CN1470148A - Bending wave loudspeaker - Google Patents

Abstract

A loudspeaker comprising a panel which is sufficiently stiff to support bending waves, the panel having a boundary, a transducer mounted to the panel to apply bending wave energy in the form of dispersive travelling waves thereto at a first location in response to an electrical signal applied to the transducer to cause the panel to vibrate and radiate an acoustic output, the loudspeaker having a frequency range extending from a lower frequency to a higher frequency and the panel having a stiffness giving a coincidence frequency above the lower frequency. Means on or associated with the panel at a second location attenuates travelling bending waves in the panel to prevent or at least substantially to moderate panel resonance.

Description

Bending wave loudspeaker

Technical field

The present invention relates to bending wave loudspeaker, it typically is the flat panel loud speaker.

Background technology

The flat panel loud speaker is real to be the most traditional loud speaker, up to date still with the piston system operation, but collapses the interference that causes desired pattern operation naturally.Particularly, the bevel-type loud speaker has different shortcomings, comprises that limited bandwidth reaches the pack at its higher operation bandwidth, and this phenomenon is relevant with diaphragm size.

Other flat panel loud speaker with utilize barrier film to stretch screen formula vibrating reed well-known, it is propagated and operation with the constant speed ripple of striding panel surface.In the case, natural size, the character and the scope of the mode in face mass density and the vibrating reed tension force major decision panel are though the intrinsic vibrating reed damping of most materials has the trend of a degree that mode is reduced to.The loud speaker of this pattern has some desirable sound characteristicses, promptly wide radiation pattern and rational wide bandwidth.But structure in nature, the very difficult quality of making unanimity of this loud speaker.

Recently, bending wave loudspeaker is developed, as is disclosed in the example of people's such as the EP 0541,646 of Heron and Azima EP 0847661, and it relies on multi-mode or distribution pattern operation.Under two situations, particularly the latter is called DML, in fact it utilize the output of plate resonance regeneration sound, to limit the new benchmark of wide-band loudspeaker, mode is by limited board size and because the size of plate, bending hardness, and the foundation of the pattern that causes of the face mass density of material causes.Shown that this kind of loud speaker can represent desirable sound characteristics, this is that prior art is beyond one's reach.When distributed mode loudspeaker, lower frequency ranges has sparse mode in some situation, at least the high fidelity purpose of limiting loudspeaker when its lower frequency operation.

Purpose of the present invention is for reaching a more efficient use bending wave, so that hang down the regeneration of job area sound at loud speaker.The present invention intends avoiding reducing comprehensively or at least in full job area or at least low operation frequency range, reduces the mode behavior of panel.Ideally, panel should be looked itself and be unlimited size, is reflected and its limited actual size from the border no matter meaning is a noenergy.Center of the present invention is desirably, and the sound hole adds infinite face plate in abstracto, more than causing in the far field of panel, reaching under the coincidence frequency, and available quiet acoustical power.

File is pointed out, the infinitely great panel of operation in curved plane wave, and its (velocity of sound arrives the frequency of its ambient air (liquid) in the panel) below coincidence frequency, radiation is very few, or non-radiating acoustic energy.For overcoming this restriction, distributed mode loudspeaker in fact applies a limited mechanical hole (with its finite size and boundary condition) on unlimited panel, therefore, sets up a mode purpose to reach this effect.The effect of this hole is the mechanical impedance that one zero (edges of clamp) or infinitely great (free edge) are provided to panel, therefore, agitates reflection to set up the natural resonance behavior in the panel.

Otherwise the present invention is defined in panel border terminal surface plate structure, with the bending wave energy of desirable absorption incident.This measure equals a unlimited panel has a limited hole the same thereon.This point differs widely with prior art, and opposite with the mode purpose.

Summary of the invention

According to the present invention, one loud speaker is provided, comprise a panel, it is enough firm in the support bends ripple, panel has a border, one transducer is contained on the panel, spread the bending wave energy of row waveshape in primary importance to apply one, be added in the signal of telecommunication of transducer with response, so that an output of panel vibration and radiation, loud speaker has a frequency range, extends to upper frequency from lower frequency, panel has a hardness, provide one to be higher than the coincidence frequency of lower frequency, and be included on panel and the member relevant of the second place, with the line bend ripple in the decay panel with panel, to prevent or to relax panel resonance at least that damping mechanism is with hole mode effect on unlimited bent plate.

Damping mechanism can be included in the mechanical impedance device on panel border, and mates the bending wave energy that arrives panel edges circle to absorb with mechanical impedance.Damping mechanism can be positioned on the panel or wherein, before arriving panel at it, and decay bending wave energy.Damping mechanism is relevant with frequency.This frequency is interdependent at the upper frequency that can make the bending wave energy, is reflected from the panel border.

Mechanical impedance mechanism can extend around the full panel border.

Damping mechanism can comprise a hardness of being scheduled to or stride the construction machine impedance profile of panel.

Mechanical impedance mechanism can increase the bending wave energy absorption, or strides at least a portion on panel border, increases the transfer of bending wave energy.

Damping mechanism can provide the non-homogeneous or mechanical impedance profile that changes in a part of striding panel at least.

The decay that damping mechanism can be provided to the panel border increases.

Damping mechanism can provide the decay to face plate center to reduce.

Damping mechanism can have a mechanical impedance, itself and in the mechanical impedance coupling at the interface between a panel part and panel frame at least.

Damping mechanism can comprise that one strides the thickness or the variable density of the part of panel at least.

Damping mechanism can be contained on the panel one deck on a surface or two surfaces, and/or incorporates in the panel.

