BG104543A - Active acoustic devices comprising panel members - Google Patents

Abstract

The invention relates to active acoustic devices, in particular panel acoustic devices and to methods for their production. They can be used for functional combination with elements with other designation such as displays, billboards, projection screens and other similar. Active acoustic device comprises a panel member (11) having distribution of resonant modes of bending wave action determining acoustic performance in conjunction with transducer means (31-34). The transducer means (31-34) is coupled to the panel member (11) at a marginal position. The argument is such as to result in acoustically acceptable action dependent on said distribution of active said resonant modes. Methods of selecting the transducer location, or improvement of location of localized marginal clamping, rely on assessing best or better operative interaction of said transducer means (31-34) and the panel members (11) according to parameters of acoustic output for the device as an acoustic radiator. 32 claims, 31 figures

Description

TECHNICAL FIELD

The invention relates to active acoustic devices and in particular to panel elements, the acoustic action or characteristic of which is based on the useful distribution of the action of bending vibrations of the resonant type in such a panel element and the associated surface vibrations; and to methods for producing and refining such active acoustic devices.

It is convenient here to use the term "distribution type (mode)" for such acoustic devices, including acoustic emitters or speakers; and for the term panel form, "to take account of such a distribution type action in the panel element, unless the context implies otherwise.

Within or as panel speakers, such panel elements act as acoustic radiators of a distribution type based on the action of the bending wave induced by input devices having a mechanical effect on the panel element; and the excitation of the bending wave of a distributor type causing surface vibrations in the acoustic output upon contact with the surroundings, usually air. Prior art related to such acoustic emitters (between a wider class of active and passive acoustic devices of the sales type) is given in our International Patent Application WO 97/09842; and in various of our later applications relating to practical applications and developments.

BACKGROUND OF THE INVENTION

Until now, transducer locations have been considered applicable and optimally effective in positions inside the panel element substantially about but offset from the center - at least for panels that are substantially isotropic in deformation resistance and exhibit in actual substantial axial anisotropy of the deformation resistance (s). The foregoing application WO 97/09842 provides specific guidance in terms of optimal proportional coordinates for such in-panel transducer locations, including alternative options; and preference for separate different coordinate combinations when using two or more converters.

Various relevant applications are envisaged, especially for panel-shaped acoustic devices, including supporting acoustic non-intrusive surface panels or layers. For example, it is possible to merge physically or merge into a monolithic or layered form, including as visually indistinguishable. A functional combination with other uses, such as display, is also feasible, including? · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · . For most applications, the ability to effectively hide in-panel converters is sufficient. However, there are possible practical applications where it would be useful to leave wider, especially central panel areas, unoccupied even by hidden converters. For example, when using panel elements for video or other visual displays, which strive for translucency, even transparency, it is pointless to have such in-panel converters, although a panel-shaped acoustic device would be much more attractive if it may provide a large mid-range with unlimited visibility.

SUMMARY OF THE INVENTION

According to one aspect of a device of the present invention, a panel-shaped acoustic device comprising an acoustic panel-type distribution element with transducers arranged in a peripheral position is arranged so as to result in an acceptable effective acoustic distribution and vibration excitation in resonant mode. The presence of such suitable peripheral positions is hereby established as a means of deploying the conversion means in addition to useful concepts relating to the reasonable selection or improvement of one or more of these positions. Such a sensible choice may be useful as a consequence or result of examining an acoustic emitting device or speaker when compared with the appropriate input of vibrating energy into the panel element, or more conveniently by assessing the parameters of the acoustic signal emitted by the panel element when it is excited, from peripheral positions or · · · · · · · · · · · · · · · · · · ·. ·· · • - · ··· ·· ··· ·· · · /> ♦ ······· • · · * + ·· ·· · · · · · · locations. The best results also apply to microphones.

Based on developments known in the invention at the time, the availability of such suitable peripheral locations is at least unexpected. Of course, the closest prior work opposed to application WO 97/09842 is the starting point for this invention and for the concept developed, namely, application WO 92/03024, towards which progress has been made, especially with respect to angular deviation arousal with her. This progress includes the assessment that the action of a bending wave of a distributive resonant type, as required for the required acoustic characteristics, results in high vibration activity at the panel angles; as a rule this is also a factor in panel edges. At least intuitive, but also significantly enhanced by the practical success of locating the converter with some displacement relative to the center, but entirely inside the panel, such high vibration activity binds specifically to the panel edges, providing obviously limited access, thus probably available effect on the material of the panel elements as a whole; this composite combination contributes to the perceived feasibility of edge excitation so far.

In the application of this invention, the appropriate acoustic panel element, or at least portions thereof, may be transparent or translucent. Characteristic panel elements can be polygonal, most often rectangular.

Much of the conversion means may be on or near different edges, at least for most of the rectangular panel elements. The converter or any converter can be piezoelectric, electrostatic

· · · · · · · · · · · · · · · · I) · · · · · · · · · · · · · · · · · · · · electromechanical. The converter or any converter may be mounted to excite compression waves in the panel edge, and / or to deflect the panel edge laterally to emit transverse bending waves along the panel edge, and / or to cause a panel angle to twist, and / or cause a lazy deflection of a separate section of the panel.

The evaluation of the acoustic output of the panel elements may be with respect to the appropriate criteria for the acoustic signal, including the amount of output power with such efficiency of converting the incoming mechanical vibration (automatic as well as causally driven electrical actuation) into an acoustic signal, smoothing the output power as a measure of equalization of the excited resonant vibrations from the action of the bending wave, control of the output power with respect to the frequencies of the excited resonant t repercussions including the number and distribution or spread of these frequencies, each of these criteria or all of them being useful indicators. Such estimates of the actual locations of the conversion agents individually and in combination are aspects of the method of this invention.

As an aid in estimating at least the output power smoothing, it has been suggested hereafter to use methods based on the mean squared deviation from a standard. The use of the mean square deviation inversion is useful for the smooth evaluation of the direct correspondence of positive values and / or images. The appropriate standard may be individual for each case considered around average, as shown graphically by

• · · · ·

average line to the actual measured output power for the selected frequency range. Significantly useful for estimating the root mean square deviation is the standard having a standardized standard format; and that the measured acoustic power output be adapted to the frame of this standard format. The standard format may be a graphical straight line, preferably a straight line, corresponding to a single constant reference value; further, it is preferable that the same line or dimension as obtained is actually referred to the panel element with the higher frequency distribution mode, where the modes and modal action are more or less dense.

