Sound box body design method based on airflow simulation

Abstract

The invention discloses a sound box body design method based on airflow simulation. The method comprises the steps that a geometric model used for simulation of the loudspeaker box is established, the loudspeaker box comprises a box body, a loudspeaker and an echo tube, the box body is provided with a first mounting hole and a second mounting hole which are communicated with an inner cavity of the box body, the loudspeaker is mounted in the first mounting hole and seals the first mounting hole, the echo tube is arranged in the box body, and the second mounting hole is communicated with the second mounting hole; the outer end of the echo tube is communicated with the outside through the second mounting hole; the geometric model comprises a vibrating diaphragm of the loudspeaker, a fluid domain in the box body and a fluid domain above the vibrating diaphragm; a simulation model is established according to the geometric model, the selected research type is a time domain, a fluid domain is set as air, a'dynamic grid 'physical field and a'turbulent flow, k-epsilon' physical field are set, and grids are drawn and solved. According to the method, airflow flowing of the sound box body is researched by using a dynamic grid technology, accurate and comprehensive airflow flowing information can be provided, only dynamic grids and fluid physics field coupling are needed, and the calculation cost is saved.

Description

Technical Field

[0001] The invention belongs to the field of vehicle-mounted speakers and relates to a speaker box design method based on airflow simulation. Background Art

[0002] The in-car audio system is an important part of the car's smart cockpit. It is responsible for the sound reproduction of the vehicle area (especially the cabin) for entertainment or remote calls, etc. The performance is directly related to the restoration of the in-car audio and the listening experience. Among them, the car audio, especially the car bass speaker, is one of the important components of the car audio system. The car speaker usually includes a box and a speaker installed in the box. During the operation of the speaker, the vibration of the diaphragm will push the surrounding air, forming sound waves and propagating outward. The airflow velocity distribution inside the speaker is one of the key factors affecting the sound quality and efficiency of the car audio. In the process of the diaphragm vibrating to generate sound waves and propagate outward, the flow of air in the internal cavity of the speaker is extremely complex. Especially at high power output, the rapid change of airflow velocity may cause turbulence and eddy current phenomena, which will not only cause energy loss, but also generate noise and affect the sound quality.

[0003] At present, the research and simulation analysis of the airflow velocity of loudspeakers mainly rely on two methods: experimental measurement and numerical simulation. Although experimental measurement can directly obtain real data, it is costly, time-consuming and difficult to cover all working conditions. Numerical simulation methods have the advantages of low cost, high efficiency and strong repeatability, and have become an important tool for studying the airflow velocity of loudspeakers. One of the methods is the fluid-solid coupling simulation method, which can analyze and predict the interaction between fluids and solids. However, the fluid-solid coupling simulation method requires the coupling of solid mechanical physics and fluid physics, which has high requirements on computing time and computer memory.

[0004] The above information disclosed in the Background section is only for enhancement of understanding of the background of the present application and therefore it may contain information that does not constitute the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0005] In view of this, the present invention provides a speaker cabinet design method based on airflow simulation, which uses dynamic mesh technology to study the airflow of the speaker cabinet. This method can provide accurate and comprehensive airflow information and provide strong theoretical support for improving the design of the speaker cabinet. In particular, this method only requires the coupling of the dynamic mesh and the fluid physical field, saving the calculation cost.

[0006] The present invention adopts the following technical solution:

[0007] A method for designing a speaker box based on airflow simulation comprises the following steps:

[0008] S1. Establishing a geometric model of a sound box for simulation, wherein the sound box includes a box body, a loudspeaker and an echo tube, wherein the box body is provided with a first mounting hole and a second mounting hole communicating with the inner cavity thereof, the loudspeaker is installed in the first mounting hole and the first mounting hole is closed, the echo tube is arranged in the box body, and the outer end of the echo tube communicates with the outside through the second mounting hole; the geometric model includes a diaphragm of the loudspeaker, a fluid domain inside the box body, and a fluid domain above the diaphragm;

[0009] S2. Establish a simulation model according to the geometric model, wherein the research type is selected as time domain, the fluid domain is set as air, the "dynamic mesh" physical field and the "turbulence, k-ε" physical field are set, and the mesh is drawn and solved;

[0010] In step S2, the effective radiation part of the diaphragm is used as the grid velocity boundary of the "moving grid" physical field and the velocity inlet of the "turbulence, k-ε" physical field; the fixed hanging edge of the diaphragm is used as the fixed boundary of the "moving grid" physical field; and the second mounting hole is used as the pressure outlet of the "turbulence, k-ε" physical field.

