CN1157998C - Panel form acoustic apparatus using bending waves modes - Google Patents

Abstract

A panel form acoustic member capable of supporting bending wave vibration has the bending wave velocity varied in the region of coincidence to provide a range of coincidence frequencies, for causing the acoustic coupling of the bending waves in the panel to occur over a broader range of angles or for making the coupling more uniform. The member may be incorporated in a loudspeaker having a panel member (1) and an exciter (3) fixed to the panel member to excite bending waves in the loudspeaker to cause an acoustic output.

Description

Adopt the tabular audio unit of bending wave mode

The present invention relates to use the tabular audio unit of bending wave mode, especially relate to the loud speaker that comprises this class plate.

By the acoustic device that can learn distribution mode in many publication, for example WO97/09842.This class device similarly is not that common loud speaker utilizes like that and moves forward and backward (piston action) film and come work, the substitute is transducer is coupled to the hard plate that can vibrate bending wave.Bending wave vibration is distributed on the required frequency range, and is coupled with air.This technology is usually used in loud speaker, and wherein transducer is the exciter that evokes the plate bending wave vibration, causes the output of sound.

In the disclosed WO98/39947 of priority date after date of the present invention, but it has illustrated the distribution mode acoustic device that moves as a kind of also piston.For barycenter being arranged in the position that is fit to place exciter, arrange the distribution of bending stiffness, allow the center of bending stiffness and the position of exciter stagger.

Use big hard plate to be good usually, big hard plate has good high and low frequency performance.On coincidence frequency, the speed of sound can be mated in bending wave propagation velocity and the air, still, when surpassing coincidence frequency, can produce strong sound bundle.

On less plate, the effect problem of coincidence is little, the low frequency performance and reduce modal density on the low frequency but the area reduction can decay, and make frequency response inhomogeneous.

Also can use not too hard plate to reduce the coincidence effect at this, but this can injure both ways to some extent to high frequency performance.At first, mass of coil has intense influence, because its impedance can be equal to mutually with the impedance of plate when low frequency, influences the high frequency frequency response and descends.The second, the gap resonance (aperture resonance) of the voice coil loudspeaker voice coil inner panel material that takes place when Lamb wave length is complementary with the exciter diameter for not harder plate, takes place on lower frequency.This effect becomes peak sound pressure and obviously.In addition, the low frequency performance of not harder big template is relatively poor relatively.

According to the present invention, it provides a tabular sound components that can support bending wave vibration, wherein the bending stiffness of plate and/mass surface density can plate the zone in the variation, to produce the coincidence frequency of a scope, the ratio of the coincidence frequency of its maximum, minimum is 1.2: 1, like this, compare with isotropic plate, the sound power and/or the directivity of bending wave just can be coupled with surrounding air more equably in the plate.

In a plurality of embodiment, 1.2: 1 coincidence frequency scope has produced moderate effect.But, at least 1.5: 1, preferably, at least 2: 1 widerly can obtain bigger effect.

The control that overlaps not is the theme of principle or textbook instruction.Though it is known overlapping effect, is considered as a difficult problem of desiring to avoid.Other method instruction increases quality or coupling layer damping to member, and these methods are isotropic processing basically.

This tabular sound components can be packed in any many possible acoustic devices, so its supporter that the acoustic absorption device can be provided, be used for acoustic resonance device, the audio amplifier that repercussion controls or use the sense of hearing assembly that comprises so tabular sound components.

Active device is coupled to transducer on the tabular sound components, is the bending wave in the member with electrical signal conversion or the bending wave in the member is converted to the signal of telecommunication.This active device has been represented a kind of important use.Correspondingly, can provide a kind of microphone, it has above-mentioned tabular sound components and the bending wave in the member is converted to the transducer of the signal of telecommunication.

A kind of application of particular importance is exactly a loud speaker.Correspondingly, a kind of loud speaker can be provided, comprise the board member that can support bending wave in the auditory frequency range, be positioned at and be used for evoking the exciter of plate bending wave on the board member with the generation voice output, wherein the bending stiffness of board member can become along with the position of board member, and so overlapping will be more smooth-going to the influence in the plate voice output.

Discontinuous or the peak value of the sound sound bundle when coincidence comprises greater than coincidence frequency to the influence in the voice output or output sound press or power, as the function of frequency, the integration on whole the place ahead hemisphere and/or specific direction.Use the present invention, any or all of these influences all can reduce.

The variation of bending stiffness causes the extra change of speed of sound in the plate, and the variation that therefore produces coincidence frequency, and the direction of acoustic radiating correspondingly changes on the surface of plate.So can arrange the variation of bending stiffness, cause the distribution of acoustic radiating that broader angle can be arranged, thereby reduce the generation of sound bundle.