In this connection, it is clearly worth noting that whatever function is required for such normalization to a substantially constant standard, it is also effective as a basis to take the equalizing function applicable to the input signals to increase the lower frequency acoustic power. This is the case where panel elements with a distribution mode and with preferred bending deformation resistances (s), as in the above patent applications, may naturally have acoustic power output parameters with respect to frequencies that indicate progressively falling to and at low frequencies where the resonance modes and modal action are less dense, but just as their frequency distribution is usually beneficial for acoustic action in this frequency range, so this equalization of the input signal may also be useful. This low acoustic power output at low frequencies is related to the free oscillation of the edges of the panel elements and as a result increases the loss of low frequency power, most of which have

• • The tendency to be weakly radiated and / or scattered, including acoustically shorted around free adjacent panel edges. As expected, these effects of low-frequency power loss are significantly greater for panel elements with transducer locations at or near their edges and / or with less deformation resistance than panel elements using intra-panel arrangement of converter. However, regardless of any alignment of the input signal, a significant mitigation of these effects is possible by mounting the panel elements by enclosing screens and / or by fixing the edges of the panel elements. Indeed spatially positioned edge locks may have useful selective advantage effects relating to frequencies with wavelengths greater than the distances between the positioned edge locks.

Interestingly, for specific panel elements with significantly high deformation resistance, the feasible peripheral locations of the transducer include positions correlating with the edges with the ordinary intra-panel transducer positions resulting from the preferred implementation of a concept or implementation similar to our individual ones. patent applications. In the use of couples in pairs, the first preference was found for the peripheral placement of converters with said ratio in accordance with the abstract surrounding the largest area. For a substantially rectangular panel element, said correlation may correspond to orthogonal or Cartesian coordinates, with said first preference represented by combining transformers with diagonally opposite quadrants. However, this is high-Q

• · • · ·· • · · · • ··· · • J? · · ·· · * · ·· · ··· h · ·· ·· ·· · *

panel element with a particularly high deformation resistance and not always accurate, even for fully (but less) rigid panels, see the following illustration of reliable action in relation to some or adjacent quadrants. For an elliptical panel element, said correlation / correspondence may be according to hyperbolic resonance-related lines, extending along its edge in the direction of intra-panel arrangements. Other, although less good, but acceptable feasible pairs of locations of the transducers at the edges have been established by examination based on rotation of the orthogonal vectors around the preferred locations of the transducer inside the panel, including close to the angle or directly at the angular positions of the panel elements. Another innovative aspect of angular or near-angular excitation involves proper compaction or fixation mainly in the known intra-panel optimum or gear location, where such thick optimum location (s) are seen to function effectively to some useful extent as a virtual source (qi) of deforming wave vibrations in the element. The latter may not allow central perturbation from thickening, but is clearly suitable for successful peripheral excitation in the corners.

Further investigations were made, including panel elements having different hardness, again characterized by significantly high but also much lower and medium hardness of the panels, in each case usually with a basic rectangular configuration and with a ratio the dimensions and resistances of axial bending deformation mainly as in WO 97/09842.

· · · · · · · · · · · · · · · · · · · ·

9 ·· ··· ·· ··· · ·· • ··· ♦ ···· 99 99 99 ··· »

For a panel element with higher deformation resistance, the estimation based on the alignment of the output power for the position of a single transducer along the longer and shorter edges is generally a confirmation of the above preferred coordinate positions, i.e. reaching the maximum, as expected, for the best zones of stand-alone converters. In addition, however, the longer edges have an expected deviation of the frequency smoothing measurement within about 15% of the maximum at transducer locations between the coordinate positions in each half of the edge and on the other side of these coordinate positions - approximately one distance apart. a third from each corner; and within about 30% for at least one quarter of the length between positions. For the shorter edges, the deviations in the smoothing measurement were within about 10% between the coordinate positions and within about 25% at the quarter length of the positions. The shorter edges actually show better power offset than the long edges shown at positions at a quarter-length at exactly one-tenth the length of the corners.

The study of combinations of two transducers has been extended in particular to the same or adjacent quadrants with one transducer, one for each longer and shorter edge. One converter may be in one best position along one of the edges of the single converter, with the other converter having a variable position on the other edge. For the change in the position along the shorter edge, the upper preference for one of the positions according to the coordinates of the preferred in-plane positions of the converter is confirmed by taking into account the best smoothness at about six tenths of a length. They also exist

positions close to go good, three-quarters of a length and very few not so good positions of one-quarter and one-third length. In addition, most positions other than those below about one-tenth of the angle are better, similar, close to good or not as bad as those associated with the coordinates of the preferred internal panel placements in the same quadrant. To change the position of the longer edge, the shorter edge converter is positioned around a preferred position close to six tenths, after which the preference for combinations of transducer locations in adjacent quadrants is determined, with the best being just below one fifth and slightly better than theses at position 0.42 at position one-third length and very few stripes from position one-tenth length. The position of one quarter of the length is in fact almost the same as the position of the average length and the position of the adjacent quadrant with the coordinates of the preferred intra-panel arrangement. Obviously, based on an iteration, these procedures can be continued and better combinations can be found.

Studies of multiple panel elements with less strain resistance based on output power equilibrium have shown maximum attenuation at peripheral transducer locations, as in the position with internally panel coordinates, but nearly as good as one quarter of the length of the transducer. panel edges, and in general noticeably less critical to the position along the edges in terms of the actual modal distribution achieved. This is explained by the interaction between the lower deflection resistance of the panel and the correspondence inside the transducer itself. Obviously, the resonance modal distribution is · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·· The panel is influenced and altered by the arrangement of the converter, at least to some extent corresponding to such arrangement. High panel deformation resistance substantially avoids such effects. However, such intrinsic compliance and the possible interaction with the panel deformation / elastic resistance is undoubtedly another factor that must be considered, including properly used.

Studies of panel elements with significantly high and very low deformation resistance clearly show quite different cases of application of peripheral excitation, including in terms of greater or less criticality, relative to the location of the transducers, whether singly or in pairs, and with regard to the smaller or larger interaction with the correspondence within the converter. Thus, it is appropriate to consider a panel element with an average strain resistance.

For such a panel element with a medium strain resistance, the expected differences relating to the very low strain rate resistance of the panel element include an increase in acoustic power output where possible by fixing the edges, a marked increase in power over the middle frequency range, and a stronger modality or maximizing low-frequency vibrations. Trends in the characteristics of the higher resistance of the panel element as the best position of the unit converter include a more rigorous preference for edge positions over the coordinate of the optimum in-panel positions of the converter, as well as a reliable possibility of passing through the midpoint, but probably also

about one-tenth of the distance inwards from the corners. For two peripherally positioned transducers, a significant advantage is obtained for the coordinates corresponding to the position of the optimum in-panel arrangement of the transducer, the extension of less good but similar feasible positions of the positions to the middle and two-thirds of the length, and equality between the corresponding coordinates of the same quadrant and positions two-thirds of the length.

