Structural acoustic device for realizing large non-reciprocal transmission of acoustic energy by using nes and verification method

Abstract

The structural sound device for realizing large non-reciprocal transmission of sound energy by NES comprises a sound cavity I, a pipeline, a sound cavity II, a diaphragm and a sound cavity III, the pipeline is connected with the sound cavity I and the sound cavity II at two ends respectively, the sound cavity II is installed in the top surface of the sound cavity III in the middle, and a through hole III is arranged in the middle of the connection of the two sound cavities; the diaphragm is installed between the sound cavity II and the sound cavity III through a clamp and completely covers the through hole III. The sound cavity I and the sound cavity III are respectively provided with a through hole I and a through hole II on the side surfaces, a volume velocity sound source is connected with the sound cavity I through the through hole I and the through hole II is closed when forward excitation; the volume velocity sound source is connected with the sound cavity III through the through hole II and the through hole I is closed when reverse excitation. The application also provides a verification method of the structural sound device for realizing large non-reciprocal transmission of sound energy by NES. The application realizes large non-reciprocal transmission of sound energy by using the characteristics that the targeted energy transfer occurs when forward excitation and no targeted energy transfer occurs when reverse excitation, and provides a method for pipeline low-frequency noise control.

Description

Technical Field

[0001] This invention relates to acoustic energy control technology using acoustic artificial structures, and more particularly to a structured acoustic device and verification method that utilizes NES to achieve large non-reciprocal transfer of acoustic energy. Background Technology

[0002] In elastic media, due to the lack of an effect that enables electromagnetic rectification and biasing, elastic media systems strictly obey Rayleigh's reciprocity theorem. The reciprocity of the system hinders the asymmetric unidirectional transmission of sound waves. If asymmetric, highly non-reciprocal transmission of sound energy could be achieved, novel acoustic components such as acoustic diodes, unidirectional acoustic lenses, sound insulators, and topological insulators could be designed. In electromagnetism, the advent of diodes triggered the Second Industrial Revolution; similarly, these novel acoustic components have wide applications in acoustic communication, sonar system structural design, noise control, and imaging control, making them a research hotspot in structural acoustics and acoustic metamaterials.

[0003] Nonlinear acoustic systems possess characteristics not found in linear systems, such as bifurcation and resonant frequencies that vary with system energy, thus enabling highly non-reciprocal transfer of acoustic energy. Cochelin et al. investigated energy transfer phenomena in structural acoustic systems, coupling large-amplitude nonlinear films with linear acoustic systems to construct nonlinear energy traps. This enabled targeted energy transfer within the acoustic system. Their research demonstrates that the nonlinear energy trap mechanism can be used to achieve directional sound wave propagation, providing a new method for low-frequency noise control.

[0004] The experimental apparatus and method for noise reduction performance of a acoustic cavity using a coupled thin-film nonlinear energy trap, disclosed in CN 112857553 A, further suppresses low-frequency noise within the acoustic cavity by leveraging the targeted energy transfer characteristics of the thin-film nonlinear energy trap. The thin-plate radiation noise suppression device based on an electroacoustic nonlinear energy trap, disclosed in CN 114758642 A, reduces the excitation threshold of the optimal target energy transfer phenomenon of the nonlinear energy trap by 19 times by increasing the electroacoustic structure and optimizing parameters such as the back cavity volume, speaker back cavity volume, and feedback gain. However, the above schemes mainly study the suppression or transfer of acoustic energy in one direction and do not investigate the bidirectional transfer of acoustic energy.

