KR100646191B1 - Active acoustic device including panel member - Google Patents

Abstract

The active acoustic device comprises a panel member 11 having a resonance mode distribution of bending wave action in combination with the transducer means 31-34 to determine acoustic performance. Transducer means 31-34 engage the panel member 11 at the boundary position. Such an arrangement forms an acoustically acceptable action that depends on the resonant mode being active. As an acoustic radiator, the method of selecting the transducer position according to the variable of the acoustic output to the device or improving with limited boundary clamping is to evaluate the optimal interaction of the transducer means 31-34 with the panel member 11. Depends.

Description

ACTIVE ACOUSTIC DEVICES COMPRISING PANEL MEMBERS}

The present invention relates to an active acoustic device and more particularly to a panel member and an active acoustic device in which a resonant mode bending wave operation in which an acoustic operation or function is preferably distributed within the panel member and an advantageous distribution of surface vibrations associated therewith. How to make or improve.

In the related art, an acoustic device including an acoustic radiator or loudspeaker is called "distributed" and is called "panel-type" when the above-described distribution operation can be predicted in the panel member unless specifically allowed.

In a panel loudspeaker, the panel member acts as a distributed acoustic radiator in dependence on the bending wave action induced by the input means for applying mechanical motion to the panel member, resulting in resonance generating surface vibrations related to the acoustic output. Mode bending wave excitation is excited by coupling to the surrounding fluid, usually air. Information on acoustic radiators (among a wide range of active and passive distributed acoustic devices) has been published in the applicant's patent application WO97 / 09842, and a number of subsequent patent applications relate to practical additions and improvements.

For panels so far isotropic at least in flexural strength and substantially constant anisotropy in the axial direction, the position of the transducer is optimal in the range which is in-board of the panel member and close to the center but deviated from it. It was thought to be effective. WO97 / 09842, above, describes specific guidelines for optimal proportional coordinates for transducer positions on or in-board, and for selecting combinations of other specific coordinates when using two or more transducers. It was started for.

Various advantageous applications for paneled acoustic devices have been illustrated, including having surface sheets or layers that are free of acoustic interference. For example, physical blocking, trimming or cladding treatments are possible, including those that are virtually invisible. It is also possible to combine functionalities with other purposes, such as displays, including photographs, posters, blackboards, projection screens, and the like. The ability to effectively hide the in-board transducer invisibly allows for a wide range of applications. In practical applications, however, there is also an area where it is advantageous to use a concealable transducer, in particular making the center of the panel wider without being obstructed by the in-board transducer. For example, in the case of video or other see-through display devices that require translucency or transparency, in-board transducers may protrude, which may not be suitable, but if a large area inside is not visible, the visibility is not disturbed. Such a panel type device would be very attractive if secured.

An apparatus according to an embodiment of the present invention is a panel acoustic apparatus comprising a distributed acoustic panel member equipped with transducer means at a boundary position such that resonance mode vibrations cause acoustically acceptable distributions and excitation phenomena. To provide. In accordance with a credible description of the proper selection or refinement of one or more of these positions, the boundary position is established as a position for the transducer means. This appropriate choice is the result of a study of an acoustic radiator device or loudspeaker related to the sufficient transfer of vibration energy into the panel member, evaluating the parameters of the acoustic output from the panel member when excited at the boundary position. Best results apply to microphones at least.

The contemporary background design of the present invention cannot predict that such marginal location can be successfully used. In fact, the closest of those cited in the prior art to WO97 / 09842 is WO92 / 03024, the starting point and revelation of the invention, from which technological advances have been made, especially in the direction of excitation from the corner interior excitation. . It is one of those advances to understand that the distributed resonant mode flexural wave operation required for desirable acoustic performance results in very high vibrations at the panel corners, which is also generally a factor for panel edges. As evidenced by the results of experiments, at least intuitively or with transducer positions within the board, such high vibrations obviously combine strongly with panel margins that allow limited access and affect the panel member material as a whole. This makes edge excitation impossible as is known in the art.

In applying the present invention, the acoustic panel member or at least a part thereof can be made transparent or translucent. Typical panel members are generally polygonal, usually rectangular. The plurality of transducer means is located at or substantially different edges with respect to the rectangular panel member. Each transducer is piezo-electric, electro-static or electro-mechanical. Each transducer either fires a compression wave into the panel edge, fires a lateral bending wave alongside the panel edge to deflect the panel position laterally, or applies a torsion across the panel corners. Or to create linear curvatures in some areas of the panel.

Depending on the appropriate criteria for sound output, the evaluation of the sound output from the panel member can be relative, which is a resonant mode of efficiency, flexural wave activity when converting mechanical vibrations (automatic and general causal motor phenomena) to sound output. Smoothness of the power output as a measure of the uniformity of the excitation, inspection of the power output with respect to the excitation resonance mode frequency including the number and distribution or spread of frequencies, and the like. The assessment of the viability of the position with respect to the transducer means constitutes the method aspect of the invention individually and in combination.

As a method of evaluating the flatness of the power output, it is proposed to use a technique based on a mean square deviation from a reference value. Using the inverse of the mean squared deviation has the advantage of providing a smoothing of the evaluation according to a positive or representative value. The reference value may vary in each case under consideration, for example it may be based on, for example, an average value shown as a smooth line through the actual measured power output in the frequency range of interest on the graph. The average deviation estimate for the reference value is preferably in a normalized standard format, and the measured acoustic output is preferably adjusted to that standard format. The standard format may be a straight line on a graph, preferably a flat straight line corresponding to a certain constant reference value, more preferably naturally for application to distributed panel members at high frequencies where modes and mode operations are more or the most dense. This is the same line or value as found.

