MXPA99008120A - Acoustic device - Google Patents

Abstract

Dispositivos acústicos tiene miembros que se extienden transversalmente respecto al espesor y son capaces de sostener ondas de flexión que originan acción acústica consecuente, por razón de distribución deárea de modos resonantes de vibración de onda de flexión naturales en armonía con acción acústica factible requerida de dicho miembro, en un intervalo de frecuencia acústica operativa deseada. La distribución deárea de rigidez que incluye variación o variaciones en la misma es utilizada para obtener localizaciones deseadas para transductores de onda de flexión y/o buena acción acústica de modo resonante desde formas de miembros inherentemente desfavorables. Son concebidos miembros con excitación de acción combinada de pistón y excitación de onda de flexión en centros de masa y geométricos.

Description

ACOUSTIC DEVICES FIELD OF THE INVENTION. This invention relates to acoustic devices capable of acoustic action by bending waves and typically (but not exclusively), for use in or as to the speakers.

BACKGROUND OF THE INVENTION. Our currently pending PCT patent application No. GB96 / D2145 includes general teachings on the nature, structure and configuration of acoustic panel members that have the capacity to maintain and propagate vibrational energy input through bending waves in area or areas. acoustically operative that extend transversely to the thickness usually (if not necessarily), to edges of the member or members. The specific teaching includes analysis of different determinations of panel configurations with or without directional anisotropy of flexural rigidity through or transversally to said area or areas in such a way as to have vibrating components of resonant mode distributed over said area or areas in a manner beneficial for acoustic coupling with -the ambient air; and in such a way as to have location or preferential locations P1470799MX determinable within said area or areas for acoustic transducer means, in particular operationally active or their part or effective moving parts in relation to acoustic vibrational activity in said area or related areas and signals, usually electrical, corresponding to the acoustic content of such activity vibrational Also contemplated are uses in such a PCT patent application for such members as "passive" acoustic devices or "passive" acoustic devices, that is, without transducer means such as for reverberation or for acoustic filtering or for acoustically "sounding" a space or enclosure; and as "active" acoustic devices or "active" acoustic devices with bending wave transducer means, which include in a remarkably wide range of loudspeakers as sound sources when supplied with input signals to be converted into said sound, and also as in microphones when exposed to sound to be converted into other signals. Our currently pending UK patent application No. (P.5840) deals with the use of mechanical impedance characteristics to achieve refinements in geometry and / or localization of bending wave transducer means for such panel members as or in acoustic devices. The content of that P1470 / 99MX United Kingdom patent application and the above PCT patent application are hereby incorporated to any extent that may be useful in or to explain, understand or define the present invention. This invention arises particularly in relation to active acoustic devices in the form of loudspeakers that use panel members to perform in general as above (and as they may be called later in this specification, distributed mode acoustic radiators or distributed mode resonant panels) , but they also achieve, in particular, satisfactory combination of piston action with flexion wave action. However, more general or broader aspects of the invention arise, as will become apparent.

SUMMARY OF THE INVENTION From a first point of view, this invention relates to active acoustic devices that depend on flexural wave action in panel members, which provide in a particular manner placement or effective placements for different bending wave transducer means of the specific teachings of the previous patent applications of the PCT and the United Kingdom, that is, different than in location or P1470 / 99MX Locations that arise from the analysis and selection in such PCT patent application, even including in the center or the centers of mass and / or geometry, and not displaced from them. From a second point of view, this invention relates to acoustic devices that depend on bending wave action in panel members, which particularly provide effective distributions of resonant mode vibration which may be different from what results according to teachings and specific preferences of the previous patent applications of the PCT and the United Kingdom even for the same configurations or geometries. From a third point of view, this invention relates to acoustic devices that depend on bending wave action in panel members, which particularly provide effective distributions of resonant mode vibration in panel members of different configurations or geometries with respect to which they are considered as inherently favorable in teachings and preferences specific to previous PCT and UK patent applications. It is considered useful to note that specific effective embodiments of this invention use members or panel members that intrinsically P147D / 99MX provide area distribution of resonant mode vibration components effective for overall acoustic performance comparable or similar, in essence, to prior patent applications of the PCT and the United Kingdom, which depend on simple excitation of such wave action of acoustic flexure intrinsically distributed with respect to the area for acoustic operation of good results; rather than provisions that in any case seem merely fragmentary to intentionally alter another acoustic action in member or panel members for which such intrinsically distributed resonant mode action is not even a design requirement in reality, usually where other provisions are made structural particulars etc. to attend to different frequency ranges and / or to selectively suppress or specifically produce or superimpose vibrations on a panel member that is not intrinsically effective as in the previous PCT and UK patent applications or herein, typically inherently not suitable as a matter of geometry and / or location of transducer means. Method and effective inventive means of the present involve distribution of area of variation in stiffness at least over area or areas of such member or panel members that are acoustically active in relation to bending wave action and Pl 17? / 'J JM \ desired acoustic operation. As will be clear here, such variation can be usefully directly directly related to displacement of transducer means from locations as specifically taught in the prior PCT and UK patent applications to different locations of this invention, and / or, with respect to such patent applications, to return unfavorable configurations or geometries of panel members more akin to favorable configurations or geometries for acoustic operation involving surface distribution of resonant modes of vibration consequential with bending wave action, and / or with real resonant mode distribution that can be at least something different, either simply due to relative distribution to area, different from its flexural rigidity or to localization or different consequent locations for transducer means, or both. The specific teaching of the prior PCT patent application extends to member or panel members having different characteristic or flexural stiffness characteristics in different directions through