CN116261089A - Structural-acoustic device and verification method for large non-reciprocal transfer of sound energy using NES - Google Patents

Abstract

Using NES to realize the structure-acoustic device with large and non-reciprocal transmission of sound energy, including acoustic chamber 1, pipe, acoustic chamber 2, membrane and acoustic chamber 3, the two ends of the pipe are respectively connected with acoustic chamber 1 and acoustic chamber 2, and acoustic chamber 2 is installed in the center on the top of acoustic chamber 3 On the surface, a through hole three is provided in the middle of the connection between the two sound chambers; the film is installed between the sound chamber two and the sound chamber three through a clamp, and completely covers the through hole three. There are through holes 1 and 2 respectively on the sides of the acoustic chamber 1 and the three sides of the acoustic chamber. When positively excited, the volume velocity sound source is connected to the acoustic chamber 1 through the through hole 1, and the through hole 2 is sealed; Hole two is connected with acoustic chamber three, and through hole one is airtight. The invention also provides a verification method for a structure-acoustic device that utilizes the NES to realize the non-reciprocal transfer of large acoustic energy. The invention utilizes the property that targeted energy transfer occurs during forward excitation, but there is no targeted energy transfer during reverse excitation, thereby realizing large non-reciprocal transfer of acoustic energy and providing a method for pipeline low-frequency noise control.

Description

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

Technical Field

The present invention relates to a technique for controlling acoustic energy by using an acoustic artificial structure, and in particular to a structural acoustic device and a verification method for realizing large non-reciprocal transmission of acoustic energy by using NES.

Background Art

In elastic media, due to the lack of electromagnetic rectification bias effects, elastic medium systems strictly follow the Rayleigh reciprocity theorem. The reciprocity of the system hinders the realization of asymmetric unidirectional transmission of sound waves. If the asymmetric large non-reciprocal transmission of sound energy is realized, new acoustic elements such as acoustic diodes, acoustic one-way lenses, sound insulators and topological insulators can be designed. In electromagnetism, the emergence of diodes triggered the second industrial revolution. The above-mentioned new acoustic elements also have a wide range of application values in acoustic communications, sonar system structure design, noise control, imaging control and other fields, and are research hotspots in the fields of structural acoustics and acoustic metamaterials.

Nonlinear acoustic systems have characteristics that linear systems do not have, such as bifurcation and resonance frequency that changes with system energy, which can achieve large non-reciprocal transfer of acoustic energy. Cochelin and other scholars studied the energy transfer phenomenon in structural acoustic systems, coupled large-amplitude nonlinear films with linear acoustic systems, and constructed nonlinear energy wells to achieve targeted energy transfer in acoustic systems. The study showed that the use of nonlinear energy well mechanisms can achieve directional transmission of sound waves, providing a new method for low-frequency noise control.

The noise reduction performance experimental device and method of the acoustic cavity coupled with a thin film nonlinear energy well invented with publication number CN 112857553 A, combined with the targeted energy transfer characteristics of the thin film nonlinear energy well, further suppress the low-frequency noise in the acoustic cavity. The thin plate radiation noise suppression device based on the electroacoustic nonlinear energy well invented with publication number CN 114758642 A, by increasing the electroacoustic structure and optimizing the back cavity volume, the speaker back cavity volume, the feedback gain and other parameters, reduces the threshold under excitation of the nonlinear energy well optimal target energy transfer phenomenon by 19 times. However, the above schemes mainly study the unidirectional suppression or transfer of acoustic energy, and do not study the bidirectional transfer of acoustic energy.

The Duffing oscillator-type structural acoustic device for realizing nonreciprocal transfer of acoustic energy, invented with publication number CN 114613349 A, realizes nonreciprocal transfer of acoustic energy by utilizing the nonlinear resonance of a Duffing oscillator simplified to a single freedom in a weak nonlinear region and the bifurcation mechanism in a strong nonlinear region, which provides a new idea for asymmetric transfer of acoustic energy in an air medium. However, this scheme is for acoustic energy transfer in a single-degree-of-freedom system, and no research has been conducted on acoustic nonreciprocal energy transfer in a two-degree-of-freedom or multi-degree-of-freedom system with a nonlinear energy sink mechanism.