In this relationship, it should be noted that normalizing the reference value of a substantial constant is also an effective basis for an equalization function applicable to the input signal for improving low frequency acoustic output. Practical distributed panel members having preferred aspect ratios and bending stiffness as in the above patent application have a characteristic in that the sound output to frequency gradually weakens in the low frequency direction, and in low frequency, resonant mode and mode operation Although less dense, such frequency distribution is usually beneficial in the low frequency range, and equalization for such input signals can be useful. Low acoustic output at low frequencies is associated with free edge vibration of panel members, including short circuiting around free adjacent panel edges, resulting in high losses at low frequencies, resulting in higher rates Attenuated or destroyed. As expected, the low-frequency loss effect is greater when the transducer is located at or near the edge, or at a lower intensity, than when the transducer is located on the board. Apart from input signal equalization, however, this effect can be mitigated by surrounding the panel member with a baffle or clamping the edge of the panel member. In practice, spacing local edge clamps optionally has a useful effect on frequencies of greater wavelength than spacing between local edge clamps.

Interestingly, for certain very rigid panel members, practical boundary transducer positions include positions that are correlated in terms of edge and transducer positions within the board preferred by the patent application. When using transducer means in pairs, the first preferred position of the correlated boundary transducer corresponds to conceptually including the largest area. For a substantially rectangular panel member, the correlation may be a correlation of the vertical or Cartesian coordinate system, wherein the first preferred position is represented by engaging the transducer means of opposite quadrants in the diagonal direction. However, this is particularly true for panel members with very rigid / high Q-panel members or smaller but with a greater degree of stiffness, but this is not always true. The following shows excellent performance with respect to the neighboring quadrants. For elliptical panel members, the correlation may be a straight line associated with a hyperbolic resonant mode that penetrates into the edge through the location in the board. Although not better, however, possible pairs of edge positions of the transducer are found in the findings obtained by rotating an orthogonal vector around the desired in-board transducer position, including the corner of the panel member or a point adjacent thereto. Another advance with respect to excitation around a corner or around a corner is to perform mass-loading or clamping at a known or optimal position in the board or at a desired drive position. It looks like a hypothetical source causing a wave. The latter does not avoid mass loading intruding into the center, but this allows for successful boundary drive at corners.

Further investigation was carried out on each of the panel members having very high, very low or medium stiffness, in which case the panel members have the aspect ratio and axial bending strength indicated in WO97 / 09842.

In the case of high rigid panel members, the evaluation based on the flatness of the power output relative to the single transducer position of the long edge and the short edge is generally the desired coordinate position, i.e. the peak point expected as the optimum position for a single transducer means. To make sure. However, for additionally long edges, good flatness within about 15% of the peak at positions between each corner and up to one third length from half of the edge, and within about 30% for at least one quarter length position. A spread is to be expected. For short edges, the distribution of flatness measurements is within 10% between coordinate positions and within about 25% at quarter length positions. The short edge shows better power flatness measurement results than the long edge pointed from 1/4 length to about 1/10 of the corner.

The study of two transducer combinations can be extended especially for placing transducers in the same or adjacent quadrants and one for each of the long and short edges. One transducer may be in the most appropriate position for a single transducer along one edge, and the other transducer may change along another edge. For changing along the short edge, one of the preferred transducer positions in the board is identified by the best flatness measurement at 6/10 length. There is a good position in the 3/4 length and a little behind the 1/4, 1/3 length position, but good. In addition, most positions that are not less than one tenth the length from the corner are better or similar but not worse than with respect to the coordinates of the desired onboard position in the same quadrant. During the transition along the long edge, the transducer is located near the preferably 6/10 length position of the short edge. The preferred combination of transducer positions in the neighboring quadrants is best just under 1/5 length, slightly better than 0.42 length position in 1/3 length position and slightly worse in 1/10 length position. The quarter length position is the same for the adjacent quadrant position of the intermediate length position and the preferred onboard position. By repeating this procedure over and over again, more desirable combinations can be identified.

Examination of the lower rigid panel member based on the flatness of the power output showed peaking at the boundary transducer position and the onboard coordinate position, and the quarter length of the panel edge showed a similar effect. It is generally of low importance for the position along the edge in the achieved mode distribution. This seems to be explained by the interaction between the low panel stiffness and the compliance of the transducer itself used. The resonance mode distribution of the panel appears to some extent affected and changed by the transducer position as it progresses to that position. The high rigidity panel substantially avoids such effects. However, the possible interactions of compliance and panel stiffness / elasticity with such transducers are other factors to consider, including those that are useful.

Investigating panel members with very high or low stiffness, even when providing boundary excitation, depends on the position of the transducer, whether it is single or paired, and the magnitude of the interaction with the transducer within the transducer. Therefore, it is appropriate to consider a panel member having medium stiffness.

For panel members with medium stiffness, such as increased acoustic output due to edge clamping compared to low rigid panel members, increased power for mid-range frequency modes, and strong modality or peaking in low frequency modes. Indicates a difference. The higher the stiffness of the panel member, the more likely it is that a single transducer is located at the edge that corresponds to the coordinates of the transducer position in the board optimally, and if it penetrates the center point, it is promising and 1/10 from the corner. Similar characteristic trends appear around the length point. For the two transducer means, it was good at the coordinates relating to the optimal onboard transducer position, and a less desirable but similarly practical distribution appeared up to the center and 2/3 length points and related to the same quadrant coordinates and 2 It was equivalent at the point of / 3 length. Differences in the material parameters of the panel members beyond the basic possibilities for maintaining flexural behavior are important for determining the position of the boundary transducers, and by using two or more transducer positions, the experimental evaluation possible by the teachings of the present application is made. You can create individual answers as needed.