[0005] The invention disclosed in CN 114613349 A, which describes a Duffing oscillator-type acoustic device for realizing non-reciprocal transfer of acoustic energy, utilizes the nonlinear resonance mechanism of a single-free Duffing oscillator in the weak nonlinear region and the bifurcation mechanism in the strong nonlinear region to achieve non-reciprocal transfer of acoustic energy. This provides a new approach for asymmetric transfer of acoustic energy in air. However, this scheme is for acoustic energy transfer in a single-degree-of-freedom system, and research on non-reciprocal acoustic energy transfer in two-degree-of-freedom or multi-degree-of-freedom systems with nonlinear energy trap mechanisms has not been carried out. Summary of the Invention

[0006] To further develop existing research on non-reciprocal acoustic energy transfer devices, a structural acoustic device using NES to achieve large-scale non-reciprocal acoustic energy transfer is proposed, providing a new method for realizing non-reciprocal acoustic energy transfer in air media and controlling low-frequency noise in pipelines.

[0007] The technical solution adopted in this invention is: a structural acoustic device that realizes large non-reciprocal transfer of acoustic energy using NES, including a pipe (2), a membrane (5), and cubic acoustic cavities of different sizes, namely, a first cubic acoustic cavity (1), a second cubic acoustic cavity (4), and a third cubic acoustic cavity (6). The length of the pipe (2) is much greater than its diameter. The two ends of the pipe (2) are respectively sealed and connected to the first cubic acoustic cavity (1) and the second cubic acoustic cavity (4), and the first cubic acoustic cavity (1) is connected to the second cubic acoustic cavity (4) through the pipe (2).

[0008] The second acoustic cavity (4) is centrally stacked on the top surface of the third acoustic cavity (6). The top surface of the second acoustic cavity (4) is provided with an end cap (3) for easy installation of the membrane (5), and the end cap (3) is sealed to the second acoustic cavity (4). A through hole (H3) is centrally opened on the wall connecting the second acoustic cavity (4) and the third acoustic cavity (6), and a membrane clamp (7) is sealed inside the through hole (H3). The membrane clamp (7) includes a ring The upper and lower covers are shaped like annular covers, and the film (5) is held between the upper and lower covers. The film clamp (7) and the film (5) completely cover the through hole three (H3). The surface of the acoustic cavity one (1) away from the pipe (2) has a through hole one (H1), and the surface of the acoustic cavity three (6) facing the pipe (2) has a through hole two (H2). The transmission medium in the acoustic cavity one (1), the pipe (2), the acoustic cavity two (4) and the acoustic cavity three (6) is air.

[0009] When positively excited, the volume velocity sound source is connected to the acoustic cavity (1) through the through hole one (H1) and the through hole two (H2) is sealed. When positively excited, an internal resonance is formed inside the device, and the sound energy is transferred to the target energy. It is irreversibly and efficiently transferred from the linear oscillator pipe (2) to the nonlinear oscillator film (5), and then transferred from the film (5) to the acoustic cavity three (6). A high response sound pressure can be measured in the acoustic cavity three (6).

[0010] When the volume velocity sound source is reverse excited, it is connected to the acoustic cavity three (6) through the second through hole (H2) and the first through hole (H1) is sealed. The wavelength of the input sound wave is much larger than the size of the cube acoustic cavity one (1), the cube acoustic cavity two (4) and the cube acoustic cavity three (6). When the device is reverse excited, no internal resonance occurs. Most of the sound energy remains in the acoustic cavity three (6). The sound energy transfer efficiency is low and the response sound pressure measured in the acoustic cavity one (1) is low. When there is a large difference in the system response between forward and reverse excitation, the device has large non-reciprocity.

[0011] Furthermore, the pipe (2) is made of stainless steel, the cross-sectional radius of the inner diameter of the pipe (2) is 17.5 mm, and the length of the pipe (2) is 1.75 m; the acoustic cavity one (1), acoustic cavity two (4) and acoustic cavity three (6) are all made of acrylic and are all cubic in shape; the cavity side length of acoustic cavity one (1) and acoustic cavity two (4) is 0.2 m, and the cavity side length of acoustic cavity three (6) is 0.3 m; the film (5) is made of silicone, the thickness of the film (5) is 0.1 mm, and the radius of the film (5) is 19 mm.