Summary of the invention

For the further development of the existing research on non-reciprocal transfer of acoustic energy, a structural acoustic device which uses NES to achieve large non-reciprocal transfer of acoustic energy is proposed, which provides a new method for achieving non-reciprocal transfer of acoustic energy in air medium and controlling low-frequency noise in pipelines.

The technical solution adopted by the present invention is: a structural acoustic device that uses NES to achieve large non-reciprocal transmission of acoustic energy, comprising a pipe (2), a film (5), and a cube acoustic cavity one (1), a cube acoustic cavity two (4), and a cube acoustic cavity three (6) of different sizes, wherein the length of the pipe (2) is much greater than its diameter, and the two ends of the pipe (2) are respectively sealed and connected to the acoustic cavity one (1) and the acoustic cavity two (4), and the acoustic cavity one (1) is connected to the acoustic cavity two (4) through the pipe (2);

The second acoustic cavity (4) is centrally stacked and installed on the top surface of the third acoustic cavity (6). The top surface of the second acoustic cavity (4) is provided with an end cover (3) for facilitating the installation of a film (5), and the end cover (3) is sealed and connected to the second acoustic cavity (4). A through hole ( _H3 ) for connecting the second acoustic cavity (4) and the third acoustic cavity (6) is opened in the center of the wall surface where the second acoustic cavity (4) and the third acoustic cavity (6) are connected, and a film clamp (7) is sealed and connected in the third through hole ( _H3 ). The film clamp (7) includes an annular upper clamp cover and an annular lower clamp cover, and the film (5) is clamped between the upper clamp cover and the lower clamp cover, and the film clamp (7) and the film (5) completely cover the third through hole ( _H3 ). The first through hole ( _H1 ) is opened on the surface of the first acoustic cavity (1) away from the pipeline (2), and the second through hole ( _H2 ) is opened on the surface of the third acoustic cavity (6) facing the pipeline (2). ); the transmission medium in the acoustic cavity 1 (1), the pipe (2), the acoustic cavity 2 (4) and the acoustic cavity 3 (6) is air;

When positively excited, the volume velocity sound source is connected to the acoustic cavity one ( ₁ ) through the through hole one (H1), and the through hole two ( _H2 ) is sealed; when positively excited, internal resonance is formed inside the device, and the acoustic energy undergoes targeted energy transfer, and 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), and a higher response sound pressure can be measured in the acoustic cavity three (6);

When reversely excited, the volume velocity sound source is connected to the sound cavity three (6) through the through hole two ( _H2 ), and the through hole one ( _H1 ) is sealed, and the wavelength of the input sound wave is much larger than the size of the cube sound cavity one (1), the cube sound cavity two (4) and the cube sound cavity three (6); when reversely excited, the device does not have internal resonance, most of the sound energy still remains in the sound cavity three (6), the sound energy transfer efficiency is low, and the response sound pressure measured in the sound cavity one (1) is low; when there is a large difference in the system response during forward excitation and reverse excitation, the device has a large non-reciprocity.

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 1 (1), the acoustic cavity 2 (4), and the acoustic cavity 3 (6) are all made of acrylic and are all in a cube shape; the cavity side lengths of the acoustic cavity 1 (1) and the acoustic cavity 2 (4) are both 0.2 m, and the cavity side length of the acoustic cavity 3 (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.

Furthermore, given the radius R _t of the pipe, the length L of the pipe, the radius R _m of the film, the density ρ _m of the film, the thickness h of the film, the Poisson's ratio v of the film, the Young's modulus E of the film, the damping coefficient η of the film, the volume V ₁ of the square acoustic cavity one, the volume V ₂ of the square acoustic cavity two, the volume V ₃ of the square acoustic cavity three, the sound source excitation amplitude Q _s , the excitation frequency ω _s , the air density ρ _a and the sound speed c ₀ , theoretical modeling is performed, and then simulation and experimental verification are performed. The steps are as follows:

1) The theoretical models of the three types of components, namely, pipes, nonlinear membranes and acoustic cavities, the expressions of the system control equations coupled by the three types of units, and the determination formula of the non-reciprocal amount of acoustic energy are established respectively:

Theoretical model of the pipeline: Since the length of the pipeline is much larger than its diameter, it can be assumed to be a one-dimensional waveguide. Assuming u _a and p _x are the displacement of the acoustic medium at the end of the pipeline and the sound pressure in the pipeline respectively, combining the acoustic wave equation and Rayleigh-Ritz simplification, and introducing the air damping coefficient c _f , the pipeline control equation can be obtained:

in,

Theoretical model of the film: The Von Karman nonlinear plate-shell model is combined with the Kelvin-Viogt viscoelastic constitutive model to establish the control equation of the film; then the parabolic function is used as the first-order modal vibration function of the film, and the control equation of the nonlinear film is obtained through the Rayleigh-Ritz price reduction modeling method:

Where _qm is the lateral displacement of the center of the film, _pm is the sound pressure on the film; _f1m is the linear first-order natural frequency of the film with prestress, obtained by experimental measurement, _f0m is the resonant frequency of the film without prestress; _k1 and _k3 are the linear stiffness and cubic nonlinear stiffness of the film, respectively, _Sm is the area of the film; _ma0 is the additional mass of the surrounding air driven by the large amplitude motion of the film, determined according to experimental results; other parameters are given by the following formulas:

Theoretical model of acoustic cavity: When the wavelength of the sound wave is much larger than the size of the acoustic cavity, the sound pressure in the acoustic cavity closed by the rigid wall can be considered to be uniformly distributed, and the sound pressure equation in the acoustic cavity can be obtained:

Combining formulas (1), (3) and (5), we can get the system control equation:

When positively motivated:

When the reverse incentive:

in,

When the square sound cavity is positively excited, the third square sound cavity (6) is the response sound cavity, and when the square sound cavity is negatively excited, the first square sound cavity (1) is the response sound cavity. The sound pressures in the cavities are:

The reciprocity NR of the acoustic energy transfer of 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).

The principle of the present invention is that under fixed frequency excitation, the first-order acoustic modal resonance of the pipe 2 can be simplified to a single-degree-of-freedom linear oscillator, the large deformation vibration of the film 5 can be regarded as a nonlinear oscillator with a dominant nonlinear stiffness, and the pipe 2 and the film 5 are coupled with weak linear stiffness through the air in the acoustic cavity 2 4, so the structural acoustic system can simplify the 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 range of high excitation of the sound source, an internal resonance is formed inside the system during forward excitation, and the acoustic energy undergoes targeted energy transfer, which 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 square acoustic cavity 3 6, and a higher response sound pressure can be measured in the square acoustic cavity 3 6; while the system does not undergo internal resonance during reverse excitation, most of the acoustic energy still remains in the square acoustic cavity 3 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 during forward and reverse excitation, the acoustic system has a large non-reciprocity.

According to the definition of reciprocity in an acoustic system, the present invention proposes a method of interchanging the positions of an excitation point and a response point, and then verifying the non-reciprocity of the system based on the ratio of the response sound pressures at the two points. Specifically, when the intensity of the system input sound source remains unchanged, the positions of the excitation input point and the response output point are interchanged, and the sound pressures at the response points before and after the interchange are measured respectively. Then, the size of the non-reciprocal quantity is determined by the ratio of the response sound pressures at the two points. When the ratio between the two is large, it can be determined that it is a large non-reciprocal system.

The beneficial effects of the present invention are as follows: the present invention utilizes the nonlinear energy sink mechanism in the structural acoustic system to construct a structural acoustic device capable of realizing large non-reciprocal transfer of acoustic energy, provides a new design idea for realizing non-reciprocal transfer of acoustic energy in the air medium, and has great application value in the field of pipeline low-frequency noise control.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural diagram of the device of the present invention.

FIG. 2 is a schematic structural diagram of a film clamp of the present invention.

FIG. 3 is a simplified two-degree-of-freedom system schematic diagram of the device of the present invention.

FIG. 4 is a curve comparison of the experimental and simulation results of the average film velocity of the device of the present invention under the same frequency and different source strength excitation.

FIG. 5 is a curve comparison of the experimental and simulation results of the response sound pressure of the device of the present invention under the same frequency and different source strength excitation.