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In addition, by testing on a substantially rectangular panel member, if a local mass loading or clamping of one or another selected boundary position of the panel member is used, most often, but not in many cases, edges or edges for less promising transducer means. It has been found that the position is significantly improved (relative to excitation causing bending wave dependent resonance mode distribution and acoustic response of the panel member). The invention comprises engaging the drive means position in a state of clamping the mass loading or the boundary position of the panel member.

For using two or more transducer means, investigating a combination of boundary positions is impractical but a method for finding the optimal and other possible boundary positions for the second transducer means for a given first transducer boundary position. Is shown. In practice, the boundary transducer position can be investigated and evaluated according to this teaching. In addition, the use of local boundary damping for some resonant modes to improve or reduce their contribution, on the contrary to interfere with other resonant modes, or to reduce the output, etc. Depending on the teaching, the extent and number can be investigated and evaluated.

It is worth considering that the lowest resonant mode is related to the length of the longest natural axis of the panel member, where the long edges in the rectangular panel, including wherever possible run as the best position to operate with a single transducer means, It is always preferred as the position of the transducer means.

It is to be understood that this applies also to the case of adding other transducer means in order to improve other resonance modes or to increase the output power in order to improve the resonance mode.

The operating frequency range of interest in relation to the general subject must be part of the position assessment for the transducer means, which naturally affects the optimum position, for example the optimum position is in the range above and below 500 Hz. May differ from Another influencing factor is the surface adjoining behind the panel member, for example, which affects acoustic performance.

The characteristics of the edge or the preferred location around the edge are assumed to be indicative of trends as introduced in the above-mentioned PCT and other patent applications, appear to allow coupling for most frequency modes, and become more uniform. It can be avoided that only a few frequency modes dominate.
This may be appropriate in the panel member, where the total actual vibration energy is locally lower than in the case where it is higher, but it is not dead in the sense that it couples little or no to any mode, rather than dead. High as regards.

Specific embodiments of the invention are schematically illustrated in the accompanying drawings with reference to examples.

Described.

1 shows a distributed acoustic panel with a suitable transducer as described in the PCT application above.

2 schematically illustrates four different ways of boundary or edge excitation in an acoustic panel.

FIG. 3 illustrates the positioning of transducers of an acoustical panel at a boundary to achieve the action shown in FIG. 2 and FIG. 3A shows a transparent panel.

FIG. 4 shows the preferred positions of the four transducers relative to the on-board position shown in FIG. 1.

5 shows four preferred positions relative to other preferred onboard drive positions and preferred complementary or phantom onboard drive positions.

6 shows how the pair and four drive transducers in such a preferred position are connected for inspection.

7 shows less preferred but possible boundary drive transducer position pairs.

Figure 8 shows the edge drive position and useful mass-loading at the desired drive position in the board.

9 and 9A show four normally undesirable boundary drive transducer positions with many boundary mass loading or clamping positions and how the experimental mass and drive transducers are associated with the panel.

FIG. 10 illustrates an unobstructed onboard area within the boundary of the drive transducer, clamp end and resilient suspension / mounting.

11A, B are graphs of output power / frequency for a single transducer position at long and short edges in a very rigid rectangular panel member.

12A and 12B are related bar charts of measuring flatness of output power.

13A, B are graphs of output power / frequency for two transducer positions that change along short or long edges.

14A and 14B are related bar charts of measuring flatness of output power.

15A, B are power flatness bar charts associated with output power / frequency graphs for a less robust panel member and a single transducer position along a long edge.

16A, B are output power / frequency graphs and power flatness bar charts for the second transducer position along the short edge.

FIG. 17 shows a comparison of the power output for a panel member with low stiffness when the transducer is located in the preferred board and at the edge.

18 a, b, c show the effects of baffling, three edge clamping and both.

19A and 19B are output power / frequency graphs and associated power flatness bar charts for a low stiff panel member with transducers positioned at the fourth edge and three edges clamped.

20A and 20B are output power / frequency graphs and associated power flatness bar charts for low rigid panel members with two parallel edges clamped and transducers located at another edge.

21A, 21B are power flatness bar charts associated with the output power / frequency graph for a low rigid panel member where the corner / middle edge points are locally clamped and the transducer is located at the other long edge.

22 is a power flatness bar chart for a low stiffness panel member where other corner / middle edge points are locally clamped.

Figures 23a, b show the location of another local clamp along the edge where the three-edge clamping and sufficient edge properties of each of the seven points for the panel member with low stiffness and the transducer means have undesirable positions; It is a bar chart which shows power supply evaluation which is not normalized with respect to the case.

24A and 24B are power flatness bar charts associated with power output / frequency graphs for a three edge clamped case evaluated with normalization.

25A, 25B are power flatness bar charts associated with power output / frequency graphs for a single transducer location along a panel member with moderate stiffness and a normalized long edge.

26A and 26B are output power / frequency graphs and power evaluation bar charts for intermediate rigid panel members with limited clamping at seven points evaluated without normalization.

27A and 27B are similar but normalized power supply flatness evaluations.

28A, 28B are power calculation graphs and power flatness bar charts for the middle rigid panel member and the second transducer position along the short edge.

29 shows limited clamping at seven and thirteen points as applied above.