Further in the bending wave plate, on coincidence frequency, have peak value, step or discontinuous usually as the power output of frequency function, utilize the change coincidence frequency can be with this irregular smoothing.

Coincidence frequency and bending stiffness are inversely proportional to, and normal can the change by changing bending stiffness, and this utilizes the thickness that changes plate just can reach.

This plate can be harder on actuator position, because benefit on high frequency for harder plate in the gap resonance that mass of coil coupling on the finite region is caused.

In addition, maximum bending stiffness is being arranged near the actuator position place.For example: this plate can be made into and is symmetrical in center rigidity maximum, and the best eccentric actuator position of the mode that so distributes plate can be near the minimum place of (thereon non-) coincidence frequency, and this coincidence frequency minimum place bending stiffness maximum normally.The meaning of " close " is enough near, and the bending stiffness that makes the exciter place is peaked 70% at least; And preferably 80%, and further preferably be higher than 90%.

In other embodiment, panel edges is also harder than middle position, and same the utilization changes rigidity and allow the coincidence frequency smoothness.

Exciter can be positioned on the thin zone of plate, and littler in the mechanical impedance of this plate, this helps low frequency energy is coupled in the plate.

This plate has maximum bending stiffness in middle section (plate central authorities vertical, horizontal 1/3rd), and past more edge stiffness is low more.Utilize the method for injection molding, begin casting by thicker zone, slave plate center and just can make this class plate.

The invention provides the benefit of large-scale hard plate and reduce some shortcoming, the particularly influence of coincidence frequency in audibility range.

But the present invention is not only applicable to large-scale hard plate, and can obtain good result on the compact board of explanation below yet.

In order to influence coincidence, bending stiffness must can compare with wavelength of sound in the correlated frequency scope or greater than linear dimension plate zone on change, this is normally 3 to 4cm for the 10kHz frequency.Therefore the unusual increase bending stiffness of zonule and be not suitable for allowing and overlap the effect smoothing, more suitable is at least 1.5 times, best 2 times, overlaps on the linear size area of wavelength and changes.At least 5%, best 10%, change helps reducing and overlaps effect on the zone of plate area.

Through the explanation of several sections of fronts, the change of bending stiffness concentrates on actuator position.For example: the gradient of bending stiffness is big near actuator position, and slowly reduces on the straight line that is extended outward by actuator position.In some embodiment, this class profile has produced and has overlapped the very useful smoothing of influence.Gradient can reduce to zero in the exciter edges of regions, otherwise change may extend to the edge of plate.

Bending stiffness can be field planting on the plate zone away from exciter, and all changes of bending stiffness all concentrate in the exciter zone.

Bending stiffness also can change in the rectangular band around the board member edge, and bending stiffness is successively decreased in the edge maximum and towards intralamellar part, perhaps increases progressively in the edge minimum and toward in.The edge clamping of this class plate is in a framework: the variation of bending stiffness can produce the coupling of expection or not match on the edge between the mechanical impedance of the mechanical impedance of plate and clamping element, so that do further voice output control.

Especially, bending stiffness can change count the rectangular band in the edge that is no more than plate length 10% from the edge in.

Rigidity near panel edges reduces the mechanical impedance that can reduce the fringe region inner panel, if the impedance that reduces is lower than the impedance of folder frame, does not then almost have energy to reach framework by slave plate.

Similarly, the increase of rigidity on every side can increase the mechanical impedance of this regional inner panel.If plate is supported on the resilient supporter, then the anti-increase of plate resistance can produce bigger not matching, and reduces to minimum will not want the energy that transfers to framework.If plate is connected to rigidity pinching framework, then can provide slave plate conversely speaking,, so help the mechanically robust degree of final structure to the more smooth-going transfer of clamped edge.

Moreover, under near the bending stiffness edge changes fast situation, the acoustical vibration energy reflection can be returned intralamellar part, so almost there is not energy can arrive framework.

But change fast in the bending stiffness edge region, and be relative definite value at intralamellar part.In addition, but the bending stiffness edge region goes up change with inner, changes in also can be near exciter zone and edge, and has a bending stiffness to have only the zone of any or no change between edge and exciter zone.

Other options are onboard by the perhaps multistage scalariform change of wave pattern bending stiffness.

The coincidence frequency f that speed is complementary in the velocity of sound and the plate _c, be changed to

$f_c=\frac{{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="C9981057400231.png,C9981057400271.png"\; state="\{\{state\}\}">c</figure-callout>}}^2}{2\mathrm{\&pi;}}\sqrt{\frac{\mathrm{\&mu;}}{B}}$

Wherein c is the velocity of sound in the air, and μ is the area density of plate, and B is a bending stiffness.