Bending wave panel can comprise a termination portion, is positioned at or in the part of panel at least.

Can there be a predetermined mechanical impedance in termination portion, and the mechanical impedance of the part of panel is the mechanical impedance of the part of panel frame in fact to stop at least.Can there be a predetermined mechanical impedance in this termination portion, to reduce the bending wave energy that moves to the panel border.

Primary importance may be positioned at face plate center.

Another characteristic of the present invention is a microphone, comprise a panel, its hardness is enough to the support bends ripple, panel has a border, one transducer is contained on the panel to produce a signal of telecommunication, with response bending wave energy, its form is the diffusion row ripple that the acoustic emanation of incident in the panel causes, and microphone has a frequency range, extends to than frequency from lower frequency, panel has a hardness, provide one to be high coincidence frequency, and a mechanism is arranged on panel or relevant, with the capable ripple bending wave in the decay panel with panel than this lower frequency, preventing or to relax panel resonance at least, decay mechanical work mode be with in unlimited twisted plate as a gap.

By another characteristic, the present invention one comprises the acoustic device of a panel, panel is enough hard with the support bends ripple, panel has the border, and the frequency range of acoustic device can extend to high-frequency from low frequency, and panel has a hardness that the coincidence frequency that is higher than lower frequency can be provided, and comprise one on panel or the mechanism relevant with it, with the capable ripple bending wave of decay in the panel, preventing or to relax panel resonance at least, damping mechanism with on unlimited twisted plate as a gap mode effect.

Two main method are arranged to reach purpose of the present invention.Bending wave purpose of the present invention can be with the combination of two technology.

Panel system should have one to have around its border ideally, in order to the structure of the mechanical impedance of the mechanical impedance that stops panel.This measure can cause reaching the abundant absorption of the bending wave energy on border.

Other method is to incorporate in the panel enough and suitable damping, no matter is intrinsic or applies damping material in its surface or internal structure, to absorb the bending wave energy of autoexcitation device radiation gradually.Therefore, when ripple arrives the border, it will lose great majority or all energy, therefore cause less or areflexia.

In fact, the combination of two technology can be in order to reach ideal performance more than.Under two situations, but damping structure specified material and/or structure design especially, to reach specific acoustic target, for example, become mode what for for desirable at upper frequency with relevant as panel with frequency.

According to two above-mentioned methods, damping can be incorporated into or around panel, reduce the bending wave energy on panel border with essence, or reduces when bending wave arrives the panel border.Do not incorporate damping into and the efficient of panel is endangered improperly but above two methods all do not relate to.Desirable damping can be striden and reaches via the predetermined hardness of striding panel or structural impedance wheel, or the form of incorporating edge termination portion into reaches.

In the form of the present invention, bending wave panel provides medium, so that at least in the part on panel border, reduce the reflection of bending wave energy.

In another bending wave panel form of the present invention, striding panel has a damping or an impedance that reduces or increase gradually.

In the bending wave panel of another form of the present invention, the increase of striding the damping of panel or impedance is actual in linear.

In the bending wave panel of another form of the present invention, stride the increase or the reduction of the damping of panel, be non-linear or index.

Another form of the present invention, a bending wave panel comprises medium, the bending wave in its counter plate has an impedance.

Here, impedance comprises reactance and/or resistance.

Herein, sound or acoustics comprise infrared sound and ultrasonic.

The invention is not restricted to the application of loud speaker, also can be used for other acoustical convertors such as microphone, and coupler etc.

Description of drawings

The present invention is to give an example and to follow accompanying drawing illustrated, wherein:

Fig. 1 a to 1k is the cross sectional side view of the different embodiment of bending wave panel;

Fig. 1 m is the stereogram of bending wave panel one embodiment;

Fig. 2 a-2n is the cut-away section end view of embodiment at the edge of bending wave panel;

Fig. 3 a is the profile edge figure of molded internal modification panel, incorporates loud speaker of the present invention into for automobile usefulness;

Fig. 3 b-3f is the front elevation of the modification panel embodiment of pattern among Fig. 3 a;

Fig. 4 is the sketch map at a damping bending wave of face plate edge;

Fig. 5 is the material figure of anti-frequency damping characteristic;

Fig. 6 is the figure of a bending wave in the panel of edge damping;

Fig. 7 is the bending wave figure in the panel of a damping;

Fig. 8 is the figure of a terminal damping;

Fig. 9 is for being the edge reflections coefficient figure of function with the frequency;

Figure 10 is the absorption maximum comparison diagram;

Figure 11 a-11b is terminal impedance and beam impedance plot;

Figure 12 a is the wave amplitude figure of reflection coefficient;

Figure 12 b is reflection coefficient phase figure;

Figure 13 a is the wave amplitude figure of reflection coefficient;

Figure 13 b is the phase diagram of reflection coefficient;

Figure 14 a is the wave amplitude figure of reflection coefficient;

Figure 14 b is the phase diagram of reflection coefficient;

Figure 15 a is the wave amplitude figure of reflection coefficient;

Figure 15 b is the phase diagram of reflection coefficient;

Figure 16 be untreated and the damping coefficient of surface treatment beam to the comparison diagram of frequency;

Figure 17 is the damping coefficient figure of the beam of application one amortisseur bar;

Figure 18 is the damping coefficient figure of the beam of application two amortisseur bars;

Figure 19 is the damping coefficient figure of the beam of application three amortisseur bars;

Figure 20 is the bending wave beam figure of edge termination portion;

Figure 21 is the reflectivity wave amplitude figure of the beam of Figure 20;

Figure 22 a is the rearview of a test panel;

Figure 22 b is the panel front view of Figure 22 a, shows an amortisseur bar device;

Figure 23 to 26 is the drive point speed of the panel of graphical display 22a at different driving point;

Figure 27 is a figure, the acoustic pressure power of the panel of displayed map 22a;

Figure 28 a-f is the not isomorphism type of a beam terminator;

Figure 29 a-f is a figure, the reflection coefficient wave amplitude of displayed map 28a edge termination device configuration;

Figure 30 a-c is the not isomorphism type that the compressed edge of a beam stops, and

Figure 31 a-c is a figure, the reflection coefficient wave amplitude of the not isomorphism type of the edge termination of displayed map 30a-c.

