KR20010042428A - Acoustic device relying on bending wave action - Google Patents

Abstract

An acoustic device comprising a member that relies on a bending wave having an advantageous distribution of resonance modes, the member having an acoustic operating region that is at least partially bounded by means that are substantially constrained to the bending wave vibrations. The operation can be performed at or below the simultaneous frequency, or in the case of an active acoustic device having an advantageous position of the flexural wave transducer means determined on the basis of the bounding means above.

Description

Acoustic device with bending wave motion {ACOUSTIC DEVICE RELYING ON BENDING WAVE ACTION}

Wanaka's US-A-3,247,925 proposed a low-frequency loudspeaker made of an extremely rigid resonant panel whose edges were bolted or bonded to a rigid frame, where the frame was a conventional voice coil that would provide flexural wave energy to the center of the panel. Support the transducer. This low frequency loudspeaker device is said to manipulate all wave simultaneous frequencies.

Bertagni also proposes a loudspeaker with a diaphragm formed by an expanded polystyrene flat plate member with a pretensioned front and an irregularly shaped rear surface.

Details of the acoustic wave operating acoustic device commonly known as the resonant panel type are described in International Patent Application W097 / 09842, which improves or optimizes the acoustic function according to panel parameters including geometry and flexural strength; In particular, those that can be usefully operated at the same time and below. The geometric parameters in question include the panel's allocation ratio or aspect ratio, including the use of passive acoustics. Parameters of flexural strength can advantageously interact with geometric parameters, including anisotropy, that is, different values of flexure that allow virtually invariability along the geometry axis that is accompanied by visible changes in geometrical allocation ratios. It is related to strength. The first built-in location for transducers of active acoustics is usefully equipped with a rate ratio regulation coordinate. Other spatial distributions of flexural strength contribute to providing other desirable positions of the transducer at the geometric and / or center of mass, which is described in International Patent Application W098, which discloses the combination of acoustic-related piston action with the above-mentioned bending wave motion. See / 00621. Acoustic operation is at least in W097 / 09842, with the description and claims of both the entire panel and part of it.

Based on the right angle, the specific analysis and design method for the resonant bend wave operation acoustic device described above is mainly based on the entire panel that is completely or substantially free of vibration when the edge is subjected to acoustically related bend wave operation and makes edge damping light. Focused on. The present invention is in accordance with the surprising results obtained through consideration, research and experimentation of the inverted-angle mode.

The present invention relates to an acoustic device of the type comprising a sound emitting member for generating an acoustic output by flexural wave operation and the resulting surface vibration.

1 and 1A illustrate a resonant rectangular panel acoustic member 10 whose edges are clamped between rectangular peripheral frame members 11A and B using bolts and nuts 12A and B useful for securing to a chassis or other parent structure. It is an enlarged perspective view and a partial sectional view showing the;

FIG. 2 is a partial cross sectional view showing an alternative edge clamp fixation / termination of the resonant panel acoustic member 20 by securing the edge to the frame 21 with adhesive 22;

3 and 3A include a rigid lip 36 intersecting a rectangular border 31, formed as a restraining edge of the acoustic panel region 30, and formed by a lip that strengthens the edge of the operative panel region 30. Partial perspective and partial sectional view of the plastic injection molding machine 35 formed as a wall member to be shown;

4 is a partial perspective view of the resonant panel acoustic member 40 extending over the frame 41 and whose edges are clamped by the peripheral clamping frame member 42;

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

4B is a partial cross-sectional view showing another embodiment of a resonant expansion panel acoustic member similar to FIG. 4A;

5A and 5B are graphs showing the frequency response of A4 and A5 sized resonant panel members, respectively, with thick lines showing clamp-fixed edge panels and fine lines showing free (unfixed) or resilient edge panels. ;

6A, 6B, 7A, 7B, 8A, and 8B graphically show mechanical impedance versus frequency for a selected aspect ratio of a clamped edge panel member;

9A, 9B and 9C graphically show the inverse deviation of the mean square horseshoe relative to the position of the transducer means;

FIG. 10 graphically depicts quarter panel mechanical impedance calculations for the clamp fixed edge panel member; FIG.