intentionally active acoustically active area or areas which may be all or less that the area or areas of the member or panel members, typically in two directions or P l 17 0 / "9 9? IX can be solved in two related directions, and substantially constant along them In contrast, advantageous member or panel members of one modality or modalities thereof have variation or variations of rigidity or flexural rigidities along any direction or di aections through said area or areas that are or are unsolvable for constancy in normal coordinates or in any direction or directions The variation, relative to area, of flexural rigidity, of course it is easily achieved by varying the thickness of acoustic panel members, but other possibilities arise, for example related to thickness and / or density and / or tensile strength of covers of sandwich type structures and / or reinforcements of structures monoliths usually of the type of material or materials combined, while practical analysis available may not always allow such an investigation. n so accurate and complete as to identify and quantify changes in real distribution, relative to area, of acoustically effective resonant mode vibration for your member or panel members - even where having substantially similar geometry and / or average address rigidities relevant as for specific isotropic or anisotropic modalities the previous patent application of the PCT- P1470 / 99MX resulting practical behavior indicates little decrease or significant degradation, if at all, in the acoustic performance achieved with good results that implies bending wave action, actually stimulates confidence in potential even to improve it. Beneficial effects (in vibrational resonance area distribution), of basically favorable geometry or configuration of the prior PCT and UK patent applications may, however, be substantially retained to very useful degree and effect in two groups or sets of inventive aspects, carrying out the previous point of view. A group or set is as already announced, specifically providing location or more convenient locations for transducer means in acoustically active panel members or their areas having configurations or geometries that are known to be favorable in isotropic or anisotropic implementations of the teachings of prior patent applications of the PCT and the United Kingdom, effectively shifting those that are now designated "natural" locations for transducer means (in accordance with these patent applications), to different locations thereof, specifically by means of a another or both flexure rigidities relatively larger and smaller on one side and at the P1470 / 99MX, respectively, of such location or natural locations. The region or regions of greater flexural stiffness effectively serve or serve to displace such a location or natural locations away from such region or regions, typically from said first side towards said second side and region or regions of lower flexural stiffness; serving the region or regions of minor flexural stiffness to move to its own region or regions. The other group or set, can be considered as involving only partially capacity to thus define at least the imaginary sub-geometry of larger general panel member geometry not specifically favorable for good acoustic operation in a distributed manner as in previous patent applications of the PCT and the United Kingdom; such a sub-geometry being incompletely circumscribed and not necessarily specifically in a favorable way by itself but having its partial definition having a significant beneficial effect on the acoustic operation in a distributed manner, for example, tending towards a type of configuration or geometry of which one knows that includes specific favorable effects but at least approaching such favorable effects; being such a favorable effect particularly for resonant modes of distribution for them at low frequencies, but not necessarily (not really P1470 / 99MX preferably) limiting higher frequency bending wave action and resonant mode distribution for such sub-geometry, i.e. allowing such higher frequency beyond and in addition to the definition of partial sub-geometry. As for easily achieving variation of required or desired area of member or flexure stiffening panel members, it may have at least one layer or core layers made first as an isotropic or anisotropic structure or structures substantially uniformly, eg, as they are used for prior patent applications of the PCT and the United Kingdom, which include structure or sandwich structures having layers of covers on a layer or core layers. Variation or thickness variations can then be easily imposed to achieve the desired area distribution of stiffness or stiffness values. For material or deformable materials, such as foam or foams, such variation in thickness can be achieved by selective compression or crushing to achieve the desired profile, for example by controlled heating and pressure application, typically to any desired profile and feasibly made even later of the application of any cover layers (according to the stretch capacity of such cover layer material). Another possibility is that the member has P1470 / 99MX stiffness or localized weakening, probably preferably in staggered series thereof. For through-cell or honeycomb materials, for example, of some suitable crosslinked section of their cells extending from cover to cover of a final sandwich structure, or non-collapsible composite bodies that rigidly hold the shape, the thickness variation may to be easily achieved by selective defoaming until contoured or profiled of desired thickness. Neither of these possibilities implies necessary change of geometrical center, but defoaming instead of crushing inevitably results in center of mass change. Additional alternatives for desired variation of thickness or core or core stiffness as discussed will be discussed including without change of center of mass as may be important for transducer means combining piston and bending wave actions, wherein the piston action is evidently better if it focuses on coincidence of center of mass and geometric center to avoid differential moments due to the distribution of mass in relation to the location or locations of the transducer and / or in relation to the unbalanced effects of air pressure. The center of mass is naturally easily located again, typically to the geometric center, by selective addition of mass P1470? 99MX or related member masses or panel members, preferably without unacceptable effects on the distribution of desired stiffness area, for example, masses also sufficiently small not unacceptable to affect low frequency bending wave action and effectively decoupled from action or acoustic actions of higher frequency, for example weight or small weights conveniently assembled semi-deformably in hole or holes in the panel also small enough not to unacceptably affect the action or actions of acoustic effect. Increasing the stiffness in one direction away from or to one side of the "natural" location or locations for location or locations of transducer locating means of prior PCT and UK patent applications, or decreasing stiffness in one direction in opposite general or otherwise will originate location or locations of transducer means thereof in general in said first direction to said first side which advantageously may be towards the geometric center. Such a relative increase or decrease in stiffness can be complex such as to cause profiling of the panel member concerned, including progressive decrease in thickness or increased stiffness at the edge of the panel member and or upward inclination of the panel member.

