BG104810A - Acoustic device relying on bending wave action - Google Patents

Abstract

The acoustic device is panel type. It has improved acoustic efficiency of energy conversion of the sound emitting component. The device includes a rectangular resonance acoustic panel element (10) with partially limited acoustic active area. The acoustic element is fixed between two rectangular elements (11A, 11B). Fixing is effected along the edges of the rectangular elements (12) by bolts and a nut (12B). 26 claims, 16 figures

Description

ACOUSTICAL DEVICE BASED ON ACTION OF BENDING TENSION

TECHNICAL FIELD

The invention relates to acoustic devices from

the type comprising a sound-emitting element based on the action of a bending oscillation and a resulting surface vibration to produce an audio output signal.

BACKGROUND OF THE INVENTION

WARNAKA is known from US-A-3,247,925 to provide a low-frequency loudspeaker comprising an extremely rigid panel, the peripheral edges of which are 15 bolted and cemented to a rigid frame, which frame supports a conventional coil-like sound converter, which transmits bending vibration energy to the center of the panel. This subwoofer has been described to operate entirely with a 20 MHz upper wave match.

It is also known from US-A-3,596,733 to BERTAGNI to provide a speaker having a diaphragm formed by an element similar to an expanded polystyrene board having a prestressed front surface 25 and a rear surface with or including an irregular shape.

The study for the detection of acoustic devices related to the action of bending oscillation, appropriately regarded as a type of resonant panel, is given in

• · · · · · · · ·

1616/00-FS International Patent Application WO 97/09842, considered to improve or optimize acoustic performance according to panel parameters, including geometry and flexural strength, in particular including functioning, 5 which is useful at and below the frequency of coincidence.

Geometric parameters of interest include the proportions or aspect ratios of the panels as such, including use as passive acoustic devices. The bending strength (s) parameters 10 may conveniently interact with the geometrical parameters, including their anisotropy, considered as different bending strength for, or achievable for, actual invariance along the axes of geometric shapes included for perspective changes in the proportions of such 15 shapes. The preferred locations for the transducers in the active acoustic panel are suitably proportional to the coordinates. Other surface flexural strength distributions may help to provide other useful 20 locations for transducers, for example, substantially at geometric centers and / or centers of mass, see International Patent Application WO 98/00621, the aforementioned bending oscillation action with an additional acoustically acting piston action 25. The acoustic action is described and claimed at least in WO 07/09842 for the entire panels and only for parts of them that are acoustically active.

On an intuitive basis, our specific analysis and design methodology for such acoustic devices with

1616/00-fC resonant type bending oscillations are mainly applied to entire panels where the edges are wholly or substantially vaulted when in acoustically relevant, desired bending oscillation action, including where 5 are subjected to slight damping at the edge. This invention results from the surprising results of counter-intuitive further examination, study and

experimenting.

SUMMARY OF THE INVENTION

Some of the emphasized requirements remain valid and are of particular technological / inventive importance, in particular for an element of an acoustic device extending transversely to its thickness and capable of supporting bending vibrations through its particularly acoustically active area, m. is a basic requirement for the so-called resonant acoustic element or panel and for parameters such as geometric parameters and flexural strength to be values in 20 according to the result distributed or a vibration from the natural bending oscillation of said element that is effective or useful in achieving the desired or acceptable acoustic action of the device in a frequency range of interest, i.e., an additional 25 requirement for the resonant acoustic element or panel.

Specific exemplary embodiments of this invention are provided for agents that aid in substantially suppressing vibration from bending oscillations, typically at the end, periphery, or other boundaries of such an element, or

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1616/00-FS panel or its acoustically active region, and furthermore generally be capable of operating at least partially below the coincidence frequency. The term "substantial suppression" as used herein intentionally introduces a greater limit on the movement of at least a portion (s) of the end (s) of the element than the specific disclosure in WO 97/09842, as in the end space (s), so and effective loading, suppression, or effective spatial effect.

There are two perspectives, effects or aspects of the invention that are considered useful with respect to such substantial end / surface restriction / peripheral suppression.