[0011] In a preferred embodiment, in step S2, when setting the "moving mesh" physical field, the entire area of ​​the geometric model established in step S1 is selected as the deformation domain.

[0012] In a preferred embodiment, in step S2, when setting the "turbulence, k-ε" physical field, the diaphragm and the fluid domain inside the box are selected.

[0013] In a more preferred embodiment, when setting the "Turbulence, k-ε" physics field, compressibility selects compressible flow.

[0014] In a preferred embodiment, in step S2, the parameters required for the box airflow simulation are set, including the operating frequency, the angular frequency corresponding to the operating frequency, the time period corresponding to the operating frequency, the end time of the transient simulation output time step, and the vibration speed of the diaphragm.

[0015] In a preferred embodiment, in step S2, the airflow velocity field distribution diagram and the vorticity size distribution diagram are output after the solution.

[0016] In a more preferred embodiment, the speaker cabinet design method further includes step S3: adjusting the size parameters of the cabinet according to the airflow velocity field distribution and the vorticity size distribution; thereafter, repeating the above steps S1 and S2.

[0017] In a further preferred embodiment, the dimension parameters of the box include at least one of the length, width, height, opening area and position of the first mounting hole, opening area and position of the second mounting hole, and shape of the echo tube.

[0018] In a preferred embodiment, in step S1, the height of the fluid domain above the diaphragm is greater than the maximum displacement of the diaphragm and less than 5 times of the maximum displacement.

[0019] In a specific and preferred embodiment, step S2 specifically includes:

[0020] S201. In the multiphysics simulation software, set the spatial dimension to 3D, select the physics interfaces as "Turbulence, k-ε" and "Moving Mesh", and select the study type as time domain.

[0021] S202, importing the geometric model in step S1;

[0022] S203, setting the fluid domain to air;

[0023] S204, input parameters required for loudspeaker airflow simulation, including operating frequency ff, angular frequency omega corresponding to the operating frequency ff, time period T0 corresponding to the operating frequency ff, end time Tend of transient simulation output time step, and vibration speed V0 of loudspeaker diaphragm;

[0024] S205, set "dynamic mesh": ① "deformation domain" selects the entire area of ​​the geometric model established in step S1; ② "specified mesh speed" is the normal direction speed of the diaphragm, which is set to V0*cos(omega*t), and the boundary selects the effective radiation part of the diaphragm; ③ "fixed boundary" selects the fixed hanging edge of the diaphragm; wherein, the diaphragm is fixed to the bracket of the speaker or the surface of the box around the first mounting hole through the fixed hanging edge;

[0025] S206, set the "Turbulence, k-ε" physical field interface: ① "Turbulence, k-ε" fluid domain selects the diaphragm and the fluid domain inside the box; ② Compressibility selects "Compressible Flow"; ③ "Inlet" selects the effective radiation part of the diaphragm, selects the velocity inlet, and gives the same velocity conditions as in the "Moving Mesh" setting. ④ "Outlet": select the pressure outlet, and the boundary selects the second mounting hole;

[0026] S207, drawing a grid;

[0027] S208, solving and post-processing, including: setting the output time step in "Research->Transient", calculating, and post-processing the simulation results after the calculation is completed, and outputting the airflow velocity field distribution diagram and the vorticity size distribution diagram.

[0028] The present invention adopts the above scheme and has the following advantages:

[0029] The speaker cabinet design method of the present invention uses the dynamic mesh technology to couple the fluid physical field to study the airflow of the speaker cabinet, which can provide accurate and comprehensive airflow information, provide strong theoretical support for improving the speaker cabinet design, and can easily adjust the speaker cabinet parameters and quickly simulate and verify their effects. In addition, the method only requires the coupling of the dynamic mesh and the fluid physical field, and does not need to include the "solid mechanics" physical field, saving calculation costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solution of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0031] Figure 1 The figure is a flow chart of a cabinet design method according to an embodiment of the present invention.