11 graphically illustrates various clamp fixed edge panel aspect ratios;

12A-H show measurements of quarter panel mechanical impedance for various aspect ratios;

13A-H show relevant acoustic outputs that are suitable for reference values;

14 shows the maximum reciprocal of the mean square deviation of power for different aspect ratios;

15A-J show composite polar coordinates of sound output for low resonance mode of a clamped panel member with a 1: 3 aspect ratio; And

16A-D show acoustical output power comparisons of specific panel structures that differ in size and / or intensity.

Important requirements continue to be applied for the acoustic device members which extend in the thickness direction and which can constrain the bending wave through the continuous and acoustically active areas and are also important in terms of technology / invention. In other words, here the parameters such as the basic condition of the resonant acoustic member or panel and the geometrical and flexural strength have a value that is consistent with the distribution of the resulting natural bending wave vibrations, which is a problem such as the requirements of the resonant acoustic member or panel. It is desirable or effective to achieve proper or desired acoustic manipulation of the device over the frequency range of. Embodiments of the present invention provide a means that substantially constrains flexural wave vibrations at the edge, periphery, or other boundary or acoustical region of the member or panel, and is typically operable at least partially below the simultaneous frequency. By "substantially constrained" is meant to constrain at least part of the edge of the member at least as described in WO97 / 09842, preferably with regard to edge size and effective loading, grip or grounding effects.

Two aspects, i.e., effects or creativity of the invention, are desirable to consider in relation to the above constraints of the substantial edge / spatial boundary / periphery.

One is to preferably combine the acoustic power generated from the oscillating flexural wave energy in which the limiting / reducing (as compared to the contents of W097 / 09842) of the flexural oscillating edge / peripheral / boundary movement of the effective member returns to the acoustic operating region. That can be. The other is that acoustically related and effective natural resonant flexural wave motion (when compared with in W097 / 09842) limits / suppresses the flexural wave vibrations at the edge / periphery / boundary of the member and thus, Reduce / remove the contribution by the lowest resonant mode that will work if the edge / periphery / boundary portion has a flexural wave distribution as published in WO97 / 09842; It also changes with the reduction / substantial suppression of the resonance mode with twist.

The resulting reduction in the magnitude or frequency of the acoustic behavior / associated resonant flexural wave mode is accompanied by a frequency of f1 in terms of accompanying a resonant plate mode correlated to each beam starting at the resonant mode frequency f1 less than the f0 frequency. In terms of the effective effect on the natural resonance mode uniformity of the direct and complex relations, it can be simply inferred and analyzed based on the equivalent level of simple beams considering the interaction.

It is divergently divergent and this leads to an energy conversion and / or very usefully increased for possible / optimal transducer positions as confirmed by mechanical impedance analysis as described in co-pending international patent application PCT / GB99 / 00404. Achieving target subregion size; And / or normally, even greater aspect ratios of spatial shape / allocation ratios of members realized for isotropic flexural strength, even at aspect ratios greater than about 1: 1 to 1: 3; And / or the feasibility of acoustics for panel materials of low intrinsic flexural strength resulting from effective fixation of the whole with the aid of edge / peripheral / boundary restraint; And / or capabilities related to high power input transducer means for loudspeaker implementation, all of which are fixed on an inertial ground base or with a larger hard / weight carrier or other heavy load method These can be provided.

One of the great advantages of the present invention is an active sound device such as a loudspeaker, which is particularly easy to manufacture, as a rugged, instantaneous assembled panel device, which is particularly improved in comparison with the sound device shown and described in International Patent Application W097 / 09842. To provide new and useful resonant panel acoustics.

According to one aspect of the present invention, there is provided a member for providing said acoustic manipulation because of the advantageous distribution of the resonant mode of flexural wave operation, being dependent on the flexural wave operation and being operable outside of synchronism, said member being at least partially An acoustic apparatus is characterized by having an acoustic operating region bounded by means having limited characteristics in relation to flexural wave vibrations.

According to another aspect of the present invention there is provided a device comprising a member depending on the advantageous distribution of the resonant mode and the advantageous position of the flexural wave transducer means, wherein the member is at least in part by means having a limiting characteristic in relation to the flexural wave vibrations. It provides an acoustic apparatus characterized by having a boundary of the acoustic operation region and the transducer means position determined in consideration of the boundary means.

