CN102004823A - Numerical value simulation method of vibration and acoustic characteristics of speaker - Google Patents

Abstract

The invention provides a numerical value simulation method of the vibration and acoustic characteristics of a speaker. The method comprises the following steps of: firstly, drawing a 3D (Three-Dimensional) geometric model diagram of the speaker by using 3D drawing software; then, adding the 3D geometric model diagram of the speaker to meshing software to mesh the 3D geometric model diagram into body elements, defining element types, materials and boundary conditions and applying a load to acquire a finite element model; establishing a boundary element model matched with the finite element model; and finally, solving the finite element model with a finite element solver to acquire the vibration characteristics of the speaker, and solving the boundary element model with a boundary element solver to acquire the acoustic characteristics of the speaker, wherein the vibration characteristics include the natural frequency, the vibration mode (vibration type), the displacement, the strain and the stress, and the acoustic characteristics include a frequency response curve and a directivity curve.

Description

The method for numerical simulation of a kind of loudspeaker vibration and acoustic characteristic

Technical field

The invention belongs to the loudspeaker field, relate to the analogy method of loudspeaker vibration and acoustic characteristic, particularly relate to the method for numerical simulation of a kind of loudspeaker vibration and acoustic characteristic.Adopt the vibration and the acoustic characteristic of this methods analyst loudspeaker, can access natural frequency, mode of oscillation (vibration shape), displacement, strain, stress, frequency response curve, the directive property curve of loudspeaker.Can be widely used in the speaker design exploitation.

Background technology

Traditional loudspeaker analysis design method has two kinds: (1) empirical method.Be generally sample and have a fling at, test, improve sample, the cyclic process repeatedly of test again, this mode must design the later stage by the time could find the loudspeaker problem, and the construction cycle is long, cost is high; (2) equivalent circuit method.When speaker operation during at low frequency, the diaphragm of loudspeaker is done whole piston motion, at this moment loudspeaker can be regarded lumped-parameter system as, according to acousto-electro-mechanical analogue, each parts equivalence is the circuit component of lumped parameter, can obtain analysis result rapidly and accurately, but when frequency is higher, because the diaphragm of loudspeaker can produce and cut apart vibration, loudspeaker becomes distributed parameter system, can't analyze loudspeaker performance with equivalent electrical circuit.

Denmark LoudSoft company has developed loudspeaker design softwares such as FINEMotor, FINECone, can analyze magnetic circuit of loudspeaker, voice coil loudspeaker voice coil, vibrating diaphragm, obtain parameters such as T/S parameter, impedance curve, frequency response curve and directive property curve, but this two software is analyzed the loudspeaker model and is necessary for axisymmetric model, for racetrack loudspeaker and vibrating diaphragm surface the loudspeaker of reinforcement is arranged, its limitation is very big.

Summary of the invention

The objective of the invention is to design the method for numerical simulation of a kind of loudspeaker vibration and acoustic characteristic.

The present invention will solve is the design later stage of must waiting until that empirical method exists could find loudspeaker problem and the construction cycle is long, cost the is high problem and the problem that can't analyze loudspeaker performance when frequency is higher with equivalent electrical circuit of equivalent circuit method existence.

The vibration of a kind of loudspeaker of the present invention and the method for numerical simulation of acoustic characteristic, concrete steps are:

(1) use three-dimensional drawing software to draw three-dimensional (3D) the geometric model figure of loudspeaker.

(2) set up the loudspeaker finite element model.Concrete steps are as follows:

A, loudspeaker 3D geometric model figure is imported grid dividing software, it is carried out grid dividing, obtain the used body unit of finite element analysis.If need to consider the influence of air, also in model, add air and be body unit its grid dividing to loudspeaker vibration.

B, definition unit type.Define the cell type that is complementary for each several part unit in the A step.

C, definition material parameter.The material parameter of each parts of definition model comprises Young modulus, Poisson ratio, density and material damping.If comprise air in the model, also need define the material parameter of air, comprise the velocity of sound, density and acoustical absorption coefficient.

D, definition boundary condition.The boundary condition of loudspeaker finite element model is as follows: 1) fixed boundary condition.Because diaphragm of loudspeaker edge is fixed on the basin frame, need at its edge definition fixed boundary condition, if loudspeaker also includes locating branch slice, the edge that it and basin bridge joint touch also should define fixed boundary condition; 2) the solid coupled boundary condition of stream.If consider air influence when analyzing the vibration characteristics of loudspeaker, coupling can take place at the surface of contact of loudspeaker and air, need the solid coupled boundary condition of interphase definition stream at loudspeaker and air.

