident sound wave can be obtained, thus estimating the incident azimuth of the sound source. This device is installed outside a scalar hydrophone. Figure 4 When the sound source signal propagates to the device ( Figure 5 ), the sound signal passes through the first The time it takes for a chord to propagate to a scalar hydrophone for:

[0052]

[0053] in, It is the time it takes for the sound source signal to travel directly to the scalar hydrophone. It is the sound wave after the first The increase in the propagation distance of each acoustic grating This refers to the speed of sound. Because the internal winding structure of each chord has a different length, the propagation time of the sound signal varies depending on the chord. The time it takes for the sound signal to directly reach the hydrophone is extracted from the signal recorded by the scalar hydrophone. and the signal time to the hydrophone along the acoustic grating By calculating the time difference between the two This yields an estimate of the propagation distance increment. This leads to an estimate of the length of the coiled structure inside the acoustic grating. By matching the length of the internal structure of the wedge-shaped acoustic grating assembly Comparison:

[0054]

[0055] When the absolute difference is minimized, the corresponding If the acoustic signal passes through a grating number, then the incident direction of the sound source is the grating number. corresponding azimuth angle .

[0056] To verify the technical effect of the present invention, a test was conducted in an anechoic pool. The sound source was set at an 80° azimuth of the scalar hydrophone, and the speed of sound in seawater was [not specified]. The specific steps are as follows:

[0057] 1. The diameter of the scalar hydrophone is The height is The honeycomb-shaped cylindrical base has a diameter of 60mm and a height of 50mm.

[0058] 2. Setting the angular resolution to 10°, the honeycomb cylindrical base is divided into 36 grids along the circumference, with the grid numbers as follows: The corresponding horizontal azimuth angle .

[0059] 3. Constructing a sound grating ( Figure 3 ), the external length of all acoustic gratings If both are 360mm, then the length of the internal coiled structure of the acoustic grating is... Propagation distance increment coefficient .

[0060] 4. Connect the acoustic grating to the base, and then fix the base to the outside of the hydrophone. Figure 4 ).

[0061] 5. Assuming the sound source is located at an 80° angle to the scalar hydrophone, when the sound source emits sound in the water, the sound wave is divided into two parts: one that directly reaches the hydrophone and the other that enters the acoustic grating and then reaches the hydrophone. For example... Figure 6 As shown, the time it takes for the sound signal to directly reach the hydrophone is extracted. and the signal time to the hydrophone along the acoustic grating speed of sound of seawater By calculating the time difference between the two This yields an estimate of the propagation distance increment. This leads to an estimate of the length of the coiled structure inside the acoustic grating. Calculate its length relative to the internal structure of the wedge-shaped acoustic grating assembly. The absolute difference is used to obtain the acoustic grating number corresponding to the smallest absolute difference. The incident direction of the sound source is numbered corresponding azimuth angle The orientation test was successful, confirming that the orientation matched the set location.

[0062] Experiments show that the single hydrophone directional device and method based on acoustic metamaterials described in this invention can accurately estimate the incident azimuth of the sound source. With an angular resolution of 10°, it can precisely identify the target location with minimal measurement error. Furthermore, the device's ability to distinguish sound signals remained stable during testing, verifying the feasibility and reliability of this invention in single hydrophone directional applications. This invention is simple in structure, low in cost, and easy to install. It can directly modify existing scalar hydrophones to enable directional functionality, has a wide range of applications, and is of significant value for micro underwater platforms and large-scale detection systems.

[0063] The above embodiments are merely preferred embodiments of the present invention and should not be considered as limiting the scope of the present invention. All equivalent variations and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A single hydrophone directional device based on acoustic metamaterials, characterized in that... Includes a honeycomb-shaped cylindrical base and a wedge-shaped acoustic grating assembly; The honeycomb-shaped cylindrical base is used to fix the wedge-shaped acoustic grating assembly; the minimum diameter of the honeycomb-shaped cylindrical base is the same as the diameter of the scalar hydrophone, and the height of the cylinder is 1 / 2 of the height of the scalar hydrophone; the honeycomb-shaped cylindrical base is divided along the circumference into... One grid, Number each grid. Each number corresponds to a horizontal azimuth angle. The horizontal azimuth angle is taken as... ; The wedge-shaped acoustic grating assembly is used to extend the arrival time of acoustic signals; The wedge-shaped acoustic grating assembly consists of multiple individual acoustic gratings, each with a wedge-shaped structure; the number of acoustic gratings in the wedge-shaped acoustic grating assembly corresponds to the number of grids on the surface of the honeycomb cylindrical base. The acoustic gratings are consistent, and each grating is fixed one-to-one with the grid of the honeycomb cylindrical base; each wedge-shaped acoustic grating has an internal coiled structure. When sound waves pass through the coiled structure inside the chord, they generate an increase in propagation distance.

2. The single hydrophone directional device based on acoustic metamaterials as described in claim 1, characterized in that... All wedge-shaped acoustic gratings in the wedge-shaped acoustic grating group have the same external length, which is 2 to 10 times the diameter of the honeycomb cylindrical base.

3. The single hydrophone directional device based on acoustic metamaterials as described in claim 1, characterized in that... Number of each base grid The length of the corresponding internal coiled structure of the acoustic grating is , represented as: in, .

4. The single hydrophone directional device based on acoustic metamaterials as described in claim 1, characterized in that... The propagation distance increment is , This is the propagation distance increment coefficient. By adjusting the tooth pitch of the coiled structure inside the acoustic grating, the incremental coefficient can be adjusted. Adjustments.

5. The single hydrophone directional device based on acoustic metamaterials as described in claim 1, characterized in that... The honeycomb-shaped cylindrical base is made of resin.

6. The single hydrophone directional device based on acoustic metamaterials as described in claim 1, characterized in that... The material of the wedge-shaped acoustic grating is silicone rubber acoustic metamaterial.

7. The single hydrophone directional device based on acoustic metamaterials as described in claim 1, characterized in that... The N=36, and the angular resolution is 10°.

8. A method for directional mounting of a single hydrophone based on acoustic metamaterials, characterized in that... The method of using a single hydrophone directional device based on acoustic metamaterials as described in any one of claims 1 to 4 includes the following steps: S1: Install the orientation device outside the scalar hydrophone so that the center of the scalar hydrophone is coaxial with the center of the honeycomb cylindrical base; S2: When the sound source signal propagates to the directional device, the sound signal passes through the first... The time it takes for a chord to propagate to a scalar hydrophone for ;in, It is the time it takes for the sound source signal to travel directly to the scalar hydrophone. It is the sound wave after the first The increase in the propagation distance of each acoustic grating It is the speed of sound; For the sound wave to pass through the first The propagation distance increment of each acoustic grating; S3: Extract the time from the signal recorded by the scalar hydrophone to when the sound source signal directly propagates to the scalar hydrophone. and the signal time to the hydrophone along the acoustic grating By calculating the time difference between the two This yields an estimate of the propagation distance increment. ; S4: Calculate the estimated length of the internal coiled structure of the acoustic grating. ,in, This is the propagation distance increment coefficient; Length of the internal structure of the wedge-shaped acoustic grating assembly Comparison: When the absolute difference is minimized, the corresponding This refers to the number of the acoustic grating through which the sound signal propagates, i.e., the direction of the sound source incident is indicated by the number. corresponding azimuth angle .

9. The method for directional mounting of a single hydrophone based on acoustic metamaterials as described in claim 8, characterized in that... In step S4, the propagation distance increment coefficient The range of values ​​for is 1≤ ≤3.

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