Acoustic emission physical model based on dolphin sonar

Abstract

The invention provides an acoustic emission physical model based on dolphin sonar. The acoustic emission physical model is realized by a specific structure combination of a transducer, an air domain, soft tissue and maxilla. The transducer is surrounded by the air domain, an acoustic soft boundary is formed by utilizing huge acoustic impedance difference between air and the transducer, sound energy is effectively prevented from leaking to the rear side, and sound waves which are originally radiated in all directions are restrained to be spread in a specific direction. Meanwhile, the soft tissue adopts the gradient design that the sound velocity is gradually increased from inside to outside, the gradual change structure of the frontal furcation, the muscular tissue and the connective tissue avoids a mutation interface of a traditional single matching layer, and sound wave reflection is remarkably reduced. In the sound wave propagation process, the frontal protrusion serves as a low-sound-velocity and low-density core area to achieve a convergence effect on sound waves, the sound wave propagation path is further regulated and controlled through gradient distribution of muscular tissue and connective tissue, and the upper jaw bone arranged below the soft tissue reflects the sound waves and has a synergistic effect with the soft tissue, so that the sound wave propagation effect is improved. And the sound wave is shaped into a narrow wave beam with strong directivity.

Description

Technical Field

[0001] The present invention relates to the field of acoustic physics, and in particular to an acoustic emission physical model based on dolphin sonar. Background Art

[0002] Acoustic waves are currently the primary means of underwater detection. Existing underwater acoustic detection devices primarily use transducers made of solid materials, typically a single-material structure that comes into direct contact with water.

[0003] Acoustic wave emission lacks directional control. When existing cylindrical transducers operate in water, the sound waves they emit exhibit an omnidirectional radiation pattern, with the sound energy spreading in all directions and failing to form a concentrated sound beam. This results in a short detection range, low resolution, and susceptibility to interference from reflected waves from the water surface and bottom. Secondly, the acoustic impedance matching problem is prominent. The large difference in acoustic impedance between solid transducer materials (such as piezoelectric ceramics) and water results in severe sound wave reflections at the transducer-water interface, resulting in low acoustic energy transmission efficiency. Traditional impedance matching layers typically use a single material and can only achieve matching within a narrow frequency band.

[0004] In contrast, the biosonar systems of toothed whales, such as dolphins, exhibit superior performance. The dolphin's sonar system has a unique multi-layered structure: an airway system that serves as a sound source, soft tissues (melanin, muscle tissue, connective tissue) with a gradient sound velocity distribution, and a bony structure that acts as a reflector. This composite structure enables dolphins to convert omnidirectional sound sources into highly directional sound beams, thereby achieving a good impedance match with the water. However, existing biomimetic sonar research has numerous shortcomings. While the method of inserting an array of steel pillars into a substrate using equivalent medium theory can simulate sound velocity gradients, it can cause energy loss due to multiple scattering, and the density distribution does not match that of actual biological tissue. Solutions using fluids of varying densities struggle to achieve a stable gradient distribution and fail to mimic the adjustable properties of biological tissue.

[0005] In view of this, this application is filed. Summary of the Invention

[0006] The invention discloses an acoustic emission physical model based on dolphin sonar, aiming to solve the problem of energy loss in existing bionic sonar.

[0007] An embodiment of the present invention provides an acoustic emission physical model based on dolphin sonar, including: transducer; an air domain, surrounding the transducer arrangement, formed of a thin-walled cavity; Soft tissue is arranged to surround the air space, and the soft tissue includes, from the inside to the outside, a melanin, muscle tissue, and connective tissue, and the soft tissue is made of a flexible material with a sound velocity gradient so that the sound velocity increases from the inside to the outside; The maxillary bone is disposed below the soft tissue.

[0008] Preferably, the air space is formed by three cavities, specifically including a first cavity adjacent to the transducer, a second cavity located above the posterior side of the melanin, and a third cavity located above the maxillary bone.