Embodiment

Many materials are arranged at present, its behavior such as modulus and loss factor, but matching design is irrelevant or relevant with frequency and temperature.In described two methods, select suitable material and correct absorption factor, should be quite easily to be fit to fabrication schedule and cost.

Edge termination can be reached by many modes, but at each in the works, and useful performance can be used damping gradually and carry out a single linear function or better index law and reach.The latter can provide with one of the damping material processing less panel area.

Molded damping material in panel to reach preferable compliance and less cost, also very desirable, conform with the injection molding program as design.Under certain situation, preferable with damping material termination panel, it has an open architecture to penetrate from it to prevent improper radiation.

Can use with suitable in the optimum performance of configuration panel with the material of FREQUENCY CONTROL damping, then useful.For example, can be the acoustics reason as panel, the part of frequency range is then even more ideal with the effect of DM mode.Internal damping

The meaning of internal damping is that damping is added on the panel away from face plate edge.In this example, can use distinct methods to build a panel, so that increase the damping that needs.This idea makes bending wave before the end that arrives panel, with its decay, to avoid from edge reflections.The method can comprise:

A) utilize the monolithic panel that high inherent damping is arranged.

B) add one deck damping material on panel, panel can be combination or monolithic panel: this layer can be single damping foam, or is coating.

C) utilize a damping layer as one deck of making panel, that is, and a mucigel or core material, or

D) make in the program at formation foam and common mode, as the part of the injection model program that adds to stock.

Surface damp can be used different common and close secret materials and reach.The mass surface density of material is an important parameter, and it should be minimum to reach optimum efficiency.Suitable material comprises the polymeric foam of open or closing structure, fiber, PVC, thin nature or comprehensive skin, paper base material, the face coat of fluent material etc.Fig. 1 a-1h demonstration applies the damping layer 2 of different-thickness on one or two surfaces of musculus cutaneus.Fig. 1 b, 1c, 1f and 1g show that one is positioned at surface or two lip-deep damping layers with uniform thickness of plate 1.Perhaps, except that providing one or two damping layers in one or two surfaces of panel, one or two damping layers can be incorporated in the structure of panel itself.Perhaps, panel 1 can be made of monolithic or low-loss synthetic material, shown in Fig. 1 d, or is made of high consumable material, shown in Fig. 1 e.

Internal damping or structural damping can select suitable material to design in panel, for example with the damping of the size of panel should be enough to lower bending wave energy reflection from the border to useful level.For making performance the best, should avoid overdamping.

For example, polyurethanes can be made into the preferable core foam of damping voluntarily with the polyester of sandwich structure.Fig. 1 j shows the panel 1 with polyurethane foam core 3 and musculus cutaneus 4.Other two kinds of structural damping methods also can adapt to, and damping material wherein injects the core cavity, suitably reach good damping to be suitable for application to provide.Fig. 1 k shows that the musculus cutaneus voluntarily according to the structural damping method passes panel 1, and then according to the panel 1 of cellular core 5 of having of the second structural damping method and musculus cutaneus (not shown), damping foam 6 is to inject wherein to Fig. 1 m.As injection material is lightweight and elasticity, and then other characteristic of panel such as hardness and face mass density can significantly not change with the matching design demand because of the modification of panel damping.

Quality spring and shock absorber system can be thought and be modeled as to edge damping.Particularly, edge damping can be thought serial spring/shock absorber system, and it increases its intensity gradually.Spring/shock absorber system can be added in the edge of panel, fringe region or be minimum part from the radiation of panel.Fig. 2 a-2n shows a mechanism, mechanism thus, and radiation or reflection from the marginal zone of panel can be minimum.

According to a method, when edge termination near the time, hardness should be strong.Hardness should increase in mode gradually, changes to avoid unexpected mechanical impedance, and reflection subsequently.Damping can also same way as increase, and the wave amplitude of bending wave also should be reduced to zero gradually when ripple arrives face plate edge.Fig. 2 a-2j display floater 1 has an edge damping 6, and it constitutes a mechanism, and it can reduce the wave amplitude of bending wave gradually when ripple arrives face plate edge.Panel hardness among Fig. 2 a-2d increases plate thickness with the part, and 7 places strengthen in the face plate edge zone.Among Fig. 2 d, damping material is fixed on rigid frame 8.Among the embodiment of Fig. 2 e-2g, panel 1 is a uniform thickness, when the damping material 6 at the edge is taper thickness.

According to other method, shown in Fig. 2 k-2m, the thickness and the hardness of panel reduce in the marginal portion, as shown in Figure 9.This measure combines with surface damp, causes the velocity of wave of marginal zone to reduce, and it is very effective at the bending wave energy that absorbs incident.The absorption of the bending wave energy of incident then more improves as utilizing at the effective damping material of frequency.