P1470 / 99MX decreased thickness or stiffness, for example to have a substantially uniform edge stiffness of the panel member. Additionally or alternatively, an inventive aspect of at least the unit group or end is observed in a panel member capable of bending acoustic wave action with a stiffness distribution or flexural stiffness values over its acoustically active area which in no direction is coincidentally centered with the center of mass and / or the geometric center of such panel member, although location or locations of the acoustic transducer means, either for bending wave action or for piston action or for both, may be substantially in that coincidental manner, frequently and benevolently in that way. It is observed at this point that there are two ways in which surface distributions of stiffness or rigidity values on a panel member can be considered or treated as centered, analogous to how the center of mass is usually determined, that is, as the first moment of stiffness to zero, thus corresponding in a sense to high rigidity (here called "high center" of stiffness); the other in an inverse way, putting the first moment of the reciprocal of rigidity to zero, in this way corresponding in another sense to weakness or low rigidity (called here P1470 / 99MX "low center" of rigidity). In panel members with isotropy or anisotropy as analyzed specifically in said PCT application, these imaginary "high" and "low" stiffness centers (hitherto so significant in such a context) are actually coincident, in addition usually also coinciding with the center of mass and with the geometric center; but, for a panel member with stiffness distribution as set forth herein, these "high" and "low stiffness imaginary centers are characteristically spaced apart and typically in addition to the center of mass and / or geometric center." Returning to effective or imaginary displacement ( by beneficial distributions of its stiffness or stiffness values) of localization or practically effective locations for bending wave action transducing means (from location or locations provided by preferred teachings or analyzes of said PCT and United Kingdom patent applications for its different location or locations thereof), such displacement can be usefully observed as to said "low center" of stiffness which would thus be along the same direction and as the desired imaginary displacement, and / or moving away from said "high center" of stiffness that can be provided in a useful way by at least one design reference position P1470 / 99MX structural to provide rigidity variations or values of flexural stiffness in its corresponding desired or required distribution. Variation of the flexure rigidity outward from such "center or lower centers" to edge or edges of member or related panel members, typically with stiffness or stiffness values that increase to different degrees and / or at different rates in several regions at least towards "center or high centers". Viable structures of the sandwich type with honeycomb cell nucleus can have desired stiffness distribution due to contributions of individual cell geometries variants as they are made, and without necessarily effect or effects on the distribution and the center of mass. In this way, desired area distributions of rigidity or stiffness values can be achieved by cell variations in any or all of the sectional area of the cell (if not also the shape), cell height (core thickness of effective manner) and wall thickness of the cell, even with such degree of progressive nature applied to increase or decrease as may be desired or required. Rigidity or variable flexural stiffness values without altering mass distribution can be achieved in such a context, for example by varying the thickness of the wall P1470 / 99MX cell and cell height for nominally the same cell area and / or by varying the cell area, and / or cell height for the same cell wall thickness, and could, of course, be increased or affected by another way by cover variations, including number and / or variable nature of layer layers. Furthermore, it is observed as an inventive concept for panel members thereof to have at least "low" centers of stiffness or stiffness values and practically the majority of effective excitation locations that are identified and oppositely typified in terms of minimum and maximum diversity of transit times to the edge or edges of the panel for imaginary or real bending waves considered as initiated from the "low center" of stiffness and from localization or transducer localizations, respectively. Returning to the second general overview above, panel members with distribution or stiffness distributions or stiffness values as here (as they could probably be called "eccentrics"), may have applicable ability to ensure that such a panel of some particular form given or desired shape (ie, configuration or geometry) can exhibit practically affective acoustic bending wave action which was not considered achievable until now for such P1470 / 99MX particular form at least not in accordance with any useful previous proposition; not only for unfavorable forms related to known favorable forms but for forms not related in this way but treatable as in the present to at least approach what until now would be characteristic of some favorable particular form. In fact, the present invention extends to the ability of some distribution of physically feasible area * of stiffness or flexural stiffness values of and for panel members still irregularly shaped capable of bending wave acoustic action, to return such an action of resonant mode satisfactorily distributed, and to provide location or locations practically effective for transducer means of flexion wave action (even by means of finite element analysis), even without taking into account and without rence to any contemplated form or objective that is He knows that it is favorable. Such procedures could be advanced to at least some degree pragmatically, by trial and error as regards area-relative stiffness distributions, but can be aided by analyzing them using analyzes such as Finite Element Analysis at least in terms of supplying useful centers "under "and" high "stiffness Pl 170 / 99MX disclosed herein to have positive (approaching or attracting) and negative (distancing or repelling) localization effects on location or effective locations for transducer means within such an area of stiffness distribution, whether analysable in itself or not. In practice, useful benefits are observed by selecting constructions and / or transformations by which derivation or derivations can be made with respect to what is known to be effective for particular panel member geometries and structures to which it can be applied. be, frequently will be, effective for a different geometry or panel structure, particularly to indicate specification I structural for such a panel geometry different in terms of distribution of rigidity of probable area of good results and in terms of location or locations of transducer excitation. In an approach considered to be inventive here, useful attention has been focused on the location or locations of the transducer, including by way of speculatively superimposing a desired or given member configuration as an objective geometry. panel and a real geometry of a panel member that is known to be effective and for which a detailed analysis is easily done or is available, so that the P1470 / 99MX desired objective transducer location matches the location of real transducer prentially effective of real geometry. Then, a graphic representation of flexural stiffness can be made in such a way that, for any or for each of the selected constructions relative to transducer locations now coincident of the objective and real geometries, and on such geometries, in such a way that the known or easily analyzed bending stiffness of the panel structure in question can be subjected to transformation with respect to the objective geometry to give substantially the same or similar distribution of stiffness comparable or "to scale, as in the actual geometry and acoustic flex wave action of good results in the objective geometry Promising such constructions includes lines that go from coincident locations of transducers to or through edges of the real and objective geometries (for example as if it represented transit or wave passages of flexion.) Related transformations considered depend on the Relative ongitudes of the same construction lines in the objective and real geometries, and a suitable ratio, which typically involves the ratio of stiffness to bending (B) and mass per unit area (μ) ie B / μ for transformations which proportionally imply the Pl 170 / 99MX third and / or fourth powers of such line lengths up to the edge of the objective and real geometries. It is preferred, at least as a more natural feel, for an objective geometry that is less than a real related geometry, additionally preferable for overlap to pretend to minimize the excess of the latter over the first, which includes minimizing the transformation process. Although general similar types of objective and real shapes can therefore be preferred, or favorable real geometry closer to the unfavorable target geometry, it is seen as feasible for the objective geometry to differ very substantially from any recognizable type of known favorable structure or configuration. This is the case that panels of the previous PCT patent application that are isometric in terms of area bending stiffness, and well studied or analyzed, are good starting points for geometries or related structures. In fact, another construction or transformation approach recognized as having potential involves seeking to match in the geometry or objective structure according to the way in which such transducer location (now common) divides rigidities at each side of the same in the geometry or objective structure. Further, P1470 / 99MX similar or related graphical representation schemes could be used not only as between different types of geometry but also in the case of wishing or requiring to give a target geometry of a type a flexural stiffness distribution such as to resemble or simulate another type of geometry or configuration, as far as practicable given the type of geometry or configuration (eg, rectangular, elliptical) that has a profound influence on the actual current distribution of resonant vibration that can be difficult to greatly alter. For loudspeaker members capable of both piston and bending wave types, the location matching of bending wave transducer means with center of mass and geometric center is particularly effective to allow a single transducer device in a location to combine and perform both piston drive and excitation by bending wave. It is, however, practicable to use separate transducers one for piston action only at the center of coincidence of the center of mass or geometric center, and another for location conveniently located as presently located for flexion wave action only, although compensating mass can then be required by adding masses (if not supplied P l 170/99"ri" in conjunction with the required distribution of flexural stiffness.) A particularly interesting aspect of the invention, concerning a single transducer that provides both piston action and distance action of bending wave but in spaced positions , it can be used if dis tanceration is achieved by location of bending wave transducer as in the present one (for example to favor convenient configuration of transducers) or left as it arose without application of the previous aspects of the invention. the application of this invention may involve mass distributions with center of mass displaced from the geometric center and / or any transducer location or whatever, in fact, variation or variations of bending and / or mass stiffness transversely to area "or at least acoustically operative areas of member or panel members may be in a lot s prescribed ways and / or distributions, usually progressively in any particular direction toward desired ends different from before, and they will generally represent anisotropy that is asymmetric at least with respect to the geometric center of mass; and the application is observed as in the previous PCT patent application. Practical aspects of invention include a Pl 1 0 / 99MX loudspeaker excitation unit comprising a frame, a transducer supported on the frame, a low weight rigid panel diaphragm coupled in drive relation to the transducer, and an elastic edge suspension surrounding the diaphragm and mounts the diaphragm in the frame wherein the transducer is arranged to excite the diaphragm by means of a piston at relatively low audio frequencies to produce an audio output and to vibrate the diaphragm in flex wave action at higher audio frequencies to cause the diaphragm to resonate to produce an audio output, the arrangement being such that the transducer is coupled to the center of mass and / or geometric center of the diaphragm and the diaphragm has a flexural stiffness distribution that includes variation in such a manner which originates acoustically effective resonant behavior of the diaphragm (at least preferably being displaced from the center of mass). The diaphragm may be circular or elliptical in shape and the transducer may be coupled to the geometric center of the diaphragm. The diaphragm may comprise a lightweight cellular core interposed between opposite covers and one of the covers may be projected further from one edge of the diaphragm, with a marginal portion of the cover projected attached to the elastic suspension.