The entire periphery of the acoustical member is substantially constrained or clamped; Alternatively, part of the entire periphery of the member, ie the rectangular panel, may be restrained or clamped at one to all side edges. This is useful as a flagged fixture that will provide the restraining force on one side by the protruding acoustic actuation region, or a fixture that will provide the restraining force on both sides by the acoustic actuation region parallel to each other and between the fixture and the restraining surface. ; In addition, it is convenient to manufacture fully handwritten or highly selective open diaphragm loudspeakers, even medium and high frequency devices. Fully or nearly completely enclosed diaphragms allow a so-called infinite baffle loudspeaker to include / control rear acoustic emission operation or otherwise be disadvantageous at mid to low frequencies.

Substantially fully restrained or clamped frames are convenient for fabricating loudspeakers of relatively robust construction (compared to resonant panel loudspeakers that extend in a resilient manner where panel edges are substantially free or lightly damped). It can be designed in a more predictable form.

Substantial restraint or clamp fixation of the periphery or edge of the acoustical member is achieved by securing the edge to the rigid frame in a suitable manner, ie by mechanical means involving the fixation of the edge between the adhesive or frame members. Preferred edge restraint / clamp fixing can be achieved as a molding technique (such as plastic injection molding) by forming a full or layered circumferential portion of sufficient strength to terminate the edge operation of the acoustical member at the edge of the member. Cavitation and edge layering of acoustic members are appropriate. The forming method is particularly suitable when the acoustic member is made of monolith and easily achieved in an economical way.

Substantial restraint or clamping fixing may also be used to define one acoustic member within the larger acoustic member. Therefore, large acoustic panels for medium and low frequency operation can be shaped to include smaller acoustic panels that are formed for high frequency operation and defined by intermediate reinforcement ribs.

Substantial restraint or clamping action can be designed to indicate mechanical termination impedance to control the reverberation time of the member, to help control the frequency response of the acoustical member, especially at low frequencies.

The size of a suitable resonant panel member may be similar or substantially different from the clear description of WO97 / 09842 regarding changes in specific shapes. For example, a substantially rectangular resonant panel member of substantially isotropic flexural strength may have an aspect ratio of 1: 1.5 or less, as will be described in detail later, and thus is generally inclusive of a substantially free edge panel member. Includes but is not limited to technology. Or may have an aspect ratio of at least 1: 1.5, as described in detail later. The change in the anisotropic / complex distribution of flexural strength is as described above.

The bounding means is at least partially close to and confines the acoustically active area and / or panel-like member to be fully acoustically up to a full area boundary / peripheral edge range, often up to 25% or more of its total.

The resonant panel member is generally self-supporting and does not require mechanical tension, in particular pre-tensioning for typical types of free edge or simple edge support applications.

For clamped panels, there is a tenfold increase in the initial bending frequency due to the natural strength of the panel member upon clamping. It can be logically sensed to substantially reduce the flexural strength characteristic to reduce the first mode frequency before the lower frequency range. In such a case, the panel member may have a strength as low as 0.001 Nm and an area density as small as 25 g / m ² .

Values in this range describe that the mechanical stability and drive means support function in the panel member can be advantageously obtained by applying the tensile force. Tensile forces may be applied uniformly or differentially, ie in different directions and / or in different tensions depending on the geometry of the effective member.

As a result, the tensioned panel exhibits much of the properties of the tensile film supporting the bending wave with significant second or non-diffusion wavelength operation (rate constant with frequency). In such 'panel' members, the resonance distribution is optimized for the desired acoustic behavior under the control of tension and boundary geometry, such as the distribution mode described in WO97 / 09842. Moreover, the preferred mode distribution can act as a transducer through the preferred / optimized placement of the exciter / sensor.

Depending on the degree of tension and the increase in density, more specifically the increase in flexural strength, there is a range in which the second flexural wave action is increased by the fourth diffusive bend action due to strength. Optimization can be made by calculations and / or experiments to provide the best results at a given condition.

It is possible to implement smaller, wideband acoustic panels with fixed edges. A practical embodiment of the present invention is shown in the accompanying drawings.

