Method and system for determining the equivalent material parameters of structural acoustic covering layers

Abstract

This invention relates to a method and system for determining the equivalent material parameters of a structural acoustic covering layer. The method includes: S1, setting the acoustic characteristic requirements of the structural acoustic covering layer, setting the value range and constraints of the equivalent material parameters, and setting the initial values ​​of the equivalent material parameters; S2, calculating the acoustic characteristic parameters that satisfy the value range and preset constraints using the transfer matrix method based on the current values ​​of the equivalent material parameters; S3, determining whether the acoustic characteristic parameters meet the acoustic characteristic requirements; if so, outputting the current equivalent material parameters; otherwise, adjusting the equivalent material parameters within the preset range according to the constraints, and returning to S2 after adjustment. This invention realizes a numerical inversion method for the equivalent material parameters of a structural acoustic covering layer. This method solves the problem of simulation and prediction of the suppression effect of the acoustic covering layer on the active detection of targets, and improves the prediction technology for evaluating the effectiveness of structural acoustic covering layers.

Description

Technical Field

[0001] This invention relates to the field of acoustic coating technology, and in particular to a method and system for determining the equivalent material parameters of a structural acoustic coating. Background Technology

[0002] Currently, when studying structural acoustic coverings, they are usually considered equivalent to uniform multilayer coverings. The thickness, Young's modulus, Poisson's ratio, density, and other parameters of the multilayer coverings are the equivalent material parameters. By studying the equivalent material parameters, the acoustic properties of the structural acoustic coverings can be studied. Therefore, it is necessary to provide a scheme that can study the equivalent material parameters of structural acoustic coverings. Summary of the Invention

[0003] To solve the above-mentioned technical problems, or at least partially solve them, the present invention provides a method and system for determining the equivalent material parameters of a structural acoustic covering layer.

[0004] In a first aspect, the present invention provides a method for determining the equivalent material parameters of a structural acoustic covering layer, comprising:

[0005] S1. Set the acoustic characteristic requirements of the structural acoustic covering layer, set the value range and constraint conditions of the equivalent material parameters of the structural acoustic covering layer, and set the initial value of the equivalent material parameters;

[0006] S2. Based on the current value of the equivalent material parameters, the acoustic characteristic parameters that satisfy the value range and the preset constraint conditions are calculated using the transfer matrix method.

[0007] S3. Determine whether the acoustic characteristic parameters meet the acoustic characteristic requirements;

[0008] If so, output the current equivalent material parameters;

[0009] Otherwise, the equivalent material parameters are adjusted within the preset range according to the constraints, and the process returns to S2 after adjustment.

[0010] Secondly, the present invention provides a system for determining the equivalent material parameters of a structural acoustic covering layer, comprising:

[0011] The data setting module is used to execute S1, set the acoustic characteristic requirements of the structural acoustic covering layer, set the value range and constraint conditions of the equivalent material parameters of the structural acoustic covering layer, and set the initial value of the equivalent material parameters;

[0012] The parameter calculation module is used to execute S2, and calculate the acoustic characteristic parameters that satisfy the value range and the preset constraint conditions based on the current value of the equivalent material parameters using the transfer matrix method.

[0013] The parameter judgment module is used to execute S3 and determine whether the acoustic characteristic parameters meet the acoustic characteristic requirements; if so, the current equivalent material parameters are output; otherwise, the equivalent material parameters are adjusted within the preset range according to the constraint conditions, and after adjustment, the module returns to the parameter calculation module to execute S2.