It is obvious that differences in the material properties of the panel elements, beyond the basic fitness to withstand the action of the deforming wave, are important for determining the peripheral locations of the transducers; and that the use of two or more such transducer positions entails highly individualized solutions requiring experimental evaluation, the opportunity of which is afforded by the considerations included here.

Also, at least specifically for the mainly rectangular panel elements tested, it is found that many, if not most, of them are likely to be referring to all or near the edge of transformers that are unreliable, such as those that can be significantly improved (with respect to the wave-dependent resonant distribution and excitation mode in the acoustic response of the element) if considered as related to localized thickening or fixation in one or more selected others peripheral position of the review panel member.

Thus, the creative aspects include linking said position of the actuators with a position peripheral to the panel element with another useful thickness or fixation.

··· · 9 · ···· • · · · · ···· · ·· ·.: 13 .. · ’· .. ·· .. · * · .. ·· .. ·

With respect to the use of two or more conversion means, a comprehensive study of combinations of peripheral locations is impractical, but information is provided in terms of how to find the best or other feasible position for a second transducer at any given peripheral location. the first converter. Indeed, other peripheral locations of the converter can be investigated and evaluated, as set out herein. The use of localized peripheral attenuation to enhance the characteristics of any given peripheral placement can also be investigated and evaluated as a degree or value, using knowledge from here, or to increase or decrease the proportion of any resonant mode (s), or otherwise. for intentionally interfering with other resonant mode (s), or mainly for increasing output power.

It is generally considered to make sense to take into account the fact that the lowest resonant vibrations are related to the length of the longest real axis of any panel element such that the longer edges of the substantially rectangular panel elements are always significantly preferred for deployment of conversion means, including by all means making the best possible arrangements for working with single conversion means. It is reasonable to consider this as an application, even when the use of other converters is encouraged or encouraged, or again for the increase of some resonant mode (s), deliberate interference with other resonant mode (s), or a basis for increasing the output power .

Also fundamentally important is the fact that our operating frequency range of interest should be part of the evaluation of the location of the conversion means and • · · · · · ·

may substantially influence and effect such placements, i.e. it may be different for all ranges extending up and down such as 500 Hz. Another influencing factor may be the presence of an adjacent surface, for example behind the panel element, at a distance that affects the acoustic characteristics.

It is understood or required, as a prerequisite, that the nature of the preferred said edge or adjacent edge position (s) should branch out, as implied in our previous PCTs or other patent applications, to the typical type that allows the most accessible frequencies to be coupled modes, and making them more offset than less offset, probably avoiding the mere dominance of only a few of the frequency modes. Such compliance may be rather lower than higher total actual vibration energy within the panel element, but sufficiently high as a statistical set of frequency modes, i. more than nothing in the sense of little connected or unconnected to any of the few modes.

DESCRIPTION OF THE FIGURES Attached

The invention is illustrated and described by way of examples and accompanying figures, in which: Figure 1 shows an acoustic panel with a distribution mode equipped with a converter, as described mainly in the above PCT application;

Figure 2 shows a schematic representation of four different ways of performing an acoustic panel located at the periphery or at the edge;

.115. * * * .. ** .. * Figure 3 shows the possible arrangement of the transducers in the periphery of the acoustic panel to achieve the actions shown in Figure 2, and Figure 3A shows a panel in a transparent embodiment;

Figure 4 shows the four preferred peripheral positions of the transducers shown in the diagram with respect to the intra-panel arrangement of Figure 1 shown by dashed lines.

Figure 5 shows the same four preferred positions with respect to another preferred intrinsic actuator arrangement and a preferred pair of additional or illusory intrinsic actuator positions;

Figure 6 shows how all pairs and all four excitation converters are connected to test at such preferred locations;

Figure 7 shows operating, albeit less preferred, pairs of peripheral locations of the excitation converter;

Figure 8 shows the angular position of the actuator and the auxiliary thickening at the preferred internal panel position of the actuator;

Figures 9 and 9A show four commonly preferred peripheral positions of the excitation converter together with a number of peripheral thick and fixed positions and how the experimental thickening and excitation transducers are connected to the panel; and

Figure 10 shows the interior panel space unaffected by the peripheral positions of the actuator (s), end clamp (s) and flexible suspension / mounting.

11A, B are graphs of output power / frequency for a substantially rectangular panel element with significantly high strain resistance and single transducer positions along the longer and shorter edges;

Figures 12A, B refer to bar charts of output power offset measurements;

13A, B are graphs of output power / frequency for two positions of the transducer, one varying along shorter or longer edges;

Figures 14A, B refer to bar charts of output power offset measurements;

15A, B are graphs of output power / frequency and corresponding bar chart of power offset for a panel member with much lower strain resistance and single transducer positions along the longer edge;

16A, B are graphs of output power / frequency and the corresponding bar chart of power offset for the second positions of the transducer along the shorter edge.

Figure 17 shows a comparison of the output power of inverters, preferably located inside the panel and at the edge for a low-resistance panel element;

Figures 18A, B, C show the effects of shielding, three-edge fixation, or both;

19A, B are graphs of output power / frequency and corresponding bar chart of power equalization for the low-impedance panel element

deformation fixed along three edges and positions of the transducer on the fourth edge;

Figures 20A, B are graphs of output power / frequency corresponding bar chart of power equalization for a low-deformation panel element fixed along two edges and positions of the transducer on the other edge;

21A, B are graphs of output power / frequency and corresponding bar chart of power alignment for panel element with low deformation resistance at localized fixation in the corners / middle of the edges and positions of the transducer on another longer edge;

Figure 22 is a bar chart of power alignment for a panel element with low deformation resistance with additional localized fixation between other angles / midpoint fixation;

Figures 23A, B are bar charts for estimating non-normalizing power for a panel element with low three-edge fixation resistance, at seven points or along the entire edge, and for the position of another local retainer along the other edge, wherein the converter has a disadvantage;

Figures 24A, B are graphs of output power / frequency and the corresponding bar chart of power offset for the case of three-edge fixation evaluated by normalization;

Figures 25A, B are graphs of output power / frequency and the corresponding bar equalization diagram for a panel element with a mean strain resistance and

• ·

single converter positions along the longer edge with normalization;

26A, B are graphs of output power / frequency and a bar chart showing the power of a panel element with a mean locking resistance localized at seven points, estimated without normalization;

Figures 27A, B are similar but with normalization of power equalization estimates;

28A, B are graphs of output power and a bar chart for power offset for a panel element with a mean strain resistance and a second position of the transducer along the shorter edge;

Figure 29 shows a seven and thirteen-point localized fixation as applied above;

Figure 30 is a schematic illustration useful in explaining the effect of deformation inside the transducer, and Figures 31A-E are bar diagrams of effective power for a panel element with lower deformation resistance at different edge parameters.