Such a limitation / reduction of the 15 active end / peripheral / boundary vibration motion of the bending oscillation of the element (compared to the specific disclosure of WO 97/09842) may effect a useful combination of the acoustic output signal obtained from the vibrating bending oscillation 20 back into acoustic energy the active area. Another is that the acting acoustically and effectively natural waves from the effects of resonant bending oscillation will be different (compared to the specific disclosure of WO97 / 09842) due to the limitation / suppression of vibration motion of 25 bending vibrations in the edge (s) / periphery / they / the boundary of the element, thus effectively reducing / eliminating the fraction (s) of the lowest resonance wave / s, which could be achieved if the edge (s) / periphery / boundary of the acoustically effective ·· ·· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · .. · ₅ · .. '· .. ·· .. · 1616/00-fC The element area was free to have bending oscillation distribution, as disclosed in particular in WO 97/09842, and reduction / substantial suppression of resonance waves introducing distortion.

The resulting nominally lower saturation or less rich content of acoustically active / vibration-related vibrational oscillation-related oscillations can be illustrated for simplified analogy and analysis based on equivalent simplified radiations, by counting 10 interactions by introducing resonance flatness oscillation with respect to each broadcast starting at the frequency f _x of the resonant mode, i.e., f _0, n further "loss" of combined vibrations, introducing a frequency f _o, but with interesting and useful effects 15 regards the uniformity of the intervals for the direct and combined related natural resonant modes introducing ^ -chestoti.

The embodiments are extensive and may be advantageous, including the achievement of improved 20 acoustic energy conversion efficiency and / or the often very useful enhancement of potential sub-areas for the transducer's perspective / optimal location (s), at least as identification through mechanical impedance analysis as studied in the 25th international patent application PCT / GB99 / 00404 in procedure. And / or generally greater range of perspectives on the shapes of the surfaces / proportions of said elements, as illustrated for isotropic tensile strength, even at about 1: 1 to about 1: 3 or more. ·· ··

1616/00-FS aspect ratio (s). And / or the prospect of the acoustic characteristic for the materials of the panel member for lower internal flexural strength, at least as an effective overall reinforcement by assisting the compression along its edge (periphery) / periphery / boundary region. And / or capabilities with respect to the high power of the input transducer for speaker performances, all including when such suppression may allow a substantial load, whether on the basis of inertial reinforcement or additional, in practice, by actually locking in a stiffer / a massive carrier or otherwise for a higher load.

A significant advantage of this invention is that it provides new and useful resonant panel acoustic devices, including active acoustic devices such as loudspeakers, with the production of devices such as panel significantly facilitating and durable, rigidly mounted type, especially improved in acoustic devices, - Special comparison with those illustrated and described in international patent application WO 97/09842.

According to one aspect of the present invention, there is provided an acoustic device based on the action of bending oscillation and capable of operating at the lower overlap, comprising an element providing said acoustic function due to the advantageous distribution of resonant vibrations with the effect of bending oscillation therein. The $ element has its acoustically active region, limiting $ µ $ partially due to the presence of i

'7

1616/00-FS is essentially suppressive in nature with bending vibration vibration.

According to another aspect of the present invention, there is provided an acoustic active device comprising a 5 element based on the action of bending oscillation with a favorable distribution of resonant oscillations therein and a favorable position of the bending oscillator, wherein the element has its acoustic © active an area at least partially limited by 10 the presence of a substantially suppressing character against the vibration of the bending oscillation and the location of its transducer, in respect of and with regard to such restrictive means.

The entire periphery of the acoustic element may therefore be substantially suppressing or fixed, or only one part (s), than the entire periphery of the element, such as a rectangular panel, may be suppressing or fixed in one or more substantially all of its lateral sides. edges. This may be useful, as well as mounting like 20 on a plate providing said substantial suppression in one side with an acoustically active region, which is therefore projecting, or as well as mounting in two parties that may be parallel and providing said substantial suppression with acoustic an active area between these mounting and 25 suppression sides. In addition, the production of fully compacted or just diaphragm speakers with very selectively drilled apertures, such as midrange / treble devices, may be facilitated. A fully or nearly fully compacted diaphragm allows the so-called reflector to be made reflective.

1616/00-FS unlimited rear acoustic emission pickup / control that could otherwise be harmful at mid to low frequencies.

Fully suppressed or lockable frames also make possible the construction of a speaker set that is more reliable from a mechanical point of view, along with facilitating the production of a speaker assembly that is relatively sturdy as an u construction (compared to a resonant speaker 10 panel, in which the edges of the panel are substantially free or are only suspended in a slightly damping elastic manner).