[0009] Preferably, The length adjustment range of the first cavity is to increase by 0 to 30 mm or decrease by 0 to 10 mm on the initial length, and the angle adjustment range of the first cavity is to adjust within the range of -10° to 20° on the initial tilt angle; The length of the second cavity is adjusted to reduce the initial length by 0 to 90 mm, and the thickness of the second cavity is adjusted to increase or decrease the initial thickness by 0 to 10 mm. The length of the third cavity can be adjusted in a range of 0 to 50 mm from the initial length.

[0010] Preferably, the air space is composed of a 3D printed thin-walled cavity with a wall thickness of 2 mm.

[0011] Preferably, the material of the maxilla is any one of steel, aluminum or plexiglass, wherein the angle adjustment range of the maxilla is adjusted within the range of -2° to -3° on the initial inclination angle, and the length adjustment range is reduced by 0 to 50 mm on the initial length.

[0012] Preferably, the soft tissue is made of silicone or hydrogel, and the speed of sound of the soft tissue is in the range of 1500 m / s to 1700 m / s, wherein: The density of the melon is 1050 kg / m³ and the speed of sound is 1500 m / s; The density of the muscle tissue is 1050 kg / m³ and the speed of sound is 1600 m / s; The density of the connective tissue is 1100 kg / m³, and the speed of sound is 1700 m / s.

[0013] Preferably, the transducer is cylindrical, with a bottom radius of 14 mm and a column height of 55 mm, radiating cylindrical waves, a center frequency of 60 kHz, and a 3dB bandwidth range of 50 kHz to 80 kHz.

[0014] Preferably, the acoustic characteristic expression of the model is:

[0015]

[0016]

[0017] in, is the wave number of the equation, is the out-of-plane wave number, is the angular frequency, is the background sound pressure, is the sound pressure, is the total sound pressure, is the complex speed of sound, is the complex density, is a dipole sound source; is a monopole sound source, is the gradient operator.

[0018] Preferably, the hydrogel is prepared by doping different proportions of glycerol into a hydrogel substrate to obtain different sound velocity values.

[0019] The present invention provides a dolphin sonar-based acoustic emission physical model, implemented by a specific structural combination of a transducer, an air domain, soft tissue, and the maxillary bone. The air domain surrounds the transducer, leveraging the significant difference in acoustic impedance between the air and the transducer to form an acoustic "absolute soft boundary," effectively preventing acoustic energy from leaking to the sides and rear, confining the otherwise omnidirectional sound waves to a specific direction. Furthermore, the soft tissue utilizes a gradient design with increasing sound velocity from the inside out. The gradual transitions in the melanin, muscle tissue, and connective tissue avoid the abrupt interface of a traditional single matching layer, significantly reducing sound wave reflections and achieving excellent impedance matching with water over a wide frequency range of 50-80 kHz. During sound wave propagation, the melanin, acting as a low-velocity, low-density core region, converges the sound waves. The gradient distribution of muscle tissue and connective tissue further regulates the sound wave propagation path. The maxillary bone, located beneath the soft tissue, reflects the sound waves and, in synergy with the soft tissue, shapes the sound waves into a narrow, highly directional beam. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a two-dimensional structural diagram of the acoustic emission physical model designed based on the Chinese white dolphin acoustic emission system; Figure 2 It is a schematic diagram of the two-dimensional model of the optimized acoustic emission physical model; Figure 3 This is a schematic diagram of the directivity of the two-dimensional cross section from 50 kHz to 80 kHz; Figure 4 Schematic diagram of the sound pressure field in the two-dimensional cross section from 50 kHz to 80 kHz; Figure 5 This is a schematic diagram of the 3D acoustic emission physical model based on dolphin sonar; Figure 6 Schematic diagram of three-dimensional acoustic emission physical model and calculation domain modeling; Figure 7Schematic diagram of the three-dimensional sound field of the three-dimensional model at 50 kHz; Figure 8 Schematic diagram of the acoustic beam pattern of the three-dimensional model in the XY plane at 50 kHz; Figure 9 Schematic diagram of the three-dimensional sound field at 50 kHz when only the sound source is included; Figure 10 Schematic diagram of the acoustic beam pattern in the XY plane at 50 kHz when only the sound source is included; Figure 11 The figure is a schematic diagram of the adjusted two-dimensional model of the acoustic emission physical model based on dolphin sonar; Figure 12 The following is a schematic diagram of the directivity of the adjusted two-dimensional model at 50 kHz~80 kHz; Figure 13 Schematic diagram of the sound pressure of the adjusted two-dimensional model at 50 kHz~80 kHz; Figure 14 A water pool experiment scene for a physical model; Figure 15 The sound pressure distribution diagram drawn from the experimental data. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention for which protection is sought, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0022] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0023] The invention discloses an acoustic emission physical model based on dolphin sonar, aiming to solve the problem of energy loss in existing bionic sonar.