P1470 / 99MX The transducer may be electromagnetic and may comprise a moving coil mounted on a coil former, the coil former being connected in drive relationship to the diaphragm. A second elastic suspension can be connected between the coil former and the armature. One end of the coil former may be connected to the diaphragm and said second elastic suspension may be disposed adjacent to said first end of the coil former, and a third elastic suspension may be connected between the other end of the coil former and the frame . The end of the coil former adjacent to the panel diaphragm may be coupled to excite the panel diaphragm substantially at one point. Tapered means may be connected between the coil former and the panel diaphragm for this purpose. The coil former may comprise a radially displaced deformable section of a rigid section for driving the diaphragm by means of a piston and for providing resonant drive out of center to the diaphragm. In other aspects the invention provides a loudspeaker comprising an excitation unit as described above; and / or is a loudspeaker drive unit diaphragm P1470 / 9DMX rigid light panel adapted to be driven by means of a piston and to vibrate to resonate, the diaphragm having a center of mass located at its geometric center and a center of rigidity that is displaced from its center of mass.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiment specific exemplary is now Illustrated or described in or with reference to the accompanying diagrammatic drawings in which: Figures 1A-D are a plan view and three views in outline cutout indicating desired placement for locating a bending wave transducer of an acoustic panel member, including an embodiment by compression of deformable core material or by core profiling or combined material; Figures 2A, B, C are a general plan view of outline and views in core cut for an elliptical acoustic panel member thereof; Figures 3A, B, C are similar views of another elliptical panel member thereof; Figures 4A, B, C indicate an acoustic panel member of an unfavorable circular shape made more favorable by forming grooves or forming elliptical slits, and model distribution charts without and with such groove or crevice formation; Pl 170 / 99MX Figures 5A, B, C are useful diagrams for explaining possible mapping or constructions or transformations to derive stiffness distribution for desired or objective geometry for a rectangular panel member and a sectional or result profile representation; Figures 6A, B, C are contour plots of interest relating to useful methodology including Figure 5; Figures 7A, B are side and plan sectional views of a high-speaker drive unit embodiment of the present invention; Figures 8A, B are side sectional views of another loudspeaker drive unit and a modification; Figures 9A, B are side views in section of a unit and modification of additional loudspeaker excitation; Figures 10A, B are a perspective view of a loudspeaker excitation coupling or actuator for spaced-apart application of piston action and bending wave, and a detail of mounting to a diaphragm member or panel; and Figures 11A, B show relationships for such actions and crossing point.

P1470 / 99KX SPECIFIC DESCRIPTION OF THE MODALITIES Referring first to Figure 1A, a substantially rectangular acoustically distributed panel member 10A is indicated as being directly resulting from the teachings of the prior PCT and United Kingdom patent applications, having thus its "natural" location 13 for bending wave transducer means spaced from its geometric center 12 and out of true diagonal shown in dashes at 11. In the application of the present invention, however, the location 13 of the transducer is for being in the geometric center 12 of the panel member 10A, that is, effectively to appear displaced along the solid line 15, which is achieved by distributing the appropriate area of rigidity to the flexure of the panel member. For this purpose, the flexural stiffness is made relatively larger and smaller on one side (right side in Figure 1A) and on the opposite side (left side in Figure 1C) of geometric center 12 and location 13 of the transducer "natural", specifically in opposite directions along line 15 and its straight line extensions 15G and 15L, respectively. Figure IB is a profile section along the line 15 that includes extensions 15G and 151, and indicates the same situation as the Figure P1470 / 99MX 1A, ie, location of "natural" transducer 13B similarly distanced from geometric center 12B of panel member 10B in a distributed manner, see projection lines 12P, 13P. Figure IB does not provide details for the actual structure of panel member 10B; but in fact it indicates the alternatives of being monolithic, see the solid lines of outer surface 16X, Y, or that are of the sandwich type, see the lines with dashes of inner surface 17x, Y that indicate covers attached to an inner core 18, typically (though not necessarily) of the type of cellular foam, or of the type of through cell honeycomb. Figure 1C indicates the use of a core 18C of material that is deformable, specifically compressible to be capable of crushing to a lesser thickness, as is typical of many foamed cellular materials suitable for distributed acoustic panel members and that are given by assumed in Figure 1C. Such crushing is indicated by the thickness of the core 18C decreasing from the right side to the left side in Figure 1C, and its cells ranging from fully rounded open (19X) to flattened (19Y) f Naturally, it is not essential for those cells that are of the same size or similar size, or of a regular arrangement, or that are rounded open completely at maximum thickness (being P1470 / 99MX frequently suitable foamed materials of the partially compressed foamed type). The core 18C is further shown with coating covers 17AB. It is possible, even normal, that the core material 18C be deformed to the desired profile before joining covers 17A, B- but is not essential as long as the panel member 10C is appropriate for distributed mode acoustic action if it is deformed by compression and with the covers 17A, B attached. Greater and lesser thickness resulting from the core 18C and the panel member 10C will correspond with greater and lower flexural stiffness; and the indicated profile of progressive thickness, likewise the stiffness, the variation is such as to cause coincidence of the location 13C of the transducer with geometric center 12C, see arrow 13S and combined reference 12C, 13C within the circle. Crushing deformation will normally be done with thermal assistance and using a properly profiled pressure plate. There will be no change to the center ^ of the mass of the panel member 10C, that is, the center of the mass will remain coincident with the geometric center 12C, now also coincident with the location 13C of the transducer. Where the contribution of core density is small, that is, the flexural rigidity is dominant, the linear factor of the contribution of the core mass can be neglected and the Pl 170 / 99M \ desired thickness distribution, relative to the area, can be achieved by shaping the thickness of an isotropic core of polymer foam or fabricated or monolithic honeycomb sandwich without a cover and a core; and any such structure can be manufactured, machined or molded as herein deemed convenient. Figure ID shows an acoustic panel member 10D in a distributed manner with progressive relief of its bottom surface in such a way that its thickness is reduced with a profile similar to that of Figure 1 C. Such a profile could be somewhat different for the same effect as is intended, that is, matching the transducer 