[0012] Furthermore, given the radius R of the pipe t The length L of the pipe and the radius R of the membrane m The density ρ of the thin film m The film thickness h, the film Poisson's ratio v, the film Young's modulus E, the film damping coefficient η, the volume V1 of square acoustic cavity one, the volume V2 of square acoustic cavity two, the volume V3 of square acoustic cavity three, and the amplitude Q of the sound source excitation. s Excitation frequency ω s air density ρ a Based on the speed of sound c0, a theoretical model is constructed, followed by simulation and experimental verification. The steps are as follows:

[0013] 1) Establish theoretical models for three types of constituent units: pipes, nonlinear membranes, and acoustic cavities; formulate the system control equations for the coupled system of these three types of units; and establish the criteria for determining the non-reciprocal quantity of acoustic energy.

[0014] Theoretical model of the pipe: Since the length of the pipe is much greater than its diameter, it can be assumed to be a one-dimensional waveguide. Let u be an example. a and p x To determine the displacement of the acoustic medium at the end of the pipe and the sound pressure inside the pipe, the acoustic wave equation and Rayleigh-Ritz simplification are combined, and an air damping coefficient c is introduced. f The pipeline control equations can be obtained as follows:

[0015]

[0016] in,

[0017]

[0018] Theoretical model of the thin film: The governing equations of the thin film are established by adopting the Von Karman nonlinear plate-shell model and combining it with the Kelvin-Viogt viscoelastic constitutive model; then, the governing equations of the nonlinear thin film are obtained by using the parabolic function as the first-order mode shape function of the thin film and the Rayleigh-Ritz reduction modeling method.

[0019]

[0020] Where q m p represents the lateral displacement of the film center. m f is the sound pressure exerted on the membrane. 1m f is the linear first-order natural frequency of the thin film under prestress, obtained by experimental measurement. 0m S is the resonant frequency of the unstressed thin film; k1 and k3 are the linear stiffness and cubic nonlinear stiffness of the thin film, respectively. m m is the area of ​​the thin film. a0 The mass is the additional mass caused by the large amplitude motion of the thin film, which drives the movement of the surrounding air. This mass is determined based on experimental results. Other parameters are given by the following formulas:

[0021]

[0022] Theoretical model of a acoustic cavity: When the wavelength of the sound wave is much larger than the size of the acoustic cavity, the sound pressure inside a rigidly walled acoustic cavity can be considered uniformly distributed, and the equation for the sound pressure inside the acoustic cavity can be obtained:

[0023]

[0024] Combining formulas (1), (3), and (5), the system control equations can be obtained:

[0025] When positive incentives are applied:

[0026]

[0027]

[0028] When reverse excitation occurs:

[0029]

[0030]

[0031] in,

[0032]

[0033] When positively excited, square acoustic cavity three (6) is the response acoustic cavity, and when negatively excited, square acoustic cavity one (1) is the response acoustic cavity. The sound pressures inside the cavity are as follows:

[0034]

[0035]

[0036] The reciprocity NR of acoustic energy transfer in the device system is defined by the following formula:

[0037]

[0038] Whether the device is a large non-reciprocal system can be determined according to formula (11).

[0039] The principle of this invention is as follows: Under fixed frequency excitation, the first-order acoustic mode resonance of pipe 2 can be simplified to a single-degree-of-freedom linear oscillator. The large deformation vibration of membrane 5 can be regarded as a nonlinear oscillator with nonlinear stiffness as the main component. Pipe 2 and membrane 5 are coupled with weak linear stiffness through the air in acoustic cavity 4. Therefore, the acoustic system of this structure can be simplified into a two-degree-of-freedom system composed of a linear oscillator and a nonlinear oscillator. Through theoretical research and analysis, it can be found that: within a certain high excitation range of the sound source, internal resonance is formed inside the system under forward excitation, and acoustic energy undergoes targeted energy transfer, irreversibly and efficiently transferred from the linear oscillator pipe 2 to the nonlinear oscillator membrane 5, and then from membrane 5 to the square acoustic cavity 6. A high response sound pressure can be measured in the square acoustic cavity 6. However, under reverse excitation, internal resonance does not occur in the system, and most of the acoustic energy remains in the square acoustic cavity 6. The acoustic energy transfer efficiency is low, and the response sound pressure measured in the square acoustic cavity 1 is low. Since there is a significant difference in the system response under forward and reverse excitation, the acoustic system exhibits high non-reciprocity.