Substantial suppression or fixation of the peripheral part (s) or edge (s) of the acoustic element may be achieved in any desired manner, for example by full fixing the edge (s) to a solid frame or the like.

I! * By adhesive or by mechanical means, in-line use of fixing the edge (s) between the elements. · _# J on the frame. The desired edge suppression / fixation for this

The aim can be achieved by means of molding technologies (such as injection molding of plastic materials) by forming the edges of the element with integral and integral, sealed enclosures with sufficient rigidity to limit movement at the edge of the acoustic element. Joint molding of the acoustic element and sealing end equipment may be appropriate. Such molding technologies can

I will be particularly suitable when the acoustic element is molded as a monolith and can be easily prepared in a cost effective manner.

1616/00-fs · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·· • Q · · · · · · · · · · · · · · · 9 9 · ·

Significant suppression or locking can also be used to define one acoustic element inside another larger acoustic element. In this way, a large acoustic panel designed to operate at mid / low 5 frequencies can be molded to incorporate a smaller acoustic panel designed to operate at high frequencies and defined by central strengthening ribs.

Significant suppressing or locking action in the existing mechanical end-impedance 10 may be designed to control the reverberation time in the acoustic element, and to assist in the control of the frequency response of the element, possibly especially at lower frequency.

The proportions of suitable resonant panel 15 elements may be as or substantially different from the specific study of WO 97/09842 with respect to variations in special forms. For example, substantially rectangular resonant panel elements for substantially isotropic flexural strength would be for an aspect ratio of 20 ratios below 1: 1.5, which is generally included in the previous study for but not limited to substantially free-edge panel elements, as will be specifically described later here, or greater than 1: 1.5, and will also be specifically described later here. The variations for 25 anisotropy / complex flexural strength (s) are provided as above.

The limiting means may be at least partly around and substantially on said acoustically active region and / or around the peripheral edge (s) of the panel-shaped element,

1616/00-FS · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 1 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · the peripheral edge value, often the whole.

Resonance panel elements are generally self-supporting and would not require prestressing for mechanical stability, in particular for types typically free-edge or for use with simple edge-mounting.

For a fixed panel element, there is a tenfold or approximately equal increase in the first bending frequency due to the natural strength of the panel element when fixed. It is logical and reasonable for a substantial reduction of the flexural strength property to decrease the first modal frequency even before the lower frequency range 15. It is contemplated that the strength of a panel element may in such cases be as low as 0.001 Nm and the surface density as small as 25 g / m ² .

From one point of view, these limits of a series of 20 values describe a panel element that, for mechanical stability and function as the basis of an excitation agent, may be assisted by the application of stresses. They can be applied equally or differently, i.e. in different directions and / or at different voltages in 25 with respect to the effective element geometry.

In the limit, the tensile panel exhibits a high percentage of the properties of a tensile film, withstanding bending vibrations and with a predominantly second order or non-dispersive wave action (constant velocity with respect to frequency). For

1616/00-fs ♦ · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·

such a "panel" element resonant distribution can be optimized for the desired acoustic behavior by controlling the voltage and boundary geometry in full accordance with the 5 distributed oscillation study, see WO 97/09842. Also, the preferred modal distribution can be further enhanced in the act of converter by the preferred / optimized position of the exciter / sensor.

Depending on the degree of tension and with the increase in density, and in particular the flexural strength, there will be a range where the action of the second order bending oscillation is overlapped and increased by the fourth order dispersive bending action 15 due to the strength. Optimizations of both can be obtained by calculation and / or experiment to provide the best results for a particular application.

Fewer wide band-width acoustic panels with edge fixing are provided in the scope of construction.