30 is a schematic diagram useful when explaining the effect of compliance in a transducer.

31A-E are power efficiency bar charts for panel members with low stiffness for different edge conditions.

FIG. 1 shows a distributed acoustic panel loudspeaker 10 with a panel member having a typical optimum position for the drive means transducer 12 near (but not in the center) center position as disclosed in WO97 / 09842. . The sandwich structure with the center 14 and the skin 15 and 16 is just one example and many other rigid and reinforced structures are possible. In any case, typical on-board transducer placement limits the transparent area available for the transmission of light, for example in the case of transparent panels.

As a transparent resonant mode acoustical panel member, a known transparent piezo-electric transducer of, for example, lanthanum doped titanium zirconate is used. However, because they are relatively expensive, an alternative approach is to select the four types of excitation shown in Figure 2, denoted by types T1-T4, to design the excitation mode acoustic panel member 10 to be designed to excite the boundary or perimeter of the panel. It is possible to make it unobstructed.

T1-when firing a compression wave to the edge of a panel member useful by inertial action or by reference plane related drive transducers.

T2-When deflecting panel edges laterally using a bending actuation drive transducer to fire a transverse flexure wave along the edge of a useful panel member.

T3-when twisting is applied to the panel member as shown across the corner between the useful edges, which is possible by the action of bending or inertial drive transducers.

 When possible by local contact by a T4-inertial actuation transducer and forming a linear deflection directly at one edge of the panel member.

FIG. 3 comprises a high tension skin 15, 16 and a central structure 14 with drive transducers / exciters 31-34 for four types of edge / boundary drive T1-T4. The composite panel 11 shown is shown. Depending on the desired operating bandwidth and the type of drive applied, fewer than four types of drive may be used simultaneously for acoustically and mechanically appropriate panels. Thus, the optimized panel is driven in one or more different drive forms.

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As shown in Fig. 3A, the acoustic edge panel of transparent edge driving is a unitary structure having a skin or core that is glass or transparent or translucent. If configured to include a pair of skins 15A, 16A sandwiching a lightweight core of aerogel material 14A using transparent adhesive 15C, 16B, the screen can be used as a loudspeaker, even if understood as a visual display unit (VDU), with a small mass Moderately high bending stiffness. The airgel material is an extremely light porous solid material, ie silica. The transparent or translucent skin is made of laminated plastic or glass or transparent plastic material such as polyester. Conventional transparent VDU screens, including acoustic excitation outside the unscreened main screen area, can be replaced with transparent acoustic radiation. Particular suitable silica airgel core material is BASF's (RTM) bassogel. Other possible core materials include lesser known airgel forming materials, including metal oxides such as iron, tin oxide, organic polymers, natural gels, carbon airgels. Particular suitable plastic skin laminates are polyethylene terephthalate (RTM) mylar (MYLAR) or other transparent materials with accurate thickness, modulus, density. Due to the very high shear modulus of the aerogels, they can be made very thin for miniaturization and other physically important factors, allowing them to operate under the distributed mode acoustic principle.

Preferably, such a transparent panel can be coupled to the existing VDU panel as a front plate or the like. In the case of plasma displays, the interior remains close to vacuum at low gas pressures and has a very low acoustic impedance. Thus, there is less acoustic interaction behind the sound emitter, improving performance and saving the front plate. In film-like display technology, the front transparent window can be made using as a distributed emitter and the back display structure can be sized and characterized to include properties that aid in the emission of sound from the front panel. For example, partial acoustic transparency to the back display structure reduces backwave reflections, improving the performance of distributed speakers. In the case of displays that emit light, they will be placed on the back of the transparent distributed panel without compromising its acoustic properties, and the image is viewed from the front.

Transparent distributed loudspeakers can be applied to rear-end systems, which can be additive to transparent screens, or can combine this functionality with surfaces suitably prepared for rear-mounting. In this case, the projection surface and the screen may be composed of one component for proper sound performance while at the same time for ease and economy. The back side is selected to hold the projected image or alternatively, the optical properties of the core are selected for projection. For example, in the case of a loudspeaker panel having a relatively thin center, complete visual transparency is not necessary or ideal and alternatively it is possible to choose a light transmission center such as an airgel or a more economical alternative. Special optical properties are combined with the core or surface to produce directional and brightness enhancement properties for the transmitted visual image.

In transparent distributed speakers with exposed fronts, value is enhanced by providing conductive pads or areas for the user to enter data or commands on the screen. Transparent panels are enhanced by visual or anti-scratch coatings to reduce reflections or improve scratch resistance.

The core and skin for the transparent panel can be selected to have a tint to enhance the visual contrast of the display used together in color shades or neutral tones or coupled to distributed transparent panel speakers. During the manufacture of transparent distributed panels, invisible wiring, eg in the form of fine wires or transparent conductive films, is combined with indicators such as light emitting diodes (LEDs) or liquid crystal displays (LCDs) and mounted inside the transparent panels to protect them. This technique reduces the damage to acoustic performance. For example, a design is possible in which only the skin of one panel is transparent, which does not require overall transparency, thereby providing transparency to the integrated display below the surface.

Depending on the design criteria, including price and performance, the transducer may be piezo-electric or electro-mechanical, and FIG. 3 shows a simple exterior element coupled to the panel with a suitable adhesive. have. For the T1-type drive excitation, an inertial transducer 31 is shown which propagates a vertically oriented compression wave to the panel. Regarding the T2 type drive excitation, the curved transducer 32 is shown to locally bend directly to send a bending wave through the loudspeaker panel. Regarding the T3-type driving excitation, the inertial transducer 33 shows an excited state in which the corners of the panel are driven diagonally, thereby bending the entire loudspeaker panel. With respect to the T4-type driving excitation, there is shown another inertial transducer 34 in the form of a block or semicircle that functions to deflect the edge of the loudspeaker panel.