[0024] See also Figure 1 The embodiment of the present invention provides an acoustic emission physical model based on dolphin sonar, including: Transducer G; Transducer G can be cylindrical, with a base radius of 14 mm and a height of 55 mm. Transducer G, serving as the sound source for the entire acoustic emission model, is placed at the core of the model, surrounded by air domain A. The cylindrical structure of transducer G enables it to generate acoustic radiation in the form of cylindrical waves, a radiation pattern that propagates evenly in all directions without the modulation of other acoustic structures.

[0025] The center frequency of transducer G can be set to 60kHz, which falls within the typical operating frequency band of the Dolphin sonar system. Transducer G's 3dB bandwidth ranges from 50kHz to 80kHz, achieving an effective operating bandwidth of 30kHz. In actual production, a commercial cylindrical transducer G, model CT-60, with a diameter of 28mm (radius of 14mm) and a height of 55mm, was selected. During the numerical simulation, transducer G was set as an acoustic radiation boundary condition, employing plane wave radiation, with the radiation boundary originating from the surface of the cylindrical sound source. In the COMSOL Multiphysics simulation, the surface of transducer G was set as the sound source boundary in the "Pressure Acoustics - Frequency Domain" physics field, and a frequency sweep calculation was performed over the frequency range of 50kHz to 80kHz. Simulation results show that the cylindrical transducer G maintains stable acoustic output characteristics throughout the entire operating frequency band.

[0026] In a water tank experiment, a signal generator (AFG3022C) was used to generate sinusoidal pulse signals with center frequencies of 50, 60, 70, and 80 kHz, respectively. Each pulse consisted of five cycles, with a peak-to-peak value of 10V and a pulse interval of 1ms. The signal was amplified by an ATA-4011 power amplifier before driving transducer G. The experimental results confirmed that transducer G operated effectively within the designed frequency range. Furthermore, through synergistic interaction with structures such as the airspace (A), soft tissue, and the maxillary bone (B), it successfully converted omnidirectionally radiated sound waves into a highly directional beam, validating the effectiveness of the proposed design.

[0027] An air domain A, surrounding the transducer G, is formed by a thin-walled cavity; It should be noted that Air Domain A is composed of three interconnected cavities, simulating the airbag structure in a dolphin sonar system. Fabricated using 3D printing technology, Air Domain A forms a thin-walled cavity structure with a thickness of 2 mm. Filled with air, its density and speed of sound are 1.21 kg / m³ and 343 m / s, respectively. This creates a significant acoustic impedance difference with the surrounding soft tissue and water, acting as an absolute soft boundary acoustically.