EXPLANATIONS OF THE FIGURES Attached

The practical implementation of this invention is schematically illustrated by way of an example of the accompanying drawings in which:

Figures 1 and 1A are perspective views in exploded view and partial cross-sectional view of a resonant, generally rectangular panel acoustic element 10 fixed in

1616/00-fs · · · • • · · · · · • 4 Ο · · · • ••• Ιο ··

its edges between opposing members 11 A, B of a rectangular perimeter frame when using screws and nuts 12A, B, which may also be useful for mounting to a chassis or other basic structure;

Figure 2 is a partial sectional view showing an alternative fixation / contouring of a resonant acoustic panel by a fixed edge to a frame 21 by means of an adhesive 22;

u figures 3 and 3A are a partial perspective view and a partial sectional view of a plastic injection molded part 35 formed as a wall element having reinforcing ribs 36 intersecting a rectangular curb 31 as a suppressing edge of the acoustically active panel area 30, such as the border 31 is also formed by convex edges, which hardens the edges of the working panel area 30;

Figure 4 is a partial perspective view of a resonant panel acoustic element 40 stretched on a frame 41 and fixed at its edges by a surrounding frame 20 fixing frame 42;

Figure 4A is a partial cross-sectional view of the embodiment of Figure 4;

Figure 4B is a partial cross-section similar to Figure 4A of an alternative embodiment of a resonant stretched panel acoustic element;

Figures 6A, B and 7A, B and 8A, B are graphical illustrations of mechanical impedance with respect to a selected aspect ratio of fixed edge elements;

Figures 9A, B, C are graphical illustrations with respect to

1616/00-FS of smooth inverse, root mean square deviation for transducer location;

Figure 10 is a calculated mechanical impedance for a quarter panel drawn for a single edge-mounted panel 5 element;

Figure 11 is a graphical representation of various aspect ratios for a fixed edge panel;

Figure 12A-H are measured for a quarter panel mechanical impedance drawn for various aspects of 10 ratios.

Figures 13A-H are graphs with respect to the acoustic output signal as adjusted to the corresponding value;

Figure 14 shows the maximum inverse root mean square deviation of power for various aspects 15 of ratios;

Figures 15A-J are a combination of polar graphs of an acoustic output signal for lower resonance vibrations, a aspect ratio of 1: 3, a fixed edge panel element, and Figures 16A-D are comparative graphs of acoustic power output for specific panel structures varying in size and / or strength.

EXAMPLES FOR THE IMPLEMENTATION OF THE INVENTION

In connection with Figures 1 and 2, the acoustic element may be and is shown to be rectangular in substance and may have aspect ratios as considered preferred in WO 97/09842, however, wider M ranges will be shown of aspect ratios that be potentially useful in

1616/00-FS p

· · · · 99 99 9999

9 9 9 9 9 9 9 9 9 99

9 9 9 9 9 9 9 9 99

999 9 9 9 999 9 9 999 • 14 · · · ····· • ···! The main objective of obtaining a high modal density and uniformity of the modal distribution in the element.

Figures 4 and 4A show an exemplary embodiment of a resonant acoustic element 40 supported on a rectangular surrounding frame 41 and fixed to a rectangular surrounding frame by means of a retaining frame 42 for securing the acoustic element in place. As an alternative, as shown in Figure 4B, the locking frame 42 may be replaced by a tensioning means 43, for example including springs 44 on a frame 45, such as the tensioner fixed at the edge of the element 40. the acoustic element for the element on the rectangular surrounding frame.

Vibratory exciters, for example tensioning means of strains of the types described in WO 97/09842, may be placed on the acoustic element in the embodiments of Figures 4, 4A and 4B to induce resonance in the acoustic elements in order to generate an acoustic output signal , so the acoustic elements can act as speakers or exciter units for the speaker. These vibration exciters are not shown in Figures 4, 4A and 4B for clarity reasons.

Strong suppression or fixation of panel edges allows the use of materials of relatively low strength (compared to the general practice for panels with substantially free edges), which can help to reduce the fundamental frequencies of bending oscillations of panels, including even lower levels, practically generally hard, essentially free edge panels along the by for (and

1616/00-FS ·· ·· • · · 4 · • · · ·

(Despite the actual loss of the lowest frequency for the free-edge type in a fully fixed panel). For example, when the strength range for a practical example of a free-edge panel of the type described in WO 97/09842 may be in the range of 0.1 to 50 Nm, the strength of a fixed-edge panel of the same general type may be low by at least one order of magnitude, even as low as 0.001 Nm. Also, when the surface density range of said practical example of free edge panels may be 100 to 1000 g / m ² , the surface density of fixed edge panels may be only one small fraction, even as low as 25 g / m ² . However, it will be appreciated that substantially strong and / or dense materials can be used for acoustic panels for this purpose, with substantial suppression or edge fixation, at least where the lowest frequency response is required. Such applications include alarms, sirens, ultrasonic reproducers.