Each form here generates the characteristic drive for the panel described in the overall loudspeaker design, including the parameters of the panel itself. Placing the transducers 31-34 along the panel edges is repeated as a panel design variable to obtain an acceptable or at least operationalally acceptable mode distribution of the flex wave. One or more audio channels are applied to the associated panel via multiple drive transducers, depending on panel characteristics such as loss control, and the position and shape of the drive near or near the edge, for example. Multichannel potential is increased by signal processing to maximize sound quality, adjust acoustic radiation characteristics, or change the perceived channel-to-channel separation and spatial effects.

Referring to 42 to 45-48 of FIG. 4, in particular, the preferred drive position at the edge of the substantially rectangular panel member is an orthogonal lateral parallel through the optimal or preferred drive transducer position in the board disclosed in the PCT application. Or located on coordinates. It is practical to use a drive transducer at at least two coordinate-related edge positions 45-48. 6 shows in-phase series and series / parallel connections for two and four drive transducers in A and B. FIG. Other drive connections are feasible and desirable, including connecting directly to each transducer means individually.

Undesired interactions between the transducers or electrical signal sources, such as differential delays, filtering, etc., with the addition of direct one-to-one connections per transducer means, are illustrated in FIG. It is possible to eliminate the interaction between the desired drive transducer positions CP1-CP4 relative to the on-board position PL. Each coordinate, i.e., pairing, may be one of CP1 and CP2, CP2 and CP3, CP3 and CP4, CP4 and CP1, and the first preferred pairing is to define the largest region containing the geometric center X. Such conceptual areas include another optimal or desirable on-board transducer position, with CP5 and CP6 being shown as the most preferred positions for complementary position CL and drive transducer pairs in the figures.

For panels with very high Q, recognizing that despite the proper variation in the high frequency range, the most desirable pair of Cartesian coordinate-related drive positions can be extended more than the desired onboard position close to the center position and produce a constant low frequency output. Interesting. The response outside the axis is similar at high frequencies but is substantially more symmetric at low frequencies.

Fig. 7 shows the results of experiments on an optional pair of transducers with a right angle relative position while maintaining the center of the transducer position on a conventional board. Particularly preferred coordinate-related boundary positions are SP1 and SP4. This was done by moving the producer relatively along the panel edges. Most practical / expected location pairs are represented by P1a, P1b to P6a, P6d pairs. FIG. 7 shows the results of another experiment, in which a pair of transducers are actually at the opposite ends of the straight line through the preferred on-board drive position SP1. P2a, P2d and P3a, P3d rarely find practical / prospective positions. Experiments with other or more pairs of edge drive positions are valuable and theoretical and systematic work is being attempted. It can be appreciated that Figure 7 is not strictly to scale, as measured by the position of the pair giving practical / expected, measured / evaluated results.

FIG. 8 shows a panel 70 consisting of a central portion 74 and surfaces 75 and 76 with mass loading at the desired transducer position in-board and transducer 72 mounted near a corner. 18), the mass loading is actually one or group farthest away from the corner excited by the transducer 72, which is particularly effective when it appears to act as a "virtual" source of flexural wave vibrations. . The transducer advantageously avoids or at least couples outside of the point where many resonant modes are known to have nodes, eg lowest frequency operation, up to 5% of the lateral dimension.

In Fig. 9, one position or each corner, half side length point, quarter side length point, 3/8 side length point is selected with respect to installing the transducer adjacent one edge or edge; An overview of the investigations involved in selecting locations for edge clamping / mass loading at edge locations around the panel is shown. For example, 92 of FIG. 9A is used with a rod / clamp by panel flanking / gripping magnets 93a / 93b as excitation transducers.

Using the corner excitation transducer position is assisted by mass loading as shown in FIG. 9A in Pos 13, 14, 18, 19 including combining with other positions. When using transducers at half lateral length points, a good single mass-loading position is Pos 6,7,8 and possibly Pos 9,11, especially Pos 12,15, including combinations with other positions. Combinations Pos 5, 11 and Pos 6, 11, including other combinations, are special values. When using transducers at quarter side lengths, good single mass-loading positions are Pos 5, 6, 7, 13, combination Pos 5, 13 and Pos 10, 13, combination Pos 6, 18.

When using a transducer at the 3/8 side length point, the best position seems to be Pos 6,18 but not as good as the other three transducer positions above.

FIG. 10 shows a panel loudspeaker 80 with a transducer 81 positioned at the border and an area 81 in the board that is free of obstacles that extend beyond the position of the preferred drive transducer in the board. The area 81 is used for the purpose of performing the display purpose directly, or for indicating that it is transmitted by the panel 80 without affecting the acoustic performance or located on the back of the transparent loudspeaker panel 80. Both volume and sound quality can be easily enhanced, with the volume being carefully calibrated by additional drive transducers (not shown), the sound quality being enhanced by local edge clamping 83 to effectively control special modal vibration points as panel ends. do. The panel 80 appears to have a localized elastic suspension 84 positioned neutrally or more advantageously in acoustic performance. The high frequency filter 85 is preferred as an input signal for driving the transducer 82, and conveniently limits the reproduction range to a range of 100 Hz or more for the best, for example, A4 size or equivalent panel. This eliminates problematic low frequency panel / excitation vibrations.