[0014] The present invention provides a method and system for determining the equivalent material parameters of a structural acoustic covering layer. First, it sets the acoustic characteristic requirements of the structural acoustic covering layer, the range of values ​​for the equivalent material parameters, constraints, and initial values. Then, it calculates the acoustic characteristic parameters based on the initial values ​​and determines whether the calculated acoustic characteristic parameters meet the acoustic characteristic requirements. If not, the parameters are adjusted and iterated until the acoustic characteristic requirements are met, thus obtaining the equivalent material parameters that satisfy the acoustic characteristic requirements. Therefore, the present invention proposes a numerical inversion method for the equivalent material parameters of a structural acoustic covering layer. This method solves the problem of simulating and predicting the suppression effect of the acoustic covering layer on active target detection, and improves the prediction technology for evaluating the effectiveness of structural acoustic covering layers. Attached Figure Description

[0015] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 and Figure 2 This is a flowchart illustrating a method for determining the equivalent material parameters of a structural acoustic covering layer according to an embodiment of the present invention.

[0018] Figure 3 This is a schematic diagram of the structural acoustic covering layer in an embodiment of the invention;

[0019] Figure 4 This is a schematic diagram of the equivalent multilayer covering layer in the embodiment of the invention;

[0020] Figure 5 This is a schematic diagram illustrating the relationship between the structural acoustic covering layer and the incident sound wave in an embodiment of the invention.

[0021] Figure 6 This is a schematic diagram showing the periodic distribution of computing units in an embodiment of the invention;

[0022] Figure 7This is a spatial schematic diagram of the incident sound wave in an embodiment of the present invention;

[0023] Figure 8 This is a schematic diagram of a computing unit in an embodiment of the present invention;

[0024] Figure 9 This is a schematic diagram comparing the reflection coefficients of the structural acoustic covering layer with one layer and four layers in an embodiment of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] In a first aspect, the present invention provides a method for determining the equivalent material parameters of a structural acoustic covering layer, such as... Figure 1 and Figure 2 As shown, the method includes the following steps:

[0027] S1. Set the acoustic characteristic requirements of the structural acoustic covering layer, set the value range and constraint conditions of the equivalent material parameters of the structural acoustic covering layer, and set the initial value of the equivalent material parameters;

[0028] Understandably, parameters reflecting the acoustic properties of a structural acoustic covering layer can include reflection coefficient, transmission coefficient, and light absorption coefficient. This solution may specifically use reflection coefficient and transmission coefficient. Before implementing this solution, the acoustic property parameters can be measured. Then, this solution is used to equivalently represent the structural acoustic covering layer, and the acoustic property parameters are calculated based on the equivalent structure. If the calculated acoustic property parameters are close to the measured acoustic property parameters, it indicates that the values ​​of the equivalent material parameters in the equivalent structure are reasonable. Therefore, in specific implementation, the acoustic property requirements may include: the difference between the calculated acoustic property parameters and the measured acoustic property parameters is less than a preset value; the acoustic property parameters may include reflection coefficient and transmission coefficient.

[0029] When studying structural acoustic overlays, they can be considered equivalent to multiple uniform overlays, referred to as equivalent multilayer overlays. For example, Figure 3 The structural acoustic covering layer can be equivalent to Figure 4The diagram shows a four-layered capping layer. The thickness of each layer in the equivalent multilayer capping layer, as well as parameters such as Young's modulus, Poisson's ratio, and density, can all be used as equivalent material parameters. Each parameter has a corresponding range of values, and extensive experimental research suggests that the equivalent material parameters of each layer are more likely to meet acoustic performance requirements when certain parameter gradient requirements are satisfied. These parameter gradient requirements can be understood as constraints.

[0030] In specific implementation, the constraints may include: the impedance of the first layer of the equivalent multilayer cover layer corresponding to the structural acoustic cover layer matches the water impedance, and the loss factor of the first layer is determined by the high-frequency reflection coefficient; the sound velocity of each layer gradually decreases with frequency; the loss factor of each layer gradually increases with frequency; and the impedance of each layer changes monotonically at the same frequency. Here, the high-frequency reflection coefficient is the reflection coefficient corresponding to a sound wave at a preset high-frequency frequency, and the loss factor of the first layer is determined by this reflection coefficient.