E, give the finite element model imposed load, apply driving force at the voice coil loudspeaker voice coil position of model.

F, above-mentioned model is saved as the finite element model file.

(3) set up the loudspeaker boundary element model.The surface of extraction loudspeaker finite element model obtains the veil lattice with finite element model body unit coupling, because baffle has very big influence to the acoustic characteristic of loudspeaker, also to set up the veil lattice of baffle, define the cell type of above-mentioned veil lattice, above-mentioned model is saved as the boundary element model file.

(4) with the finite element solving device finite element model file is found the solution.The finite element model file is imported the finite element solving device and carries out model analysis, can obtain the natural frequency and the mode of oscillation (vibration shape) of loudspeaker, carry out frequency analysis again, can obtain displacement response, strain-responsive and the stress response of loudspeaker.

A, finite element model is carried out model analysis

The fundamental equation of dynamic analysis is as follows:

$\left[M\right]\left\{\stackrel{\·\·}{u}\right\}+\left[C\right]\left\{\stackrel{\·}{u}\right\}+\left[K\right]\left\{u\right\}=\left\{F\right\}$

In the following formula, [M] is the mass of system matrix, and [C] is the system damping matrix, and [K] is the system stiffness matrix,

Be the node vector acceleration,

Be the node speed vector, { u} is the nodal displacement vector, and { F} is the load vector that applies, with time correlation.

Suppose that loudspeaker does undamped-free vibration, equation is:

$\left[M\right]\left\{\stackrel{\·\·}{u}\right\}+\left[K\right]\left\{u\right\}=\left\{0\right\}$

For linear system, suppose that system does simple harmonic motion

{u}＝{u} _i?cosω _it

The above-mentioned equation of motion becomes

([K]-ω _i ²[M]){u} _i＝{0}

Find the solution above-mentioned equation and can obtain ω _i{ u} _i, ω _iBe the intrinsic circular frequency in i rank, { u} _iBe proper vector, i.e. the mode of oscillation (vibration shape) of the intrinsic circular frequency correspondence in i rank.

It is i rank natural frequency.

B, finite element model is carried out frequency analysis

In frequency analysis, { F}, { u} is a simple harmonic quantity.Have:

{F}＝({F ₁}+i{F ₂})e ^iΩt

{u}＝({u ₁}+i{u ₂})e ^iΩt

([K]-Ω ²[M]+iΩ[C])({u ₁}+i{u ₂})＝{F ₁}+i{F ₂}

In the following formula, { u ₁, { u ₂Be respectively the real part and the imaginary part of displacement, { F ₁, { F ₂Being respectively the real part and the imaginary part of loading force, Ω is the angular frequency of loading force.

Find the solution above-mentioned equation and can obtain the real part { u of displacement ₁And imaginary part { u ₂, further can derive strain and stress by displacement.

(5) the finite element solving device is found the solution the displacement and the boundary element model file that obtain and be submitted to the boundary element solver, can find the solution the frequency response curve and the directive property curve that obtain loudspeaker.

In isotropic ideal fluid medium, for the sound wave that simple harmonic quantity changes, acoustic pressure satisfies Helmholtz equation:

▽ ²p(r)+k ²p(r)＝0

According to divergence theorem, above-mentioned equation can be become borderline integral equation:

$p\left(r\right)={\∫}_S[p\left(r_q\right)\frac{\∂G(r,r_q)}{{\∂n}_q}-\frac{\∂p\left(r_q\right)}{{\∂n}_q}G(r,r_q)]\mathrm{dS}$

In the formula, k is the wave number of sound wave, and p (r) is the acoustic pressure of any arbitrarily in the outer sound field of loudspeaker, r _qFor on the border a bit, G (r, r _q) be Green function, n _qUnit normal vector for the border.

Sound pressure level

In the formula, p ₀=2 * 10 ^-5Pa is a reference acoustic pressure.

Solve the sound pressure level of loudspeaker under ad-hoc location (referring generally to the position along acoustic axis line direction apart from loudspeaker acoustic centre of source 1m) different frequency and can obtain frequency response curve, the sound pressure level that solves loudspeaker space diverse location under a certain characteristic frequency can obtain the directive property curve.

Used loudspeaker comprises various dynamic loudspeakers.