EXAMPLES FOR THE IMPLEMENTATION OF THE INVENTION

In Figure 1, the panel acoustic loudspeaker with distribution mode 10 is as described in WO 97/09842, the panel element 11 having a typical optimum close- (but not inside)

c) the center location of the actuating transducer 12. The sandwich-type lamellar structure shown with the core 14 and the surface layers 15,16 is merely exemplary, with many options available with monolithic and / or reinforced and other structures. In each case, usually the in-panel location of the converter .: 19 .. · * · .. ·· .. · * · .. ·· .. · potentially limits the available transparent area, such as transmitted light in the case of a transparent or translucent panel.

Transparent or translucent resonant-type acoustic panel elements may utilize mainly known transparent piezelectric transducers, for example from lanthanum-doped titanium zirconate. However, this is relatively expensive and therefore an alternative to this approach in which the acoustic panel element of the resonant type 10 can remain substantially transparent and unobstructed by optimizing the speaker construction selected from the four types of excitation shown in Figure 2, directed to the periphery and along the perimeter of the panel and designated as types ΊΊ - T4, as follows: T1 - excitation of compression waves inside the edge (shown hereinafter in 18A) of the panel element 11 - by inertial action or by corresponding standard flat excitation converters

T2 - transverse excitation of deformation waves along the edge (also shown hereinafter in 18A) of the panel element 11 - due to lateral deflection of the panel edge using exciter transducers with deforming action

TK - application of distortion of the panel element 11, as shown transversely to the angle between the edges 18A, B - due to the action of one of the two types of excitation converters deforming or inertial

T4 - induction of linear deviation / curvature / directly at the edge of the panel member 11, as shown for the edge of 18B - in a separate section, by interaction with excitation transducers with inertial action.

Figure 3 is part of a general view of composite panel I showing highly tensile surface layers 15, 16 and interior structure 14 with drive transducers / exciters 31 - 34 for the above mentioned four types ΤΙ - T4 of edge / peripheral drive. In practice, less than four drive types can be used in the panel element at the same time, which can be useful for acoustically and mechanically optimizing the required bandwidth and for the particular drive type used. In this way, the optimized panel can be actuated by any one or more of the different types of actuator.

The transparent or translucent edge-driven acoustic panel may be monolithic, for example entirely glass or using translucent / transparent materials suitable for the interior and surface, see Figure 11. An Interpretation with Video Display Device (VDU) may enable the screen to be used also, as a loudspeaker, have a suitably high resistance to deformation and, at the same time, a small mass if the pair of covering layers 15A and 16A pressed in the form of a sandwich inside of an aerogel 14A lightweight material used transparent adhesives 15B and 16B. Aerogels are extremely light porous solids, such as silica. The transparent or translucent coating layer or layers may be of laminate structure and / or made of transparent plastic material, such as polyester or glass. Ordinary transparent VDU screens can be replaced with such a transparent acoustic radiator panel, including acoustic excitation outside the non-obstructed area of the main screen. A suitable quartz airgel material for the interior is (RTM) .21 ··· · · · · · ···

BASOGEL by BASF. Other possible interior materials may include lesser known aerogel-forming materials, including metal oxides such as iron and tin oxide, organic polymers, natural gels and carbon aerogels. Particularly suitable plastic roof laminates can be polyethylene terephthalate (RTM) MYLAR, or other transparent materials of specified thickness, mechanical parameters and density. The very high coefficient of transverse elasticity of the aerogels allows extremely thin composite materials to be made for a suitable reduction in size and other important physical parameters, operating according to the acoustic principles of the mode of distribution.

If necessary, such a panel can be added to the existing VDU panel, for example mounted as a monolithic faceplate. For the plasma type display, the interior is subjected to low vapor pressure, close to vacuum and with very low acoustic impedance. Therefore, there will be little acoustic interaction behind the sound emitter as a result of the improved performance and the retention of the usual front panel. For tape type display technology, the front transparent window can be rebuilt using distributor-type emitters, while the rear display structures can be sized and selected with such acoustic properties as to facilitate the sound output from the front panel. For example, the partial acoustic transparency of the rear display structures will reduce the reflection of the waves and improve the characteristics of the speaker element of the distribution type. In the case of a light-emitting class display, this may be from the rear surface of the transparent distribution panel without

significantly reflect its acoustic properties and the images will be visible on the front.

A transparent distribution speaker may also have an application in the rear of projection systems where it can be added to a translucent screen or this feature may itself be combined with a suitably tailored / prepared / rear projection surface. In this case, the projection surface and the screen can be one component - both for convenience and economy, as well as for optimization of acoustic performance. The back cover layer may be selected to accommodate the projection image, or alternatively, the optical properties of the interior may be selected to be used for projection. For example, if the speaker panel has a relatively thin interior, complete optical transparency may not be required or may not be perfect, which allows the choice of alternate interiors for light transmission, such as other brands of aerogels or more economical substitutes. Individual optical properties may be combined with the interior and / or the roof surfaces to give an increase in the directional and luminous properties of the transmitted optical images.

When a transparent distribution speaker has an open front surface, it can be enlarged, for example, by providing conductive layers or areas, visible or transparent, for input on the data screen or commands from the user. The transparent panel may also be improved by optical coatings to reduce reflections and / or to improve scratch resistance or only by scratch coatings.

The transparent panel interior and cover layers may be selected to have an optical image, for a color or neutral image, to improve the visual contrast ratio of the display used with or included in the transparent panel speaker. During the production of the transparent distribution panel, invisible reinforcement, for example with micro-wires or with transparent conductive films, such as light-emitting diodes (LEDs), liquid crystal displays (LCD) or the like, can be made together with indicators, for example it is possible to integrate them into the transparent panel and to obtain as a result of this protection while minimizing acoustic performance. Such constructions can also be manufactured when full transparency is not required, for example when only one cover layer of the panel is transparent and provides an image of the monolithic display below that surface.