[0031] Understandably, in this step, within the range of equivalent material parameters, initial values ​​are set for the equivalent material parameters to participate in subsequent steps.

[0032] S2. Based on the current value of the equivalent material parameters, the acoustic characteristic parameters that satisfy the value range and the preset constraint conditions are calculated using the transfer matrix method.

[0033] In practice, S2 can include the following steps:

[0034] S21. Divide the structural acoustic covering layer into computational units that are periodically distributed and infinitely extended along both the x and y directions;

[0035] To facilitate calculation and description, the structural acoustic covering layer can be divided into multiple computational units in the x and y directions. These computational units are periodically distributed and extend infinitely in the x and y directions, making each computational unit the smallest unit representing the structural acoustic covering layer. Based on Bloch theory, the computational scope is reduced to a finite region. Wave system expansion is used outside the computational unit, and the basis functions are constructed using the single moment method within the computational unit. Then, the basis functions are solved using the finite element method to obtain the acoustic characteristic parameters.

[0036] The acoustic covering material is a viscoelastic material, see [link / reference] Figure 6 The computational units are periodically distributed and extend infinitely in the x and y directions, with intervals of a and b between adjacent computational units, respectively. See also... Figure 5 Unit harmonic plane wave p in The wave is incident on water, with wave number k, and the time factor e is ignored. jωt See also Figure 7The angle between the incident direction of the sound wave and the z-axis is θ, and the angle between the projection of the incident direction of the sound wave onto the xy-plane and the x-axis is θ.

[0037] Since the computational units are periodically distributed and extend infinitely in the x and y directions, according to the Bloch theory of periodic physical fields, the sound pressure or displacement function F can be expressed by the following formula, which represents the periodic relationship between the various computational units:

[0038]

[0039] S22. The basis functions of any point within the computing unit are constructed using the basis function clusters of the upper and lower interfaces of the computing unit, and the boundary conditions of each order component of the basis functions are constructed; wherein, the basis functions are used to represent the sound pressure field or displacement field of the arbitrary point; the upper interface is the interface of the upper layer of the computing unit in contact with water, and the lower interface is the interface of the lower layer of the computing unit in contact with water.

[0040] For a computing unit, such as Figure 8 As shown, this space is divided into three regions along the z-axis. Regions I and III are semi-infinite media, and region II is a computational unit in the overlay layer. The upper interface of the computational unit is S. ab The lower screen is S und The four sides of the computing unit are S1, S2, S3, and S4.

[0041] For region I (the first region below), there are incident and reflected waves. Expanding the reflected wave into a Fourier series, the total sound field corresponding to the first region can be expressed as:

[0042]

[0043] For region III (i.e., the third region below), only transmitted waves exist, therefore the total sound field of the third region can be expressed as:

[0044]

[0045] In the above formula, m and n are orders, and p in For the sound field of the incident wave, p s For the sound field of the reflected wave, p t For the transmitted wave sound field, k mn 2 =|k| 2 -(2mπ / a+k x ) 2 -(2nπ / b+k y ) 2 V mnT is the amplitude of the (m,n)th order reflected wave. mn It is the amplitude of the (m,n)th order transmitted wave.

[0046] For region II, define a family of basis functions. In a fluid medium, it is the sound pressure field p; in an elastic medium, it is the displacement field u; and the upper interface S of the computational unit. ab With the lower interface S und Since the boundary conditions are different, to ensure the completeness of the basis functions, the family of basis functions is represented as:

[0047]

[0048] Among them, the basis function family of the upper interface The basis function family of the lower interface To calculate the field ψ (sound pressure field or displacement field) at any point in the element corresponding to the (m,n)th component of the basis function family, it can be represented by basis functions:

[0049]

[0050] In the formula, ψ(x,y,z) is the basis function corresponding to the point with coordinates (x,y,z) within the calculation unit. Let m be the (m, n)th order component of the basis function family of the upper interface. Let m be the (m, n)th order component of the basis function family of the lower interface. for The expansion coefficients, for The expansion coefficients.