[0028] The first cavity A1 is located adjacent to the transducer G, corresponding to Figure 1The A1 area in the cavity directly affects the initial propagation direction of the sound wave. During the optimization process, it was found that when the length of the first cavity A1 was increased by 10mm based on the initial design and the angle was adjusted to -10°, the best sound beam guidance effect could be obtained (such as Figure 2 (As shown). This downward-sloping design helps sound waves propagate forward and reduces upward energy leakage. The length of the first cavity A1 can be adjusted from 0 to 30 mm or 0 to 10 mm from the initial length, and the angle can be adjusted from -10° to 20°. This adjustability allows the model to adapt to different sound beam requirements.

[0029] The second cavity A2 is located above and behind the melanin D, corresponding to Figure 1 The A2 area in the dolphin's vestibular sac is simulated. Experiments show that when the length of the second cavity A2 is reduced by 90mm and the thickness is increased by 10mm based on the initial design, the combination of the cavity and the sound source is the best (e.g. Figure 2 (As shown). This cavity primarily prevents sound waves from propagating backward, while its geometry influences the sound wave propagation path in the melanin D region. The length of the second cavity A2 can be reduced by 0 to 90 mm, and its thickness can be increased or decreased by 0 to 10 mm. Adjusting these parameters can optimize the sound wave propagation characteristics.

[0030] The third cavity A3 is located above the maxillary bone B, corresponding to Figure 1 The A3 area in the dolphin simulates the maxillary B sac structure. This cavity works with the maxillary B to affect the reflection and propagation of sound waves. The optimization results show that the effect is better when the length of the third cavity A3 is reduced by 50mm from the initial length (e.g. Figure 2 The length of the third cavity A3 can be adjusted by reducing the length by 0 to 50 mm based on the initial length.

[0031] The three cavities form an airspace A, which extends from -31mm to 77mm in the X-axis and -58mm to 33mm in the Y-axis, for a total area of ​​approximately 29cm². This unique structure, in conjunction with transducer G, soft tissue, and maxillary bone B, successfully constrains and guides the omnidirectional sound waves generated by transducer G into a directional beam, fulfilling the core function of bionic sonar. In actual production, the entire airspace A structure is formed in one piece via 3D printing.

[0032] Soft tissue is arranged to surround the air space A, and the soft tissue includes, from the inside to the outside, a melanin D, muscle tissue E, and connective tissue C. The soft tissue is made of a flexible material with a sound velocity gradient so that the sound velocity increases from the inside to the outside; In this example, soft tissue serves as the core acoustic control structure of the acoustic emission physical model, surrounding an air domain A to simulate the soft tissue system of a dolphin's forehead. From the inside out, the soft tissue comprises three layers: the melanin D, muscle tissue E, and connective tissue C. Made entirely of a flexible material with a sound velocity gradient, the soft tissue achieves a gradual increase in sound velocity from 1500 m / s to 1700 m / s.

[0033] The melanopsis D is located in the innermost layer, directly surrounding the air domain A. It is made of hydrogel material with a density of 1050kg / m³ and a sound speed of 1500m / s. As the area with the lowest sound speed and density in soft tissue, the melanopsis D plays a preliminary converging role on sound waves. In the optimized model, the melanopsis D is 16.3cm long in the X direction and 5.3cm long in the Y direction. Its center is roughly on the same horizontal line as the center of the circular sound source, with a horizontal distance of about 12cm, and the closest distance to the sound source is within 2cm. The shape of the melanopsis D can be adjusted by anisotropic scaling in the Y direction with the coordinate point (145mm, -10mm) as the center, with a scaling factor of 0.6 to 1. At the same time, the angle can be adjusted from -5° to 5° with the coordinate point (47mm, -8mm) as the center. Experiments show that the best effect is achieved when the horizontal position is adjusted by -24mm, the vertical position is adjusted by 2mm, and the angle is adjusted by 2° (such as Figure 2 shown).