It is advantageous to adjust the acoustic impedance loading to be relatively low in the periphery of the drive transducer 82 which tends to have a particularly high surface speed at the boundary or in the surrounding area in the panel 80. Such control means include sufficient clearance (for example about 1-3 centimeters) for the local planar member, slots or openings in adjacent peripheral frames, supports or grill elements.

It is feasible and desirable to arrange mechanical damping so as to cause acoustic changes, including loss in the region 81 or in the region including its boundaries, so as not to be disturbed at least at high frequencies. This is done by selecting a rigid polycarbonate or acrylic or suitable surface coating or laminate structure. As a result, acoustic radiation can be effectively concentrated in the surrounding area around the plurality of drive transducers, and performing nearer than one acoustic channel for near field listening for computer games or applications with at least localized sound stages is desirable. Remarkably easy. In addition, mixing multiple energized sound sources is not a problem when integrated at least for audiovisual presentations.

The following table provides the appropriate physical parameters of the actual panel members used in the studies in which FIGS. 11-28 are relevant.

Low rigid panel Rigid panel Medium rigid panel Central substance Rohacell A1 honeycomb Rohacell Center thickness 1.5mm 4mm 1.8mm Epidermal substance Melinax Black glass Black glass Cuticle thickness 50 u m 102 um 102 um Panel area 0.06 m ² 0.06 m ² 0.06 m ² Shape ratio 1: 1.13 1: 1.13 1: 1.13 Bending stiffness 0.32 Nm 12.26 Nm 2.47 Nm Mass density 0.35 kgm-2 0.76 kgm-2 0.6 kgm-2 Zm 2.7 Nsm-1 24.4 Nsm-1 9.73 Nsm-1

11-14 relate to high rigid panel members of the first column, FIGS. 15-24 relate to lower rigid panel members of the second column, and FIGS. 25-28 relate to panel members with intermediate rigidity of the third column. have.

All graphs have sound output power (db / W) as the vertical coordinate and frequency as the horizontal coordinate, and the sound output measured with respect to the frequency is indicated by the dotted line. Most graphs show true adjustment of the true power line. As mentioned in the introduction, the ability to normalize to a flat straight line can be used to evaluate the resonant modality without the effect of power drop-off, which often occurs at low frequencies. The flatness of the power source can make a significant contribution to the quality of the sound. From the normalized value of the actual power output, it is beneficial to evaluate the flatness by the inverse of the mean squared deviation and the bar coordinates are such a form.

The high rigidity panel member with respect to FIGS. 11-14 is actually slightly less rigid than that used in FIGS. 7-9 above, but the first optimally positioned arrangement of the transducers in the board, i.e. 3/7 from the corner. , It is preferred to place a single transducer at a position corresponding to a 4/9 length, i.e. 0.42-0.44 length coordinates. However, on each side there is a substantial distribution of possible positions between and beyond these positions, in practice being within about 10% and 15% of the intermediate region of the short and long sides, respectively, and further This corresponds to 28% and 30% of the quarter length position.

Other intervals may be up to 0.09 length coordinates, but at least in most cases the test position for the edge of the transducer and its placement around the edge is the difference between the desired coordinate value of 0.42 for the onboard transducer position and the midpoint of the edge 0.5. Is based on equivalent intervals. Common test points are 0.08, 0.17, 0.28, 0.33, 0.42, 0.50.

Referring to Fig. 23, the graphs and bar graphs shown represent the best and expected positions for the transducers, and illustrate the potential for improving less desirable transducer positions with respect to localized clamping.

Only by placing a single transducer at the edge or near edge, as shown in Figs. 15 and 25, two types of test panel members, one of low rigidity and one of intermediate, are also in the same board based on the power flatness. Indicates coordinate preference. However, the low rigid panel member exhibits similarly superior points in the range from one quarter to less than one tenth of a corner. Interestingly, if the evaluation is performed based on efficiency such as power output-such as when the midline through the true output power plot is the basis for the mean squared deviation-the band will be oblique to emphasize the quadrant length position and the board Most preferred for my coordinate position (see inverse mean square deviation bar chart in FIG. 31A). The panel member with a moderate stiffness is approaching in the direction of the feature of the highly rigid panel member in that it shows a probable distribution between the desired coordinate positions in the board, and is also viewed from the 1/10 length position.

One skilled in the art can examine the true output power plot to assess the difference between optimal viable transducer edge positions in terms of the effect on the predicted quality of sound reproduction, where modality for sound reproduction is the resonance mode. It is considered important factors such as the number and uniformity here. Evaluate the flatness of the output power and, if a feature such as modality is considered more promising for the preferentially illustrated position, process the input signal as it appears after the normalization and selectively boost the low frequencies in the form of signal conditioning or equalization. It is possible to let. This achieves usable output (actually exceeding this) using an optimized location in terms of efficiency, but it is clear that it is not efficient because more input power must be used.

Thus, other methods of increasing low frequency power, such as baffling or selectively positioned local clamping or full edge clamping, have been studied as described above. Figures 18a, b and c show low frequency output by enclosing more than 60% of the area of low stiffness panel with baffles, fixed clamping of three edges that do not accept transducers, or both baffling and clamping. Such baffles tend to maintain modality but are not always feasible in certain applications. Therefore, it is worth studying clamping for alternative transducer edge positions for low rigid panel members. Referring to the bar charts of Figs. 31B, C, and D, evaluating in terms of efficiency is to clamp two parallel edges or all three edges without clamping along the length at the edge with the transducer and Fig. 29 Local clamping of the 7 points in the corners and in the middle, as indicated by X, tends to emphasize the 1/4 point in both. However, clamping at 13 points marked 'X' and 'O' in FIG. 29 highlights the desired coordinate position on the board. Referring to Figures 19A, 20B, 21B, 22, the evaluation of the clamped panel member based on power flatness yields approximately the same results with respect to the best transducer position, but with a significant difference for the next suitable position. This is confirmed by a survey of the actual output.