Reach ground transport in the air, i.e. vehicle inside model panel fine setting and structure can provide the useful application of this technology.As shown in Figure 3, automobile fine setting panel 10 is with sound active panel area 11, and by shaking transducer 12 excitations and constituting, its performance is improved by the panel area that utilizes damping 6 outside active region.This technology is also very effective in other application, and the active region function of its structure is a loud speaker television cabinet, and computer is sealed etc.

Fig. 4 is damping system 13 sketch maps, and this system is used for an end or the edge 14 of beam bundle 15, and it is by the transducer excitation vibrations of arrow 16 indications.But the damping system of Fig. 4 can be used on the panel.In damping system, spring, 17 represent hardness, and 18 represent damping or loss.In fact, damping system is a distributed architecture.It is variable striding panel as hardness and damping value, and this value changes comparatively desirable to end of panel.

Some polymer material can be designed to have required hardness and damping characteristic, this hardness and damping characteristic and frequency-independent.This kind can be in order to the behavior of mating surface plate in polymer material.For example, damping can reduce when high-frequency, and in the hope of keeping mode when this equifrequent, it can be suitable for the radiation characteristic of special applications.Fig. 5 is the figure of the hardness and the damping characteristic of certain material, and this characteristic can be by design control.This kind material can be favourable in order to reach the particular design target of panel loudspeaker.For example, as material regulation have ' damping coefficient (a) ' then damping will increase and reduce with frequency, panel will become mode in high-frequency.Because mode is just often quite close at high-frequency range, and a stray radiation is provided, this can be an ideal design target.

Fig. 6 strides the figure of the panel of an edge damping to the face plate edge expansion for bending wave.From Fig. 6 as seen, still have high-energy level towards the bending wave of face plate edge, but when being subjected to the approaching face panel edges, restriction of Zeng Jiaing or hardness loss gradually.The increase of hardness and impedance causes damping or loss, and it absorbs the bending wave energy in mode gradually, so do not have or a little energy reflects from face plate edge.Edge damping can have the material of suitable mechanical property, face plate edge is provided and reaches, shown in Fig. 2 a-2j.Perhaps, edge damping can constitute a panel and reach for pointed or flame-shaped gradually, as shown in Fig. 2 a-2d.The gradually cusp edge of panel can have linearity or exponential profile in a side or two sides of panel.With the method, panel hardness can increase, and hardness can increase bending wave speed.Hardness increases and corresponding damping increases, and can cause a ratio of the energy of bending wave, has been consumed when arriving face plate edge.This technology can have the possibility that forms framework voluntarily in order to manufacturing.

Fig. 7 strides the surface or to the bending wave expander graphs of the internal damping panel of face plate edge.As shown in Figure 7, the amplitude of bending wave is because speed, and autoexcitation is put to face plate edge and changed.According to internal damping panel method, when bending wave autoexcitation point transferred to the edge of panel, panel had enough dampings to absorb the bending wave energy.The most desirablely be, internal damping can be enough, loses big portion or all energy when causing bending wave to arrive face plate edge.Even but the part of projectile energy is reflected in face plate edge, also be not enough in panel, set up actual resonance mode.Therefore very less or not have model frequency preferential, can exist owing to the finite size result in the panel.Therefore, very less or noenergy reflect from face plate edge, panel is the energy of the original bending wave of radiation only, it produced in first when example.From Fig. 7 as seen, the bending wave wave amplitude of " not damping " panel is when bending wave reduces when face plate edge is transmitted.The reduction that it should be noted that wave amplitude is because ripple expansion, energy loss no thanks to.The reverberation colour

In in panel, providing or face damping and edge damping, the further advantage of low-loss DML panel can be provided under certain situation.As long as the panel reverberation time is less than 10ms, panel resonance promptly can't be heard, and can increase the popularity of sound.But in the low-loss panel or the small panel of utmost point soft and low bending wave speed is arranged, the reverberation time in the panel can surpass the threshold value that can hear, so sound takes echo type to protect colouration, and it can lower sound quality and good intelligibility.Described damping method can reduce even eliminate this effect.The suboptimum of damping is applied in and reduces on the problems referred to above, and the stretch journey is still arranged.The free layer damping

Explanation now is about using the background theories of free layer on a plate.Use this processing very effective on the panel, to provide panel one broad band damp, as one embodiment of the invention the following stated.Use foam strip on the panel, can absorb in the particular frequencies produce power, this mechanical property and size with damping layer is relevant, and details are as follows:

Viscoelastic material with mechanical property and time interdependence often directly is added on the panel with liquid coating or sheet, to increase the damping characteristic of system, shakes to eliminate or to reduce improperly.When viscoelastic layer directly is added on the jolting plate and when not having any restriction, is called " free layer ", this layer and just plate surface are to extend/to be compressed into parallel operations.Free layer was once widely studied and was announced in the effect of the kinetic characteristic of plate.It is by mixing loss factor control that damping is handled, as equation 1: ${\mathrm{\η}}_s=A\frac{E_2}{E_1}{\left(\frac{H_2}{H_1}\right)}^2{\mathrm{\η}}_2$

Wherein

η s=system damping factor

The A=system constants

H ₁=groundwork thickness

H ₂=free layer thickness

E ₁=free layer young's modulus

E ₂=free layer young's modulus

η ₂=free layer damping coefficient

Therefore, say simply that the system loss factor is with layer thickness (relative with basic unit), free layer modulus (relative), and free layer damping and increasing with basic unit.But this equation can not be contained all configurations.Find that the free layer damping method is ' local reaction ', when containing by free layer processing institute fully as panel, effect and condition shape or frequency-independent, but can provide suitable wide band energy to absorb.