[0051] It can be seen that the sound pressure field p and the displacement field u can both be represented by the aforementioned basis functions.

[0052] Each basis function component satisfies the Helmholtz equation and boundary conditions. If the computational unit is divided into four layers from top to bottom, the boundary conditions for each order component of the basis functions can include the following formulas:

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059]

[0060]

[0061] In the formula, S ab For the above interface, k mn 2 =|k| 2 -(2mπ / a+k x ) 2 -(2nπ / b+k y ) 2 , The magnitude of k is the wave number of the sound wave, and its direction is the incident direction of the sound wave. θ is the angle between the incident direction of the sound wave and the z-axis. Let be the angle between the projection of the incident sound wave onto the xy plane and the x-axis; a is the distance between adjacent computational units along the x-axis, and b is the distance between adjacent computational units along the y-axis; S und S1, S2, S3, and S4 are the four sides of the computing unit.

[0062] S23. Construct a first boundary condition corresponding to the continuous nodal pressure and a second boundary condition corresponding to the continuous normal vibration velocity of the mass point for the upper and lower interfaces of the computing unit.

[0063] Understandably, the upper and lower interfaces of the computational unit satisfy the conditions for continuous nodal sound pressure and continuous normal particle velocity. The boundary condition for continuous nodal sound pressure is the first boundary condition, and the boundary condition for continuous normal particle velocity is the second boundary condition.

[0064] The first boundary condition may include:

[0065]

[0066]

[0067] Since the upper and lower interfaces are composed of the same medium, the normal continuity of the particles is equivalent to the reciprocal continuity of the pressure. Therefore, the second boundary condition may include:

[0068]

[0069]

[0070] In the formula, R ab For S ab The set of nodes in the midplane; R und For S und The set of nodes in the midplane; p t p represents the transmitted sound field corresponding to the third region located above the upper interface. inp is the incident wave acoustic field in the first region below the lower interface. s The sound field is the reflected wave in the first region below the lower interface, and the sound wave is incident from the first region below the lower interface.

[0071] S24. Finite element formula for the coupling of fluid and elastic body;

[0072] In practical implementation, the finite element formula may include:

[0073]

[0074] In the formula, ω is the angular frequency, and ρ L K is the density of the fluid. L M is the stiffness matrix of the fluid. L Let K be the mass matrix of the fluid. S M is the stiffness matrix of the viscoelastic body. S Let L be the mass matrix of the viscoelastic body. 耦合 Let be the coupling matrix between the viscoelastic body and the fluid; u is the displacement matrix in the viscoelastic field, p is the pressure vector in the fluid field, and Q is the displacement vector in the fluid field. S Q is the nodal load matrix vector of the viscoelastic body. L is the nodal load matrix vector of the fluid.

[0075] Among them, u and p can be represented by the basis function ψ mentioned above.

[0076] S25. Based on the boundary conditions of each order component, the first boundary condition, and the second boundary condition, solve the basis function and the finite element formula to obtain the reflected wave amplitude and transmitted wave amplitude of each order in each layer of the calculation unit.

[0077] Understandably, p and u in the finite element formula are represented by the aforementioned basis function ψ. Then, the finite element formula is solved, and the solution process is constrained by the boundary conditions of each order component in the basis function, the first boundary condition, and the second boundary condition, thereby obtaining the amplitude V of each order plane wave. mn T mn In fact, the coefficients of the basis functions can also be calculated at the same time.

[0078] S26. Calculate the reflection coefficient of each layer based on the amplitude of the reflected wave at each order in each layer; calculate the transmission coefficient of each layer based on the amplitude of the transmitted wave at each order in each layer.