[0032] Figure 2 Schematic diagram of a geometric model of a sound box according to an embodiment of the present invention.

[0033] Figure 3 The present invention is a simulated mesh model of a sound system according to an embodiment of the present invention.

[0034] Figure 4 The "Moving Mesh" velocity boundary and the "Turbulent, k-ε" velocity inlet for the mesh model are shown.

[0035] Figure 5 The "moving mesh" fixed boundaries of the mesh model are shown.

[0036] Figure 6 The "Turbulent Flow, k-ε" fluid domain of the mesh model is shown.

[0037] Figure 7 The "Turbulent Flow, k-ε" pressure outlet for the mesh model is shown.

[0038] Figure 8 and Fig. 9 This is the fluid velocity field distribution diagram.

[0039] Fig.10 This is the distribution diagram of fluid vortex size. DETAILED DESCRIPTION

[0040] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0041] Figure 1 The structure of the object to be processed (speaker, typically a car bass speaker) can be found in Figures 2 to 7 This design method is a simulation method that couples the speaker diaphragm motion with the fluid through dynamic mesh technology. This method does not need to include the "solid mechanics" physical field, further saving computing costs.

[0042] Combination Figures 2 to 7 As shown, the sound box includes a box body 1, a loudspeaker and an echo tube 3. The box body 1 is provided with a first mounting hole 11 and a second mounting hole 12 which are connected to its inner cavity. The loudspeaker is installed in the first mounting hole 11 and closes the first mounting hole 11. The echo tube 3 is arranged in the box body 1, and the outer end of the echo tube 3 is connected to the outside through the second mounting hole 12. The box body 1 includes a top plate, a side plate and a bottom plate. An inner cavity surrounded by the top plate, the side plate and the bottom plate is formed in the box body 1. The sound box is an elongated sound box. In one embodiment, the aspect ratio L / W of the box body 1 satisfies the following condition: 1<L / W≤10. The width of the top of the box body 1 is greater than the width of the bottom. Furthermore, the width of the box body 1 gradually decreases from top to bottom.

[0043] The first mounting hole 11 is provided with a speaker and is closed by the speaker; the second mounting hole 12 is used to set the echo tube 3, so it is connected to the outside. Therefore, except for the second mounting hole 12 that is connected to the outside atmosphere, the other boundaries of the inner cavity of the box body 1 are closed boundaries and are closed by the box body 1 or the speaker.

[0044] The loudspeaker has a diaphragm 2, and the diaphragm 2 blocks the first mounting hole 11. In order to conveniently display the position of the diaphragm 2, the internal structure of the loudspeaker (voice coil, positioning support plate and magnetic circuit system, etc.) is not shown. The loudspeaker is a dynamic loudspeaker. The diaphragm 2 has an effective radiation part that can be elastically deformed and a fixed suspension 21 surrounding the effective radiation part. The fixed suspension 21 is connected to the box 1 (the hole wall or outer surface surrounding the second mounting hole 12) or the bracket of the loudspeaker. When the loudspeaker is working, as the diaphragm 2 vibrates, it causes the air in the inner cavity to vibrate and form an airflow. In the specific example of the diaphragm 2, the diaphragm 2 includes a cone, and the above-mentioned effective radiation part includes the cone, that is, the part of the diaphragm 2 that participates in the vibration is its effective radiation part; components that do not participate in the vibration, such as the fixed suspension 21, are not included in the effective radiation part.

[0045] The echo tube 3 is a hollow tubular component with both ends open, which is used to guide and realize the gas flow between the inner cavity and the external atmosphere. In this embodiment, the echo tube 3 is located in the inner cavity, and the echo tube 3 also has an outer end connected to the second mounting hole 12 and an inner end far from the second mounting hole 12. The outer end of the echo tube 3 extends from the second mounting hole 12 into the inner cavity. The length of the echo tube 3 is preferably greater than half of the height, width or length of the box body 1.