But work as the special area that a free layer only is added in panel, the relevant free layer thickness of layer therewith will be arranged, the modulus in tension force/compression, the resonance frequency that density and free layer damping are relevant.Shown in following equation 2: $f_r\∝\sqrt{\frac{K}{M}}$

Wherein

f _r=resonance frequency (Hz)

Effective hardness of K=tension force/compression

M=free layer quality

The availability of free layer is controlled by following equation 3: $K\∝\frac{\mathrm{EA}}{t}$

Wherein

Young's modulus in E=tension force/compression

A=free layer surface area

The free layer damping that t=free layer thickness is added in the full surface of panel provides a broad band damp, as described in equation 1.

The free layer of bar shaped or separate piece can be used for the special area of panel surface, inhales with the energy under the frequency range that is provided at controlling level and control. The edge absorbs

The purpose that the edge absorbs is for absorbing some or all energy from an exciter incident one edge.

The ripple of exciter emission is striden the expansion of bending wave plate by distance.When it arrived face plate edge, its curvature significantly reduced, and is close to a plane wave.Big minister's degree on the border of this almost plane ripple is effectively, and apart from the farthest the best in the corner of panel.

When the almost plane ripple becomes one dimension, promptly be incident in the plane wave of planar boundary, can be with problem reduction.This problem can be thought one dimension (ID) wave beam, along the ripple of its propagation, and solves at edge termination.Importantly, experiment and theory subsequently are not to mean to analyze to be restricted to the panel similar to beam.ID beam by the impedance termination

Consider the device of Fig. 8 explanation:

This device is a pipeline problem, contains with the lower part: (a) ID waveguide; (b) ripple is incident in the edge; (c) terminal impedance; And (d) wave reflection at edge.

Boundary condition as the edge is known, and this problem is easy to solve, and condition is:

(a) terminal impedance only is coupled to lateral velocity, and any torque impedance promptly is not provided, thereby the crooked moment at edge is equalled zero, and

(b) velocity ratio at transverse shearing force and edge equals terminal impedance.

This measure causes the following result of edge reflections coefficient: $R=\frac{-\frac{Z_r}{Z_B}-i}{\frac{Z_r}{{\mathrm{<figure-callout\; id="1"\; label="Z\; B\; +"\; filenames="A0181253800224.png,A0181253800231.png"\; state="\{\{state\}\}">Z</figure-callout>}}_B}+1}$

Z wherein _TBe the terminal impedance of foam, Z _BBe the mechanical impedance of the end of beam, by the following formula table it: $Z_B=\frac{{\mathrm{<figure-callout\; id="3"\; label="Bk"\; filenames="A0181253800241.png"\; state="\{\{state\}\}">Bk</figure-callout>}}^3}{2\mathrm{\&piv;}}(1+i)$

Wherein B is a material bending hardness, is angular frequency, and k is the wave vector of bending wave, by standard bending wave dispersion relation gained (μ is a material surface density): $k=\sqrt{\mathrm{\&piv;}\sqrt{\frac{\mathrm{\&mu;}}{B}}}$

Equation is learnt the following thus: 1. the ratio of beam-ends impedance and terminal impedance determines reflection coefficient; 2. the beam impedance is relevant with frequency, and proportional with the square root of frequency; 3. the beam impedance is real number and reactivity in waiting weighting (i.e. 45 degree phase angles); 4. reflection coefficient is how relevant with frequency.

These factors can be assisted engineer/design beam terminal.The damping of example 1-real impedance

Consider a typical panel material in first example, it has a real impedance damping at the edge; Material is the thick sound 66 of 5mm, and it is a phenol mixture made of paper, and a honeycomb heart is arranged, and its material parameter is as follows:

B＝18.4Nm

＝0.44kgm ^-2

Fig. 9 be apply the resistance damping scope be the amplitude of the reflection coefficient of function with the frequency.Following several points of this curve shows real impedance damping:

1. the frequency of system when the impedance level that applies increases absorbs maximum;

2. irrelevant in the absorption and the impedance of this point, equal 0.41, and

3. absorption maximum is not 100%, but very useful.

Figure 10 is the modulus and the comparison that is added in the resistance impedance of beam terminal of beam terminal impedance.It is clear to show this two when equal, absorbs maximumly, and this moment, coefficient was 0.41 (41%).

1. with the real impedance damping, the minimal reflection coefficient is 0.41, takes place when beam terminal impedance modulus equals the value of resistance impedance.

2. the trend of the value of reflection coefficient is two sides in this frequency.

3. Fan She phase place is when frequency increases, and changes to-pi/2 with-π.Example 2: stop with an impedance and a compliance

Utilize composite impedance that bigger elasticity can be arranged, and in order to stop a beam, for example in a narrow-band.For reflection coefficient is equalled zero, following relationship can be satisfied: $\frac{-\frac{Z_{T1}}{Z_B}-i}{\frac{Z_T}{Z_B}+1}=0$ $\&DoubleRightArrow;\frac{Z_T}{Z_B}=-i$ $\&DoubleRightArrow;\mathrm{Re}\left[Z_T\right]=\mathrm{Im}\left[Z_B\right]$

Im[Z _T]＝-Re[Z _B]

To have compliance and the resistance impedance stops a beam, can realize that this condition is as figure, as shown in figure 11.Figure 11 a shows that (x) is the imaginary part of the real part and the beam impedance of terminal impedance, and Figure 11 b shows that (y) is the imaginary part of terminal impedance and the negative real part of beam impedance.The parameter that stops is: mechanical impedance=40Ns/m compliance=4.8 * 10 ^-6N/m

With this parameter of selecting, above-mentioned condition can reach when 820Hz.Reflection coefficient after the calculating as shown in figure 12, the null value of being hoped during this frequency.Reflected phase will under this condition changes to-pi/2 from π.