In fact, with simultaneously or do not change bending stiffness, can change any parameter and change the speed in the plate and therefore change coincidence frequency.Correspondingly, can change the Young's modulus on top layer or the area density of top layer or core.

On the other hand, but provide the method for the sound components of a kind of making support bends ripple vibration, wherein velocity of wave can change in overlapping the zone clearly, to produce the coincidence frequency of a scope.

The method further comprises option board material and plate size, option board initial bending rigidity form, the step of change web wheel exterior feature or the surface tension rigidity of pulling over, change frequency and the angular response that near the interior velocity of wave of the plate of coincidence frequency improves plate so that utilize, to produce the scope of coincidence frequency.In the step of option board profile of pulling over, also can be with the resonance mode distribution optimization on the frequency in the plate.

In invention on the other hand, a kind of method of making speaker system is provided, comprise option board material, plate size and exciter kind, initial plate bending stiffness form is selected in the initial excitation device position on the option board, pull over and change actuator position and plate form, select the position and the profile of best plate frequency and angular response, compare, to reduce the effect that overlaps with flat board, the plate of the web wheel exterior feature of the selection of pulling over being provided, and exciter is additional to the position of pulling over and selecting.

Size, profile and actuator position can be selected to produce distribution mode loud speaker, and wherein low frequency modal can have good distribution in frequency, wherein, and the channel effect minimum on the high frequency.

With reference to the accompanying drawings, only by way of example.Specific embodiments of the invention are described, wherein:

Fig. 1 explanation is according to loud speaker of the present invention;

Fig. 2 explanation is according to employed plate form in the loud speaker of the present invention;

Fig. 3 to 6 shows the velocity of sound and the voice output from the loud speaker of thickness, with the usefulness of making comparisons;

Fig. 7 shows the loud speaker parameter according to first embodiment of the invention;

Fig. 8 to 10 is for using the result that loud speaker obtained of Fig. 7 explanation;

Figure 11 shows the parameter of second embodiment of the invention;

Figure 12 to 14 is for using the result that loud speaker obtained of Figure 11 explanation;

Figure 15 illustrates the third embodiment of the present invention;

Figure 16 illustrates that the coincidence frequency on Figure 15 plate changes;

Figure 17 and 18 is for using the result that loud speaker obtained of Figure 15 explanation;

Gap resonance effects in the plate that Figure 19 to 21 key diagram 9 shows;

Figure 22 and the another kind of method that reaches the bending stiffness change of 23 explanations; And

Figure 24 shows another kind of plate form.

Fig. 1 shows a kind of loud speaker, comprises that one is equipped with the plate 1 of an exciter 3 on it.Exciter 3 evokes the resonance bending wave in the plate, causes plate to be sounded, and electric conductor 5 is connected to amplifier with exciter.This plate 1 is made by a core 7 and two top layers 9 in present embodiment.In addition, plate is also integrally formed.

Employed plate can be distribution mode plate in the loud speaker, and as illustrated in WO97/09842 and other applications, its utilization is evenly distributed in resonance mode reaches useful frequency response in the frequency, and this has its benefit when modal distribution is on plate.

In order to obtain good field wave modal distribution, select the shape and the actuator position of plate.WO97/09842 has provided some concrete suitable shapes, and for example for isotropic plate, length-width ratio is the rectangle of 1: 0.882 or 1: 0.707.And can do some adjustment to these ratios according to the thickness profile of plate.

The position of exciter is also very important, and actuator position should be coupled to the distribution resonance mode, and some good actuator position are very approaching but be not positioned in the plate central authorities.With regard to the isotropism rectangular slab, the coordinate of this class position can be (3/7,4/9) side edge length, near the central authorities of the plate on (1/2,1/2) coordinate.Certainly, for the plate with the aforesaid bending stiffness change of the present invention, preferable coordinate can depart from these numerical value.But these numerical value still just can be used as suitable starting point, find out best position by on probation and error.In addition, laser or computer for analysis will help to find out effective actuator position.

Making the bending wave plate by injection moulding is a kind of cost effective and efficient manner.This not only has moderate unit cost and produces consistent finished product, and plate is installed on some installation feature and fixed structure of exciter and plate support frame, also can be included in the mould, as a body component of plate, has saved parts and assembly cost.Injection moulding is for making aforesaid thick middle and very effective toward the plate of edge thinning.