According to FIGS. 1 and 2, the acoustic member may be substantially rectangular or rectangular, and in view of the general purpose of the member for obtaining high mode density and uniformity of mode distribution, a wider aspect ratio range is useful. In spite of the gender, it may have an aspect ratio which is preferably examined in WO97 / 09842.

4 and 4A illustrate an embodiment of a resonant acoustic member 40 that extends over the rectangular peripheral frame 41 and is clamped to the rectangular peripheral frame by a clamping frame 42 that holds the acoustic member in place. Tensile force is applied to the member 40 in the direction of arrow F. FIG. Alternatively, as shown in FIG. 4B, the clamping frame 42 may be replaced with a tensioning means 43 comprising a tension spring 44 on the frame 45. The tensioning means is fixed to the edge of the member to extend the acoustic member over the rectangular peripheral frame.

In order to excite the resonance to the acoustic member in order to produce an acoustic output, for example, a vibration exciter of the kind described in WO97 / 09842 may be placed in the acoustic member according to the embodiment of FIGS. 4, 4A and 4B. Thus, the acoustic member can operate as a loudspeaker or loudspeaker driving means.

The use of relatively low strength materials is possible by the strong restraint or clamping fixation of the panel edges (compared to the normal operation of practical free edge panels). It is possible to lower the panel's basic bend mode frequency, typically below the level useful for high intensity, substantially free edge panels (although the lowest frequency free edge mode is lost in a fully clamped panel). For example, when the strength range for an embodiment of a free edge panel of the type described in W097 / 09842 reaches 0.1 Nm to 50 Nm, the strength of the clamped edge panel of the same kind is 0.001 in order of at least one grade, Can be reduced to about Nm. In addition, when the surface density range of the free edge panel is 100gm2 to 1000gm2, the surface density of the clamped edge panel is very small and may be as low as 25g / m2. However, it should be noted that a material of considerable strength and / or density may be used for the acoustical panel following substantial edge restraint or clamping fixation, where at least the lowest frequency performance is not required. Such applications include tweeters, siren, ultrasonic regenerators, and the like.

Relatively low intensity panel materials can be used to achieve higher matching frequencies, for example frequencies above the normal voice band. This improves the uniformity of voice directionality of the resonant loudspeaker panel. Lower intensity panels also effectively increase the mode density at lower registers, resulting in better speech quality.

As shown, a useful variant of a completely peripheral edge / boundary-restraining / clamping fixation is to omit one shown in three sides or one shown in two sides for a substantially rectangular panel member / operating area. Less substantial substantial restraint / clamping fixation, which may be a face or two parallel faces.

The acoustic diverging member is excited in the manner presented in WO97 / 09842, for example by at least one inertial electromechanical excitation device. This excitation device or each excitation device is arranged at the most suitable geometric position of the acoustic member to excite the diverging member; This is done according to the principles of WO97 / 09842, mechanical impedance analysis of PCT / GB99 / 00404 or experimental results. Such vibration excitation is omitted in FIG. 1 for clarity.

Applicable types of exciters are mentioned in W097 / 09842, the positions of which are the same as those presented in PCT / GB99 / 00404, with the necessary differences in the actual position according to comparison with W097 / 09842 and / or W097 / 09842. Can be determined.

A useful study of acoustically actuating devices, particularly resonant panel members, which are fully edge clamped into or within a loudspeaker, was first described in connection with FIGS. 11 to 16 of pending PCT / GB99 / 00404, filed February 9, 1999. Was initiated; The figures are shown respectively in FIGS. 6 to 11 of the present invention. Of course such studies are based on analyzes relating to the parameters of power transition, in particular to the smoothness of the input power, especially in relation to mechanical impedance; It is also based on an analysis that affects the optimized transducer position and panel member shape, in particular the aspect ratio of the transducer based on at least substantially rectangular panel members and polar coordinates. Therefore, in the graphical depiction of FIGS. 6A, 6B, 7A, 7B, 8A and 8B for the mechanical impedance with the frequency of the panel member isotropic with respect to the flexural strength with the selected aspect ratio, in particular the inverse of the standard deviation of the expected transducer position A graphical illustration of FIGS. 9A, 9B, 9C is followed for a smooth mechanical impedance measured by the square. Precisely calculated preferred aspect ratios 1.160, 1.341 and 1.643 are also shown with preferred transducer position polar coordinates (0.437, 0.414), (0.385, 0.387) and (0.409, 0.439) which are also correctly calculated. FIG. 10 shows the calculated quarter panel impedance for aspect ratio 1.16 and shows the actual area width for the transducer location in two separate areas (shaded parts). 11 compares the preferred clamped edge aspect ratio and transducer position, including an aspect ratio of 1.138.