[0040] Based on the definition of reciprocity in acoustic systems, this invention proposes a method to verify the non-reciprocity of a system by interchanging the positions of the excitation point and the response point, and then verifying the non-reciprocity of the system based on the ratio of the response sound pressure at the two points. Specifically, with the system input sound source intensity unchanged, the positions of the excitation input point and the response output point are interchanged, and the sound pressure at the response point before and after the interchange is measured. Then, the magnitude of the non-reciprocity is determined by the ratio of the two response sound pressures. When the ratio is large, it can be determined that it is a large non-reciprocal system.

[0041] The beneficial effects of this invention are: by utilizing the nonlinear energy trap mechanism in the structured acoustic system, this invention constructs a structured acoustic device that can realize large non-reciprocal transfer of acoustic energy, providing a new design idea for realizing non-reciprocal transfer of acoustic energy in air medium, and has significant application value in the field of low-frequency noise control in pipelines. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the structure of the device of the present invention.

[0043] Figure 2This is a schematic diagram of the structure of the thin film clamp of the present invention.

[0044] Figure 3 This is a simplified two-degree-of-freedom system schematic diagram of the device of the present invention.

[0045] Figure 4 This is a comparison graph of experimental and simulation results of the average velocity of the thin film under the same frequency and different source strength excitation of the device of the present invention.

[0046] Figure 5 This is a comparison of experimental and simulation results of the sound pressure response of the device of the present invention under the same frequency and different source strength excitation.

[0047] Figure 6 This is a comparison graph of experimental and simulation results of the non-reciprocal acoustic energy of the device of the present invention under the same frequency and different source strength excitation.

[0048] Explanation of reference numerals in the attached drawings: 1. Acoustic cavity one; 2. Pipe; 3. End cap; 4. Acoustic cavity two; 5. Membrane; 6. Acoustic cavity three; 7. Membrane clamp. Detailed Implementation

[0049] The technical solution of this invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0050] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0051] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0052] like Figure 1 As shown, the device consists of a first acoustic cavity 1, a pipe 2, a second acoustic cavity 4, a diaphragm 5, and a third acoustic cavity 6. The two ends of the pipe 2 are sealed to the first acoustic cavity 1 and the second acoustic cavity 4, respectively. The second acoustic cavity 4 is centrally mounted on the top surface of the third acoustic cavity 6. An end cap 3 is provided on the top surface of the second acoustic cavity 4 to facilitate the installation of the diaphragm 5. The end cap 3 is sealed to the second acoustic cavity 4 by a sealing ring and bolts. A through hole 3H3 is provided at the central connection between the second acoustic cavity 4 and the third acoustic cavity 6. The diaphragm 5 is installed between the second acoustic cavity 4 and the third acoustic cavity 6 by a clamp, completely covering the through hole 3H3. The diaphragm clamp 7 is sealed to the acoustic cavity by screws and a sealing ring. The sides of the first acoustic cavity 1 and the third acoustic cavity 6 have through holes 1H1 and 2H2, respectively. During forward excitation, the volume velocity sound source is connected to the first acoustic cavity 1 through through hole 1H1 and the through hole 2H2 is sealed. During reverse excitation, the volume velocity sound source is connected to the third acoustic cavity 6 through through hole 2H2 and the through hole 1H1 is sealed.