Significantly different is that a useful Control Parameter is a coincidence frequency in distribution mode loud speaker, and mainly is the position at its place in frequency spectrum.And its reason is to be higher than coincidence frequency and to be lower than coincidence frequency, and plate can operate under different radiation theories.The coincidence frequency f of some actual flexion ripple plate _cBe usually located in the auditory frequency range, have counter productive acoustically.On coincidence frequency, the acoustic radiating of wide angle emitted can be stronger, and this angle is along with frequency increase meeting reduces towards normal axis.From being lower than coincidence frequency to surpassing coincidence frequency, the angle of radiation change can cause dimensional energy to shift, and this is not that we are desired.Further, channel effect has limited the more not high frequency performance of hard plate.The distribution mode loud speaker that clamps can use not harder plate, but the mass density of being unwilling usually to increase, because can cause losing efficient like this.

What can take into account is that the bending stiffness of utilization change plate is launched in a frequency range, controls the counter productive of coincidence frequency to utilize the energy content that reduces on the single-frequency.Clean effect is can not be transferred to the radiation pattern with high energy content suddenly, and can extensively overlap smooth-going transfer.

Because the change of bending stiffness on the plate, near the bending wave wavelength overlapping in the frequency field can change.For example: under the situation that thickness increases outward from central authorities, velocity of wave can be incremented to panel edges.On the contrary, when thickness from central authorities outward gradually during attenuation velocity of wave can successively decrease.So will change characteristic vector relevant on the plate surf zone with bending wave.

The rigidity gradient of plate can have several to shift gears, and suitable method comprises:

1. handle the varied in thickness of making whole plate by the foaming in the injection moulding.Fig. 2 shows some variation of this mode, and increases the increase that thickness may cause quality like this.The quality that increases is relatively less than the rigidity that increases because with the quality of a small amount of increase (foam quality density is very little) by comparison, rigidity can increase sharply along with thickness (when sandwich, approximately be thickness square).

2. under the situation of using integrally formed casting, can use rigidity gradient and superficial density gradient (seeing also Fig. 2).In the case, double thickness can provide 8 times rigidity, and mass surface density then only doubles, so this still is feasible integrally formed method.

3. utilize foam material to be compression molded into the making that required shape can be reached rigidity gradient, for example coat the Rohacell plate or the clamping plate of foaming core with the top layer.Keep mass density on the plate surface in the case.

4. utilize so-called " intelligent polymer " can reach the making of rigidity gradient, it has the modulus gradient along with size or area.Variable area or regional rigid polymer can be sheets, for use in stratified mixture or be used for injection moulding and other manufacturing and handle.At this, plate can be kept its consistent thickness, is issued to the rigidity gradient of expection in the situation that does not influence quality.

5. the use of web wheel exterior feature, curvature or gauffer, this technology can produce moderate rigidity gradient, unless used very little radius of curvature.The method can be used for some " external form " need with application that style combines in, see also Figure 22 and 23.

Core can grind or sand milling to required shape, and ground or the top layer can be sticked in core two sides that sand milling is crossed.

Shooting Technique is fit to connect in batches very much, low-cost and consistent mode, is used for making the bending wave plate.And integrally formed radiant body directly mode cast, but may not be suitable for some occasion.

These technologies have solved the casting problem of " not increasing cost " mode because when foaming required additional materials few in the extreme.The stiffness variation of being done by factor 2 can have about 40% extension (for example from 10kHz to 14kHz) in coincidence frequency, this is quite helpful and enough extend coincidence frequency/energy concerning most application.

Show in Fig. 2 that some has the twisted plate of this class stiffness variation.A kind of preferred approach that is fit to molding is to set up a thickness that changes outward by forward or negative sense gradient.Utilize the blowing agent in the control board core, can in plate, form bigger rigidity gradient.In integrally formed plate, rigidity can by thickness cube and change, in clamping plate rigidity then approximately by thickness square and become.

At rigidity gradient is under the situation of successively decreasing toward the panel edges direction, can obtain following one or more advantage.At first be because near the higher rigidity of plate central authorities will be hanged down the channel effect that the limited size of exciter coil produces.Moreover, can reach in some is used and have the approximate Flagless of benefit, and have the smooth-going advantage that is transferred to plate supporter or framework.The 3rd, begin casting by slave plate central authorities, it is feasible utilizing injection moulding, so can produce low-quality foaming core.

Conversely speaking, when rigidity gradient be under the situation about increasing progressively toward the panel edges direction, utilize design can increase rigidity and set up the smooth-going gripper edge listrium design that is transferred to, fortune can increase the mechanical strength of final structure.

The excitation of plate can any expection mode reach, for example described in our many previous patent applications.Therefore target still is an excitation plate mode fifty-fifty, and will reach the mechanical impedance (being used for the input of mechanical output) and/or the acoustic radiating power of good evenness in the design frequency range.Can obtain this class optimum position, for example the FE method or the rule of thumb by analyzing.