Described by finding the solution the undamped-free vibration secular equation analysis of loudspeaker finite element model, the multiple mode of oscillation of analysis loudspeaker comprises plug vibration, rocking vibration, flexural vibrations, twisting vibration and compound vibration thereof.

Described three-dimensional drawing software is Pro/E, draws the 3-D geometric model figure of loudspeaker with its, and Pro/E is the incorporate three-dimensional software of a CAD/CAM/CAE, and function comprises that Element Design, mould design, sheet metal component design, virtual assembling and engineering publish picture.

Described grid dividing software is HyperMesh, can divide grid to loudspeaker 3D geometric model with it.

Described finite element solving device is finite element software ANSYS, is used for finding the solution structure, fluid, heat, electromagnetic problem.The boundary element solver is LMS Virtual.Lab, sunykatuib analysis vibration noise characteristic.

Advantage of the present invention is: the present invention designs finite element method and Application of Boundary Element Methods in the loudspeaker analysis, overcome the shortcoming that equivalent circuit method is confined to low frequency effectively, and can have a fling at the performance of estimating loudspeaker early stage at sample, thus accelerate the loudspeaker design progress, reduce cost of development.

Description of drawings

Fig. 1 is the invention process method flow diagram.

Fig. 2 is the 3D geometric model figure of a 6.5 inches auto loud hailers.

Fig. 3 is the diagrammatic cross-section of Fig. 2.

Fig. 4 is the finite element model of 6.5 inches auto loud hailers.

Fig. 5 is the boundary element model of 6.5 inches auto loud hailers.

Fig. 6 A is one of typical mode of oscillation of 6.5 inches auto loud hailers.

Fig. 6 B be 6.5 inches auto loud hailers typical mode of oscillation two.

Fig. 6 C be 6.5 inches auto loud hailers typical mode of oscillation three.

Fig. 7 is the displacement response curve of 6.5 inches auto loud hailers.

Fig. 8 is the sound pressure frequency response curve of 6.5 inches auto loud hailers.

Fig. 9 is 6.5 inches auto loud hailer directive property utmost point figure (frequency is 1kHz).

Embodiment

The present invention is further illustrated below in conjunction with drawings and Examples.

The present invention is an example with 6.5 inches auto loud hailers, its vibration of sunykatuib analysis and acoustic characteristic.As shown in Figure 1, step of the present invention is as follows:

Step 1: use three-dimensional drawing software Pro/E to create loudspeaker 3D geometric model figure.

Fig. 2 is the 3D geometric model figure of this loudspeaker 1, and Fig. 3 is the diagrammatic cross-section of this loudspeaker 1, as seen from the figure, this loudspeaker 1 is made up of three parts: (1) magnetic circuit system, comprise T iron 11, magnet steel 10 and train wheel bridge 9, mainly produce magnetic field, can produce driving force energized coils; (2) vibrational system comprises paper awl 6, dust cap 2, ring 3, locating branch slice (bullet ripple) 7, skeleton 8 and voice coil loudspeaker voice coil 8-1, vibration and radiation sound under driving force; (3) backup system comprises basin frame 5 and flanging 4, supports to reach fixedly vibrational system.

Step 2: set up loudspeaker finite element model (see figure 4).Concrete steps are as follows:

1) the loudspeaker three-dimensional model is imported in the HyperMesh software,, provide driving force, in the numerical simulation process, be equivalent to the effect of load to speaker vibration system because the magnetic circuit of loudspeaker mainly produces uniform magnetic field.Loudspeaker backup system significant feature is fixing vibrational system, may instead be fixed boundary condition in the numerical simulation process.Like this, only need in HyperMesh, paper awl 6, ring 3, dust cap 2, voice coil loudspeaker voice coil 8-1 and skeleton 8 to be carried out the body unit that grid dividing obtains each several part.

2) definition unit type.Cell type is selected the Solid45 unit for use.

3) definition material parameter.For this routine loudspeaker 1, vibrating diaphragm and dust cap 2 selected materials are polypropylene (pp), ring 3 materials are rubber, locating branch slice (bullet ripple) 7 materials are cotton, skeleton 8 materials are polyimide (kapton), voice coil loudspeaker voice coil 8-1 material is a copper, and the material properties of definition above-mentioned material comprises Young modulus, Poisson ratio, density and material damping.

4) definition boundary condition.Because loudspeaker ring 3 and locating branch slice 7 edges are fixed on the basin frame 5, at the edge of loudspeaker ring 3 and locating branch slice 7 definition fixed boundary condition (along coordinate system x, y, the translation of z axle and rotation displacement are 0).