[0053] The transmission medium in both the acoustic cavity and the pipe is air. Pipe 2 is made of stainless steel, with an inner diameter radius of 17.5 mm and a length of 1.75 m. The acoustic cavities are all made of acrylic and are all square. The side lengths of acoustic cavities 1 and 4 are both 0.2 m, and the side length of acoustic cavity 6 is 0.3 m. The membrane 5 is made of silicone, with a thickness of 0.1 mm and an effective radius of 19 mm.

[0054] like Figure 2 As shown, the film clamp 7 consists of two parts, upper and lower. The film is evenly and flatly installed in the middle of the clamp to reduce the prestress generated during installation. At the same time, in order to ensure the stability of the film boundary conditions, a rubber pad needs to be installed on the inner ring of the clamp. Then the upper and lower parts of the clamp are fastened with screws.

[0055] like Figure 3 As shown, under fixed-frequency excitation, the first-order acoustic mode resonance of pipe 2 can be simplified to a single-degree-of-freedom linear oscillator, and the large deformation vibration of membrane 5 can be regarded as a nonlinear oscillator with nonlinear stiffness as the main component. Pipe 2 and membrane 5 are coupled with weak linear stiffness through the air in acoustic cavity 4. Therefore, the acoustic system of this structure can be simplified into a two-degree-of-freedom system composed of a linear oscillator and a nonlinear oscillator. Within a certain range of sound source intensity excitation, internal resonance is formed inside the system under forward excitation, and acoustic energy undergoes targeted energy transfer, irreversibly and efficiently transferred from the linear oscillator pipe 2 to the nonlinear oscillator membrane 5, and then from membrane 5 to acoustic cavity 6. A high response sound pressure can be measured in acoustic cavity 6. Under reverse excitation, internal resonance does not occur in the system, and most of the acoustic energy remains in acoustic cavity 6. The acoustic energy transfer efficiency is low, and the response sound pressure measured in acoustic cavity 1 is low. Since there is a significant difference in the system response under forward and reverse excitation, the acoustic system exhibits high non-reciprocity.

[0056] The verification method for a structured acoustic device that utilizes NES to achieve large non-reciprocal transfer of acoustic energy is characterized by: given the radius R of pipe 2 t The length L of pipe 2 and the radius R of membrane 5 m The density ρ of film 5 m The following parameters are considered: thickness h of film 5, Poisson's ratio υ of film 5, Young's modulus E of film 5, damping coefficient η of film 5, volume V1 of square acoustic cavity 1, volume V2 of square acoustic cavity 4, volume V3 of square acoustic cavity 6, and amplitude Q of the sound source excitation. s Excitation frequency ω s air density ρ a Based on the speed of sound c0, a theoretical model is constructed, followed by simulation and experimental verification. The steps are as follows:

[0057] 1) Establish theoretical models for three types of constituent units: pipes, nonlinear membranes, and acoustic cavities; formulate the system control equations for the coupled system of these three types of units; and establish the criteria for determining the non-reciprocal quantity of acoustic energy.

[0058] Theoretical model of the pipe: Since the length of the pipe is much greater than its diameter, it can be assumed to be a one-dimensional waveguide. Let u be an example. a and p x To determine the displacement of the acoustic medium at the end of the pipe and the sound pressure inside the pipe, the acoustic wave equation and Rayleigh-Ritz simplification are combined, and an air damping coefficient c is introduced. f The pipeline control equations can be obtained as follows:

[0059]

[0060] in,

[0061]

[0062] Theoretical model of the thin film: The governing equations of the thin film are established by adopting the Von Karman nonlinear plate-shell model and combining it with the Kelvin-Viogt viscoelastic constitutive model; then, the governing equations of the nonlinear thin film are obtained by using the parabolic function as the first-order mode shape function of the thin film and the Rayleigh-Ritz reduction modeling method.