The behavioural characteristic of bending wave plate is the bending wave on the low frequency, and at this moment, plate has consistent bending stiffness and mass density.But,, may cause being offset the prediction of being done according to the static calculation value as overlapping and gap this class effect that resonates at high frequency.Because on these high frequencies, plate shearing largely comes work, and its feature can be the bending stiffness that falls within on the high frequency.Accurate high frequency behavior can only decide by the complete understanding to sheet material matter shearing characteristic, but this not necessarily always is feasible.Therefore, can not react the real behavior that overlaps near some sheet material matter from the possibility of result of deciding bending stiffness fundamental equation gained.When desiring the sound property according to decision plate of the present invention, vibration analysis and test must be arranged.

Sound power is the integration of sound press size on all angles.The feature of frequency smooth function is the factor of sound quality normally.With plate thickness attenuation gradually, can in frequency, stretch the unevenness in the output of bending wave power output plate on overlapping.Increase can extend to low frequency with coincidence away from the rigidity of drive point part; On the contrary, reduce rigidity and scope can be extended to high frequency.

If we consider large-scale thistle board, the radiation stiffness of coupling that increases on the coincidence means that the energy of most of tablets is all from radiating near energized position.Exciter further away from each other, plate speed reduces gradually, almost no longer gives off energy.Therefore, the variation of plate thickness should quite be concentrated and be approached exciter, otherwise a part of plate can change, and does not have strong radiation, and has only effect slightly.This has further benefit, is exactly the change that the variation of plate thickness can not cause low frequency performance: can reduce greatly in (under overlapping) radiation efficiency on the low frequency, energy can be in the mode of resonance mode of flexural vibration, is distributed in the frequency and is distributed in whole plate surface.

In addition in the plate of Heavy Weight, lower and sound can radiation on the zone bigger than plate with the coupling of radiation.Therefore the change on panel stiffness/velocity of wave converges and concentrates on the bigger zone.

If the damping of structure material greater than radiation damping, then utilizes identical sign, will distribute the zone that should vibrate according to the damping of structure material.

Generally speaking, disperse the required form of coincidence effect to depend on mass density, bending stiffness, shearing characteristic and the damping characteristic of plate.

On principle, the change of plate bending stiffness also can add wide directionality.For the plate of the rigidity of successively decreasing from actuator position, acoustic radiating can extend to the angle to plate normal Cheng Gengda.On the contrary, for the plate that rigidity increases progressively, acoustic radiating can extend to the angle to plate normal Cheng Gengxiao.On both side, angular range all increases to some extent.

In practice, it is suitable more to have much difficulty in healing than sound power from the radiation directivity of plate, as following discussion is illustrated.

Consideration from the radiation sound bundle of part plate, has speed v on overlapping below _PanelSound bundle angle from position on the axle is determined by following equation:

$\mathrm{\&theta;}={\sin }^{-1}\left(\frac{c}{v_{\mathrm{panel}}}\right)$

At the characteristic frequency place, have on the different plate portions of differently curved velocity of wave, cause becoming the acoustic energy particular pole coordinate diagram of directivity function along the radiation of different directions.

When frequency increased, according to above-mentioned equation, the speed of plate can increase and the angle of radiation sound can be successively decreased towards the axis of orientation position.The angle difference relevant with speed can be big more for wide-angle, and angle is reduced in the position on the axis of orientation.Therefore when frequency increased, sound can send with the pattern that form changes, and energy can be concentrated on normal axis becomes narrower bundle.

Polar diagram can increase and the change shape along with angle.By changing the bending stiffness on the plate particularly, on given frequency, can reach more consistent voice output, but the summation of output can produce a little output of a smooth-going degree difference on other frequencies.

In addition, can arrange one to listen to sound press degree on the angle to keep relative definite value.But other local sound press then no longer are definite values and can show the sound Shu Xiaoguo of enhancing.

Gather, can't reach the maximum smooth-going polar diagram at all frequency places, perhaps the maximum smooth-going frequency response on.It is a kind of useful compromise that the designer will reach, and being implemented on the point of certain limit has smooth-going relatively response and relative smooth-going polar diagram is arranged on the certain frequency scope.

Experimental result

The plate that Fig. 4 to 10 tests is clipped by the thick surface layer of glass of 100 μ m and does not compress Rohacell and constitute.By the top layer is layered on the Rohacell plate that grinds to form the profile of wanting in advance, form the plate of attenuation gradually.Select sizable plate to emphasize to overlap effect, size following (midi demonstrates size) at this:

Plate length: 544mm

Plate width: 480mm

Plate area: 0.26m ²

Drive point is chosen in the central authorities of plate to simplify the profile of test board, and exciter is 4 ohm of NEC electro-dynamic exciters with 13mm diameter voice coil loudspeaker voice coil.