[0079] In practical implementation, the formula for calculating the reflection coefficient of each layer may include:

[0080]

[0081] In practical implementation, the formula for calculating the transmission coefficient of each layer may include:

[0082]

[0083] In the formula, V mn Let T be the amplitude of the reflected wave of the (m, n)th order in each layer. mn Let V be the amplitude of the transmitted wave of the (m, n)th order in each layer, V be the reflection coefficient of each layer, and T be the transmission coefficient of each layer.

[0084] At this point, the acoustic characteristic parameters of each layer are obtained.

[0085] S27. Based on the current values ​​of the equivalent material parameters of each layer and the projection coefficient and reflection coefficient of each layer, construct the third boundary conditions corresponding to the pressure continuity and particle velocity continuity between each layer.

[0086] Understandably, the third boundary condition is constructed based on the current values ​​of the equivalent material parameters and acoustic characteristic parameters of each layer. The third boundary condition reflects the pressure continuity characteristics and the particle velocity continuity characteristics between each layer.

[0087] S28. Based on the third boundary condition, the transfer matrices of each layer are concatenated to obtain the total transfer matrix.

[0088] S29. Calculate the corresponding total input impedance based on the total transfer matrix; and calculate the reflection coefficient and projection coefficient of the calculation unit based on the total input impedance.

[0089] Understandably, the calculation process for transmission parameters is similar, thus obtaining the acoustic characteristic parameters.

[0090] As can be seen, after calculating the acoustic characteristic parameters of each layer, the transfer matrices of each layer are connected according to the boundary conditions corresponding to the continuity of nodal pressure and particle velocity between each layer, so as to obtain the total transfer matrix of the multilayer structure. The input impedance of the entire layer system can be obtained from the boundary conditions of the interface on the last semi-infinite medium, and thus the acoustic characteristic parameters of the entire layer system can be obtained.

[0091] For example, the general process of S27 to S29 can be seen in the following flowchart:

[0092] Taking the nth layer as an example, the transfer matrix in the fluid and elastomer media layers is given, where the layer thickness and density are d and d, respectively. (n) and ρ (n) The subscripts S and T represent fluid and elastomeric media, respectively.

[0093] If the nth layer is a fluid medium, and there are longitudinal waves propagating in the positive z-direction and longitudinal waves propagating in the negative z-direction, the corresponding potential function can be expressed as:

[0094]

[0095] The sound pressure p in the layer (n) Normal velocity υ z (n) The relationship with the potential function is as follows:

[0096]

[0097] Based on the above formula, for the upper interface of the nth layer, z = d (n) (omitting factors) ),have:

[0098]

[0099] The lower interface of the nth layer, i.e., z = 0, has:

[0100]

[0101] In the formula, superscript (n+) and (n - ) Let represent the values ​​of the physical quantity at the upper and lower interfaces of the nth layer of medium, respectively. Based on the continuity condition of the upper and lower interfaces, we can obtain:

[0102]

[0103] In the formula, A S (n) Let be the transfer matrix of the fluid medium.

[0104] If the nth layer is an elastic medium, and longitudinal and transverse waves propagate along the positive z and negative z directions respectively, the corresponding potential functions are:

[0105]

[0106]

[0107] Where σ=k x =κ x , k and κ are the P-wave and S-wave wave numbers, respectively.

[0108] The particle velocity component at any point in the layer is:

[0109] υ y =0,

[0110] The stress tensor components are:

[0111] σ y =0,

[0112] Where μ and λ are Lamé constants, u x u z For displacement components:

[0113]

[0114] The expression above can be used to calculate υ. x υ z σ x and σ z .

[0115] When z = d, we can obtain:

[0116]

[0117] The coefficient matrix on the right-hand side of the equation is denoted as A4. (n) When z = 0, we have:

[0118]

[0119] We can obtain:

[0120]

[0121] The coefficient matrix on the right-hand side of the equation is denoted as B4. (n) Therefore:

[0122]

[0123] A T (n) is the transfer matrix of the elastic medium.