5) imposed load.Apply size and be the power of Bil on voice coil loudspeaker voice coil 8-1, direction is parallel to voice coil loudspeaker voice coil 8-1 direction of motion, and wherein B is a magnetic density, and i is the electric current of flowing through voice coil 8-1, and l is the length of voice coil loudspeaker voice coil 8-1 lead.

6) preserve the finite element model file.

Step 3: set up the boundary element model (see figure 5).From paper awl 6, ring 3, the body unit surface extraction of dust cap 2 and the veil lattice that body unit is complementary, set up baffle veil lattice again.The veil lattice are selected the shell63 unit for use, preserve the boundary element model file.

Step 4: the finite element model file is imported ANSYS, carry out model analysis, obtain the natural frequency and the mode of oscillation of loudspeaker, several typical mode of oscillations are seen Fig. 6 A～Fig. 6 C; Carry out humorous response analysis, calculate loudspeaker under a series of frequencies response and obtain displacement, stress, strain curve with frequency change.Fig. 7 is the displacement curve of analog computation.

Step 5: the displacement result of boundary element model file and step 4 is imported LMS Virtual.Lab, find the solution the frequency response curve and the directive property curve that obtain loudspeaker.Fig. 8 is the frequency response curve of analog computation.Fig. 9 is the directive property utmost point figure of the 1kHz of analog computation.

Above embodiment only in order to the explanation the present invention and and unrestricted technical scheme described in the invention.Therefore, although this instructions has been described in detail the present invention with reference to each above-mentioned enforcement,, those of ordinary skill in the art should be appreciated that still and can make amendment or be equal to replacement the present invention; And all do not break away from the technical scheme and the improvement thereof of the spirit and scope of the present invention, and it all should be encompassed in the claim scope of the present invention.

Claims (7)

1. the method for numerical simulation of loudspeaker vibration and acoustic characteristic is characterized in that this method may further comprise the steps at least:

(1) use three-dimensional drawing software to draw the 3-D geometric model figure of loudspeaker;

(2) set up the loudspeaker finite element model, concrete steps are as follows:

A, loudspeaker 3-D geometric model figure is imported grid dividing software, it is carried out grid dividing, obtain the used body unit of finite element analysis; If need to consider the influence of air, also in model, add air and be body unit its grid dividing to loudspeaker vibration;

B, definition unit type: define the cell type that is complementary for each several part unit in the A step;

C, definition material parameter: the material parameter of each parts of definition model comprises Young modulus, Poisson ratio, density and material damping; If comprise air in the model, also need define the material parameter of air, comprise the velocity of sound, density and acoustical absorption coefficient;

D, definition boundary condition: the boundary condition of loudspeaker finite element model is as follows: 1) fixed boundary condition: because diaphragm of loudspeaker edge is fixed on the basin frame, need at its edge definition fixed boundary condition, if loudspeaker also includes locating branch slice, the edge that it and basin bridge joint touch also should define fixed boundary condition; 2) the solid coupled boundary condition of stream: if consider air influence when analyzing the vibration characteristics of loudspeaker, coupling can take place, need the solid coupled boundary condition of interphase definition stream at loudspeaker and air at the surface of contact of loudspeaker and air;

E, give the finite element model imposed load: the voice coil loudspeaker voice coil position at model applies driving force;

F, above-mentioned model is saved as the finite element model file;

(3) set up the loudspeaker boundary element model: the surface of extraction loudspeaker finite element model obtains the veil lattice with finite element model body unit coupling, because baffle has very big influence to the acoustic characteristic of loudspeaker, also to set up the veil lattice of baffle, define the cell type of above-mentioned veil lattice, above-mentioned model is saved as the boundary element model file;

(4) with the finite element solving device finite element model file is found the solution: the finite element model file is imported the finite element solving device and carries out model analysis, can obtain the natural frequency and the mode of oscillation of loudspeaker, carry out frequency analysis again, obtain displacement response, strain-responsive and the stress response of loudspeaker;

A, finite element model is carried out model analysis

The fundamental equation of dynamic analysis is as follows:

$\left[M\right]\left\{\stackrel{\·\·}{u}\right\}+\left[C\right]\left\{\stackrel{\·}{u}\right\}+\left[K\right]\left\{u\right\}=\left\{F\right\}$

In the following formula, [M] is the mass of system matrix, and [C] is the system damping matrix, and [K] is the system stiffness matrix,