On each plate, carry out following measurement:

1) the sound press degree is the function around the angle of plate

Measuring distance=1m

The plate gross area=the 1m of sound panel shape ²

The result represents with the dB of unit

Data are not carried out smooth-going.

2) the single-frequency polar diagram of desire display direction

Measuring distance=1m

The plate gross area=1m in the sound panel shape ²

The result represents with the dB of unit

It is smooth-going that data have been carried out third octave, with the most detailed variation feature of smooth-going twisted plate radiation, and therefore given prominence to the coincidence aspect.

3) sound power

Measuring distance=1m

The plate gross area=the 1m of sound panel shape ²

The result represents with the dB of unit

Data are not carried out smooth-going.

4) measure the speed of drive point with laser velocimeter system

The result represents with the mm/s/V of unit

Data are not carried out smooth-going.

5) distribution of scanning board speed on its zone, this is with deciding wavelength in given driving frequency upper plate, and the therefore bending wave speed of gained.

At first, will present from the fruit of relatively hardening with definite value bending stiffness.

Fig. 3 a shows for being three kind of different uniform thickness plate of 4mm, 3mm and 2mm respectively, the crooked velocity of wave that is obtained by sheet material matter calculation of parameter.

Fig. 3 b shows the speed of these plates that experiment is determined, is obtained from the image of inplane vibration pattern on the fixed frequency.Predicted value is similar to experimental result on low frequency.But on high frequency, owing to be subjected to the influence of shearing, the speed of measuring is lower than predicted value.At high frequency, be used for the speed ratio of frequency variation that pure bending is desired divides the root relation equally slowly.

Chart also shows a line that is denoted as " c " in Fig. 3, represents the speed of sound in the air.The frequency at this line and each plate thickness speed track cross place is exactly a coincidence frequency.When plate thickness is reduced to 2mm from 4mm, the predicted/calculated result of static state or low frequency bending stiffness points out that coincidence frequency approximately increases to 8.5kHz from 5kHz.And in practice, this change of thickness causes coincidence frequency from the bigger change of 5kHz to 14kHz.The plate of 4mm has the coincidence frequency of 5kHz, and 3mm has the 7kHz coincidence frequency, and 2mm then has the coincidence frequency of 14kHz.

Shuo Ming the thickness of the plate of attenuation gradually on drive point is 4mm after a while, and the edge is reduced to 2mm.

Fig. 4-6 has illustrated the coincidence effect that the present invention points out, has shown the measurement result for the 4mm flat board.

Fig. 4 show that axle is gone up and 40 ° and 80 ° on offset direction axle on the single-point frequency response.Position on angle increases away from axle, because some sound negative function, so low frequency can be decayed.High frequency peaks betides the place near 5kHz on 80 °, and this is the coincidence frequency of this plate.Peak value voice output on 80 ° reaches 80dB, and this exceeds 14dB than the response of this frequency on axle.And then the peak value of response of decay is the feature of coincidence effect in the large-scale hard plate to a certain degree.

Fig. 5 shows that 6kHz, 9kHz and 15kHz go up the polar diagram of sound press degree in the different directions.Narrowing down of radiation is significantly, starts from 90 ° on the 6kHz, be decreased on the 15kHz less than 60 °.The sound bundle of this radiation on an angle reduces with the increase of frequency, is the feature of coincidence effect.

Fig. 6 shows the sound power as frequency function.The variation of power is very slow on low frequency, but further increases when frequency, and power can be promoted to the maximum near coincidence frequency, descends on higher frequency then.This maximum is much wideer than the sound press degree track that seems in Fig. 5, and this is because power measurement for the integration of sound press degree on all angles, does not therefore reflect the directivity of change, total only reflect rather slowly the voice output with frequency change.Maximum in this power response also is the feature of coincidence effect, as being seen in the large tough curved arm beam.

The following describes according to loud speaker first embodiment of the present invention.This loud speaker has the plate of attenuation gradually.

Fig. 7 a shows the profile of the plate of attenuation gradually, is the function to the fractional expression distance of panel edges.This plate forms this profile after grinding x and y face, form a Pyramid in middle section.What Fig. 7 b showed is corresponding coincidence frequency figure, bigger variation is arranged quite approaching actuator position.

Single-point frequency response when Fig. 8 demonstration increases around the plate angle, response is similar to reference plate on the axle on high and low frequency extend.

In this embodiment, the shown coincidence maximum of first plate can decay up to 10dB.This maximum width also can increase by factor 2.

In according to the plate of present embodiment, do not present when surpass overlapping with comparative example in respond the high attenuation of sound press degree on relevant 80 ° on the observed axle, and significantly improve the high frequency off axis response.