The transducers may be piezoelectric or electrodynamic, according to design requirements, including price and functional characteristics, and are presented in Figure 3 as simple sketched elements, usually associated with the panel element by means of a suitable adhesive (s). For the upper type of driving excitation T1, the inertial transducer 31 is shown as compression wave propulsion directed vertically to the panel 30. For the upper type of driving excitation T2, the transducer of the deforming type 32 is shown to act for direct local deformation through the excitation of the transducer of the excitation of the panel

30. For the upper type of excitation drive T3, the inertial converter 33 is shown to serve to bend the panel angle by moving the excited wave diagonally and therefore inside the entire speaker panel 30. For the upper

mun driving excitation T4 another inertial converter 34 is shown as a block or semi-circular shape that serves to bend the edge of the speaker panel 30.

Each type of excitation will produce its own characteristic of the drive of the panel 30, which takes into account the overall construction of the speaker, including the parameters of the panel itself 30. The position of the transducers 31 - 34 along the edge of the panel is practically quoted repeatedly with the parameters of the design of the panel for the optimum or at least operationally acceptable modal distribution of the deforming waves. It is obvious that according to the characteristics of the panel, including such as controlled loss and location (s) and type (s) of the peripheral edge or near-edge propulsion, more than one audio channel may be fed to the panel 30, for example via multiple drive converters. This multi-channel switching capability can be enhanced by processing the signal to optimize the sound quality and / or to control the properties of the transmitted sound, and / or even modify the perceived channel separation and spatial effects.

Particularly suitable locations of the drive inverter along the edges of the substantially rectangular panel element are the positions on the edges obtained by orthogonal side-by-side lines or coordinates through the intra-panel optimum or preferential position of the drive inverter according to your upper 42 PCT request - 48 in Figure 4). Particularly practical is the use of actuators at at least two such coordinates associated with locations 45-48 at the edge, Figure 6 shows a serial connection in series and in parallel with

two and four drive inverters at A and B. Other connections of drive inverters are possible, and it is often preferable to directly switch on one at a time all the inverters; as may be applied any desired signal tuning, eg differential delay (s), filtering, etc., for example for the appropriate reduction of undesired interaction between the converters and / or with the electrical signal sources and the favorable positions of the CPI-CP4 drive inverter of Figure 5 with respect to the intra-panel preferential arrangement PL. Pairs of all coordinates can be obtained, ie CPI and CP2, CP2 and CP3, CP3 and CP4, CP4 and CP1 and the first preferred pairing is definitely abstract and includes an area that is actually larger, along with the geometric center X. Such an abstract area will of course pass through or it will contain another optimal or preferential position of the drive converter inside the panel - see the additional location of CL and the designations at CP5 and CP6 the first preferred pair of positions of drive transducers.

It is interesting to note about the very high Q-mun panel that the preferred and most preferred pairs of orthogonal coordinates at the respective positions of the drive inverters can produce a low output frequency that can be no-stretched and uniform even from the excited one from preferential positions much closer to the center inside the panel, albeit with a moderate change in the higher frequency range. The off-axis effect is similar at high frequencies, but is in fact somewhat no-symmetric at low frequencies.

Figure 7 shows selected results of an experiment in which pairs of transducers for which the orthogonal angular relative compliance is maintained centered relative to the upper normal preferential position of the transducer in the panel, determined to be more useful for coordinates relating to the peripheral positions of the transducers SP1 and SP4, but the transducers were tested in positions moved around the panel edge. The most suitable / promising position pairs are indicated for the pairs in positions la, lb go 6a, 6d. Figure 7 also shows the results of another experiment in which pairs of transducers are at opposite ends of straight lines, passing through the preferential arrangement of transducer SP1, 2 inside the panel. Less suitable / promising positions were found at positions 2a, 2d and 3a, 3d. More experimental work is needed related to other pairs or more edge driving positions, as well as theoretical / systematic work. From the cited dimensions and from the positions measured in pairs, giving appropriate / promising measured / estimated results, it can be seen that Figure 7 does not give the exact dimensions.

Figure 8 shows a panel 70 with a core 74 and cover layers 75, 76 having a near-converter 72 with a significant thickness 78 practically in the otherwise normal inner-panel preferred converter, in fact one or the group furthest from the excitation angle caused by the transducer 72, which has been found to be particularly effective with its behavior as a virtual source of deformable wave vibration. It may be advantageous for the converter to avoid or at least associate an external position with location coordinates, mainly centered at 5% of the dimensions of the angles, such as

in which many resonant modes were found to have nodes, i. low vibration activity.

Referring to Figure 9, the sketch shows a study involving the selection of single positions for mounting the converter on one edge or adjacent to the edge, see STI -ST4, respectively, for installation inside the corner, half the length of the side, a quarter of the length of the side and three-eighths of the length of the country; and selected positions for edge fixing / bolding for edge positions around the panel. An excitation transducer was used, see 92 in Figure 9A, connected to the panel 90, in addition to the loads / fixings on the panel, by lateral positioning, magnet pull 93A / B.

An embodiment utilizing the ST1 position of the angular excitation converter is assisted by thickening as in Figure 9A at positions 13, 14, 18, 19 - including subsequent combinations with other positions. For the position of the ST2 excitation transducer, good single positions for thickening are positions 6, 7, 8, perhaps 9, in particular 11, 12, 15 - again including in combination with other positions. The 5 + 11 and 6 + 11 combinations are especially valuable, including in other combinations. For the position of the ST3 excitation converter, good stand-alone thickening positions are positions 5, 6, 7, 13, and in particular combinations 5 + 13 and 10 + 13, the combination 6 + 18, and in combination with other combinations.

For the position of the ST4 excitation converter, the best positions appear to be 6 and 18, but none are as good as those for the other STI - ST3 excitation positions.

Figure 10 shows a panel-shaped loudspeaker 80 having a non-obstructed area 81 inside the panel extending through and beyond the normal preferred internal panel arrangement of the drive converter and peripherally

located transducer 82. The area 81 may directly serve as a display or represent something transmitted from the panel 80 without changing the acoustic characteristics, or something beyond which the speaker panel 80 passes, for example in an enclosed space and / or transparent or translucent. Both the volume and the sound quality are immediately increased, the first through additionally positioned actuators (not shown here), and the quality by a localized edge lock (s) 83, useful for effectively controlling certain modal vibration points such as panel ends. The panel 80 is further shown with localized flexible suspensions 84 arranged in neutral or even in favor of the corresponding acoustic characteristic. The high pass filter 85 is preferred for the input signals to the drive converter (s) 82, usually to limit the best playbacks to a certain number, for example, not below 100 Hz for an A4 size panel or similar panels. In this case, there should be no problematic vibration on the low pass panel / exciter.