[0063]

[0064] Where q m p represents the lateral displacement of the film center. m f is the sound pressure exerted on the membrane. 1m f is the linear first-order natural frequency of the thin film under prestress, obtained by experimental measurement. 0m S is the resonant frequency of the unstressed thin film; k1 and k3 are the linear stiffness and cubic nonlinear stiffness of the thin film, respectively. mm is the area of ​​the thin film. a0 The mass is the additional mass caused by the large amplitude motion of the thin film, which drives the movement of the surrounding air. This mass is determined based on experimental results. Other parameters are given by the following formulas:

[0065]

[0066] Theoretical model of a acoustic cavity: When the wavelength of the sound wave is much larger than the size of the acoustic cavity, the sound pressure inside a rigidly walled acoustic cavity can be considered uniformly distributed, and the equation for the sound pressure inside the acoustic cavity can be obtained:

[0067]

[0068] Combining formulas (1), (3), and (5), the system control equations can be obtained:

[0069] When positive incentives are applied:

[0070]

[0071]

[0072] When reverse excitation occurs:

[0073]

[0074]

[0075] in,

[0076]

[0077] When positively excited, square acoustic cavity three (6) is the response acoustic cavity, and when negatively excited, square acoustic cavity one (1) is the response acoustic cavity. The sound pressures inside the cavity are as follows:

[0078]

[0079]

[0080] The reciprocity NR of acoustic energy transfer in the device system is defined by the following formula:

[0081]

[0082] Whether the device is a large non-reciprocal system can be determined according to formula (11).

[0083] This invention establishes theoretical models for three types of constituent units: pipes, nonlinear membranes, and acoustic cavities; expressions for the system control equations formed by the coupling of these three types of units; and determination formulas for the non-reciprocal quantities of acoustic energy.

[0084] In this invention, the length of the pipe is much greater than its diameter, therefore it can be assumed to be a one-dimensional waveguide, with u respectively assumed to be...a and p x To determine the displacement of the acoustic medium at the end of the pipe and the sound pressure inside the pipe, the acoustic wave equation and Rayleigh-Ritz simplification are combined, and an air damping coefficient c is introduced. f The pipeline control equation can be obtained as formula (1).

[0085] In this invention, the vibration of the thin film is large, and linear theory will no longer be applicable. Therefore, the Von Karman nonlinear plate and shell model is adopted, combined with the Kelvin-Viogt viscoelastic constitutive model, to establish the control equation of the thin film. Then, the parabolic function is used as the first-order mode shape function of the thin film, and the control equation of the nonlinear thin film is obtained by Rayleigh-Ritz reduction modeling method as formula (3).

[0086] In this invention, the size of the acoustic cavity is much smaller than the wavelength of the sound wave. Therefore, the sound pressure inside the acoustic cavity sealed by the rigid wall can be considered to be uniformly distributed, and the equation for the sound pressure inside the acoustic cavity can be obtained as formula (5).

[0087] Based on the theoretical models of each component established above, the system control equations for positive and negative excitation are Equations (6) and (7), respectively, and the sound pressure response formulas for the response cavity are Equations (9) and (10), respectively. The reciprocity of the system's acoustic energy transfer, NR, is defined by Equation (11).

[0088] The magnitude of the non-reciprocal quantity of the system can be calculated by formula (11) to determine whether it is a non-reciprocal system.

[0089] In the experiment, the first-order natural frequency of the thin film was obtained as 62Hz by frequency sweep measurement under low source intensity excitation. The nonlinear cubic stiffness of the thin film was determined by fitting the measurement results of the large deformation data of the thin film. In this invention, a 100µm thick PDMS thin film was used, and its cubic nonlinear stiffness k3 was obtained as 3.0×10⁻⁶ by fitting the experimental data. 6 N / m 3 .

[0090] In order to output high source intensity excitation in the experiment, a JL Subwoofer and Brüel & 8-inch sensor were designed. A high-intensity volume velocity sound source composed of volume velocity source intensity probes; using Brüel & A 1 / 4-inch microphone was used to measure the sound pressure of the system's response cavity and the center point of the duct under forward and reverse excitation; a laser Doppler vibrometer (model: Polytech PSV400) was used to measure the vibration velocity at the center point of the diaphragm.