[0124] When solving for the reflection coefficient, the initial matrix needs to be determined first. If medium 1 is a fluid, then:

[0125]

[0126] If the medium is an elastic body:

[0127]

[0128] In the formula, D represents the independent variable matrix, and M... (n) =A (n) ·M (n-1) A (n) This is the transfer matrix.

[0129] If the incident medium n+1 is a semi-infinite fluid medium, then at its lower interface:

[0130]

[0131] A is the transfer matrix of the fluid or elastic medium.

[0132] The calculated total input impedance can be:

[0133]

[0134] Note: Impedance = Sound pressure / Vibration velocity, because Given independent variable matrices, after division and cancellation, the impedance can be expressed as a matrix. The (1,1)th order variable is divided by the (2,1)th order variable.

[0135] Therefore, the reflection coefficient V can be obtained:

[0136]

[0137] Among them, Z (n+1) =ρ (n+1) c (n+1) / cosθ (n+1) .

[0138] S3. Determine whether the acoustic characteristic parameters meet the acoustic characteristic requirements;

[0139] If so, output the current equivalent material parameters;

[0140] Otherwise, the equivalent material parameters are adjusted within the preset range according to the constraints, and the process returns to S2 after adjustment.

[0141] Understandably, if the calculated acoustic characteristic parameters meet the acoustic characteristic requirements, it means that the equivalent material parameters at this time meet the requirements for equivalence of the covering layer, and the equivalent material parameters at this time can be used as the final equivalent material parameters, thus exiting the iteration process. If the calculated acoustic characteristic parameters do not meet the acoustic characteristic requirements, it means that the equivalent material parameters at this time do not meet the requirements for equivalence of the covering layer, and adjustments need to be made based on the current values ​​before entering the next iteration process.

[0142] Understandably, this invention, based on the acoustic characteristics of the actual covering layer, treats the covering layer as an equivalent homogeneous viscoelastic medium. According to the acoustic characteristic requirements, a parameter matching search method is used to obtain the thickness of each layer and parameters such as the equivalent density, Young's modulus, loss factor, and Poisson's ratio of each layer. In other words, constructing a multi-layered covering layer with similar acoustic characteristics based on the acoustic parameters measured in a laboratory acoustic tube is the inverse problem. The parameters of each layer in the acoustic covering layer are obtained using the parameter matching search method according to the control requirements of the acoustic characteristics. This invention can construct multi-layered acoustic covering layers with similar acoustic characteristics in a single frequency or broadband range, obtaining an equivalent characterization method for acoustic covering layers in low-frequency sound scattering problems using equivalent material parameters.

[0143] Understandably, this invention uses the finite element method to solve the basis functions because the finite element method can solve arbitrary boundary problems and the sound propagation mechanism is clear.

[0144] Understandably, based on physical laws, the value ranges of each equivalent material parameter are set, and these parameters must meet certain conditions, such as the variation law of the loss factor and the variation law of the impedance. Parameters that meet the conditions are searched based on the value range and constraints. Then, it is determined whether the calculated acoustic characteristic parameters meet the acoustic characteristic requirements. If not, further corrections are made based on the current values ​​of each parameter. Through continuous correction, parameters that finally meet the acoustic characteristic requirements are obtained.

[0145] Understandably, this invention is based on a theoretical prediction model of the low-frequency acoustic target intensity of an elastic shell laminate with an acoustic covering layer, and proposes a numerical inversion method for the equivalent material parameters of the structural acoustic covering layer. One of the key aspects of this invention is the numerical inversion method for the equivalent material parameters of the structural acoustic covering layer, proposed in conjunction with simulation technology for the low-frequency acoustic target intensity of a target with an acoustic covering layer. This method is a crucial element for predicting the low-frequency acoustic target intensity of a target with an acoustic covering layer. The numerical inversion method for the equivalent material parameters of the structural acoustic covering layer provided by this invention solves the problem of simulating and predicting the suppression effect of the structural acoustic covering layer on active target detection, thus improving the prediction technology for evaluating the effectiveness of the structural acoustic covering layer.