The polar diagram of the sound press degree on Fig. 9 demonstration and 6kHz shown in Figure 5,9kHz and the 15kHz same frequency.Clearly can find out, according to the polar diagram of first embodiment and reference plate by comparison, significantly reduce boundling from the comparison of this two picture group.

Figure 10 shows the sound power that plate radiated according to first embodiment, when with reference plate shown in Figure 6 response by comparison, can find out to overlap maximum decay 5dB, and widen high frequency, the same with the prediction of the plate of attenuation gradually with past edge reduction rigidity.

Generally speaking, test board is all having significant improvement than flat board aspect all problems of coincidence effect initiation.This representative has in all be significantly improved aspect each good compromise with the web wheel exterior feature of COINCIDENCE PROBLEMS, has also kept good frequency response simultaneously.

Figure 11 to 14 shows is the result of the loud speaker that alters a great deal according to second embodiment of the invention plate inside gradient, is very similar to the result of Fig. 7 plate.

Two kinds of plates have all demonstrated good compromise, have improved all aspects that overlap radiation characteristic, and second plate shows that still, its single-frequency polar diagram result has the improvement of a little than first poor a little one group of single-point frequency response and sound power rail mark.Though optimization is always a kind of compromise, the designer can select according to the needs of applicable cases.

Two embodiment are relevant with medium sized plate, and the 3rd following embodiment will discuss small size, (A5-210 * 148.5mm).

The profile of Figure 15 and 16 display panels.As can be seen, its size reduce ground very big.This plate becomes 10.8mm and edge compression to become 1mm to make intermediate compression by the thick Rohacell of 14.5mm, and the control flat board then shortens whole surface pressure into 9.8mm.It is on the position of the best, to utilize this actuator position for isotropic plate that exciter is fixed in the plate back, even the plate of attenuation can both be obtained good result gradually, certainly, it will also be appreciated that the position of further optimization exciter.

Figure 16 shows the coincidence frequency figure of position function calculation on the pressing board.Figure 17 show the 10mm of same size dull and stereotyped with the comparative result of attenuation plate gradually.Show the sound power measurement result in Figure 18 a (flat board) and Figure 18 b (attenuation plate gradually).

As can be seen, this plate shows suitable excellence directivity widely: though still can average radiation on 13kHz to the place ahead hemisphere.The power response of the plate of attenuation does not show significant step yet near 5kHz gradually; This class step is high-visible in the reference plate response.Please note that these test boards all are fixed on the very shallow chest, can about 500Hz, form a maximum like this, in the loud speaker of reality, need to use electronic filter or other devices to control.This is because chest is caused, is not that attenuation causes.

Also carried out many tests on other plates, its result has confirmed that in according to plate of the present invention the caused many effects of coincidence effect are improved.In order to make the directivity effect smooth-going, so profile is very important, yet reaching aspect whole sound power smooth-going, accurate profile is just far inessential.

Figure 19 to 21 shows the drive point velocity measurement of three plates that encouraged by the voice coil loudspeaker voice coil transducer with 25mm diameter.Figure 19 shows the result of 4mm flat board, and Figure 20 is the result from the plate of first embodiment, and Figure 21 is the result of 2mm flat board.

Precipitous peak value in the speed track between 10kHz and the 20kHz is exactly the evidence of gap resonance.For the plate of 4mm and attenuation gradually, resonance occurs on the 13.1kHz.For the 2mm plate, resonance occurs on the 11.8kHz.

As what expect, the rigidity that increases plate just can increase dull and stereotyped resonance frequency.The resonance frequency of the plate of attenuation is determined by the plate thickness on the drive point gradually, therefore is similar to the thick flat board of 4mm.

This demonstrates, and gap resonance is determined by the thickness on the drive point.Therefore, the hard plate portion that has on the actuator position can be reduced to this gap resonance minimum.

When (not shown) also pointed out that change when bending stiffness concentrates near the panel edges as a result, the effect on the radiation feature of coincidence frequency top will be very little.But this processing to plate has favourable effect, will discuss as following.

In order to make the loud speaker of a reality, this plate is fixed in some framework/support usually, its objective is vibrational energy is maintained in the plate, and it is minimum that the energy that is transferred to framework is reduced to.This is that impedance mismatching bigger between backup plate and the framework is reached.The borderline impedance of the controlled making sheet/framework of plate thickness on the change edge, and can not influence whole radiation feature.The example of some these class methods benefits will be provided below.

Near near the edge, plate is become extremely thin thickness gradually, can be with the impedance drop of plate to very little value.If this impedance is lower than the impedance of clamping frames, then only can transmit quite low energy.

The thickness that increases panel edges can significantly increase impedance, if plate is connected to the framework (and quite low impedance) with soft terminal, then the anti-increase meeting of plate resistance produces great mismatch on the edge, and makes the energy minimum that transfers to framework.