When impedance and compliance value can't be mated in this way, absorb less than maximum.As shown in figure 13, compliance stops the variation up and down of compliance in the best.The frequency and the value that also prove reflection coefficient are determined by selected compliance.

Analysis is pointed out:

1. can utilize the complete terminating edge of composite impedance.This available one impedance with impedance and compliance part reaches.

2. stop fully as the edge, reflection coefficient becomes less and narrower in frequency.

3. reflected phase will changes to-pi/2 from π.

4. all do not match in any frequency as the impedance of terminal and compliance and edge, still have absorption maximum, but not dark, its frequency is relevant with selected value with intensity.Example 3: with impedance, compliance and quality stop

Increase quality for this situation of the unlikely change of edge termination impedance.Still the impedance to of possibility edges matched is perfect absorbs, but considers the imaginary part of terminal impedance, and compliance and quality all should be taken into account.Moreover, when oneself is matched to and does not match when terminal impedance, be absorbed in the displacement of the frequency and the degree of depth.Reflected phase will changes to-π from π now.

When considering when stopping a panel with actual damping foam, effective impedance, compliance and foam quality are usually and frequency dependence.But each foam/panel material characteristics showed behavior and absorption level can be assessed.With composite impedance, stop near match-on criterion

Under this case, system is chosen as the Miers foam, and it is a soft pvc closed cell foam, the thick termination sound 66 of 5mm, and 5mm is thick.The behavior of this system is as with compliance, and the matched termination of resistance and quality component causes a sharp-pointed absorption, and as Figure 13, shown in the 14a, phase place changes to-π from π.Stop with impedance

In this example, with a beam by carbon fiber leather one-tenth, on the thick AL honeycomb of the 5mm heart.This beam stops with comprehensive condensate damper, and it is well-known with high impedance Sorbothane 30 " 00 ".Last absorption coefficient shows the characteristic phase place and the amplitude change of a real impedance terminal as shown in figure 15.This is to absorb minimum wave amplitude near 0.4, phase change and a π extremely-pi/2 is similar.The effect that energy absorption in the mode behavior of an exemplary bent corrugated plate is handled

This purpose is to illustrate on the special material with the beam form, the effect of energy absorption, and extending this analysis afterwards is a full-scale panel.

Select a low resistance, the benefit that the beam of high rigidity is handled with the explanation energy absorption.Utilize epoxy viscose, a carbon fiber skin is built layer at an aluminium honeycomb in the heart.Its mechanical property is listed in the table below in 1:

Panel number	Panel is spent (mm) most	Plate surface density (kgm -2)	Bending rigidity directions X (Nm)	Bending rigidity Y direction (Nm)	The spillage of material factor
							t	μ	D1	D2	η
1	5.25	0.882	82.83	82.83	0.0025

So the beam of this kind material is accepted following processing, and the specificity analysis of this beam is as follows: the effect of the edge treated of beam

Fill polymeric film, contain condensate, stride the full surface of the beam that is added in the table 1 with embedding lead button.The untreated beam damping coefficient of the damping coefficient of the increase of this system and Figure 16 relatively.

From Figure 16 as can be known, the condensate damping layer is that system increases considerable damping from 300Hz to 10kHz.The average damping value of untreated beam is 0.003 in this frequency range, and after handling, damping coefficient increases to 0.0194 (increase of factor 6.5).

The full surface that the polymer layer of filling is striden beam has increased the extensive level of damping, the damping layer that the measuring of reflection coefficient is added in panel and influenced.Low modulus foam strip

As mentioned above, the filling polymer layer that is added on the panel can produce an extensive band damping effect.But as above-mentioned, also can add a low modulus foamed material bar, its a certain special area and particular frequencies at panel absorbs energy.

Under this situation, low modulus PVC foam, it is excellent closed cell, applies the bar of a wide 5mm along beam length in the table 1.This foam strip has one and thickness, modulus in compression, the resonance frequency of material damping and this density phase.Figure 17 shows single damping coefficient that is added in (table 1) on the beam along beam length with low modulus foam.

Figure 17 points out when 3.3kHz, the resonance of foam strip, and it is significantly to improve near the damping this frequency.The energy absorption of this device of foam resonance effectively having increased.

The two low modulus foam strips that use in the precedent are the upper edge beam length configurations at another, and the absorption frequency of foam changes as shown in figure 18.From equation 3, be to obtain optimal absorption, effective hardness of foam doubles then should reduce by 2 factors as the quality of free layer, thereby causes the reduction of the factor 2 in the absorption frequency.

Figure 17 and 18 relatively, the reduction of resonance frequency is as from equation 2 and 3 factors of being surveyed 2.

Apply three foam strips on beam along each beam, it is identical that absorption frequency keeps, but since the damping that increases, i.e. the damping of Zeng Jiaing, and peak value becomes wideer.Figure 19 shows this effect.

During along each beam, the peak value damping coefficient is about 0.058 with three foam strips, but absorption frequency is about 3.3kHz.This can be with when the 3.3kHz of single foam strip, than small leak damping coefficient 0.036 relatively.The Sorbothane edge termination

Increasing edge termination as above fully analyzes in the benefit of panel.Apply two polyurethanes, 6 edges of high machinery consumption compliance condensate Sorbothane to the beam 15 of table 1.As shown in figure 20, the useful degree of energy absorption can reach.The gap that bar size and beam-ends and framework are 8 can be the best, with energy below the absorption 500Hz and the energy more than the 6kHz, the reflection coefficient that a beam top edge as shown in figure 21 stops.The damping that adds to panel is handled

The purpose of this section is showing the three above-mentioned effects of handling, i.e. the polymer layer of Tian Chonging hangs down the panel mode behavior in modulus foam strip and the table 1 and the edge treated of acoustic performance.