In terms of acoustic performance, it is advantageous to control the acoustic impedance load on the panel 80, for example, to be relatively low in the periphery or in the peripheral regions, especially adjacent to the drive transducer (s) 82, where surface velocity tends to be high. The benefit of such control involves considerable clearance in the mounting of the individual surface elements (for example, about 1-3 centimeters) and / or cracks or other openings when installing the adjacent peripheral frame or supplying support or grid elements.

Furthermore, it is feasible and advantageous to carefully avoid that mechanical attenuation will result in acoustic modification, including losses in area 81, or even that its periphery is not obstructed at least at high frequencies. This can be done by selecting materials, for example, monolithic polycarbonate or polyacryl, and / or a suitable surface coating or laminate structure.

The resulting effective concentration of acoustic radiation to the peripheral regions around the plurality of drive transducers particularly facilitates the reproduction of more than one audio channel, at least for close-up listening, such as computer games or the application of virtual sound stages located at specific locations. Further, it should not be problematic to merge even a plurality of powered audio sources, at least such as audio-visual reproduction.

The following table shows the corresponding physical parameters of the actual panel elements used for the study, to which Figures 11-28 correspond.

Panel with low resistance to deformation Panel with high resistance to deformation Panel with medium deformation resistance Core material Rohacell (polymethacrylamide foam) porous A1 (honeycomb type) Rohacell Core thickness 1.5 mm 4 mm 1.8 mm

• · · · · · · · · · ·

Coating material Melinex (polyethylene etheral foil) black glass black glass Coating thickness 50 cm 102 cm 102 cm Panel area 0.06 m ² ) .06 m ² 0.06 m ² Axial ratio 1: 1.13 1: 1.13 1: 1.13 Bending deformation resistance 0.32 Nm 12.26 Nm 2.47 Nm Density of the table 0.35 kg ² 0.76 kg ' ² 0.6 kg ² Zm 2.7 Nsm ' ¹ 24.4 Nsm ' ¹ 9.73 Nsm ¹

Figures 11-14 refer to panel elements with a high deformation resistance of the first column, Figures 15-24 - to panel elements with much less deformation resistance than the second column, and Figures 25-28 - to panels elements with an average resistance to deformation from the third column.

All graphs have the acoustic power output (dB / W) and the abscissa frequency, thus showing the measured acoustic power output as formed by a frequency usually depicted on the graph by a dashed line. Most of the graphs also show the adjustment of the top of the real power line. As mentioned in the preface, this tuning is intended to apply functions that normalize to the straight line and allow the estimation of the resonant oscillation mode, free from the common effects of low frequency power reduction. Power equalization has been found to significantly improve sound quality. From such a normalized value of real output power, it is convenient to obtain an equalization estimate by inversion of the mean square deviation, and most graphs are of this type.

The panel element with higher deformation resistance of Figure 11-14 is in fact with slightly less resistance than that used in the previous Figures 7 and 9, but shows a clear preference for positioning single position converters corresponding to the intra-panel coordinates converter positions previously found to be optimal, i.e. at about 3/7, 4/9 distance from any angle or. about 0.42-0.44. However, the possible reliable positions, both between and outside such positions for each corner, have been significantly increased here, in fact within the range of about 10% and 15% respectively for the middle regions of the shorter and longer edges, and furthermore between 28% and 30% at quarter-length positions.

At least for the majority of the experimental positions of the transducer in the edge or near edge position shall be placed at a distance corresponding substantially to the difference between the value 0.42 of the preferential coordinates for the inward panel positions of the transducer and the midpoint (0.5) of the edge, though and with a periodic increase in distances to 0.09. Usually the tested positions are 0.08, 0.17,0.28,0.33 0.42 0.50.

Illustrated graphs and bar charts are generally considered to be self explanatory, showing the best and most reliable transducer positions, and localized fixation as an opportunity to improve less reliable transducer locations, see Figures 23.

As far as the position of a single transducer on or near the edge is concerned, the other two tested panel elements with much lower and average deformation resistances show the same preference for intra-panel coordinates based on power offset, see Figures 15 and 25. The low however, the deformation resistance of the panel element shows another strip of near-reliable positions, arranged from about one-fourth to less than one-tenth of the distance to the corners. Interestingly, if the evaluation is performance-based, that is, output power level - as would be the case for the average line passing through the actual output power graph, used mainly for the root mean square deviation - the above line is skewed, emphasizing a quarter-length position, and is mainly preferred for coordinates corresponding to the internal - panel positions, see the bar graph of the inversion of the mean square deviation of Figure 31 A. The panel elements with the average deformation resistance change in the direction of the characteristics of the nels with high deformation resistance in that they show reliable spread between the coordinates of the preferred intra-panel positions, and also give an indication of positions at about one tenth of a length.

9 ··· ···· • 999 9 ···· · · · 9 • 9 <2 <b · ·· · · ···

999 »V 99 * 9 9999

When examining the graphs of the actual output power, one skilled in the art can appreciate that there are differences between the best-known and feasible edges of the transducers on the edge in terms of the impact on the expected quality of sound reproduction - for which the form, t. e. the number and uniformity of the excitation of resonant modes is usually taken as an important factor. If the characteristics, such as the form mentioned, seem more reliable for the positions indicated as preferred based on an estimation of the power output equalization, it is possible, of course, to process the input signals in the direction shown in the above normalization - to increase it selectively low frequency in the form of quality attainment and signal alignment. Available power can be achieved, of course, and surpassed by utilizing performance-optimized positions; but obviously not the efficiency itself but the power input should be used.

Alternatively, other pathways for increasing the low-frequency power, as provided above, were investigated, namely, shielded and / or selectively remote local fixations or full-edge fixation. Figures 18A, B, C give an idea of the main useful increase of the low-frequency signal when shielding with an area of more than 60% larger than the panel with low resistance to deformation, stable fixation of all three edges, preventing the positioning of the transducer, and both - screened and fixed. Such shields tend to maintain the form, but for some specific applications, they may not always be feasible. Accordingly, a complete study of the fixings makes sense for alternate positions of the transducer at the edge of panel elements with little • ♦ ··· · · · · · · · · · · · · deformation resistance. The results show that the efficiency-based estimate tends to impose a quarter-length point for fixing both along the entire edge length at parallel edges or at three edges, and at 7-point local edge fixation at angles and midpoints as well as at points' X 'in Figure 29, with the transducer edge not fixed along its length, see the bar chart of Figures 31B C and D, respectively. However, the 13 point fixation, as in the points X '+ Ό' in Figure 29, strongly shifts the attention to positions with preferred intra-panel coordinates. The evaluation of panel elements with power-based locking gives largely the same results in indicating the best positions of the converter (see bar charts in Figures 19A, 20B, 21B and 22), but with significant differences from the following favorable positions , as basically confirmed by the graphical rendering of the real power check.