[0091] Analysis of experimental results and theoretical research results:

[0092] like Figures 4 to 6As shown, under low source strength excitation, the average velocity of the thin film and the response sound pressure increase almost linearly with the increase of the input source strength, indicating a low level of acoustic energy non-reciprocity. However, due to the nonlinearity of the system, the acoustic pressure response of the pipe is limited by the hardening effect of the nonlinear thin film. The higher the input source strength, the more pronounced this limitation becomes, until the input energy exceeds a threshold value, at which point the system enters the strongly nonlinear interaction region, and the acoustic energy non-reciprocity reaches its maximum value. Under high source strength excitation, the average velocity of the thin film and the response sound pressure still increase linearly under reverse excitation, while under forward excitation, the average velocity of the thin film and the response sound pressure increase gradually, and the acoustic energy non-reciprocity transfer decreases.

[0093] Figures 4 to 6 The theoretical analysis results and experimental results are generally in agreement, verifying the theoretical model of the system and revealing the mechanism by which the acoustic device achieves non-reciprocal transfer of acoustic energy. It achieves a large non-reciprocal transfer effect of nearly 3.5 times the acoustic energy, providing a new method for low-frequency noise control in pipelines.

[0094] The embodiments described in this specification are merely examples of implementations of the inventive concept. The scope of protection of this invention should not be considered as limited to the specific forms stated in the embodiments. The scope of protection of this invention also extends to equivalent technical means that can be conceived by those skilled in the art based on the inventive concept.

Claims

1. A structural acoustic device that utilizes NES to achieve large non-reciprocal transfer of acoustic energy, characterized in that: Includes a pipe (2), a membrane (5), and cubic acoustic cavities of different sizes: one (1), two (4), and three (6). The length of the pipe (2) is much greater than its diameter. The two ends of the pipe (2) are sealed to acoustic cavities one (1) and two (4), respectively, and acoustic cavity one (1) is connected to acoustic cavity two (4) through the pipe (2). The second acoustic cavity (4) is centrally stacked on the top surface of the third acoustic cavity (6). The top surface of the second acoustic cavity (4) is provided with an end cap (3) for easy installation of the membrane (5), and the end cap (3) is sealed to the second acoustic cavity (4). A through hole (H3) is centrally opened on the wall connecting the second acoustic cavity (4) and the third acoustic cavity (6), and a membrane clamp (7) is sealed inside the through hole (H3). The membrane clamp (7) includes a ring The upper and lower covers are shaped like annular covers, and the film (5) is held between the upper and lower covers. The film clamp (7) and the film (5) completely cover the through hole three (H3). The surface of the acoustic cavity one (1) away from the pipe (2) has a through hole one (H1), and the surface of the acoustic cavity three (6) facing the pipe (2) has a through hole two (H2). The transmission medium in the acoustic cavity one (1), the pipe (2), the acoustic cavity two (4) and the acoustic cavity three (6) is air. When positively excited, the volume velocity sound source is connected to the acoustic cavity (1) through the through hole one (H1) and the through hole two (H2) is sealed. When positively excited, an internal resonance is formed inside the device, and the sound energy is transferred to the target energy. It is irreversibly and efficiently transferred from the linear oscillator pipe (2) to the nonlinear oscillator film (5), and then transferred from the film (5) to the acoustic cavity three (6). A high response sound pressure can be measured in the acoustic cavity three (6). When the volume velocity sound source is reverse excited, it is connected to the acoustic cavity three (6) through the second through hole (H2) and the first through hole (H1) is sealed. The wavelength of the input sound wave is much larger than the size of the cube acoustic cavity one (1), the cube acoustic cavity two (4) and the cube acoustic cavity three (6). When the device is reverse excited, no internal resonance occurs. Most of the sound energy remains in the acoustic cavity three (6). The sound energy transfer efficiency is low and the response sound pressure measured in the acoustic cavity one (1) is low. When there is a large difference in the system response between forward and reverse excitation, the device has large non-reciprocity.