Figure 22 a size of display panels and be used for these the vibration four actuator position.Panel as shown below, single electric power exciter (25mm diameter) is failed banishs four positions that place following explanation, to measure upward acoustic pressure power of drive point speed and axle.These measurements give repetition with above-mentioned three kinds of processing that add to panel.These processing are as described below:

1. the polymer layer of Tian Chonging is added in 1 side on full panel surface,

2. (individual layer and 3 double-deck 1 sides that are added in panel become spoke configuration (bar is long=560mm) stride panel mid point) to low modulus foam strip, see Figure 22 b joint

3. the full Sorbothane rim condition drive point tachometric survey of describing in detail as Figure 20 on every side along panel

When panel encouraged with a constant power, the modal distribution that encourages in the panel can be made optimal representation in the speed characteristics of drive point, the success that the smoothness degree of speed is removed in order to pattern in the display panel.

Free panel and damping are handled the drive point speed of panel shown in Figure 27-30.In the plate of one 560mm * 530mm, the actuator position of every figure summary following (from the bottom, left angular measurement, see Figure 26 a):

Figure 23 panel driving point (280mm, 265mm)

Figure 24 4/9Lx, and the 3/7Ly position (310mm, 300mm)

Figure 25 face plate edge mid point, (280mm, 430mm)

Figure 26 panel corner (460mm, 430mm)

From Figure 23-26, different damping is handled the influence in the mode behavior of panel, and is high-visible.Be that the effect of actuator position is handled by damping and reduced.Free panel sharp-pointed, low resistance (high Q) pattern, damped processing significantly reduces, and the result is in the speed of exciter drive point, during to 20kHz, quite level and smooth and flat at the frequency height.Acoustic pressure power is measured on the axle

Figure 27 shows that free panel handles panel actuator position 1 (panel mid point) to damping, axle go up acoustic pressure power.

From Figure 27, the low resistance pattern in free panel is handled owing to add the damping of panel as can be known, and its intensity significantly reduces.

When the acoustic response of the panel of the pattern behavior of the panel among Figure 23 and Figure 27 relatively the time, visible more vibration in acoustic response.This is not because diffraction and radiation are shown in the tachometric survey.

A) pattern of the free layer damping of energizing quantity absorption and edge damping processing is panel material and the useful behavior of experiment confirm of energy absorption processes and displays.

B) utilize energy absorption to handle after, the mode activity of panel can significantly reduce.

C) the reflection coefficient analysis of single panel mode and system damping factor can make things convenient in the panel behavior, the prediction of the effect of different disposal.The change of the shape/form of edge termination is to the effect of reflection coefficient

The change of foam shape is on reflection coefficient (wave amplitude and phase place) and damping coefficient, and to the effect of carbon fiber aluminium honeycomb beam as mentioned above, self-criticism is should give in the influence of shape on free layer.

Low modulus PVC foam strip is with isomorphism type not, and the full duration of striding beam is added in the end of the beam of table 1, shown in Figure 28 a-28f.With the speech of the configuration among Figure 28 d-28f, the continuous segment or the wedge shape of foam are added on the beam.With all configurations, beam is free configuration, and promptly non-loaded or compression is added in rim condition.Correspondence pattern 29a-29f shows the reflection coefficient of these configurations.

Among Figure 28 a, the square bar 19 of low modulus PVC foam is added in two of end of beam, and with four, three, two, one independent stratum adds, as shown.

Figure 28 b has identical bar with the configuration of Figure 28 a, but layer is a different arrangement, and basic unit and intermediate layer are four, and top layer is two, as shown.

The configuration of Figure 28 c is similar to Figure 28 b, but the arrangement of foam strip is opposite.

Figure 28 d configuration comprises a relative low modulus PVC remittance foam wedge 20, is fixed in the reverse side of beam end.

Figure 28 e configuration is similar to Figure 28 d configuration, but the direction of foam wedge 20 is opposite.

The configuration of Figure 28 f is similar to Figure 28 d and 28e, but its foam wedge is replaced by the low modulus PVC foam section 21 of rectangle.The volume of the foam section in this configuration is identical, and is therefore, identical in its quality and foam wedge and Figure 28 d and the 28e configuration.Shape is to the effect of limiting layer

The continuous wedge and the Duan Eryan of the foam that uses with Figure 28 a-28f configuration analyze and give repetition, but another compression are added on foam section or the wedge through framework 8.

Figure 30 a utilizes identical wedge section 20 as Figure 28 d configuration employee, but foam section is compressed to 10mm thickness by original thickness 28mm.

The configuration of Figure 30 b utilizes same wedge section 20 as Figure 28 e, but foam edge is compressed to 10mm by original 28mm.

The configuration of Figure 30 c utilizes identical rectangular section 21, and as Figure 28 f, but foam edge is from original 14mm boil down to 10mm.

Very clear, being the shape of edge termination and pattern has very big influence to the EAC of boundary condition, from the absorption characteristic of Figure 28 a and 28b configuration more as can be known, the effect of altitude of discrete absorber absorbs, its resonance frequency with these sections is relevant, as previously mentioned.The configuration of Figure 28 a has one to be the absorption lower at center with the low frequency, and is different with Figure 28 b, and this is because it has bigger foam height, i.e. 4 sections but not 3 sections.