Naturally, a very large overall correlation was found between preferences based on the pilot test and the estimation according to the power output equalization. This, in turn, leads to the confirmation of at least a slight preference for such an assessment, unless there are practical reasons that lead to a preference for productivity rather than quality, although they cannot differ much.

Another application of localized edge fixation is in connection with improving the non-perspective position of the edge converter, see the bar diagrams in Figures 23A and B, showing predominantly right side left edges, otherwise reflected in the drawings. The cases relate to a panel element with low deformation resistance at full fixation by three of edges and seven-point fixing, with the localized latch changing its position along the same edge as the conversion devices.

In both cases, a useful improvement is achieved at a position approximately one quarter of the angle farther from the exciter - see the comparative pole to the right of Figure 23B for non-fixing conditions. The spread is greater for the case of complete fixation of the edges, see Figure 23A.

Where there are differences between performance-based and power-level ratings, it should be borne in mind that every corner-edge panel to the edge to which the converter is effectively connected has zero gain in the angle. Thus, for resonance modes triggered before vibration activity can reach nodal peaks, this should be within half of the wavelength. If, when evaluating the offset power, an advantage is found with respect to the position of the transducer directly in the corner, it must be carefully considered, as it could be with low power / efficiency, even in equilibrium due to joining any form of resonance signal type, and refer to maybe very small increments in signals. For this reason, it is advisable to compare it with the corresponding power / efficiency rating. Of course, it is best when there is a significant correspondence between the two bases of assessment, or a certain compromise, particularly suitable for a particular application; and it is also preferable for the purpose of the evaluation to take into account the expert evaluation of the power / frequency graphs, mainly with but also without any normalization.

• · · · · · · · · · · · · · · · · · · · · · ·

For the investigated panel elements with higher and average deformation resistances, there is a significant evaluation of the stability of the best positions of the converter on the edge, but with quite marked differences with other reliable positions. A panel element with much lower resistance to deformation is markedly less critical with respect to the hopes of the positions of the transducer at the edge.

This position is even more apparent when considering the use of more than one converter connected to the edge of the same panel element. The position of the increasing coupling of the resonant modes of the panel element is accompanied by the complexity of their inevitably combined interaction with the standard for the natural distribution of the resonant vibrations of the panel element and the assumption that such a standard for the distribution of vibrations is only for the panel edges. There are significant deviations from the simple rules based on the coordinates of the converter's preference positions inside the panel. However, the estimation methods used here provide valuable tools for finding good combinations of transducer positions in the edge.

In the panel with higher deformation resistance than the top Table and Figures 13A and 14A for the preferred position 0.42 of a single converter along the longer edge, the converter is positioned at the position with the highest tolerance in the range of about 0.38 - 0.45. The position of the second transducer varies along the nearest shortest edge and Figure 14A shows a preference for the periphery - for the farthest preferred position 0.42, i.e. centralized at 0.58 compared to a number of other positions at a distance of about a quarter, one third and two thirds

from the general angle. Interestingly, fixing the second converter around a preferred position 0.58 along the shorter edge of the panel, and varying the position of the other converter along the longer edge of the panel (see Figures 13B, 14B), and close to the best preferred positions at about one-fifth (0.17) and one-quarter length along the longer edge of the panel, both showing better power offset compared to the starting position (about 0.42). This method is obviously appropriate for further application in repeated cases, although it is recommended that one or both of these assessments be used - power / efficiency and expert judgment, especially if there is no similarity in the assessed situation or any good position indicated is practically less than expected (or before the assessment).

16A, B show the results of a panel element study with a much lower strain resistance, with a preferred transducer position of about 0.42 used for the longer edge, and with a second transducer changing its position along the closest short edge. There is no big difference here in increasing power alignment, with the top three approaching the angle and the nearest preferred position 0.42, with some common preference for placing combinations in another quadrant.

The same study for a panel element with a mean strain resistance shows a strong preference for the adjacent quadrant of the preferred position of the transducer 0.42 (in fact 0.58), see Figures 28A, B.

Going back to the case of a panel element with much less rigidity, two effects are seen as contributing to less 3 · 3 · 3 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · * ♦ · * · • · · w- '· · · · · · · The determined best / closest to the best position of the exciter. One is that the optimizable frequency ranges for this type of panel are higher than the rigid panel elements. The panel element is therefore closer to the continuum, and the output power offset is less dependent on the transducer position, in particular the position of the second transducer.

The other effect is related to the much lower mechanical impedance of the panel element, which leads to a lower dependence of the energy transmission on the position of the converter. The mechanism used will now be explained.

The mechanical impedance (Zm) of the panel element determines the motion due to the applied point load, see 100, 101 in Figure 30. The object connected to the panel, with mechanical impedance turned on, much smaller and even approaching the impedance of the panel will deviate strongly the movement where the object is located. The connection of the exciter converter of the mobile coil type to the panel is equivalent to the connection of the panel to the ground table (converter magnetic cup, see 102) by means of a spring (suspension of the converter coil, see 108). When the impedance of such a coil is too close to the impedance of the panel, this will partly determine the movement of the panel in the converter. There should be no dependence of the input power on the position of the exciter within the limits of the full determination of the point motion of the converter from the spring. In practice, the ratio of the impedance of the spring to the impedance of the panel can very seriously affect the best position of the transducer and the results of the transducer. ί · ··· * ++ 99 99 9999 The ratio of the best / closest to the best positions of the converter is no longer so clear.

This low mechanical impedance has a greater effect on the position of the transducer on the edge than on the location of the transducer inside the panel, with the mechanical impedance lower on the edge of the panel, which means that the suspended spool has a greater effect on the transducer . Typical for a panel with low deformation resistance from the above Table:

the mechanical impedance in the body of the panel is

Zm body = 2.7 Nsm ^{4 the} mechanical impedance at the edge of the panel element is approximately half of the Zm body, i.

Zm edge = 1.3 Nsm ^-1

The elastic deformation of the spool suspension of the transducer used is:

Cms = 0.52 x IO ³ mN ⁴

The mechanical impedance of each of the modal frequencies can be a series of values smaller than the average impedance, Zm edge. It is therefore possible to determine the characteristic frequency at which the exciter has a strong effect on the panel element, for example when the impedance of the suspension of the spool is about one fifth of the average impedance of the panel edge. Then, 11

----- = --x Zm edge ωχ Cms 5 and gives a value of 1200 Hz below which the converter and the panel are considered to be connected and which is within the optimized frequency range.