2. The structural acoustic device for realizing large non-reciprocal transfer of acoustic energy using NES as described in claim 1, characterized in that: The pipe (2) is made of stainless steel, the inner diameter of the pipe (2) has a cross-sectional radius of 17.5 mm, and the length of the pipe (2) is 1.75 m; the acoustic cavity one (1), acoustic cavity two (4) and acoustic cavity three (6) are all made of acrylic and are all cubic in shape; the cavity side length of acoustic cavity one (1) and acoustic cavity two (4) is 0.2 m, and the cavity side length of acoustic cavity three (6) is 0.3 m; the film (5) is made of silicone, the thickness of the film (5) is 0.1 mm, and the radius of the film (5) is 19 mm.

3. The verification method for a structured acoustic device utilizing NES to achieve large non-reciprocal transfer of acoustic energy, based on claim 1 or 2, is characterized in that: Given the radius R of pipe (2) t The length L of the pipe (2) and the radius R of the membrane (5) m The density ρ of the thin film (5) m The thickness h of the thin film (5), the Poisson's ratio υ of the thin film (5), the Young's modulus E of the thin film (5), the damping coefficient η of the thin film (5), the volume V1 of square acoustic cavity one (1), the volume V2 of square acoustic cavity two (4), the volume V3 of square acoustic cavity three (6), and the amplitude Q of the sound source excitation. s Excitation frequency ω s air density ρ a Based on the speed of sound c0, a theoretical model is constructed, followed by simulation and experimental verification. The steps are as follows: 1) Establish theoretical models for three types of constituent units: pipes, nonlinear membranes, and acoustic cavities; formulate the system control equations for the coupled system of these three types of units; and establish the criteria for determining the non-reciprocal quantity of acoustic energy. Theoretical model of the pipe: Since the length of the pipe is much greater than its diameter, it can be assumed to be a one-dimensional waveguide. Let u be an example. a and p x To determine the displacement of the acoustic medium at the end of the pipe and the sound pressure inside the pipe, the acoustic wave equation and Rayleigh-Ritz simplification are combined, and an air damping coefficient c is introduced. f The pipeline control equations can be obtained as follows: in, Theoretical model of the thin film: The governing equations of the thin film are established by adopting the Von Karman nonlinear plate-shell model and combining it with the Kelvin-Viogt viscoelastic constitutive model; then, the governing equations of the nonlinear thin film are obtained by using the parabolic function as the first-order mode shape function of the thin film and the Rayleigh-Ritz reduction modeling method. Where q m p represents the lateral displacement of the film center. m f is the sound pressure exerted on the membrane. 1m f is the linear first-order natural frequency of the thin film under prestress, obtained by experimental measurement. 0m S is the resonant frequency of the unstressed thin film; k1 and k3 are the linear stiffness and cubic nonlinear stiffness of the thin film, respectively. m m is the area of ​​the thin film. a0 The mass is the additional mass caused by the large amplitude motion of the thin film, which drives the movement of the surrounding air. This mass is determined based on experimental results. Other parameters are given by the following formulas: Theoretical model of a acoustic cavity: When the wavelength of the sound wave is much larger than the size of the acoustic cavity, the sound pressure inside a rigidly walled acoustic cavity can be considered uniformly distributed, and the equation for the sound pressure inside the acoustic cavity can be obtained: Combining formulas (1), (3), and (5), the system control equations can be obtained: When positive incentives are applied: When reverse excitation occurs: in, When positively excited, square acoustic cavity three (6) is the response acoustic cavity, and when negatively excited, square acoustic cavity one (1) is the response acoustic cavity. The sound pressures inside the cavity are as follows: The reciprocity NR of acoustic energy transfer in the device system is defined by the following formula: Whether the device is a large non-reciprocal system can be determined according to formula (11).

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