Using panel materials with relatively low hardness may result in a higher frequency of matching, for example, over a normal audio tape, which can improve the sound uniformity of a resonant panel speaker. Also, less rigid panels can allow for an effective increase in modal density in the lower registers, and therefore improved sound quality.

Useful variants of overall peripheral fixation / boundary suppression / edge, as illustrated, include any substantially less substantial suppression / fixation that is substantially rectangular

1616/00-FS · ♦ ··

Sat.

panel element / active area would be one side, by omitting what is shown for three sides or two, usually parallel sides, by omitting what is shown for the other two parties.

For this purpose, the acoustic emitting elements may be excited in any of the proposed ways in WO 97/09842, for example by means of at least one inertial electromechanical excitation device. The excitation tube or any excitation device may be positioned for excitation of a radiating element at any suitable geometric position (s) on the surface of the acoustic element. Be it according to the principles as in WO 97/09842 or in accordance with mechanical impedance analysis as in PCT / GB99 / 00404, or as determined experimentally.

Such vibration exciters are omitted in Figure 1 for clarity.

Reference is made to WO 97/09842 as applicable types of pathogens and the positioning of such I ф pathogens may be as determined in accordance with I20 with the same principles as investigated in WO 97/09842 and / or PCT / GB99 / 00404, generally with a difference that is valid for current situations compared to WO 97/09842.

Some useful studies of fully edge-resonant panel elements such as or in active 25 acoustic devices, in particular loudspeakers, were initially disclosed in and with respect to Figures 11 to 16 of PCT application in PCT / GB / 00404 procedure, as filed 9 _h in February 1999, and these figures are repeated herein as figures 6 'to 11, respectively. These studies are, of course, grounded

1616/00-FS on an analysis introducing energy transfer parameters, in particular the uniformity of the input energy, in particular as related to mechanical impedance, and in particular as an effect on the perspective to optimum locations of the transducer and the shapes of the panel element, specific aspect ratios for at least substantially rectangular panel elements and transducer locations based on proportional coordinates. Thus, the graphical illustrations of Figures 6A, B and 7A, B and 8A,

Frequency mechanical impedance B for panel elements of selected aspect ratio and isotropic as flexural strength are accompanied by graphical illustrations of Figures 9A, B, C for smooth mechanical impedance, as measured by the inverse square of the mean standard deviation of the site in particular promising converter locations. Precisely calculated favorable aspects of ratios 1.160, 1.341 and 1.643 are shown together with similarly accurately calculated coordinates of the preferred location of 0 converter (0.437, 0.414), (0.385, 0.387) and (0.409, 0.439), respectively, Figure 10 is a graph for the quarter panel impedance for aspect ratio 1.16 and shows the substantial size of the areas that are promising for transducer location, even two such separate areas (shaded). Figure 11 provides a comparison of such a preferred aspect ratio for fixed edge and transducer locations, including additionally for aspect ratio 1.138.

Other studies for this purpose are based on current measurements of mechanical input energy, including

OYIM ·: Π 1 .48 * ........ 1616/00-FS being substantially rectangular resonant panel elements having increased aspect ratios and in each case adjusting the frequency response to the corresponding value or straight line for decades above the lowest operating frequency of resonant oscillation. Figures 12A-H are graphs for the fourth panel contour of the inverse of the mean square deviation of such fit including the same or close to the above aspect ratios (Figures 12A, B, D) and the corresponding straight-line figures 13A-H. frequency adjustments, respectively, the lightest color / shade represents the most promising location (s) and the discontinuity in discrete areas of indicated perspective at a higher aspect ratio.

Extending these additional studies to an aspect ratio as high as 1: 4 is noteworthy, perhaps specifically the establishment of a clear perspective, from beginning to end, in or near the square. This is unexpected, to put it mildly, at the heart of our preliminary work of detecting and investigating resonant edge panel elements that are essentially free of vibration with bending vibrations. Also the hitherto unexpected increase in operating power, as found here in Figures 5A, B for aspect ratio 1.41, has been further found compatible, due to the study of another aspect of relationships now. There was also another unexpected remarkable decrease in the criticality of the aspect ratio to determine even the intervals of the resonance oscillation frequencies as favorable for acoustic action, which is the reason for the additional .e ·· ·· • ·::: · · · · * · «49 ·· ·· ·· ·· • · · · · · · · · · · · · · · 1616/00-FS Discussion and Analysis. The following result is presented in terms of simplified radiation theory for substantially rectangular resonant panel elements having substantially isotropic bending strength.