[0046] Reference Figure 1 As shown, the speaker box design method includes the following steps:

[0047] S1. Establish a geometric model of the speaker for simulation, which includes the diaphragm 2 of the speaker (which can be drawn into a sheet), the fluid domain inside the box 1 (considering the echo tube 3, the fluid domain inside the box 1 needs to remove the tube wall part of the echo tube 3) and the fluid domain 4 above the diaphragm 2;

[0048] S2. Establish a simulation model based on the geometric model, wherein the research type is selected as time domain, the fluid domain is set to air, the "dynamic mesh" physical field and the "turbulence, k-ε" physical field are set, the mesh is drawn and the solution is obtained;

[0049] Determine whether the simulation results after solution and post-processing meet the requirements. If so, end the simulation; if not, adjust the box parameters and return to step S1, repeat steps S1 and S2 until a simulation result that meets the requirements is obtained, and use the box parameters corresponding to the simulation result as the final parameters to obtain the optimized final box shape.

[0050] In step S1 , the height of the fluid domain 4 above the diaphragm 2 is greater than the maximum displacement of the diaphragm 2 and less than 5 times of the maximum displacement.

[0051] The physical field is set according to the working principle of the speaker and the relevant theory of fluid. "Dynamic mesh" needs to set the free deformation domain, specify the mesh speed, and fix the boundary. "Turbulence, k-ε" needs to set its compressibility and the inlet and outlet of the fluid. Step S2 specifically includes:

[0052] S201. In the multiphysics simulation software, set the spatial dimension to 3D, select the physics interfaces as "Turbulence, k-ε" and "Moving Mesh", and select the study type as time domain.

[0053] S202, importing the geometric model in step S1;

[0054] S203, setting the fluid domain to air;

[0055] S204, input parameters required for loudspeaker airflow simulation, including operating frequency ff, angular frequency omega corresponding to the operating frequency ff, time period T0 corresponding to the operating frequency ff, end time Tend of transient simulation output time step, and vibration speed V0 of loudspeaker diaphragm;

[0056] S205, set "dynamic mesh": ① "deformation domain" selects the entire area of ​​the geometric model established in step S1; ② "specify mesh speed" is the normal direction speed of the diaphragm, which is set to V0*cos(omega*t), and the boundary selects the effective radiation part of the diaphragm; ③ "fixed boundary" selects the fixed suspension edge of the diaphragm; wherein the diaphragm is fixed to the bracket of the speaker or the surface of the box around the first mounting hole through the fixed suspension edge;

[0057] S206, set the "Turbulence, k-ε" physical field interface: ① "Turbulence, k-ε" fluid domain selects the diaphragm and the fluid domain 4 inside the box; ② Compressibility selects "Compressible Flow"; ③ "Inlet" selects the effective radiation part of the diaphragm, selects the velocity inlet, and gives the same velocity conditions as in the "Moving Mesh" setting. ④ "Outlet": select the pressure outlet, and the boundary selects the second mounting hole;

[0058] S207, draw the grid; directly use the COMSOL automatic grid division function, control the grid through the physical field and select the appropriate unit size. It should be noted that the grid should not be too coarse;

[0059] S208, solving and post-processing, including: setting the output time step in "Research->Transient", calculating, and after the calculation is completed, post-processing the simulation results, outputting the airflow velocity field distribution diagram and the vortex size distribution diagram. Among them, the output time step of the transient simulation is set, and the time interval of the output time step cannot be too large.

[0060] In step S3, the size parameters of the box include at least one of the length, width, height of the box, the opening area and position of the first mounting hole, the opening area and position of the second mounting hole, and the shape of the echo tube.

[0061] Simulation Example

[0062] In engineering applications, the model of the sound system to be analyzed is reasonably simplified to save computing power and adapt the calculation model. For example, the bracket, magnetic circuit and other components of the speaker with non-parametric vibration are omitted.

[0063] like Figure 1 As shown, this simulation example performs COMSOL simulation on the airflow of the speaker, including the following steps.