FIG. 6 is a curve comparison diagram of the experimental and simulation results of the non-reciprocal amount of acoustic energy of the device of the present invention under the same frequency and different source intensity excitations.

Explanation of the accompanying drawings: 1. Acoustic cavity one; 2. Pipe; 3. End cover; 4. Acoustic cavity two; 5. Film; 6. Acoustic cavity three; 7. Film clamp.

DETAILED DESCRIPTION

The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

In the description of the present invention, it should be noted that the orientations or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

As shown in Figure 1, the device consists of a sound cavity 1, a pipe 2, a sound cavity 4, a film 5 and a sound cavity 3 6; the two ends of the pipe 2 are sealed and connected to the sound cavity 1 1 and the sound cavity 2 4 respectively, the sound cavity 2 4 is centrally installed on the top surface of the sound cavity 3 ₆ , the top surface of the sound cavity 2 4 is provided with an end cover 3 for convenient installation of the film 5, and the end cover 3 and the sound cavity 2 4 are sealed and connected by a sealing ring and a bolt; a through hole three H3 is provided in the center of the connection between the sound cavity 2 4 and the sound cavity 3 6, the film 5 is installed between the sound cavity 2 4 and the sound cavity 3 6 by a clamp, and completely covers the through hole three _H3 , and the film clamp 7 is sealed and connected to the sound cavity by screws and a sealing ring. A through hole 1 _H1 and a through hole 2 _H2 are respectively opened on the sides of the sound cavity 1 ₁ and the sound cavity 3 6. During forward excitation, the volume velocity sound source is connected to the sound cavity 1 1 through the through hole 1 H1 and the through hole 2 _H2 is sealed. During reverse excitation, the volume velocity sound source is connected to the sound cavity 3 6 through the through hole 2 _H2 and the through hole 1 _H1 is sealed.

The transmission medium in the acoustic cavity and the pipe is air. 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 is made of acrylic and is square, where the side lengths of the acoustic cavity 1 and the acoustic cavity 2 4 are both 0.2 m, and the side length of the acoustic cavity 3 6 is 0.3 m; the film 5 is made of silicone, the thickness of the film 5 is 0.1 mm, and the effective radius of the film 5 is 19 mm.

As shown in Figure 2, the film clamp 7 consists of two parts, the upper and lower parts. The film is installed evenly and flatly 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 by screws.

As shown in Fig. 3, under fixed frequency excitation, the first-order acoustic modal resonance of pipe 2 can be simplified to a single-degree-of-freedom linear oscillator, and the large deformation vibration of film 5 can be regarded as a nonlinear oscillator dominated by nonlinear stiffness. Pipe 2 and film 5 are coupled with weak linear stiffness through the air in acoustic cavity 2 4, so the structural acoustic system can be simplified to a two-degree-of-freedom system composed of a linear oscillator and a nonlinear oscillator. Within a certain range of sound source intensity excitation, an internal resonance is formed inside the system during forward excitation, and the acoustic energy undergoes targeted energy transfer, which 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 3 6, where a higher response sound pressure can be measured; during reverse excitation, the system does not undergo internal resonance, and most of the acoustic energy remains in the acoustic cavity 3 6, with low acoustic energy transfer efficiency, and the response sound pressure measured in the acoustic cavity 1 is low; since there is a significant difference in the system response during forward and reverse excitation, the acoustic system has a large non-reciprocity.

The structural acoustic device verification method for realizing large non-reciprocal transfer of acoustic energy by using NES according to claim 1 or 2 is characterized in that: given the radius R _t of the pipe 2, the length L of the pipe 2, the radius R _m of the film 5, the density ρ _m of the film 5, the thickness h of the film 5, the Poisson's ratio υ of the film 5, the Young's modulus E of the film 5, the damping coefficient η of the film 5, the volume V ₁ of the square acoustic cavity 1, the volume V ₂ of the square acoustic cavity 2, the volume V ₃ of the square acoustic cavity 3, the sound source excitation amplitude Q _s , the excitation frequency ω _s , the air density ρ _a and the sound speed c ₀ , theoretical modeling is performed, and then simulation and experimental verification are performed, and the steps are as follows:

1) The theoretical models of the three types of components, namely, pipes, nonlinear membranes and acoustic cavities, the expressions of the system control equations coupled by the three types of units, and the determination formula of the non-reciprocal amount of acoustic energy are established respectively:

Theoretical model of the pipeline: Since the length of the pipeline is much larger than its diameter, it can be assumed to be a one-dimensional waveguide. Assuming u _a and p _x are the displacement of the acoustic medium at the end of the pipeline and the sound pressure in the pipeline respectively, combining the acoustic wave equation and Rayleigh-Ritz simplification, and introducing the air damping coefficient c _f , the pipeline control equation can be obtained:

in,

Theoretical model of the film: The Von Karman nonlinear plate-shell model is combined with the Kelvin-Viogt viscoelastic constitutive model to establish the control equation of the film; then the parabolic function is used as the first-order modal vibration function of the film, and the control equation of the nonlinear film is obtained through the Rayleigh-Ritz price reduction modeling method:

Where _qm is the lateral displacement of the center of the film, _pm is the sound pressure on the film; _f1m is the linear first-order natural frequency of the film with prestress, obtained by experimental measurement, _f0m is the resonant frequency of the film without prestress; _k1 and _k3 are the linear stiffness and cubic nonlinear stiffness of the film, respectively, _Sm is the area of the film; _ma0 is the additional mass of the surrounding air driven by the large amplitude motion of the film, determined according to experimental results; other parameters are given by the following formulas:

Theoretical model of acoustic cavity: When the wavelength of the sound wave is much larger than the size of the acoustic cavity, the sound pressure in the acoustic cavity closed by the rigid wall can be considered to be uniformly distributed, and the sound pressure equation in the acoustic cavity can be obtained:

Combining formulas (1), (3) and (5), we can get the system control equation:

When positively motivated:

When the reverse incentive:

in,

When the square sound cavity is positively excited, the third square sound cavity (6) is the response sound cavity, and when the square sound cavity is negatively excited, the first square sound cavity (1) is the response sound cavity. The sound pressures in the cavities are:

The reciprocity NR of the acoustic energy transfer of 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).

The present invention establishes theoretical models of three types of components, namely, pipelines, nonlinear films and acoustic cavities, expressions of system control equations formed by coupling the three types of units, and determination formulas for the non-reciprocal amount of acoustic energy:

In the present invention, the length of the pipeline is much larger than its diameter, so it can be assumed to be a one-dimensional waveguide. Assuming u _a and p _x are the acoustic medium displacement at the end of the pipeline and the sound pressure in the pipeline respectively, combining the acoustic wave equation and Rayleigh-Ritz simplification, and introducing the air damping coefficient c _f , the pipeline control equation can be obtained as formula (1).

In the present invention, the vibration of the film is large, and the linear theory will no longer be applicable. Therefore, the Von Karman nonlinear plate-shell model is used in combination with the Kelvin-Viogt viscoelastic constitutive model to establish the control equation of the film; then a parabolic function is used as the first-order modal vibration function of the film, and the control equation of the nonlinear film is obtained as formula (3) through the Rayleigh-Ritz price reduction modeling method.

In the present invention, the size of the acoustic cavity is much smaller than the wavelength of the sound wave, so the sound pressure in the acoustic cavity closed by the rigid wall can be considered to be uniformly distributed, and the sound pressure equation in the acoustic cavity can be obtained as formula (5).

Combining the theoretical models of the components established above, the system control equations for the system under forward and reverse excitation are formulas (6) and (7), and the sound pressure response formulas of the response sound cavity are formulas (9) and (10). The reciprocity NR of the system sound energy transfer is defined by formula (11).

The acoustic energy transfer of the system can be calculated by the size of the system non-reciprocal quantity using formula (11), so as to determine whether it is a non-reciprocal system.

In the experiment, the first-order natural frequency of the film was measured by sweeping frequency under low source strength excitation and was found to be 62 Hz. The nonlinear cubic stiffness of the film was determined by fitting the measurement results of the large deformation data of the film. In the present invention, a 100 um thick PDMS film was used, and its cubic nonlinear stiffness k ₃ was found to be 3.0×10 ⁶ N/m ³ by fitting the experimental data.