The study is based on actual measurements of mechanical input power, including substantially rectangular resonant panel members with increasing aspect ratios; In each case an accurate frequency response to the reference value or flat line is made for 10 years above the lowest effective resonant mode frequency. Quarter panel contours against such square deviations of conformity are shown in FIGS. 12A-H including aspect ratios equal to or similar to the aspect ratios (FIGS. 12A, 12B, 12D) and corresponding FIGS. 13A-H for the parallel frequency suitability. have. The brightest coloring / shading represents the most desirable transducer location and is a distinct area with survivability at higher aspect ratios.

It is noteworthy that more in-depth studies of aspect ratios as high as 1: 4 achieved clear overall viability at or near the square. This is not expected in the prior art disclosure of resonant panel members having substantially free edges for background and flexural wave vibrations. Unexpected increases in operating power as introduced in FIGS. 5A and 5B for aspect ratio 1.41 are consistently introduced in other aspect ratios investigated. Unexpected reduction in aspect ratio criticality to give resonant mode frequency spacings useful for acoustic operation requires further attention and analysis. The following results are obtained for the simplified beam theory for a substantially rectangular resonant panel member having substantial isotropic strength.

In general, according to the prior art, for a substantially pre-edge panel member, the lowest resonant mode frequency is determined by the longer side size. Most preferred when associated with a shorter lateral size corresponding to the next higher resonance mode frequency giving a related series of higher resonance mode frequencies.

Indeed, the substantially high aspect ratio of the free edge panel results in a second frequency of the resonance mode frequency of the panel member directly due to the longer edge size. This is lower than the original frequency due to the shorter edge size. Therefore, the frequency spacing is too large for satisfactory acoustic performance, which relies on flexural wave operation at lower frequencies.

In contrast, the initial effective resonant mode frequency of a fully edge clamped resonant panel member is attributed to the original resonant mode resulting from the shorter edge length, i.e., the edge-parallel axis, as expressed in the resonance mode spectral equation. A first combination mode is required for plate vibration operation for two series of sets x, y (fx1, fx2 ... fxn), (fy1, fy2 ... fym).

n ≥1, m ≥1

The effect of this quadratic equation relationship is that the high aspect ratio can produce a series of closely spaced resonance mode frequencies resulting from the contribution of the longer edge related set before the contribution of the next higher and shorter edge related set. Is there. FIG. 14 shows the maximum reciprocal of the mean square deviation of power versus aspect ratio, and shows an increase in smoothness of power (above the lowest effective resonance mode) with an aspect ratio peak increasing at about 1: 3. Effectively, the higher aspect ratio of the boundary constraining member has a closer resonance mode frequency, and vice versa, applied to the relative free edge panel of WO97 / 09842.

These results, of course, do not in any way undermine the useful results for acoustic devices using resonant panel members that have a smaller aspect ratio and are fully edge clamped; This is also practical with desirable acoustic device operation of resonant mode frequency interleaving, as illustrated in the analysis of PCT / GB99 / 00404.

On the one hand, the design possibilities are even greater. In certain specific cases and in the preferred application of the acoustic device, the specific spectrum of the resonant mode frequency varies depending on the aspect ratio or the ratio of the given flexural strength; And it is selected according to the calculated or measurable or perceived results for the desired or satisfactory acoustical device performance.