[0034] Muscle tissue E is located in the middle layer, surrounding the melanin D. It is also made of hydrogel material with a density of 1050 kg / m³ and a sound velocity of 1600 m / s. The optimized muscle tissue E ranges from 25 mm to 266 mm in the X direction and from -66 mm to 60 mm in the Y direction, with an area of ​​approximately 113.7 cm². The thickness of the muscle tissue E at the interface with the water area is adjustable. When the thickness is reduced by 35 mm, the side lobes are minimized (e.g., Figure 2 This adjustment directly affects the characteristics of sound waves radiating into water.

[0035] Connective tissue C is located in the outermost layer, in direct contact with the water. It is made of hydrogel material with a density of 1100kg / m³ and a sound speed of 1700m / s. The optimized connective tissue C has an X-axis range of -31mm to 141.4mm and a Y-axis range of -66mm to 65.5mm, with an area of ​​approximately 53.56cm² (e.g. Figure 2 Connective tissue C can be scaled horizontally by a factor of 0.8 to 1.2, with the best effect achieved when the factor is 1. As the outermost layer in contact with water, the sound velocity of connective tissue C (1700 m / s) is closest to that of water (1500 m / s), achieving a good impedance transition.

[0036] The preparation of hydrogel materials uses doping technology to achieve different sound velocity values. By doping different proportions of glycerol into the hydrogel base, the acoustic properties of the material can be precisely controlled. When making connective tissue C, a small amount of glycerol is added to obtain a sound velocity of 1750m / s. When making muscle tissue E, an appropriate amount of glycerol is added to obtain a sound velocity of 1650m / s. When making the melanin D, a larger amount of glycerol is added to obtain a sound velocity of 1550m / s. As a flexible material of high molecular weight polymerization, hydrogel not only has good acoustic property control capabilities, but also has excellent mechanical properties. It can be stretched and deformed without breaking, providing a material basis for the subsequent dynamic control of the sound beam.

[0037] The soft tissue design of the three-layer gradient structure successfully simulates the acoustic characteristics of the dolphin's forehead. It avoids sound wave reflection at the sudden interface through continuously changing sound velocity distribution, achieves good impedance matching with water in the wide frequency band range of 50kHz to 80kHz, and at the same time plays a role in converging, guiding and shaping the sound waves. It is a key structure for realizing directional sound beam emission.

[0038] The maxillary bone B is disposed below the soft tissue.

[0039] In this embodiment, maxilla B is positioned beneath the soft tissue, simulating the bony structure of a dolphin's sonar system. It plays a crucial role in sound wave reflection and beam shaping within the entire acoustic emission system. Maxilla B is constructed from plexiglass, which exhibits excellent acoustic properties. Its pressure wave velocity is 2700 m / s, shear wave velocity is 1300 m / s, and density is 1180 kg / m³. These parameters are similar to the acoustic properties of biological bone, effectively simulating the acoustic function of dolphin maxilla B.

[0040] Taking the center of transducer G as the coordinate, the positive X-axis is the primary direction of sound wave propagation, and the positive Y-axis is vertically upward. Maxillary bone B is located in the negative Y-axis region, approximately 35mm to 175mm below the center of transducer G. In the X-direction, it extends from approximately 5mm behind transducer G to approximately 347mm forward, forming a long, reflective structure with a total area of ​​approximately 181 cm². Maxillary bone B is slightly tilted forward and downward. This tilt allows reflected sound waves to better overlap with the direct sound wave, enhancing the energy of the forward sound beam.

[0041] Numerical simulations and experimental optimization revealed that the inclination angle of maxillary bone B significantly affects acoustic performance. Based on the initial design, the angle can be fine-tuned within a range of -2° to -3°, with negative angles tilting the front end downward relative to the rear end. This subtle angle adjustment alters the direction of reflected sound waves, optimizing their coherent superposition with the direct sound wave, thereby improving the directivity and energy concentration of the sound beam.