的体积速度源强探头组成的高源强体积速度声源；采用Brüel&

的1/4英寸传声器测量正向、反向激励时系统的响应声腔以及管道中心点的声压；采用激光多普勒测振仪(型号：Polytech PSV400)测量薄膜中心点的振动速度。In order to output high source intensity excitation in the experiment, a 8-inch JL Subwoofer and Brüel &

The high source intensity volume velocity sound source is composed of volume velocity source intensity probes; using Brüel &

A 1/4-inch microphone was used to measure the response cavity of the system and the sound pressure at the center of the pipe during forward and reverse excitations. A laser Doppler vibrometer (model: Polytech PSV400) was used to measure the vibration velocity at the center of the film.

Analysis of experimental results and theoretical research results:

As shown in Figures 4 to 6, under low source intensity excitation, the average velocity of the film and the response sound pressure increase almost linearly with the increase of the input source intensity. At this time, the system has a low amount of acoustic energy nonreciprocity. However, due to the nonlinearity of the system, the pipe sound pressure response is limited by the hardening effect of the nonlinear film. The greater the input source intensity, the more obvious the phenomenon of the pipe sound pressure response being limited, until the input energy exceeds the threshold value, the system enters the strong nonlinear interaction region, and the acoustic energy nonreciprocity reaches the maximum value. Under high source intensity excitation, the average velocity of the film and the response sound pressure still increase linearly during reverse excitation, but during forward excitation, the average velocity of the film and the response sound pressure increase gently, and the amount of acoustic energy nonreciprocity transfer decreases.

The theoretical analysis results and experimental results in Figures 4 to 6 are generally consistent, which verifies the theoretical model of the system and reveals the mechanism of the structural acoustic device to achieve non-reciprocal transfer of acoustic energy, achieving a non-reciprocal transfer effect of nearly 3.5 times the acoustic energy, providing a new method for pipeline low-frequency noise control.

The contents described in the embodiments of this specification are merely an enumeration of the implementation forms of the inventive concept. The protection scope of the present invention should not be regarded as limited to the specific forms described in the embodiments. The protection scope of the present invention also extends to equivalent technical means that can be conceived by those skilled in the art based on the inventive concept.

Claims (3)