In general, there is confirmation from current practice / theory that, for panel elements with edges that are substantially free, the resonant oscillation with the lowest frequency, as determined by the larger size, and best in combination with the shorter-sized side corresponding to the next higher frequency resonance oscillation give relatively corresponding higher frequency series that are substantially different in value. In practice, a high aspect ratio for such a panel, which has substantially free edges, would affect the second (and perhaps even more) of the resonant-type frequencies of the panel element that are immediately inherent in the edge with greater length, and also be lower than the first, inherent at the edge of smaller length, wherein the frequency gap (s) which is too large for a real, satisfactory acoustic characteristic under the influence of bending oscillation at said lower frequency.

On the contrary, the first type of effective resonant frequency for a fully fixed edge resonant panel element requires support from the first resonant oscillation, which is characteristic of a shorter edge length, i.e., the first combination of plane vibration action oscillation for both series (fx _l5 fx ₂ ...... fx _n ) and (fy ^ fy ₂ ..... fy _n ) for the axes parallel to the edge x, y, as illustrated by the spectrum equation

1616/00-FS of resonant oscillation:

The effect of this quadratic dependence is that a high aspect ratio can produce a sequence of very closely spaced resonant 10 frequency types that are inherent in the portions of those subsequent higher series associated with the longer edge before the next fraction of subsequent series related to the shorter edge. Figure 14 shows the maximum of the inverse root mean square energy deviation for the respective aspect ratio and 15 shows an increase in energy uniformity (above the lowest resonant oscillation) with an aspect ratio rising to about 1: 3. In fact, the higher aspect ratio for boundary suppression elements therefore has closer resonance 20 oscillation frequencies, whereas the opposite is applied in relatively free edge panels in WO 97/09842.

This result, of course, does not in any way take away the good and useful results for acoustic devices using a smaller aspect ratio, which are all 25 edge-fixed resonant panel elements, which are also virtually desirable for acoustic operation a resonant frequency type device as provided for in the above analysis and also in PCT / GB99 / 00404.

However, there are significantly larger ones

1616/00-FS • ·

• · · · · · · · · Constructive capabilities. In each particular case and the desired application for acoustic devices, therefore, the specific frequency spectrum of the resonant type will obviously vary with the aspect of the ratio of a given 5 bending strength or its ratios and the choice will often be made on computable, measurable or achievable results, as for the desired or acceptable characteristic of an acoustic device.

Another important factor has been identified and investigated, namely 10 the geometric axis and / or position related acoustic action and characteristic, for which differences may be significant and useful / effective in the design of specific acoustic devices for particular applications, especially when such differences may be 15 positively desired or may be undesirable, or some special combinations are preferred or acceptable, Figures 15A-J are a combination of polar graphs for a resonant panel element with aspect of 1: 3 ratio for lower resonant oscillation frequencies, respectively, and in each case 20 show plans in landscape-position (solid line) and portrait-position (dashed line), i.e., longer in horizontal or vertically, respectively. In general, as expected, the radiation patterns are significantly different, with the plan for the smaller length being generally smoother and the plan for the 25 longer length being more diffuse. Design choices include the admissibility of the higher frequency of the lowest resonant oscillation as being directly dependent on the structure of each specific panel element from a aspect aspect ratio; directivity admissibility when

1616/00-fs w «a · · ·· '·· o:: - · *.: .. .. 22 ·· ··

the vibration of the panel element is markedly different in different axial directions; consistently different energy uniformity in the respective emission plans; selection related to the orientation or position of the 5 panel elements used; and valid balances between the energy uniformity in the different planes and / or the overall energy uniformity in terms of similarity or otherwise of the characteristics in landscape / portrait or azimuth / vertical orientation plans.