13D location with the geometric center 12D, for example according to the material or materials used for the panel member 10D. Such materials can be reinforced monolithic combined materials or any kind of cellular material, typically then as a core provided with cover even of the honeycomb type with through cells extending from one cover to the other. The indication 19Z similar to the foamed cell of Figure ID could correspond to the use of foamed material which is by non-selective selection. crushed or not suitable for crushing; but it is intended to do no more than indicate that there is no significant change in density. Then, of course, there must be a change in the distribution P1470 / 99MX of mass and the center of mass of the panel member 10D which as such will be distanced from the center "geometric, generally in the direction of the arrow CM. In order to achieve a match of the general center 5 of the mass with the geometric center 12D, the panel member 10D is shown with at least one additional compensation mass 22 indicated mounted inside the receiving hole 23 preferably blind, further preferably by means 24 which can yield to a certain degree, for example, in a suitable bushing or liner secured mechanically or by adhesive, such that its inertial compression is progressively decoupled from the panel member 10D at higher frequencies of distribution desired vibrations. There can be more than one compensating mass (22), for example in a place of less ) from 180 a through the imaginary extension line 15L, or some other set arrangement and do not all need to be of the same mass, for example that mass decreases progressively away from line 15L. More simply, the thickness can simply be tapered forward through the section of Figure IB although a more conical The complex is normal, including up to a common edge thickness equal and / or progressively smaller away from the line 15-15G, L. Geometric relationships of bending frequency to size are P1470 / 99MX used requirement that must be taken into account. For any given form, increasing its size decreases the fundamental frequencies of vibration, and vice versa. The effective displacement of preferential transducer location can be observed as equivalent to decreasing the effective size of the panel in relation to bending along the direction of such displacement. Turning now to Figures 2A-C and 3A-C, All panel members are illustrated as being generally elliptical in shape, with those referenced as 20A, 30A being isotropic, thus showing coincidence at 25, 35 of the geometric center and the center of mass. significant for geometries and isometric panel structures, the stiffness distributions will naturally also be centered at 25, 35- either as "high center" (rigidity as such) or as "low center" (softness or deformability). Further, Figures 2A, 3A show at 26, 36 a preferentially good or better location (as in the previous PCT patent application) for a bending wave action transducer for acoustic operation in resonant mode of the panel member 20A, 30A, for example as or in a loudspeaker. Turning to Figures 2B, C and 3B, C the center positions of panels 10B, 20B, 30B are P1470 / 99MX now labeled 25, 26 and 35, 36 and still correspond both to the geometric center and to the center of mass (25, 35), but now also in addition to location of acoustically effective bending wave transducer (26, 36). In comparison with Figures 2A, 3A the locations 26, 36 of transducers have been effectively displaced by a distribution of stiffness or bending stiffness, close to this, and accompanying displacements of "high" and "low" stiffness centers, they are indicated at 27, 28 and 37, 38 as opposed to the geometrical centers 25, 35 in general. This different asymmetric stiffness distribution is shown as being achieved by progressive changes to the cells 29, 39 in particular in terms of their heights , in this way the thickness of the panel members 20A, 30A; but also in terms of their areas and population density (see Figures 2B, C), or in terms of their areas and wall thicknesses but not in terms of their population density (see Figures 3B, C) achieving this means the desired distribution of stiffness without at least operationally significant alteration to the mass distribution, in this way the center of mass is now coincident with both the geometric center and the location of the transducer (25, 26, 35, 36). There are additional possible approaches for stiffness or variable rigidity values, in this way P1470 / 99 X area distribution; for example, introducing different flat formations, such as curves, curves, etc. that affect the rigidity in general of understood levers; or such as grooves, grooves or notches in surfaces to reduce stiffness or rib formations to increase rigidity, progressively including by spaced apart arrays of such arrangements, for example, along the line extensions 15G, L of Figure 1A ( Not illustrated but calculable using the means provided by the Finite Element Analysis). Figure 4A shows another application of channeling, grooving or ridging within the surface, specifically to improve the flexion wave action in a distributed manner for an acoustic panel member 40 that is currently of a configuration or geometry, especially circular, which is known to be unfavorable as an acoustic panel member in distributed mode, especially with central location of transducer driving means. This known unsatisfactory operating capacity is indicated by the modal frequency distribution in Figure 4B as it will be easily recognized and understood by those skilled in the art, which corresponds specifically to concentric vibration modeling. It has achieved marked improvement over what P1470 / 99MX shown in Figure 4C forming channels, grooving or notching as indicated at 45 in _. _o_ ™ of p * rte of an ellipse, that is. in a class of configurations or geometries that are known to include something highly favorable as acoustic panel members in distributed mode (as in Figures 2, 3 above), although not really in accordance with such known favorable particular ellipse. However, the effect on the action The lower frequency modality is markedly better distributed than the symmetry of centrally excited simple circular shapes, and the higher frequency modal action is able to extend further and further away from the open ends of the flute 45. The shape of the groove 45 was developed using Finite Element Analysis, see the indicated complex element modeling, such general value techniques being for detailed implementation of its teachings about this. _ Minor arched formations spaced asymmetrically relative to the center of a circular panel member have also shown promise, and must be redefined easily by additional Finite Element Analysis. Figures 5A, B indicate constructions and transformations in a great way as discussed above, specifically shown for rectangular objective (51A, B) and configurations or P1470 / 99MX real geometries (52A, B). Construction lines 53A, B processed according to different lengths and desired or required bending stiffnesses show highly promising effectiveness of the approach at least as it applies to shapes of the same rectangular type. The methodology of Figure 5B is particularly attractive because the actual geometry or configuration 52B is efficiently constructed from the '10 configuration or objective geometry 51B located in a corner by extensions from that corner such that a location 54B of preferential transducer of an isometric form 52B well understood and analyzed simply coincides with the geometric center of the objective form 51B. Figure I 5C indicates a typical cut through the objective