[0042] The length of the maxillary bone B is another key parameter influencing acoustic performance. By extending the maxillary bone B forward by 48 mm, bringing its front end approximately 395 mm in front of the transducer G, experimental results demonstrate that this extended design provides more reflection surface for sound waves, enhancing the focusing effect of the sound beam. The length of the maxillary bone B can be adjusted by reducing it by 0 to 50 mm from the initial design. This length adjustment modifies the size of the reflection surface, thereby affecting the proportion of sound waves that are reflected.

[0043] The interface between the maxillary bone B and the soft tissue has important acoustic significance. 6 kg / m²·s) is significantly higher than that of soft tissue (about 1.6-1.9×10 6 kg / m²·s), generating strong acoustic wave reflection at the interface between the two. According to acoustic theory, this impedance difference results in approximately 20-30% of the acoustic energy being reflected. The reflected sound wave not only includes specular reflection components but also excites surface waves that propagate along the maxillary B-soft tissue interface. The interaction of these waves enhances the complex control capabilities of the acoustic beam.

[0044] In actual production, the plexiglass sheet is laser cut or machined into the desired shape, with the surface roughness controlled to within 1 / 10 of the acoustic wavelength to ensure excellent specular reflection properties. The maxillary bone B is mounted at the base of the model using appropriate fixtures, maintaining close contact with the soft tissue. The entire maxillary bone B structure works synergistically with the transducer G, the air domain A, and the soft tissue. The reflected sound waves coherently superimpose with the direct sound waves modulated by the soft tissue, forming a highly directional sound beam, successfully achieving the core function of bionic sonar.

[0045] Please see the attached Figure 3 As shown in the figure, by plotting the radiation pattern based on the outdoor sound pressure level, it can be observed that the two-dimensional model has strong directivity in the frequency range of 50kHz~80kHz.

[0046] Please see the attached Figure 4 As shown in the figure, from the perspective of sound pressure, it can be intuitively observed that the sound beam of the two-dimensional model is narrow and the energy is concentrated in the frequency range of 50kHz~80kHz.

[0047] Please see the attached Figure 5 As shown in the figure, the optimized 2D model is stretched 6 cm in the Z direction to obtain a 3D acoustic emission physical model based on dolphin sonar. Its structures include: cavity I, maxillary bone II, soft tissue (connective tissue III, muscle tissue IV, and melanopsoid protuberance V). VI is the sound source, representing the transducer, which is 55 mm tall and symmetrically contained within the connective tissue. The dimensions of the 3D model are 378 mm * 240 mm * 60 mm.

[0048] Please see the attached Figure 6As shown in the figure, a 3D model is simulated. A cylindrical computational domain and a cylindrical perfectly matched layer are established. The mesh in the 3D simulation is generated using a free tetrahedral mesh.

[0049] Please see the attached Figure 7 As shown, the three-dimensional model has a 50kHz three-dimensional beam.

[0050] Please see the attached Figure 8 The figure shows the directivity of the 3D model in the XY plane at 50 kHz. At 50 kHz, the directivity of the 3D model is roughly similar to that of the 2D cross-section.

[0051] Please see the attached Figure 9 As shown, a control group containing only a sound source and water is set up. It can be observed that the beam of the control group has no directionality in three-dimensional space, but presents 360° omnidirectional radiation.

[0052] Please see the attached Figure 10 As shown in the figure, the radiation pattern of the control group in the XY plane is not directional. Through comparison, it is effectively verified that the physical model based on dolphin acoustic emission achieves directionality after multi-phase structure regulation.

[0053] In this embodiment, the maxillary bone is extended by 48 mm along the x direction without changing its shape. Figure 11 As shown, the shapes and materials of other structures are the same.

[0054] The simulation process is the same as that of the specific embodiment.

[0055] By plotting the radiation pattern based on the outdoor sound pressure level, it can be observed that the adjusted two-dimensional model has strong directivity in the frequency range of 50kHz~80kHz. Figure 12 From the perspective of sound pressure, it can also be intuitively observed that the sound beam of the adjusted two-dimensional model is narrow and the energy is concentrated in the frequency range of 50kHz~80kHz. Please refer to the attached Figure 13 shown.