We found many differences in the implementation and research of another relevant variable, namely axis- and / or position-related acoustic motion and functions, and in particular the design aspects of specific acoustic devices for special applications where these differences may or may not be positively required. In or when a particular combination is preferred or acceptable. 15A-J show composite polar coordinates for one resonant panel member each with an aspect ratio of 1: 3 at low resonance mode frequencies; In each case, the measurement plane (solid line) and the similar plane (dashed line) are indicated as horizontal planes and vertical planes of long dimensions, respectively. In general, as expected, the radial patterns are significantly different from one another, such as being generally smoother in the short length plane and more diffuse in the long length plane. Design conditions include high frequency capacity in the lowest resonant mode directly related to the specific panel member structure on the aspect ratio; Directional capacity when the panel member vibrations are significantly different on different axial directions; Continuously varying power smoothness at the corresponding radial plane; Selectivity of the relationship of orientation or position of the panel member used; And the actual average of the overall power smoothness for similarity or responsiveness in other plane power smoothing and / or survey / similar or azimuth / plane.

The panel member of FIG. 16A includes a 4 mm thick aluminum honeycomb structure wrapped in a 0.05 mm thick black glass surface, resulting in an anisotropic flexural strength of 12.26 Newton meters, a mass density of 0.76 kg / m ^2, and a simultaneous frequency of 4.6. It is in kHz. The panel member of FIG. 16B includes a 1.8 mm thick Rohacel core wrapped in a 0.102 mm thick glass surface, resulting in an anisotropic flexural strength of 2.47 Newton meters, a mass density of 0.60 kg / m ^2, and a simultaneous frequency. It becomes 9.1kHz. Figure 16C is a panel member of mellitic Annex Loja ^TM comprises a cell core of 1.5mm thick, and wrapped in the surface and virtually yigyeol anisotropic flexural strength of 2.47 Newton meters, mass density of 0.60 kg / m ² and a co-occurrence frequency of thickness 0.05mm Becomes 9.1 kHz. These panel members are all driven by an exciter with a similar aspect ratio of 1.13 to 1.14 and an operating diameter of 13 mm and an input impedance of 8 ohms. Each has a measured acoustic output at all panel edges that cause free vibration for the resonant flexural wave operation of the panel and at all edges clamped to the vibrations described above. Figures 16A-C show a better effect of clamping so that a higher frequency than the simultaneous frequency does not, but the sound output at a lower frequency is increased so that the greater the simultaneous frequency, the lower the flexural strength of the associated panel member. have.

The panel member of Figs. 16D-E is the same most robust configuration of Fig. 16A, compared to the larger sizes 360mm * 315mm and 545mm * 480mm, respectively 260mm * 230mm from Figs. 16A to D; 400 Hz for the smallest panel member (FIGS. 16A-C) and larger or larger panel members have improved acoustic output from the simultaneous frequency to the lowest resonant mode frequency when clamping the entire clamp for the panel member characterized by lower than this. Demonstrates providing power. It is also noted that the larger the panel member, the closer the mode is to a given frequency shape that approximates a sine wave.

The mechanical input power was measured at the free vibration edge and at the fully clamped edge. As a result, all panel members used almost the same power.

This, in accordance with the contents of WO97 / 09842, relates to practical acoustic emission, which, prior to other text of WO97 / 09842, may be ineffective below the range of simultaneous frequencies based on the same theory as considered in perfect sine waves in unlimited plates. Consider the assumption that sound emission useful as an assumption is effective at a limiting plate below the coincident frequency, that is, such an emission occurs from a part of the limiting plane oscillating away from the full sine wave distribution, which is mainly the lowest frequency mode and As shown on both sides of the near and free oscillating edges of the excited transducer, the latter case is emphasized here. However, it has been mentioned that the confinement of the edges in relation to the current flexural wave vibration force provides an advantageous effect of gaining efficiency gains in acoustically coupled air, in particular below the coincident frequency. Of course, phenomena occurring within the self-proven acoustic output relationship must be net related to losses in the resonant panel member and acoustic proximity region, and at least the latter acoustic proximity region is around the constrained edge. It can be greatly reduced by the edge restraining which effectively cancels the acoustic circuit short of.

In the absence of reflection, the above-mentioned energy with improved binding to air in the middle of the panel member or the panel member should be emitted from the panel member when it is included in the bending wave vibration of the resonance mode frequency of the panel member in the acoustic range and thus as acoustic energy. Only based on, can reasonably estimate the increase in acoustic coupling to air below the coincidence frequency accompanied by the reflection of the energy lost in the acoustic proximity region. The rise above the simultaneous frequency is of course not affected. That is, within the relationship of the effective resonance mode final member, it is necessary to eliminate the twisting vibration in such a manner that everything is effectively reduced or eliminated by edge restraint, preferably clamp clamping.