member 50 of the objective form 51A resulting from the methodology according to Figure 5B. Inspection of the quotient B / μ or of the values of the parameters B and / or μ, specifically only with the other maintained constant, in the different radial directions 53B, and making mathematical graphical representation of the panel of form 52B to the panel of the form 51B, allows distribution of its rigidity to be computed in these directions (53B) additionally using a power ratio including fourth power of length and second or third powers of thickness depending P1470 / 99MX whether the required bending stiffness is of the structure panel with different alternating elements of the provided core or a solid monolithic combined structure not provided with a cover. Figure 6 A shows measurement results of length planimetry relationships for the methodology of Figure 5B and Figure 6B shows the manner in which the required bending behavior (objective) is related to the relationship measurement results of the Figure 6A and with material-related properties, specifically stiffness alone involving the fourth power of length (solid line), thickness of a sandwich structure involving a fourth power (dotted line), and thickness of a monolith structure involving a power of 4/3 (dashed line). For a sandwich structure the coating stiffness (tensile strength) would also imply fourth power of length; and coating thickness a power of 4/3. Figure 6C shows the graphical representation of modal density with 3% damping for a target square panel member, without its flexural stiffness distribution, an isometric aspect ratio panel of 1,134: 1 of the patent application of the previous PCT, and that involves relative adjustment only to a side difference; and the square panel improved by stiffness distribution to P1470 / 99MX bending according to deck parameters, specifically thickness (h) and Young's modulus (E). Referring to Figures 7A and 7B, a loudspeaker drive unit comprises a frame 71 in the form of a frame shaped like a circular shallow basket or plate having a peripheral flange 71F projected outwardly perforated with holes due to which the exciter unit can be mounted on a '10 acoustic screen (not shown), for example, in a loudspeaker enclosure (not shown) in generally conventional form. The frame 71 supports a transducer 72 in the form of an electrodynamic drive motor comprising a magnet 73 interposed between pole pieces 74A, B, and that provides a I annular free space in which a tubular coil former 75 carrying a coil is mounted 75C which forms the coupling or mobile excitation actuation member of the motor. The coil former is mounted on elastic suspensions 76A, B at their opposite ends to guide the coil former 75 for axial movement in the free space of the magnet assembly. One end of the coil former 75 is secured, for example, by the union 77, to the rear face of a rigid and lightweight panel 70 which forms an acoustic radiator diaphragm of the loudspeaker excitation unit and which comprises P1470 / 99MX a light cell core 70C, for example, a honeycomb material, interposed between opposite covers 70F, R and back. The panel 70 is in general as taught herein, specifically with flexural stiffness distribution that provides mass center coincidence and location of preferential flex wave exciter as its geometric center. In the illustrated example, the front cover is conveniently of conventional circular shape that integrates with the contour and in some cases is combined in effective operation with the peripheral suspension or the normal suspension. The back cover is selected to be rectangular to form a combined panel conforming to the distributed mode teaching (it can be operated directly by the differential coupler of Figures 10A and 10B). For a simple central excitation, or equivalent central excitation, the distributed mode panel section will be designed with preferential modal distribution according to the invention generated here, for example by control of area stiffness, in such a way as to place it in a useful manner. the point or region of modal excitation at or near the geometric center and the center of mass. In this way, good modal excitation at higher frequencies and piston operation at frequencies is obtained P1470 / 99K lower for a conventional construction style and exciter geometry. The cover 70F which faces the front of the panel 70 is extended beyond the edge of the panel and its peripheral margin is attached to a peripheral suspension of roller or suspension 77 supported by the frame 71 due to which the panel is free to move by piston. The transducer 72 is arranged to move the panel 70 by piston at low frequencies and to vibrate the panel 70 at high frequencies to impart bending waves to the panel, due to which it resonates as discussed amply before. The arrangements shown in Figures 8A and 8B are generally similar to that described above except that in these cases the frame 81 is even shallower, the motor 72 is largely outside the frame 81 and the coil former of the coupler / actuator 85 projects within the frame with consequential modification of its suspension 86. Modification of Figure 9B involves the use of an engine 82N smaller neodymium and sectional end reduction 85A of coil former 85. The arrangements illustrated in the Figures 9A and 9B are very similar to those illustrated in Figures 8A and 8B except that the extended end 95A, B of the coil former 95 is formed with a P1470 / 99MX [module] of double conical section, the pointed end 95P of which is attached to the face "Rear of diaphragm 90 of light rigid panel at its geometric center 5" Figures 10A, B show a diaphragm coupler or actuator 100, conveniently a coil former of a drive motor (not shown), which has a greater arched peripheral portion 108 of its drive end, which is suitable for being joined (107) to a lightweight rigid panel 100 made of a semi-deformable material; and with arcuate peripheral part 109 of the same rigid end. The excitation applied to panel 100 will be a piston at low frequencies through both parts 108, 109 of peripheral arched end. At high frequencies the coupler or actuator will excite action > of bending wave by the smaller part 109, in this way vibrational energy in the panel 100 in a position displaced from the axis of the coupler or actuator 105. By its semi-redundant nature, the largest arched peripheral end part 108 will be substantially unsthouted at high frequencies. In this way the true actuator position of the exciter is dependent on the although applied in the same manner and by the same means 105. The illustrated simple case of a direct coupling section and a semi-ceding section may P1470 / 99MX be extended to multiple firm contact points and more complex semi-redundant arrangements, for example, two or more preferential distributed-mode panel member transducer locations may be involved. The semi-ceding section can be tapered or stepped or plurally stepped in thickness or mass property, to provide an interactively coupled stiffness grading calculated with the acoustic performance criterion of the panel to improve overall performance, either with an acoustic panel of distributed mode with location of bending wave transducer spaced apart from the geometric center or center of mass to satisfy convenient structure for the coupler or actuator 105, or with the latter suitable for those transducer locations of the previous patent applications of the PCT and the Kingdom United. Such differential frequency coupler (105) can be used with the usual motor coil used in electrodynamic drivers. While such coupler 105 may be a separate component of predetermined