[0056] A physical model was made. The air domain was composed of a 3D-printed thin-walled cavity with a wall thickness of 2 mm.

[0057] Furthermore, the hydrogel with the sound velocity gradient is prepared by doping different proportions of glycerol into the hydrogel base. Figure 2 The speed of sound in regions C, D, and E is 1750 m / s, 1650 m / s, and 1550 m / s, respectively.

[0058] Pool experiment Figure 14As shown in the figure, a CT-60 cylindrical transducer (28 mm diameter, 55 mm height) was used as the sound source. A signal generator, AFG3022C, generated five-cycle sinusoidal pulses with center frequencies of 50, 60, 70, and 80 kHz, a peak-to-peak voltage of 10 V, and a 1 ms pulse interval. The pulses were amplified by an ATA-4011 power amplifier (Aigtek, Xi'an, China) and transmitted to the transducer. The receiver used an RHC-7 hydrophone (China Shipbuilding Industry Corporation, 715th Research Institute, Hangzhou, China), with a 20 mm step size on both the X and Y axes. The received signal was displayed on an oscilloscope MDO032 (Tektronix), which was connected to a computer and stored synchronously. The hydrophone collected data at 29 x 31 locations, with a distance from the transmitting transducer ranging from -300 mm to 260 mm in the x-axis and from 400 mm to 1000 mm in the y-axis.

[0059] The peak-to-peak value of the signal collected by the hydrophone is plotted to obtain the result Figure 15 It is proved that the dolphin-like acoustic emission model can control the sound beam of an omnidirectional sound source into a directional sound beam, thereby performing directional detection.

[0060] In one possible embodiment of the present invention, the acoustic characteristics of the acoustic emission physical model are described and calculated using the governing equations of pressure acoustics in the frequency domain. These governing equations comprehensively account for the propagation, reflection, and interaction of sound waves in different media, enabling accurate simulation of the acoustic behavior of the Dolphin Sonar system.

[0061] The acoustic characteristic expression of the model is:

[0062]

[0063]

[0064] in, is the wave number of the equation, is the out-of-plane wave number, is the angular frequency, is the background sound pressure, is the sound pressure, is the total sound pressure, is the complex speed of sound, is the complex density, is a dipole sound source; is a monopole sound source, is the gradient operator.

[0065] When implementing this equation in COMSOL Multiphysics, the material properties for each domain, including the complex velocity and density, are first defined within the pressure acoustics physics field. A plane wave radiation boundary condition is then applied to the transducer G surface, effectively specifying the source term. Boundary conditions between different media automatically ensure continuity of the acoustic pressure and normal velocity, ensuring both pressure and normal velocity at the interface. For fluid-solid interfaces, the solid mechanics equations must also be coupled to ensure continuity of the normal stress.

[0066] By solving the governing equation in the frequency range of 50kHz to 80kHz, the sound pressure distribution of the entire model can be obtained. The calculation results show that after the sound wave is emitted from the transducer G, it is constrained by the air domain A, regulated by the gradient of the soft tissue, and reflected by the maxillary bone B, ultimately forming a well-directional sound beam. The angular distribution of the radiated sound pressure can be obtained by integral calculation in the far field, verifying the effectiveness of the model in converting the omnidirectional sound source into a directional sound beam. This numerical simulation method based on physical equations can not only predict the acoustic performance of the model, but also provide theoretical guidance for structural optimization.