[0064] (1) Geometry drawing: Figure 2It is a model diagram used to simulate the airflow of a speaker, including the diaphragm body, the fluid domain inside the box, and the fluid domain above the speaker diaphragm.

[0065] (2) Establishing COMSOL simulation model:

[0066] 1) Open COMSOL Multiphysics and add the spatial dimension, physics interface, and study type. In this case, the spatial dimension is 3D, the physics interface is "Turbulence, k-ε", "Moving Mesh", and the study type is time domain.

[0067] 2) Import the geometric figures in "Geometry" and process them in COMSOL if necessary.

[0068] 3) Set the material parameters and set the fluid domain to air (built-in).

[0069] 4) Input the parameters required for the loudspeaker airflow simulation, including the operating frequency ff, the angular frequency omega corresponding to the operating frequency ff, the time period T0 corresponding to the operating frequency ff, the end time Tend of the transient simulation output time step, and the vibration speed V0 of the loudspeaker diaphragm.

[0070] 5) Set "Dynamic Mesh": ① Select the geometry (all) in "Deformation Domain", such as Figure 3 ② "Specify grid speed" specifies the normal velocity of the diaphragm, which is set to V0*cos(omega*t), and the boundary selection is as follows Figure 4 The blue area is shown. ③ "Fixed Boundary" selection Figure 5 blue area.

[0071] 6) Set up the "Turbulence, k-ε" physics interface: ① Select the "Turbulence, k-ε" fluid domain as follows Figure 6 ② Select "Compressible flow (Ma<0.3)" for compressibility ③ Select "Inlet" Figure 4 In the blue area, select the velocity inlet and give the same velocity conditions as in the “Moving Mesh” setting. ④ “Outlet”: Select the pressure outlet and the boundary selection is as follows: Figure 7 shown.

[0072] 7) Draw the mesh. Directly use the COMSOL automatic meshing function.

[0073] 8) Solution and post-processing

[0074] a) Set the output time step in "Study->Transient". The output time interval cannot be too large. In this case, it is set to T0 / 50.

[0075] b) Click Calculate.

[0076] c) After the calculation is completed, the simulation results are post-processed and the airflow velocity field diagram (such as Figure 8 and Fig. 9 ) and vorticity size diagram (as shown in Fig.10 shown).

[0077] Post-process the simulation results and determine whether the design needs to be optimized. If optimization is required, repeat the above steps and compare the simulation results to determine whether the new optimized design is feasible.

[0078] The above method can optimize the shape design of the speaker box in the early stage of product design by simulating and modeling the speaker airflow, reducing trial and error time and cost expenditure. In addition, the simulation model is simplified, which greatly reduces the simulation time and calculation difficulty while ensuring the calculation accuracy. This method does not need to include the "solid mechanics" physical field, further saving calculation costs.

[0079] As shown in this specification and claims, the terms "comprises" and "includes" only indicate the inclusion of explicitly identified steps and elements, and these steps and elements do not constitute an exclusive list, and the method or device may also include other steps or elements.

[0080] It is further understood that in the present disclosure, "plurality" refers to two or more than two, and other quantifiers are similar thereto.

[0081] It is further understood that the terms "first", "second", etc. are used to describe various information, but such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other, and do not indicate a specific order or degree of importance. In fact, the expressions "first", "second", etc. can be used interchangeably. For example, without departing from the scope of the present disclosure, the first information can also be referred to as the second information, and similarly, the second information can also be referred to as the first information.

[0082] The above embodiment is only for illustrating the technical concept and features of the present invention, and is a preferred embodiment. Its purpose is to enable people familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention.