size or diameter, it is convenient to consider its application as part of the addition plane of a motor spool of similar diameter which can be selected as indicated above to encompass one or more of the locations of P1470 / 99MX preferential impulse transducer of a distributed-mode acoustic panel member, specifically in and excited by part or rigid end portions 108 such as the intended higher frequency response is by bending mode vibration in a diaphragm member 100 of acoustic panel in distributed mode. At lower frequencies the semi-elastic parts or inserts 108 become more cooperative, and progressively put into effect the full circumference of the actuator or coupler 105 for balanced center of mass action, and thus satisfactory piston operation at low frequencies. The fundamental frequency of bending of the panel member 100 and the elasticity of the part or parts of coupler or actuator 108 are selected to allow satisfactory uniform transition in acoustic power from the regions of vibration to piston to the regions of vibration by bending of the range of frequency. Such a transition can be further aided by plural staggering of the part or portions 108, or by tapering as indicated in 108A. The understanding of the operation of this coupler 108 is aided by Figure HA, which outlines the desired variation of speed applied to the acoustic panel, including in the crossover region. At low frequencies the part or parts semi-assignor 108 P1470 / 99MX contribute effective power to the panel member 100 in a piston balanced manner. Such a piston action similarly decreases with increasing frequency as the mechanical impedance of the vibrating panel member 100 becomes predominant and is excited in the preferential eccentric position or positions. In this way the contribution of active speed to higher frequencies arises from the sector or rigid sectors, displaced from the coupler. Figure 11B further shows the displacement of the effective variation of the piston excitation and excitation points distributed mode with the frequency. At low frequencies the piston excitation point is predominantly at the center and at the center of mass. With increasing frequency there is a transition to an excitation point to bending waves displaced from the center, aligned by suitable selection of the panel design and also the diameter of the complex coupler actuator and separates the geometry to excite at or near the point of distributed mode preferred for satisfactory favorable distribution of vibration modes. In Figures 7A, B above, bending wave transducer means of this type with a general diameter comprised within the range of 150 to 200mm would operate location or locations of P1470 / 99MX "natural" transducer of a panel member of distributed mode of satisfactory operation of bending mode starting in the range of 150Hz to 500Hz. The piston operation will be effective from lower frequencies, eg, from 30Hz for a suitable acoustic assembly, and would decline in its upper range as the panel member enters the flex mode range. The differential frequency capability of couplers of this invention allows subtle refinements for use of acoustic panel members in a distributed manner. For example, in a given panel a change in the excitation point can often be found convenient for frequency control purposes observed in particular applications such as close to wall mounting in small enclosures and related environments that modify the responses. More than one degree and / or size or area of semi-yielding inserts or parts may be used in appropriate coupling geometries in an affective manner, for gradually or stepwise moving between more or most effective excitation points of the modal design frequently. , and advantageously modify the radiated sound.

P1470 / 99MX

Claims (45)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property: 1. Acoustic device that includes a member that extends transversely with respect to its thickness and which is capable of sustaining bending waves that cause direct consequent acoustic action by reason of area distribution of resonant modes of vibration of natural bending waves on its surface in harmony with the required acoustic action required of said member in a range of operating acoustic frequency desired, the member having a distribution of flexural stiffness that varies- in the area of the member, in order to make said member more favorable to the distribution of resonant-area e-ways for acoustic action, and the center of rigidity when the member is flexed, it is off center from the geometric center of the member.
2. 2. Acoustic device according to claim 1, wherein the center of mass of the member is located at its geometric center.
3. Acoustic device according to claim 2, wherein said variation in flexural stiffness includes relatively higher and lower flexural stiffness for different sides, respectively, of said location for Pl 170 / 99MX bending wave transducer means.
4. Acoustic device according to any preceding claim, wherein said variation in flexural stiffness includes relatively higher and lower flexural stiffness for different sides, respectively, of the geometric center of said member or said area.
5. 5 . Acoustic device according to claim 3 or claim 4, wherein the high center of flexural stiffness, wherein the first stiffness moment is zero, is to one side of the geometric center of the member and the low center of stiffness to flexion where the first moment of reciprocal rigidity is on the other side of the geometric center of the member.
6. Acoustic device according to any preceding claim, wherein major and minor thicknesses of said member correspond to upper and lower rigidities respectively, of said flexural stiffness distribution.
7. Acoustic device according to any preceding claim, wherein said member has a further mass or masses supplied selectively that substantially have no effect on the desired acoustic action.
8. 8. Acoustic device according to claim 7, wherein the mass or each mass P1470 / 99MX of sufficiently low mass that the lowest frequency acoustic action is practically unaffected and has means of association with said substantially effective member to decouple the mass or each additional mass for higher frequency acoustic action.
9. Acoustic device according to claim 7 or claim 8, wherein the additional mass or masses are located for each center of mass of said member plus said additional mass is in a desired position of said member.
10. 10. Acoustic device according to claim 9, wherein said desired position coincides with the geometric center of said member.
11. 11. Acoustic device according to claim 6, wherein said member is of sandwich structure having coatings on a core having walls defining cells that extend through a variable thickness between said coatings and defining size cells different cross section to provide the prescribed distribution of mass on said member.
12. 12. Acoustic device according to claim 6, wherein said member is of sandwich structure having coatings on a core having walls defining cells P1470 / 99MX which extend through varying thickness between said liners and wherein the cell defining walls are of different thicknesses to provide the prescribed dispensing distribution of mass on said member.
13. 13. Acoustic device according to claim 11 and / or claim 12, wherein said prescribed mass distribution is centered on the geometric center of said member or said area.
14. 14. Acoustic device according to claim 1, wherein the variation of flexural stiffness includes at least one localized adaptation of the member which is a relative weakening groove, groove or cut within said member.