[0146] This invention matches the material parameters of the acoustic covering layer based on the gradient requirements (i.e., constraints), value range, and acoustic characteristic requirements of the uniform multilayer acoustic covering layer. For example, the covering layer material is divided into one layer and four layers. Based on the reflection characteristic requirements, the parameter matching method is used to obtain the material parameters of each layer, as shown in Table 1 below. A comparison of the reflection coefficients of the anechoic tiles in the cases of one layer and four layers can be found in [reference missing]. Figure 9 The results show that, using parameter matching technology, equivalent material parameters that meet the requirements for controlling the acoustic properties of the structure can be obtained. The range of material parameters that meet the requirements varies depending on the backing structure.

[0147] Table 1. Equivalent material parameters for 1-layer and 4-layer structures

[0148]

[0149] In a second aspect, the present invention provides a system for determining the equivalent material parameters of a structural acoustic covering layer, comprising:

[0150] The data setting module is used to execute S1, set the acoustic characteristic requirements of the structural acoustic covering layer, set the value range and constraint conditions of the equivalent material parameters of the structural acoustic covering layer, and set the initial value of the equivalent material parameters;

[0151] The parameter calculation module is used to execute S2, and calculate the acoustic characteristic parameters that satisfy the value range and the preset constraint conditions based on the current value of the equivalent material parameters using the transfer matrix method.

[0152] The parameter judgment module is used to execute S3 and determine whether the acoustic characteristic parameters meet the acoustic characteristic requirements; if so, the current equivalent material parameters are output; otherwise, the equivalent material parameters are adjusted within the preset range according to the constraint conditions, and after adjustment, the module returns to the parameter calculation module to execute S2.

[0153] It is understood that explanations, examples, specific implementation methods, and beneficial effects of the system provided in this aspect can be found in the corresponding content in the first aspect, and will not be repeated here.

[0154] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0155] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0156] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as RON / RAN, magnetic disk, optical disk), and includes several instructions to cause a terminal (which may be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in the various embodiments of the present invention.

[0157] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for determining the equivalent material parameters of a structural acoustic covering layer, characterized in that, include: S1. Set the acoustic characteristic requirements of the structural acoustic covering layer, set the value range and constraint conditions of the equivalent material parameters of the structural acoustic covering layer, and set the initial value of the equivalent material parameters; S2. Based on the current value of the equivalent material parameters, calculate the acoustic characteristic parameters that satisfy the value range and the constraint conditions using the transfer matrix method; S3. Determine whether the acoustic characteristic parameters meet the acoustic characteristic requirements; If so, output the current equivalent material parameters; Otherwise, within the range of values, the equivalent material parameters are adjusted according to the constraints, and the process returns to S2 after adjustment; The calculation of acoustic characteristic parameters that satisfy the value range and the constraint conditions based on the current value of the equivalent material parameters using the transfer matrix method includes: The structural acoustic covering layer is divided into computational units that are periodically distributed and infinitely extended along both the x and y directions; The basis functions of any point within the computing unit are constructed using the basis function clusters of the upper and lower interfaces of the computing unit, and the boundary conditions of each order component of the basis functions are constructed; wherein, the basis functions are used to represent the sound pressure field or displacement field at the arbitrary point; the upper interface is the interface of the upper layer of the computing unit in contact with water, and the lower interface is the interface of the lower layer of the computing unit in contact with water. For the upper and lower interfaces of the computing unit, construct a first boundary condition corresponding to the continuous nodal pressure and a second boundary condition corresponding to the continuous normal vibration velocity of the mass points. Constructing the finite element formula for fluid-elastic coupling; Based on the boundary conditions of each order component, the first boundary condition, and the second boundary condition, the basis functions and the finite element formula are solved to obtain the reflected wave amplitude and transmitted wave amplitude of each order in each layer of the calculation unit. The reflection coefficient of each layer is calculated based on the amplitude of the reflected wave at each order in each layer; the transmission coefficient of each layer is calculated based on the amplitude of the transmitted wave at each order in each layer. Based on the current values ​​of the equivalent material parameters of each layer and the transmission and reflection coefficients of each layer, construct the third boundary conditions corresponding to the pressure continuity and particle velocity continuity between each layer. Based on the third boundary condition, the transfer matrices of each layer are concatenated to obtain the total transfer matrix; Based on the total transfer matrix, the corresponding total input impedance is calculated; and based on the total input impedance, the reflection coefficient and transmission coefficient of the calculation unit are calculated.