1. A structural acoustic device for realizing large non-reciprocal transmission of acoustic energy by using NES, characterized in that it comprises a pipe (2), a film (5), and a cube acoustic cavity one (1), a cube acoustic cavity two (4), and a cube acoustic cavity three (6) of different sizes, wherein the length of the pipe (2) is much greater than its diameter, and the two ends of the pipe (2) are respectively sealedly connected to the acoustic cavity one (1) and the acoustic cavity two (4), and the acoustic cavity one (1) is connected to the acoustic cavity two (4) through the pipe (2); The second acoustic cavity (4) is centrally stacked and installed on the top surface of the third acoustic cavity (6). The top surface of the second acoustic cavity (4) is provided with an end cover (3) for facilitating the installation of a film (5), and the end cover (3) is sealed and connected to the second acoustic cavity (4). A through hole ( _H3 ) for connecting the second acoustic cavity (4) and the third acoustic cavity (6) is opened in the center of the wall surface where the second acoustic cavity (4) and the third acoustic cavity (6) are connected, and a film clamp (7) is sealed and connected in the third through hole ( _H3 ). The film clamp (7) includes an annular upper clamp cover and an annular lower clamp cover, and the film (5) is clamped between the upper clamp cover and the lower clamp cover, and the film clamp (7) and the film (5) completely cover the third through hole ( _H3 ). The first through hole ( _H1 ) is opened on the surface of the first acoustic cavity (1) away from the pipeline (2), and the second through hole ( _H2 ) is opened on the surface of the third acoustic cavity (6) facing the pipeline (2). ); the transmission medium in the acoustic cavity 1 (1), the pipe (2), the acoustic cavity 2 (4) and the acoustic cavity 3 (6) is air; When positively excited, the volume velocity sound source is connected to the acoustic cavity one ( ₁ ) through the through hole one (H1), and the through hole two ( _H2 ) is sealed; when positively excited, internal resonance is formed inside the device, and the acoustic energy undergoes targeted energy transfer, and 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), and a higher response sound pressure can be measured in the acoustic cavity three (6); When reversely excited, the volume velocity sound source is connected to the sound cavity three (6) through the through hole two ( _H2 ), and the through hole one ( _H1 ) is sealed, and the wavelength of the input sound wave is much larger than the size of the cube sound cavity one (1), the cube sound cavity two (4) and the cube sound cavity three (6); when reversely excited, the device does not have internal resonance, most of the sound energy still remains in the sound cavity three (6), the sound energy transfer efficiency is low, and the response sound pressure measured in the sound cavity one (1) is low; when there is a large difference in the system response during forward excitation and reverse excitation, the device has a large non-reciprocity. 2. The structural acoustic device for realizing large non-reciprocal transmission of acoustic energy by using NES as claimed in claim 1, characterized in that: 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 1 (1), the acoustic cavity 2 (4) and the acoustic cavity 3 (6) are all made of acrylic and are all in the shape of a cube; the cavity side lengths of the acoustic cavity 1 (1) and the acoustic cavity 2 (4) are both 0.2 m, and the cavity side length of the acoustic cavity 3 (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. A method for verifying a structural acoustic device using NES to achieve large non-reciprocal transfer of acoustic energy based on claim 1 or 2, characterized in that: given the radius _Rt of the pipe (2), the length L of the pipe (2), the radius _Rm of the film (5), the density _ρm of the film (5), the thickness h of the film (5), the Poisson's ratio υ of the film (5), the Young's modulus E of the film (5), the damping coefficient η of the film (5), the volume _V1 of the square acoustic cavity one (1), the volume _V2 of the square acoustic cavity two (4), the volume _V3 of the square acoustic cavity three (6), the sound source excitation amplitude _Qs , the excitation frequency _ωs , the air density _ρa and the sound speed _c0 , theoretical modeling is performed, and then simulation and experimental verification are performed, the steps are as follows: 1) The theoretical models of the three types of components, namely, pipes, nonlinear membranes and acoustic cavities, the expressions of the system control equations coupled by the three types of units, and the determination formula of the non-reciprocal amount of acoustic energy are established respectively: Theoretical model of the pipeline: Since the length of the pipeline is much larger than its diameter, it can be assumed to be a one-dimensional waveguide. Assuming u _a and p _x are the displacement of the acoustic medium at the end of the pipeline and the sound pressure in the pipeline respectively, combining the acoustic wave equation and Rayleigh-Ritz simplification, and introducing the air damping coefficient c _f , the pipeline control equation can be obtained:

in,

Theoretical model of the film: The Von Karman nonlinear plate-shell model is combined with the Kelvin-Viogt viscoelastic constitutive model to establish the control equation of the film; then the parabolic function is used as the first-order modal vibration function of the film, and the control equation of the nonlinear film is obtained through the Rayleigh-Ritz price reduction modeling method:

Where _qm is the lateral displacement of the center of the film, _pm is the sound pressure on the film; _f1m is the linear first-order natural frequency of the film with prestress, obtained by experimental measurement, _f0m is the resonant frequency of the film without prestress; _k1 and _k3 are the linear stiffness and cubic nonlinear stiffness of the film, respectively, _Sm is the area of the film; _ma0 is the additional mass of the surrounding air driven by the large amplitude motion of the film, determined according to experimental results; other parameters are given by the following formulas:

Theoretical model of acoustic cavity: When the wavelength of the sound wave is much larger than the size of the acoustic cavity, the sound pressure in the acoustic cavity closed by the rigid wall can be considered to be uniformly distributed, and the sound pressure equation in the acoustic cavity can be obtained:

Combining formulas (1), (3) and (5), we can get the system control equation: When positively motivated:

When the reverse incentive:

in,

When the square sound cavity is positively excited, the third square sound cavity (6) is the response sound cavity, and when the square sound cavity is negatively excited, the first square sound cavity (1) is the response sound cavity. The sound pressures in the cavities are:

The reciprocity NR of the acoustic energy transfer of 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).

Images