The panel element of Figure 16A includes solid black glass coatings, 0.05 mm thick on Aluminum with a cellular structure and 4 mm thick, resulting in a substantially isotropic bending strength of 12.26 Newtonmeters, mass distribution-0.76 kilograms / square and frequency coincidence (resonant frequency) 4.6 kHz. The panel element of Figure 16B includes thick black glass coatings, 0.102 mm thick, on a 1.8 mm thick Rohacell core, resulting in a substantially isotropic bending strength of 2.47 Newtonmeters, mass density 0.6 kg / m ² and 20 socket frequency day (resonance frequency) 9.1 kHz. The panel element of Figure 16C includes thick 0.05 mm thick Melinex ™ coatings on a 1.5 mm thick Rohacell core, resulting in a substantially isotropic bending strength of 0.32 Newtonmeters, a mass density of 0.35kg / m ² and 25 frequencies matching -19.2 kHz. All these panel elements have a similar aspect ratio of 1.13 to 1.14 and are driven by similar exciters with an active diameter of 13 mm and an input impedance of 8 ohms. Each has an output acoustic signal, measured along all panel edges, ·· ·.

• :::. · ··: ···· ··.

·· ··.

• · ·; ····.:: ::: · .. · .. ·· ··

1616/00-FS free to vibrate under the influence of the bending resonance wave of the panels and at all edges fixed for such vibration, Figures 16A-C show that the fixing achieves a significant increase in the output acoustic signal below the coincidence frequency, but not above such that there is a greater beneficial effect for fixing at higher coincidence rates and for lower flexural strength of the panel element in question.

The panel elements of Figures 16A-E are of the same dense structure as in Figure A, but larger in size, namely 360 mm x 315mm and 545mm x 480 mm, respectively, compared to 260mm x 230mm for figures 16A to D; and there is confirmation of full fixing, providing improved acoustic power output from frequency matching down to the lowest resonant frequency of the panel element in question, in particular to about 400 Hz for the smallest panel elements (Figures 16A-C) and -lower for larger and largest panel elements. It is worth noting that the larger panel elements have closed forms of oscillation for a certain frequency, which are approaching a sine wave.

Control measurements of mechanical input energy were made for each of these panel elements when excited with vibration-free edges and fully fixed edges, and each of these panel elements was shown to absorb approximately the same energy.

It may be of interest to reflect on the assumption that precedes the opposite theory of WO 97/09842 with respect to

1616/00-FS

the fact that useful acoustic radiation does not exist below the frequency of coincidence, which is based on the theory that full sinusoidal waves can be expected in an infinite (unlimited) plate and the assumptions resulting from the 5 theories of WO 97/09842 which clearly define, that useful acoustic radiation exists in a bounded plate below the frequency of coincidence, namely that such radiation is manifested by parts of the bounded plate that vibrate, deviating from the full sinusoidal distribution, as 10 seems to be mainly the case with the lowest frequency vibrations and in the vicinity of both the excitation transducer and the edges free to vibrate. Therefore, of course, the latter is meant here. However, it is clear from previous theory that partial edge 15 suppression to the vibration ability of bending oscillation has beneficial effects on acoustic coupling with air, in particular having increased efficiency, consequently, below the coincidence frequency. This is obtained, of course, in the clear position that the 20 acoustic energy output is required to be directly related to the losses in the resonant panel element and in the nearby acoustic field, at least the latter clearly being significantly reduced by the bounding of the edge, such as this effectively eliminates the acoustic short circuit for such 25 edge (s) subject to such restriction.

It seems reasonable to determine the increased acoustic coupling with the air under the coincidence with the reflection of such energy that would otherwise be lost in the near acoustic field, if only on the basis that this · · · · · · · · · ·

··

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energy is in the vibration of the bending oscillation of the frequencies of the resonant oscillation of the panel element in an acoustic range of interest, and must leave the panel element as acoustic energy, either as an improved 5 connection with the air in the suppressed edges, or in the middle of the panel element . The position above the coincidence rate is, of course, unaffected. This, of course, is entirely in the additional context of the actual resonant vibrations of the edge-suppressed panel members, which are necessarily 10 without the distorting vibrations of vibration, which are effectively reduced or eliminated by edge-suppression, preferably fixation.