2. The method according to claim 1, characterized in that, The constraints include: the impedance of the first layer of the equivalent multilayer cover corresponding to the structural acoustic cover layer is matched with the water impedance, and the loss factor of the first layer is determined by the high-frequency reflection coefficient; the sound velocity of each layer gradually decreases with frequency; the loss factor of each layer gradually increases with frequency; and the impedance of each layer changes monotonically at the same frequency.

3. The method according to claim 1, characterized in that, The acoustic characteristic requirements include: the difference between the calculated acoustic characteristic parameters and the measured acoustic characteristic parameters is less than a preset value; the acoustic characteristic parameters include the reflection coefficient and the transmission coefficient.

4. The method according to claim 1, characterized in that, The basis functions for any point within the computational unit include: In the formula, The basis functions are the points with coordinates (x, y, z) within the computational unit. Let m be the (m, n)th order component of the basis function family of the upper interface. Let m be the (m, n)th order component of the basis function family of the lower interface. for The expansion coefficients, for The expansion coefficients.

5. The method according to claim 4, characterized in that, If the computational unit is divided into four layers from top to bottom, the corresponding boundary conditions for each order component of the basis function include: In the formula, The upper interface is mentioned above. , , , The magnitude is the wave number of the sound wave, and the direction is the incident direction of the sound wave. Let be the angle between the incident direction of the sound wave and the z-axis. denoted as , where is the angle between the projection of the incident sound wave onto the xy plane and the x-axis; a is the distance between adjacent computational units along the x-axis, and b is the distance between adjacent computational units along the y-axis. The lower interface; , , , These are the four sides of the computing unit.

6. The method according to claim 4, characterized in that, The finite element formula includes: In the formula, Angular frequency, For the density of the fluid, Let be the stiffness matrix of the fluid. The mass matrix of the fluid. Here is the stiffness matrix of the viscoelastic body. Here is the mass matrix of the viscoelastic body. This represents the coupling matrix between the viscoelastic body and the fluid. Let be the displacement matrix in a viscoelastic field. This is the pressure vector in the fluid field. The nodal load matrix vector of the viscoelastic body. is the nodal load matrix vector of the fluid.

7. The method according to claim 4, characterized in that, The first boundary conditions include: The second boundary conditions include: In the formula, for The set of nodes in the midplane; for The set of nodes in the midplane; This refers to the transmitted sound field corresponding to the third region located above the upper interface. The incident wave acoustic field in the first region below the lower interface. The sound field is the reflected wave in the first region below the lower interface, and the sound wave is incident from the first region below the lower interface.

8. The method according to claim 7, characterized in that, The formula for calculating the reflection coefficient of each layer includes: The formula for calculating the transmission coefficient of each layer includes: In the formula, Let (m, n) be the amplitude of the reflected wave of the (m, n)th order in each layer. Let (m, n) be the amplitude of the transmitted wave of order (m, n) in each layer. The reflection coefficient of each layer, is the transmission coefficient of each layer.

9. A system for determining the equivalent material parameters of a structural acoustic covering layer, characterized in that, Used to implement the method according to any one of claims 1 to 8.

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