Indeed, it has been found that there is a strong correlation between adoption based on expert review and evaluation of power output flatness. There is no big difference, but if there is no practical factor that prioritizes efficiency rather than sound quality, it tends to confirm at least some preference for such an assessment.

Another use of local edge clamping relates to ameliorating undesirable transducer positions, in which the bar charts of Figures 23A and B show the right side rather than the left side of the associated edge in the figure. Cases covered are low rigidity panel members, full clamping on three edges and seven point clamping, and local clamps moving on the same edge as the transducer.

Referring to the reference bar on the right of FIG. 23B under unclamped conditions, in both cases it is usefully improved at a quarter length point from a corner further from the transducer. Referring to FIG. 23A the spread is greater in the case of full edge clamping.

If the estimates based on power efficiency and power flatness are inconsistent, it should be remembered that the panel member whose corner is clamped at the edge with which the transducer is associated has no effect on the corner. Until the vibrational motion reaches the anti-node top, there must be half of the wavelength of the associated resonant mode. If power supply flatness evaluation favors a transducer position close to the edge, the rise is small in the waveform and must be handled carefully because of low power and efficiency, even if flat in combination with all relevant resonant mode waveforms. It is advisable to check with the corresponding power / efficiency assessment. In practice, the best one is when the results from the two evaluation methods match or are compromised to suit a particular application, with or without other normalizations for evaluation purposes or adding power / frequency graph reviews by the skilled person. It is preferable.

For panel members with high or moderate stiffness, the optimum transducer edge position is fairly constant but certainly different for other promising positions. Low stiffness panel members for promising transducer edge positions are not very important.

This position is clear when considering using more than one transducer on the edge of the same panel member. Positions for increasing the resonant mode coupling of the panel members are accompanied by inevitable interactions in which the naturally distributed resonant vibration patterns of the plurality of panel members are combined and the distributed vibration patterns useful only at the panel edges are mixed. There is a notable change from the simple rule based on the coordinates of the preferred on-board transducer position established. However, the evaluation procedure can accommodate a valuable tool for finding a combination of transducer positions coupled to the edge.

For the rigid panel of FIGS. 13A and 14A above, one transducer means is located within a tolerance of 0.38-0.45 for the preferred 0.42 position of a single transducer means along the long edge. The second transducer means is modified along the nearest short edge, and Fig. 14A shows the 0.42 position, centered at 0.58, farthest from other positions of length 1/4, 1/3, 2/3 from the corner. Is preferred. Interestingly, fixing the second transducer means at the desired 0.58 position along the short panel edge and changing other transducers along the long panel edge (see FIGS. 13B, 14B) will result in 1/15 (0.17) and 1 along the long panel edge. Optimal preference appears at the / 4 location point and looks better than the starting point (about 0.42) in terms of power flatness. If no convergence occurs along the way, or if the point indicated is not better than the actual expected performance or the point found in the previous procedure, it is recommended to perform both power / efficiency measurements and expert review, but this is clearly Iterative methods can be applied.

16A and 16B show the irradiation results when the 0.42 point of the long edge is the preferred transducer position for the panel member having very low rigidity and the second transducer is changed along the adjacent short edge. Although the association in the quadrant is generally preferred, the optimal three approaching corners and the closest preferred 0.42 position do not differ in terms of increasing power flatness.

Referring to FIGS. 28A and 2B, the middle rigid panel member was examined together, showing a strong preference for the 0.42 transducer position (actually 0.58) for the adjacent quadrants.

Returning to the case of panel members with less rigidity, one can see two effects that contribute to an optimal or optimally similar excitation location that is not very well defined. One is that the panel mode in the frequency range of the optimum state is higher than the panel member with high rigidity. The panel member is an approximation close to the continuum, and the flatness of the output power is less dependent on the transducer position, in particular the second transducer position.

Another effect is that the low mechanical impedance of the panel member makes it less dependent on the transducer position for energy transfer. The mechanism related to the following is demonstrated.

Referring to (100) and (101) in Fig. 30, the mechanical impedance Zm of the panel member determines the movement formed with respect to the application point force. If an object with an impedance that is much less than or equal to the panel impedance is mounted on the panel member, the movement of the panel is strongly canceled at the position where the object is mounted. Associating a moving coiled excitation transducer with the panel connects the panel to the base mass (see transducer's magnet cup, 102) via a spring (see transducer's voice coil suspension, 108). It's like letting go. When the impedance of such a spring is very close to the panel impedance, the transducer determines some of the panel movement. At the boundary at which the spring determines the movement in the transducer as a whole, the input power source does not depend on the excitation position. In practice, the ratio of the spring impedance to the panel member greatly affects the optimal transducer position, and as a result is no longer clear for the optimal transducer position.

Since the mechanical impedance is lower at the panel edge, i.e. the voice coil suspension has a greater effect, the low mechanical impedance affects the edge transducer position more than the on-board transducer position. Specifically for panels with low stiffness from the table:

The mechanical impedance in the panel body is

Zmbody = 2.7 Nsm-1

At the panel edge, the mechanical impedance is half the Zmbody, i.e.