Additional research has also been done on

the ratio of the location conducive to a second converter based on a measured effect, using a second converter capable of changing position / displacement and with respect to discrete suppression / fixation at the edge when using inertial masses in localized positions. The result with respect to 20 locations of a second converter mainly emphasizes the degree and complexity of the interaction between the effects in a resonant panel element with two transducers. In fact, the best indicated positions for the second converter relative to the advantageously positioned first converter for a 25 resonant panel element with a substantially rectangular shape and substantially isotropic flexural strength are positions actually at or near the center and at or about three quarters of the length of the position on the axis bounding one-fourth of the panel in which it is

1616/00-FS located the first converter and the quality of the output acoustic energy tends to be adversely affected (despite the lack of doubt about the prospect for some applications). The result of discrete 5 suppression / locking is particularly interesting in the indicated potentially useful transition region from near-equal to continuous suppression / locking for an acoustic passive pass filter that operates at longer intervals and connection (s) for a length of 10 the wave of bending waves in the particular panel element.

Claims (22)

An acoustic device based on the action of bending oscillation and capable of operating below the frequency of coincidence, comprising an element allowing said acoustic function due to the favorable distribution of resonant oscillations, with the action of a bending wave in this respect, characterized by at least partially limiting the element, the means having substantially suppressing characters with respect to the vibration of the bending wave element, wherein the limiting means are at the peripheral edge of the Emmen and are continuous around the circumference over at least 25% of said edge. An active acoustic device comprising an element based on the action of a bending oscillation with a favorable distribution of resonant oscillations therefor, and an advantageous position of a bending oscillating transducer, characterized by at least a partial limitation of the element, the agent being substantially suppressing in nature with respect to the vibration of the bending element and the location of its transducer is determined with respect to and taking into account such a limiting means, the restraining means being at the peripheral edge of the element and being continuous at the periphery over at least 25% of said edge. An acoustic device according to claim 1 or I ···· 1616/00-FS claim 2, wherein the limiting means is for and at least partially defined by said acoustically active region, the element being or being part of a larger structure. An acoustic device according to any preceding claim, wherein the restraining means extends along one side of the substantially rectangular said region or panel element. An acoustic device according to claim 4, wherein the restraining means also extends on the opposite parallel side of said area or panel element. 15 An acoustic device according to any one of the preceding claims, wherein the restraint extends completely around said area or edge. 7. An acoustic device according to any preceding one 20, wherein the limiting means contributes significantly to the overall strength of the element, being effective for the desired acoustic action. An acoustic device according to claim 1, at 25 which has a bending strength of the element in said acoustically active region below 5 Newtonmeters. The acoustic device of claim 8, wherein said flexural strength is greater than about 0.001 1616/00-FS Newtonmetres. An acoustic device according to claim 7, 8 or 9, wherein the surface density of the element in said acoustically active region is about 25 grams / square meter. An acoustic device according to any preceding claim, wherein said area of the element is 10 isotropic bending strength. An acoustic device according to any one of claims 1 to 10, wherein said area of the element has a bidirexial (bidirectional) anisotropy of 15 bending strength. An acoustic device according to any one of claims 1 to 10, wherein said area of the element has a flexural strength distribution, 20 suitable for the desired favorable location for the converter. An acoustic device according to any preceding claim, wherein said area is substantially 25 is rectangular, with isotropic flexural strength therefor, and has an aspect ratio of 1: 1 to 1: 1.5. An acoustic device according to any one of the preceding claims 1 to 13, wherein said 1616/00-FS • The area is substantially rectangular, with isotropy of flexural strength for it, and has an aspect ratio greater than 1: 1.5. An acoustic device according to claim 15, wherein said aspect ratio is about 1: 3 or more. An acoustic device according to any of the preceding claims, wherein the limiting means serves at least to limit the resonant vibrations from the action of the bending 10 waves that introduce distortion. An acoustic device according to any preceding claim, wherein the limiting means is at least to reduce the cancellation of the acoustic energy output of the 15 near field. An acoustic device according to any preceding claim, wherein the limiting means serves to increase the acoustic energy output of the action 20 of resonant bending oscillation. 20. An acoustic device according to any preceding claim, wherein the element is stretched. 25 21. An acoustic device according to claim 20, wherein the element is stretched in two mutually intersecting directions. An acoustic device according to claim 21, in the case of an optical device according to claim 21; 1616/00-FS, which is the same in both directions. 23. Acoustic device according to any by claims from 20 to 22, wherein the strength of bending on 5 items in the acoustically active area is low. 24. Acoustic device according to any by claims 20 to 23, wherein the surface density of the element in the acoustically active region is low. An acoustic device according to any preceding claim, wherein the limiting means is integrated with the element. The acoustic device of claim 25, wherein the restricting means is integral with the member.