• · · · · · · · · · · · · · · · ·

Considering the converter, such low mechanical impedance and the panel element as one connected system, the converter partly determines the impedance of the panel element and the output power equalization is less dependent on the position of the converter.

Repeating such an analysis for a panel with high deformation resistance yields a frequency of 130 Hz, which is outside the operating frequency range, respectively.

Claims (32)

Patent Claims An active acoustic device, characterized in that it comprises a panel element with a distribution of the bending oscillations of the resonant type, a converter for excitation of the bending oscillations of the resonant type connected to the panel element in a peripheral position adjacent to the edge of the panel element, characterized by provided that at least a portion of the edge of the panel member is fixed so as to produce an acoustically acceptable action dependent on said resonant-type bending oscillation distribution. An active acoustic device according to claim 1, characterized in that at least one edge lock is provided for fixing the edge in at least one separate position. An active acoustic device according to claim 2, characterized in that the position of the edge retainer is determined to improve the acoustic emission of the device in contact with the transducer located in a peripheral position, which position itself is not selected for the best operational interaction with said panel element. An active acoustic device according to claim 2, characterized in that it has a plurality of edge locks at a plurality of individual edge locations. An active acoustic device according to claim 3 or 4, characterized in that said panel element is multifaceted and said localized edge fixing means is connected to more than one side. · · · · · · · · · · · · · · · · · · · · · · · · 42 · · · · · · · · · · · An active acoustic device according to claim 5 and claim 4, characterized in that said panel element is substantially perpendicular to said plurality of localized edge fixing means connected to three sides and unconnected with said transducer. An active acoustic device according to claim 6, characterized in that said plurality of localized edge locking means are at each corner and at the midpoints of said three sides. An active acoustic device according to claim 1, characterized in that said edge-locking means is disposed at the edge of said panel element. An active acoustic device according to claim 8, characterized in that said panel element is multifaceted and said edge-locking means is disposed at least along one side, which is not connected to said converter. An active acoustic device according to claim 9, characterized in that said panel element is substantially rectangular and said edge-locking means is arranged along two parallel sides. An active acoustic device according to claim 9, characterized in that said edge-locking means is disposed on more than three sides. An active acoustic device according to any preceding claim, characterized in that the edge locking means includes a thickening of the panel. · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · An active acoustic device according to any preceding claim, characterized in that it further comprises a second transducer located in a peripheral position close to the edge of the panel. An active acoustic device according to claim 13, characterized in that said panel element is multifaceted and said transducer is connected to the edges of at least two of the sides. 15. Active acoustic device, characterized in that it comprises a substantially rectangular panel element with resonant-type bending oscillations and with longer and shorter sides, a first transducer for resonant bending oscillations connected to the panel in a peripheral position on the longer side, and a second transducer for excitation of the resonant bending oscillations connected to the panel in a peripheral position on the shorter side. An active acoustic device according to any preceding claim, characterized in that at least one of said peripheral positions is spaced from the closest angle along the corresponding edge. An active acoustic device according to any preceding claim, further comprising a screen located around or behind the panel element. An active acoustic device according to any preceding claim, characterized in that the 44 acoustic device is acoustic device according to any preceding claim. Said panel element is at least partially transparent or translucent. An active acoustic device according to any preceding claim, characterized in that said transducer is of electromechanical type. 20. An acoustic device according to any preceding claim, characterized in that said transducer excites bending vibrations in the panel by at least one of the compression waves that occur at the edge of the panel element, diverting it laterally from the transverse bending vibrations along said panel element. twisting the edge of said panel member, and by producing linear deviations of the local edge portion of the panel member. 21. An active acoustic device, characterized in that it comprises a panel element with a bending oscillation distribution of a resonant type, a converter connected to the panel element in a peripheral position adjacent to the edge of the panel, characterized in that the transducer is located at distance from the angle between 0.32 and 0.5 times the length of said edge. An active acoustic device according to claim 23, characterized in that the panel element has a rectangular shape with longer and shorter edges. An active acoustic device according to claim 22, characterized in that said edge is the shorter edge and the transducer is spaced at an angle between 0.38 and 0.46 times the length of said edge. · · · · · · · · · · · · · · · · · · ·: 45 · · · · · · · · · · · · An active acoustic device according to claim 22, characterized in that said edge to which the transducer is adjacent is the longer edge. 25. A method of manufacturing an acoustic device comprising a panel element with a resonant type bending oscillation distribution useful for an acceptable acoustic characteristic, in contact with a transducer suitably coupled to the panel element, characterized in that it comprises the addition of an acoustic device. localized fixing means for improving the acoustic performance as a result of any particular peripherally located transducer, evaluating the acoustic performance resulting from the applying the said localized fixing means of a large number of different peripheral positions on the slab element and selecting said peripheral position to achieve acceptable acoustic characteristic, and determining the fixing of the selected peripheral position. 26. The method of claim 25, wherein said evaluation of said acoustic signal is limited to a frequency range suitable for the intended use and acceptable characteristic of said active acoustic device. A method according to claim 25 or 26, wherein said evaluation is for an active acoustic device acting as a sound emitter or speaker with respect to its acoustic signal using said various peripheral positions. • · 46 · · · · · · · · · · · · · · · · · · · 28. The method of claim 27, wherein said evaluation of said acoustic signal comprises evaluating at least one of many such resonant modes, their frequencies, their distribution and uniformity, and their contribution to said acoustic signal. 29. Active acoustic device, characterized in that it comprises a panel element with a bending oscillation distribution of a resonant type, a panel transducer connected to the panel element in a peripheral position relative to the panel element, characterized by thickening or fixing at the actuator position, disposed away from the edge, and at the preferred position for providing a pathogen to connect to the bending vibrations in the panel. 30. An active acoustic device according to any preceding claim, characterized in that the peripheral position is selected for the best or best operative interaction of said transducer, as provided herein, with said panel element in terms of number and frequencies of said resonant type included in the operation of said transducer in contact with said panel element. An active acoustic device according to any preceding claim, characterized in that said peripheral position is selected for the best or best operative interaction of said transducer according to its location with ··· ·· * · · · ··· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · or speaker. 32. An active acoustic device according to any preceding claim, characterized in that said peripheral position is selected for the best or best operative interaction of said transducer according to its location with said panel element with respect to equalization of acoustic power output as an acoustic emitter or speaker.