Be the node vector acceleration,

Be the node speed vector, { u} is the nodal displacement vector, and { F} is the load vector that applies, with time correlation;

Suppose that loudspeaker does undamped-free vibration, equation is:

$\left[M\right]\left\{\stackrel{\·\·}{u}\right\}+\left[K\right]\left\{u\right\}=\left\{0\right\}$

For linear system, suppose that system does simple harmonic motion,

{u}＝{u} _i?cos?ω _it

The above-mentioned equation of motion becomes

([K]-ω _i ²[M]){u} _i＝{0}

Find the solution above-mentioned equation and can obtain ω _i{ u} _i, ω _iBe the intrinsic circular frequency in i rank, { u} _iBe proper vector, i.e. the mode of oscillation of the intrinsic circular frequency correspondence in i rank;

It is i rank natural frequency.

B, finite element model is carried out frequency analysis

In frequency analysis, F}, u} is a simple harmonic quantity, has:

{F}＝(F ₁}+i{F ₂})e ^iΩt

{u}＝({u ₁}+i{u ₂})e ^iΩt

([K]-Ω ²[M]+iΩ[C])({u ₁}+i{u ₂})＝{F ₁}+i{F ₂}

In the following formula, { u ₁, { u ₂Be respectively the real part and the imaginary part of displacement, { F ₁, { F ₂Being respectively the real part and the imaginary part of loading force, Ω is the angular frequency of loading force;

Find the solution above-mentioned equation and can obtain the real part { u of displacement ₁And imaginary part { u ₂, further can derive strain and stress by displacement.

(5) the finite element solving device is found the solution the displacement and the boundary element model file that obtain and be submitted to the boundary element solver, can find the solution the frequency response curve and the directive property curve that obtain loudspeaker.

In isotropic ideal fluid medium, for the sound wave that simple harmonic quantity changes, acoustic pressure satisfies Helmholtz equation:

▽ ²p(r)+k ²p(r)＝0

According to divergence theorem, above-mentioned equation can be become borderline integral equation:

$p\left(r\right)={\∫}_S[p\left(r_q\right)\frac{\∂G(r,r_q)}{{\∂n}_q}-\frac{\∂p\left(r_q\right)}{{\∂n}_q}G(r,r_q)]\mathrm{dS}$

In the formula, k is the wave number of sound wave, and p (r) is the acoustic pressure of any arbitrarily in the outer sound field of loudspeaker, r _qFor on the border a bit, G (r, r _q) be Green function, n _qUnit normal vector for the border;

Sound pressure level

In the formula, p ₀=2 * 10 ^-5Pa is a reference acoustic pressure;

Solve the sound pressure level of loudspeaker under the ad-hoc location different frequency and can obtain frequency response curve, the sound pressure level that solves loudspeaker space diverse location under a certain characteristic frequency promptly obtains the directive property curve.

2. the method for numerical simulation of loudspeaker vibration according to claim 1 and acoustic characteristic is characterized in that loudspeaker comprises various dynamic loudspeakers.

3. the method for numerical simulation of loudspeaker vibration according to claim 1 and acoustic characteristic, it is characterized in that by finding the solution the undamped-free vibration secular equation analysis of loudspeaker finite element model, analyze the multiple mode of oscillation of loudspeaker, comprise plug vibration, rocking vibration, flexural vibrations, twisting vibration and compound vibration thereof.

4. the method for numerical simulation of loudspeaker vibration according to claim 1 and acoustic characteristic, it is characterized in that three-dimensional drawing software is Pro/E, draw the 3-D geometric model figure of loudspeaker with it, Pro/E is the incorporate three-dimensional software of a CAD/CAM/CAE, and function comprises that the design of Element Design, mould, sheet metal component design, virtual assembling and engineering publish picture.

5. the method for numerical simulation of loudspeaker vibration according to claim 1 and acoustic characteristic is characterized in that grid dividing software is HyperMesh, can divide grid to loudspeaker 3D geometric model with it.

6. the method for numerical simulation of loudspeaker vibration according to claim 1 and acoustic characteristic is characterized in that the finite element solving device is finite element software ANSYS, is used for finding the solution structure, fluid, heat, electromagnetic problem.

7. the method for numerical simulation of loudspeaker vibration according to claim 1 and acoustic characteristic is characterized in that the boundary element solver is LMS Virtual.Lab, sunykatuib analysis vibration noise characteristic.

Images