Claims

1. A method for designing a speaker box based on airflow simulation, characterized in that: The steps include: S1. Establishing a geometric model of a sound box for simulation, wherein the sound box includes a box body, a speaker and an echo tube, wherein the box body is provided with a first mounting hole and a second mounting hole communicating with the inner cavity thereof, the speaker is installed in the first mounting hole and the first mounting hole is closed, the echo tube is arranged in the box body, and the outer end of the echo tube is communicated with the outside through the second mounting hole; the geometric model includes a diaphragm of the speaker, a fluid domain inside the box body, and a fluid domain above the diaphragm; S2. Establish a simulation model according to the geometric model, wherein the research type is selected as time domain, the fluid domain is set to air, the "dynamic mesh" physical field and the "turbulence, k-ε" physical field are set, and the mesh is drawn and solved; In step S2, the effective radiation part of the diaphragm is used as the grid velocity boundary of the "moving grid" physical field and the velocity inlet of the "turbulence, k-ε" physical field; the fixed hanging edge of the diaphragm is used as the fixed boundary of the "moving grid" physical field; and the second mounting hole is used as the pressure outlet of the "turbulence, k-ε" physical field.

2. The method for designing a speaker box according to claim 1, characterized in that: In step S2, when setting the "dynamic mesh" physical field, the entire area of ​​the geometric model established in step S1 is selected as the deformation domain.

3. The method for designing a speaker box according to claim 1 or 2, characterized in that: In step S2, when setting the "turbulence, k-ε" physical field, the diaphragm and the fluid domain inside the box are selected.

4. The method for designing a speaker box according to claim 3, characterized in that: When setting up the "Turbulence, k-ε" physics, select Compressible flow for Compressibility.

5. The method for designing a speaker box according to claim 1, characterized in that: In step S2, the parameters required for the box airflow simulation are set, including the operating frequency, the angular frequency corresponding to the operating frequency, the time period corresponding to the operating frequency, the end time of the transient simulation output time step, and the vibration speed of the diaphragm.

6. The method for designing a speaker box according to claim 1, characterized in that: In step S2, after solving, the airflow velocity field distribution diagram and the vorticity size distribution diagram are output.

7. The method for designing a speaker box according to claim 6, characterized in that: The speaker box design method further includes step S3: adjusting the size parameters of the box according to the airflow velocity field distribution and the vorticity size distribution; thereafter, repeating the above steps S1 and S2.

8. The method for designing a speaker box according to claim 7, characterized in that: The size parameters of the box include at least one of the length, width, height, opening area and position of the first mounting hole, opening area and position of the second mounting hole, and shape of the echo tube.

9. The method for designing a speaker box according to claim 1, characterized in that: In step S1, the height of the fluid domain above the diaphragm is greater than the maximum displacement of the diaphragm and less than 5 times of the maximum displacement.

10. The method for designing a speaker box according to claim 1, characterized in that: Step S2 specifically includes: S201. In the multiphysics simulation software, set the spatial dimension to 3D, select the physics interfaces as "Turbulence, k-ε" and "Moving Mesh", and select the study type as time domain. S202, importing the geometric model in step S1; S203, setting the fluid domain to air; S204, input parameters required for loudspeaker airflow simulation, including operating frequency ff, angular frequency omega corresponding to the operating frequency ff, time period T0 corresponding to the operating frequency ff, end time Tend of transient simulation output time step, and vibration speed V0 of loudspeaker diaphragm; S205, set "dynamic mesh": ① "deformation domain" selects the entire area of ​​the geometric model established in step S1; ② "specified mesh speed" is the normal direction speed of the diaphragm, which is set to V0*cos(omega*t), and the boundary selects the effective radiation part of the diaphragm; ③ "fixed boundary" selects the fixed hanging edge of the diaphragm; wherein, the diaphragm is fixed to the bracket of the speaker or the surface of the box around the first mounting hole through the fixed hanging edge; S206, set the "Turbulence, k-ε" physical field interface: ① "Turbulence, k-ε" fluid domain selects the diaphragm and the fluid domain inside the box; ② Compressibility selects "Compressible Flow"; ③ "Inlet" selects the effective radiation part of the diaphragm, selects the velocity inlet, and gives the same velocity conditions as in the "Moving Mesh" setting; ④ "Outlet": selects the pressure outlet, and the boundary selects the second mounting hole; S207, drawing a grid; S208, solving and post-processing, including: setting the output time step in "Research->Transient", calculating, and after the calculation is completed, post-processing the simulation results to output the airflow velocity field distribution diagram and the vorticity size distribution diagram.

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