For further studies, advantageous location for the second transducer on the basis of the effect measured using the repositionable / movable second transducer; And separate edge restraint / clamp clamps using inertial masses at local locations. The result of considering the second transducer position is an analysis of the expansion and complexity of the interaction between the effects of the resonant panel members of the two transducers. Indeed, the optimal position of the transducer to add additionally to the substantially rectangular resonant panel member and to the first transducer in an advantageous position in substantial isotropic flexural strength is at the center and near the center and the first transducer is located and the quality of the sound output. It was a position of or close to three quarters of length along the axis that bounds the quarter-panel (which in some cases could survive) which tended to be counterproductive.

Embodiments of the present invention provide a means that substantially constrains flexural wave vibrations at the edge, periphery, or other boundary or acoustical region of the member or panel, and is typically operable at least partially below the simultaneous frequency.

Claims (28)

An acoustic device comprising a member that is dependent on a flexural wave operation and can be operated at a frequency lower than the coincident frequency, and which provides an acoustic operation by an advantageous distribution of resonance modes of the flexural wave operation. And wherein said member has an acoustic operating region substantially at least partially bounded by means having substantially restraint against flexural wave vibrations of said member. In an active acoustic device comprising a member depending on the bending wave operation with an advantageous distribution of the resonance mode of the bending wave and an advantageous position of the bending wave transducer means, The member has an acoustic operating region that is at least partially bounded by means substantially constrained by flexural wave vibrations of the member and the position of the transducer means is determined with reference to the bounding means Sound system. The method according to claim 1 or 2, Said bounding means being for at least partly confining said acoustical operating region and wherein said member is of an expanded structure or part thereof. The method according to claim 1 or 2, Said bounding means being located at a panel-shaped end edge and said member is fully acoustic as said acoustically active region. The method according to claim 3 or 4, Said bounding means receiving up to at least 25% of said area or edge continuously at said periphery. The method of claim 5, Said bounding means extending along one side of said substantially rectangular area or panel member. The method of claim 5, And said bounding means also extend along a parallel plane opposite said area or panel member. The method of claim 5, And said bounding means extends over said area or the entire panel member. In any of the foregoing, And said bounding means contributes greatly to the overall strength of the member effectively for the desired acoustic operation. The method of claim 9, And wherein the flexural strength of the member in the acoustic operating region is less than or equal to about 5 Newton meters. The method of claim 10, Wherein said flexural strength is greater than about 0.01 Newton meters. The method according to claim 9, 10 or 11, An acoustic apparatus, characterized in that the surface density of the member in the acoustic operating region is about 25 g / m ² . In any of the foregoing, The region of the member has an isotropic flexural strength. The method according to any one of claims 1 to 12, And the region of the member has anisotropic flexural strength in both directions. The method according to any one of claims 1 to 12, The region of the member has a flexural strength distribution that will provide an advantageous location for the transducer means. In any of the foregoing, The region being substantially rectangular with isotropic flexural strength and having an aspect ratio between 1: 1 and 1: 1.5. The method according to any one of claims 1 to 15, The region being substantially rectangular with isotropic flexural strength and having an aspect ratio greater than 1: 1.5. The method of claim 17, And the aspect ratio is about 1: 3 or more. In any of the foregoing, And said bounding means at least limits the resonant mode of the bending wave accompanying the torsion. In any of the foregoing, And said bounding means serves to reduce near field dissipation of the sound output. In any of the foregoing, And said bounding means serves to increase the sound output from the energy of the resonant bending wave motion in said region. In any of the foregoing, Acoustic device, characterized in that the member is tensioned. The method of claim 22, And the member is tensioned in two mutually crossing directions. The method of claim 23, wherein Acoustic device, characterized in that the tension in both directions is equal. The method according to any one of claims 22 to 24, An acoustic device, characterized in that the bending strength of the member in the acoustic operating region is small. The method according to any one of claims 22 to 25, An acoustic apparatus, characterized in that the surface density in the acoustic operation region is small. In any of the foregoing, And the bounding means is integrated with the member. The method of claim 27, And said bounding means is integrally molded with said member.