Except above-mentioned two examples, the body of plate is returned energy reflection in plate thickness unexpected increase/minimizing meeting on the border.For example: the thickness that increases suddenly on the panel edges can provide and clamp the similar situation in border, and is incident in borderline energy meeting reflected back plate, just can clamp safely or bearing edge then, because it comprises considerably less vibrational energy.

The change that reaches bending stiffness by the thickness that changes plate is optional.But Figure 22 shows to have the plate that the equal thickness radius of curvature changes on the plate zone, and this can cause the change in the bending stiffness.Figure 23 illustrates another kind of mode, and plate is a gauffer as shown, reaches middle section than having higher bending stiffness in the exterior lateral area.

The thickness of plate also can change by above-mentioned plain mode, and for example: bending stiffness can change on corrugated surface, or changes in the lip-deep a series of steps of plate.Show some available profiles in Figure 24, utilize wavy or step or other modes in the respective panels thickness just can obtain this class profile.

Claims (25)

1. but the tabular sound components (1) of support bends ripple vibration, wherein bending wave and/or the mass surface density in the plate changes in plate (1), and the coincidence frequency of generation certain limit, wherein, the ratio of maximum coincidence frequency and minimum coincidence frequency is 1.2: 1 at least, like this, compares with isotropic plate, aspect sound power and/or directivity, bending wave is coupled to air more equably in the plate.

2. acoustic device comprises tabular sound components as claimed in claim 1 and is fixed in a exciter on this member.

3. a loud speaker comprises a plate as claimed in claim 1 (1) and is installed to this plate (1) and goes up the exciter (3) that causes a voice output to evoke the bending wave in the member, and wherein coincidence effect obtains smooth-going to the influence of voice output.

4. loud speaker as claimed in claim 3, wherein the bending stiffness of plate (1) can change on the zone of 10% plate area at least.

5. as claim 3 or 4 described loud speakers, wherein bending stiffness has a maximum, and exciter (3) is coupled on the plate (1) to have on the peaked position of 70% bending stiffness at least.

6. as each described loud speaker of claim 3 to 5, wherein the thickness of plate changes on the zone of plate (1), with bending stiffness that certain limit is provided and therefore obtain the certain limit coincidence frequency.

7. as each described loud speaker of claim 3 to 6, wherein bending stiffness has a maximum in the middle section of plate (1), and successively decreases to the edge.

8. loud speaker as claimed in claim 7, wherein exciter (3) is coupled on the plate (1), is positioned at middle section.

9. as each described loud speaker of claim 3 to 8, wherein exciter (3) is positioned at that plate (1) is gone up, the position of bending stiffness value maximum.

10. as each described loud speaker of claim 3 to 7, wherein panel stiffness has minimum value in plate (1) central authorities, and increases progressively toward the edge of plate (1).

11. loud speaker as claimed in claim 10, wherein exciter (3) be positioned at the central authorities of plate (1), than the low zone of mean rigidity of plate (1).

12. as claim 10 or 11 described loud speakers, an edge of clamping plates (1) at least wherein, and maximum bending stiffness is arranged at least one plate of clamping (1) edge.

13. as each described loud speaker of claim 3 to 12, wherein the gradient of bending stiffness is at the position at exciter place height.

14. loud speaker as claimed in claim 13, wherein the gradient of bending stiffness reduces along the line that extends outward from actuator position.

15. as each described loud speaker of claim 2 to 14, wherein bending stiffness changes at the board member fringe region.

16. loud speaker as claimed in claim 15, wherein bending stiffness is the highest on the edge of plate (1), and descends towards the inside of plate (1) smoothly.

17. as claim 15 or 16 described loud speakers, wherein a supporter is clamped an edge at least.

18. loud speaker as claimed in claim 17, wherein the bending stiffness on plate (1) edge is designed to make the mechanical impedance on plate (1) edge and the impedance of supporter (13) not to match.

19. as each described loud speaker of claim 3 to 6, wherein the bending stiffness of plate is by wavy pattern change, so the coincidence effect in the voice output is by smooth-going.

20. as each described loud speaker of claim 3 to 19, wherein plate is the distribution mode plate with many resonance mode of flexural vibration by frequency distribution.

21. an acoustic absorption body comprises tabular sound components as claimed in claim 1 (1).

22. the acoustic resonance body of the control that is used to echo comprises tabular sound components as claimed in claim 1 (1).

23. an audio amplifier comprises the tabular sound components (1) as claim 1.

24. the supporter of an audio components comprises tabular sound components as claimed in claim 1 (1).

25. an acoustic device as claimed in claim 2, transducer is converted to the signal of telecommunication with the bending wave in the plate (1), so this device is as microphone.

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