15. 15. Acoustic device according to claim 14, wherein localized variations of flexural stiffness distribution partially define a non-circumscribed sub-geometry of said limb, and the arrangement is favorable to the acoustic action of bending wave with distribution of suitably effective area of lower frequency modes of vibration dependent on the bending wave relative to said location for bending wave transducing means.
16. 16. An acoustic device according to claim 15, wherein said localized variations of flexural stiffness distribution. P1470 / 99MX allow higher frequency modes of vibration dependent on the bending wave beyond said localized variations.
17. 17. Acoustic device according to any of claims 1 to 5, wherein the member is of structure provided with coating and the variation of flexural rigidity is given by parameter or coating parameters.
18. 18. Acoustic device according to claim 17, wherein the thickness of the coating is a parameter of said coating.
19. 19. Acoustic device according to claim 17 or claim 18, wherein the Young's modulus of the coating is a parameter of said coating.
20. 20. An acoustic device according to any preceding claim, wherein one or said location for bending wave transducing means for producing said acoustic action also serves for acoustic, piston-acting transducer means.
21. 21. An acoustic device according to claim 20, comprising acoustic transducer means in said location and having both bending and piston wave actions.
22. 22. Loudspeaker excitation unit that P1470 / 99MX comprises a frame, a supported transducer, on the frame a rigid lightweight panel diaphragm which is an acoustic device according to any of the preceding claims, the panel diaphragm is coupled in excitation relationship to the transducer, and an elastic edge suspension surrounding the diaphragm and mounting the diaphragm in the frame, wherein the transducer is arranged to excite the diaphragm by means of a piston at relatively low audio frequencies to produce an audio output and to vibrate the diaphragm with bending waves at higher audio frequencies to cause the diaphragm to resonate to produce an audio output, the transducer is operatively coupled to the center of mass and / or geometric center of the diaphragm.
23. 23. Loudspeaker excitation unit according to claim 22, wherein the diaphragm is circular or elliptical in shape.
24. 24. Loudspeaker excitation unit according to claim 22 or claim 23, wherein the diaphragm comprises a lightweight cell nucleus interposed between opposing coatings.
25. 25. A loudspeaker drive unit according to claim 24, wherein one of the liners is extended further from one edge of the diaphragm, a portion being attached. P1470 / 99MX marginal coating extended to the elastic suspension.
26. 26. The loudspeaker excitation unit according to any one of claims 22 to 25, wherein the diaphragm is a resonant panel in a distributed manner.
27. 27 ^. Loudspeaker excitation unit according to any of claims 22 to 26, wherein the transducer is electromagnetic and comprises a moving coil mounted on a coil former, the coil former being operatively coupled to the diaphragm.
28. 28. The loudspeaker excitation unit according to claim 27, comprising a second elastic suspension connected between the coil former and the frame.
29. 29. The loudspeaker excitation unit according to claim 28, wherein one end of the coil former is connected to the diaphragm, said second elastic suspension is disposed adjacent the said end of the coil former, and a third elastic suspension is connected to the coil former. between the other end of the coil former and the frame.
30. 30. Loudspeaker excitation unit according to any one of claims 27 to 29, wherein the end of the coil former adjacent to the panel diaphragm is coupled to P1470 / 99MX excite the panel diaphragm substantially at one point.
31. 31. The loudspeaker excitation unit according to claim 30, comprising conical means connected between the coil former and the panel diaphragm.
32. 32. A loudspeaker comprising an excitation unit as defined in any one of claims 22 to 31.
33. 33. A diaphragm of a high-volume rigid panel exciter unit adapted to be piston-driven and vibrate. to resonate with bending waves, the diaphragm having a center of mass located at its geometric center, and a distribution of centered stiffness displaced from its center of mass.
34. 34. Acoustic device according to any of claims 1 to 21, wherein the member has a flexural wave transducer means for producing the acoustic action, in a location determined by surface distribution of flexural stiffness.
35. 35. Loudspeaker excitation drive actuator comprising displaced excitation coupling portions rigid and rigid to drive a diaphragm by means of a piston centered on an axis and to provide resonant excitation off center to said diaphragm. P1470 / 99HX
36. 36. Loudspeaker drive unit actuator according to claim 35, wherein the dropping part is adapted to excite the piston diaphragm at lower frequencies and wherein the resonance excitation displaced from the center is provided to the diaphragm. , by at least one rigid part at higher frequencies.
37. 37. An acoustic excitation unit comprising a loudspeaker drive unit actuator according to claim 35 or 36, coupled to a diaphragm for causing the acoustic action in a distributed manner in the diaphragm in at least the upper frequencies by means of minus a rigid part.
38. 38. Actuator according to claim 35, 36 or 37, wherein the rigid part or portions also contribute to the pis- ton drive.
39. 39. Actuator according to any of claims 35 to 38, wherein said parts are end peripherals of a tubular member.
40. 40. A loudspeaker excitation unit comprising an actuator according to claim 39, wherein the tubular member is secured to the diaphragm.
41. 41. Method for making a panel member of or for an acoustic device, according to any of claims 1 to 21, the method P1470 / 99MX includes: determining the nominal location of the bending wave transducer means in the absence of flexural stiffness variation, and adjusting the flexural stiffness surface distribution for the limb including variations in flexural stiffness for displacing the nominal location for the bending wave transducer means to a desired location, providing relatively higher and lower bending stiffnesses on opposite sides of the desired current location and also on opposite sides of the nominal location.
42. 42. Method according to claim 41, wherein the relatively higher and lower bending stiffnesses are along extensions of an imaginary straight line through said desired and nominal locations.
43. 43. Method according to claim 41 or 42, the method includes: imaginatively superimposing as a target geometry, a desired or proportionate configuration of the panel member and a subjective geometry of a panel member that is known to be effective and for the which detailed analysis is available, so that the desired target transducer location matches the preferentially effective real transducer location of the subjective geometry. P1470 / 99MX
44. 44. Method according to claim 43, wherein said known configuration or geometry is a construction by extension from some edge or edges of the actual configuration or unfavorable geometry.
45. 45. Method according to any one of claims 43 to 44, wherein said transformations involve fourth power of flexural stiffness length as such and other relevant powers that determine parameters such as thickness of monolithic structure of the member or core of sandwich structure of the member or coating or coatings of the latter or Young's modulus. P1470 / 99MX