[0067] The present invention provides a dolphin sonar-based acoustic emission physical model, implemented by a specific structural combination of transducer G, air domain A, soft tissue, and maxillary bone B. Air domain A surrounds transducer G, leveraging the significant acoustic impedance difference between air and transducer G to form an acoustic "absolute soft boundary," effectively preventing acoustic energy from leaking to the sides and rear, confining the otherwise omnidirectional sound waves to a specific direction. Furthermore, the soft tissue utilizes a gradient design with increasing sound velocity from the inside out. The gradual transitions in the melanocord D, muscle tissue E, and connective tissue C avoid the abrupt interface of a traditional single matching layer, significantly reducing sound wave reflections and achieving excellent impedance matching with water over a wide frequency range of 50-80 kHz. During sound wave propagation, the melanocord D, acting as a low-velocity, low-density core, converges the sound waves. The gradient distribution of muscle tissue E and connective tissue C further regulates the sound wave propagation path. The maxillary bone B, located beneath the soft tissue, reflects the sound waves and, in synergy with the soft tissue, shapes the sound waves into a narrow, highly directional beam.

[0068] The above are only preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention.

Claims

1. A physical model of acoustic emission based on dolphin sonar, characterized in that: include: transducer; an air domain, surrounding the transducer arrangement, formed of a thin-walled cavity; Soft tissue is arranged to surround the air space, and the soft tissue includes, from the inside to the outside, a melanin, muscle tissue, and connective tissue, and the soft tissue is made of a flexible material with a sound velocity gradient so that the sound velocity increases from the inside to the outside; The maxillary bone is disposed below the soft tissue.

2. The acoustic emission physical model based on dolphin sonar according to claim 1, characterized in that: The air space is formed by three cavities, specifically including a first cavity adjacent to the transducer, a second cavity located above the posterior side of the melanin, and a third cavity located above the maxillary bone.

3. The acoustic emission physical model based on dolphin sonar according to claim 1, characterized in that: The length adjustment range of the first cavity is to increase by 0 to 30 mm or decrease by 0 to 10 mm on the initial length, and the angle adjustment range of the first cavity is to adjust within the range of -10° to 20° on the initial tilt angle; The length of the second cavity is adjusted to reduce the initial length by 0 to 90 mm, and the thickness of the second cavity is adjusted to increase or decrease the initial thickness by 0 to 10 mm. The length of the third cavity can be adjusted in a range of 0 to 50 mm from the initial length.

4. The acoustic emission physical model based on dolphin sonar according to claim 1, characterized in that: The air domain is composed of a 3D-printed thin-walled cavity with a wall thickness of 2 mm.

5. The acoustic emission physical model based on dolphin sonar according to claim 1, characterized in that: The material of the maxilla is any one of steel, aluminum or organic glass, wherein the angle adjustment range of the maxilla is adjusted within the range of -2° to -3° on the initial inclination angle, and the length adjustment range is reduced by 0 to 50 mm on the initial length.

6. The acoustic emission physical model based on dolphin sonar according to claim 1, characterized in that: The soft tissue is made of silica gel or hydrogel, and the speed of sound of the soft tissue is in the range of 1500m / s to 1700m / s, wherein: The density of the melon is 1050 kg / m³ and the speed of sound is 1500 m / s; The density of the muscle tissue is 1050 kg / m³ and the speed of sound is 1600 m / s; The density of the connective tissue is 1100 kg / m³, and the speed of sound is 1700 m / s.

7. The acoustic emission physical model based on dolphin sonar according to claim 1, characterized in that: The transducer is cylindrical, with a bottom radius of 14 mm and a column height of 55 mm. It radiates cylindrical waves with a center frequency of 60 kHz and a 3dB bandwidth range of 50 kHz to 80 kHz.

8. The acoustic emission physical model based on dolphin sonar according to claim 1, characterized in that: The acoustic characteristic expression of the model is: in, is the wave number of the equation, is the out-of-plane wave number, is the angular frequency, is the background sound pressure, is the sound pressure, is the total sound pressure, is the complex speed of sound, is the complex density, is a dipole sound source; is a monopole sound source, is the gradient operator.

9. The acoustic emission physical model based on dolphin sonar according to claim 6, characterized in that: The hydrogel is prepared by doping glycerol in different proportions into a hydrogel substrate to obtain different sound velocity values.

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