With foam section clamp and restriction in addition, compare with the free situation of all foams/beam configuration, can change the edge absorption characteristic.Therefore, edge impedance is significantly changed by the compression of foam, and this point also influences absorption characteristic.

After all case self-criticism, added foam produces the useful level that a wide band energy that is higher than 2kHz absorbs.This is demonstrated being higher than the wave amplitude that changes between this frequency 0.6-0.8 by reflection coefficient.

The advantage of loudspeaker of the present invention can comprise following each point:

1. panel produces all frequencies at its full job area, and is not subjected to the sparse Effect of Mode of low scope, as the DML situation.

2. panel-shaped and geometry nothing impact on the performance of loudspeaker. Different from DML, the axial symmetry driving method can be the preferred approach of excitation. In fact, a round panel is energized in the centre, and effective answer can be provided, and has and stride all-round even termination of enclosing.

Actuator arrangement become inessential, in the edge terminating method, as long as it is not interposing at too approaching face edges of boards circle.

4. the mechanical impedance of drive point is constant and level and smooth, and without the desirable unlimited sized panel behavior of the suffered impact of DML loudspeaker-reached.

Radiation characteristic and effective radiation area can configuration to be suitable for the selection of suitable damping strategy, i.e. the interdependent intensity of its frequency.

6. low frequency output level can be controlled, in order to move to provide the LF power of reduction with driver from face plate center, uses being suitable for.

7. apply damping and reduced the sensitivity of performance to actuator position with the behavior of control mode, and can comprise middle position.

Claims (20)

1. loud speaker, comprise a panel, it is enough hard with the support bends ripple, panel has a border, one transducer is contained on the panel, apply the bending wave energy in primary importance to spread capable ripple mode, add to the signal of telecommunication of transducer with response, to cause the output of panel vibration and radiation sound, the frequency range of loud speaker extends to upper frequency from lower frequency, and panel has a hardness, can provide one to be higher than this and to cut with scissors low-frequency coincidence frequency, and comprise mechanism second place or relevant on panel with it, with the capable ripple bending wave in the decay panel, to prevent or to relax panel at least and resonate.

2. loud speaker as claimed in claim 1, wherein, damping mechanism comprises the panel mechanical impedance of at least one panel border and coupling, is fed to the absorption of the bending wave energy that reaches the panel border.

3. loud speaker as claimed in claim 1 or 2, wherein, damping mechanism is positioned on the panel or wherein, so that before bending wave arrives the panel border, decay bending wave energy.

4. as each described loud speaker among the claim 1-3, wherein, damping mechanism is the frequency interdependence.

5. loud speaker as claimed in claim 4, wherein, the frequency interdependence is that the upper frequency of bending wave energy is from the edge reflection of panel.

6. as each described loud speaker among the claim 2-5, wherein, mechanical impedance mechanism extends around the full panel border.

7. the described loud speaker of each claim as described above, wherein, damping mechanism comprises a predetermined hardness or a construction machine impedance profile of striding panel.

8. as each described loud speaker among the claim 2-7, wherein, mechanical impedance mechanism increase the bending wave energy absorption, and the bending wave energy shifts in the part on panel border at least.

9. the described loud speaker of each claim as described above, wherein, damping mechanism strides at least that the part of panel provides mechanical impedance profile non-homogeneous or that change.

10. the described loud speaker of each claim as described above, wherein, damping mechanism provides the decay of increase to the border of panel.

11. the described loud speaker of each claim as described above, wherein, damping mechanism provides a decay that reduces to the center of panel.

In fact and the mechanical impedance coupling at the interface between the framework of the part of panel at least and panel 12. the described loud speaker of each claim as described above, wherein, damping mechanism has a mechanical impedance, and it.

13. the described loud speaker of each claim as described above, wherein, damping mechanism comprises strides at least the plate thickness of the part of panel or the variation of density.

14. the described loud speaker of each claim as described above, wherein, damping mechanism comprises panel one or two lip-deep one decks, and/or incorporates in the panel.

15. the described loud speaker of each claim as described above, wherein bending wave panel comprises a termination portion, be equipped with in or to the part place on the border of panel.

16. loud speaker as claimed in claim 15, wherein there is a predetermined impedance in termination portion, with in fact with the impedance matching of the part of the mechanical impedance of at least a portion of panel and panel frame.

17. as claim 15 or 16 described loud speakers, wherein, there is a predetermined mechanical impedance in termination portion, to reduce the bending wave energy that moves to the panel border.

18. the described loud speaker of each claim as described above, wherein, primary importance is for being positioned at face plate center.

19. microphone, comprise a panel, it is enough hard with the support bends ripple, panel has a border, one transducer is contained on the panel to produce a signal of telecommunication, to respond the bending wave energy of diffusion travelling-wave type formula in the panel that causes by the incident sound radiation, microphone has a frequency range, to upper frequency, panel has a hardness can provide one to be higher than the coincidence frequency of lower frequency, and comprises a mechanism from lower frequency, to be contained on the panel or relevant with it, with the capable ripple bending wave in the decay panel, to prevent or to relax panel resonance at least that damping mechanism works on a unlimited twisted plate in the mode of sound hole.

20. acoustic device, comprise a panel, it is enough hard with the support bends ripple, and panel has a border, and this device has a frequency range, extend to upper frequency from lower frequency, panel has a hardness can provide one to be high coincidence frequency than this lower frequency, and comprises a mechanism on panel or relevant with it, with the capable ripple bending wave in the decay panel, to prevent or to relax panel resonance at least that damping mechanism moves in sound hole mode on an infinite plate.

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