Zmedge = 1.3 Nsm-1

The mechanical impedance at each frequency is lower than the average impedance Zmedge. It is possible to predict the typical frequency at which excitation has a stronger effect on the panel member, ie the voice coil suspension is one fifth of the average impedance at the panel edge.

therefore,

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Given an approximate 1200 Hz, below this the transducer and panel are intentionally connected, but within the optimum frequency range.

If we consider the transducer and the panel member with low mechanical impedance as one system, the transducer partially defines the impedance of the panel member and the flatness of the output power is less dependent on the position of the transducer.

Repeated analysis of the rigid panel yields a corresponding frequency of 130 Hz, which is outside the optimized frequency range.

Accordingly, the present invention provides a panel-type acoustic device comprising a distributed acoustic panel member which is assembled in the form of distributing and excitation which can acoustically accommodate resonance mode vibration, and having a transducer means mounted at a boundary position. to provide.

Claims (48)

A panel member having a plurality of side surfaces; And Includes a transducer coupled to the boundary position of the panel member, The panel member comprises an in-board point having an anti-node of a plurality of low frequency resonant bending wave modes in an operating frequency range, The boundary position is a distributed active acoustic device, characterized in that the point where the Cartesian coordinate axis originating from the point on the board intersects the side surface of the panel member. The distributed active acoustic device of claim 1, wherein a portion of the plurality of side surfaces is clamped. 3. The distributed active acoustic device of claim 2, wherein the clamping is local. 4. The distributed active acoustic device of claim 3, wherein a plurality of local clampings are present. Claim 5 was abandoned upon payment of a set-up fee. 5. The distributed active acoustic device of claim 4, wherein the distance between the plurality of local clampings is smaller than the wavelength in the low frequency resonant mode. Claim 6 was abandoned when the registration fee was paid. 3. The distributed active acoustic device of claim 2, wherein the clamping is coupled to one or more sides. Claim 7 was abandoned upon payment of a set-up fee. 7. The distributed active acoustic device of claim 6, wherein the panel member is rectangular and the clamping is coupled to three sides where the transducer is not present. Claim 8 was abandoned when the registration fee was paid. 8. The distributed active acoustic device of claim 7, wherein the clamping is located at each intermediate point and at each corner of the three sides. 3. The distributed active acoustic device of claim 2, wherein the clamping extends along the panel member. 10. The distributed active acoustic device of claim 9, wherein the clamping extends along at least one edge where the transducer is not present. Claim 11 was abandoned upon payment of a setup registration fee. 11. The distributed active acoustic device of claim 10, wherein the panel member is rectangular and the clamping extends along two parallel edges. Claim 12 was abandoned upon payment of a registration fee. 11. The distributed active acoustic device of claim 10, wherein the clamping extends along three sides. The panel member according to any one of claims 1 to 10, wherein the panel member is rectangular, and the boundary position is between 10% and 15%, respectively, about the midpoint of the short side and the midpoint of the long side, respectively. Distributed active acoustic device, characterized in that located in. The panel member according to claim 1 or 10, wherein the panel member is rectangular, and the boundary position is located between 28% and 30% about a quarter length position of the panel member. Distributed active acoustics. The distributed active acoustic device according to any one of claims 1 to 10, wherein the panel member is rectangular, and the boundary position is located at a length of 0.38 to 0.45 from a corner of the panel member. Claim 16 was abandoned upon payment of a setup registration fee. 16. The distributed active acoustic device of claim 15, wherein the boundary position is located at a length of 0.42 to 0.44 from a corner of the panel member. The distributed active acoustic device of claim 1, wherein the panel member includes two or more transducers. 18. The distributed active acoustic device of claim 17, wherein the two or more transducers are coupled to at least two sides with the panel member. Claim 19 was abandoned upon payment of a registration fee. 19. The distributed active acoustic device of claim 17 or 18, wherein the panel member is rectangular and the at least two or more transducers are coupled to the transverse and longitudinal sides of the panel member. A panel member having a plurality of side surfaces; A transducer coupled to the boundary position of the panel member; And Mass coupled at one point on the side or at least two points spaced from each other Distributed active acoustic device comprising a. A panel member having a plurality of side surfaces; And Includes a transducer coupled to the boundary position of the panel member, A distributed active acoustic device, characterized in that one point on the side or two or more points spaced apart from each other are clamped. Claim 22 was abandoned upon payment of a registration fee. The method according to any one of claims 1, 20 or 21, And a baffling extending around and beyond the panel member. The method according to any one of claims 1, 20 or 21, And wherein said panel member comprises a transparent or translucent region. Claim 24 was abandoned when the setup registration fee was paid. 22. The distributed active acoustic device of claim 1, 20 or 21, wherein the transducer is of electro-mechanical drive. 22. The transducer according to any one of claims 1, 20 or 21, wherein the transducer launches a compression wave to the side, launches a transverse bending wave that laterally deflects the side, A distributed active acoustic device, characterized in that it applies twisting across a corner, linearly deflects local areas of the side, or combines them. A method for improving acoustic operation of a distributed active acoustic device comprising a panel member having a plurality of sides and a transducer coupled to a boundary position of the panel member, the method comprising: Coupling a mass to one point or two or more spaced points of said side. A method for improving acoustic operation of a distributed active acoustic device comprising a panel member having a plurality of sides and a transducer coupled to a boundary position of the panel member, the method comprising: Clamping the panel member at one point or at least two spaced apart points of the side surface. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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