CN1271508A - Resonant Panel Loudspeaker - Google Patents

Abstract

A resonant panel-form loudspeaker characterised by suspension means arranged in at least one low average velocity panel region. A method of making a resonant panel-form acoustic device characterised by locating at least one low average velocity panel region and arranging the suspension means in that region. The method includes determining the acoustic effect area of a large panel, such as an automotive trim panel, by grooving or slotting the panel in a low average velocity panel area.

Description

Resonant Panel Loudspeaker

The present invention relates to a loudspeaker, in particular to a plate-type loudspeaker suitable for producing a sound output by emitting bending waves to a resonant plate and causing it to resonate. Such a loudspeaker is described in the applicant's International Patent Application WO 97/09842 and is referred to as a distributed mode loudspeaker.

In a conventional pistonic loudspeaker, a moving membrane, usually a paper cone, is held in place on a frame or chassis by at least one flexible member, forming a resilient suspension. The suspension mode has at least the following functions, that is: 1. The position in the frame of an assembly includes the film and a vibrator, and the vibrator usually includes a moving coil motor; 2. Make the film move along the axis direction, However, restricting the movement of the film in a direction perpendicular to the axis; and 3. providing a certain degree of damping of the vibration of the film through the selection and treatment of the film material.

These needs are usually met by a flexible undulating molded member, sometimes called an undulating perimeter, which is usually made of a rubber-like material and is attached between the outer perimeter of the membrane and the surrounding frame; and an undulating flexible A permanent member, sometimes called a loudspeaker support ring, is attached between the apex region of the membrane and the frame. Although infrequently used, the common method of using two separate suspension members produces satisfactory performance of the three preceding functions. In conventional dynamic loudspeakers, placement of the suspension elsewhere can cause unwanted resonances and disturb the vibration characteristics of the membrane.

It is an object of the present invention to provide a suspension device which is suitable for the requirements of a resonant panel loudspeaker. In resonant panel loudspeakers, it was found that certain regions of the panel had low average velocities due to the inherent characteristics of the panel, and it was deduced that a suspension could be placed at or near these locations on the panel. The low velocity in this region meant that, on the whole In other words, the suspension has little or no effect on the vibration characteristics of the plate.

According to an aspect of the invention there is provided a resonant panel loudspeaker comprising a suspension arranged in one or more low average velocity panel regions. The suspension means may be used to suspend the plate in a support and/or support a vibratory oscillator above the plate.

The support system includes a surrounding area of the panel, which is an acoustically dead zone. The resonant panel loudspeaker may comprise a panel having an acoustically active area and a low mean velocity panel area surrounding the acoustically active area, slots or grooves in the panel structure defining the acoustically active area. The slots or grooves only partly pass through the plate structure.

The concept of using low energy areas of the plate as mechanical support for the plate itself or for oscillators on the plate can be extended to include the use of slots or cuts through the plate for the purpose of zone definition of the desired acoustically active area, Instead, it is intended for distributed mode operation, or at least has the desired acoustic-vibration behavior, or is part of a larger plate assembly. For example, the slotted seam as a whole design allows the production of a wide range of distributed mode vibration plates, resulting in automotive trim panels with arbitrary shapes. The slots can be of any shape suitable for the desired vibration over the frequency range. Finite Element Analysis (FEA) technology facilitates rapid design and analysis of the shown slot boundary shape and finished product geometry.

The advantage of low vibration energy in the suspension area is that stronger suspension elements can be used than would otherwise be possible, thus increasing the durability of the finished assembly.

A flexible suspension may be formed by cutting the panel to form finger-shaped cantilever members integral with the panel. Cutting may include a pair of parallel slots through the plate structure. Cantilevered members can be straight or other shapes, such as curved. When considering a suspension for use as a vibratory oscillator, a straight cantilevered member is best because of its ease of spanning the low average velocity region and the distance of the high active region where the oscillator is coupled to the plate. The suspension may comprise a set of such cantilevered members. Thus, the cantilevered members into which the board may be cut remain rigid in the plane of the board, yet flexible in the plane of the frame or the like supporting the board. Alternatively or additionally, independent flexible suspensions of rubber-like material are secured to the plate in said low mean velocity region by means of adhesive or the like. In addition to the case where a rubber-type suspension is also used for the suspension, the rubber suspension can be attached to the suspension.

A resonant panel loudspeaker may comprise a distributed mode acoustic radiator, such as the type defined in International Patent Application WO97/09842.

Another object of the invention is a decorative panel, such as for a car or the like, in which the aforementioned loudspeaker is incorporated.

Another aspect of the invention is a motor vehicle, such as a car, comprising the aforementioned loudspeaker or trim panel.

Another aspect of the invention is a method of manufacturing a resonant panel sounder, characterized by locating at least one panel region of low average velocity and positioning the suspension in this region.

The method includes forming the panel suspension by surrounding the location of the acoustically active area with a panel area of low average velocity, defining an acoustically active area of a panel, and then cutting the panel in the area. The method may include defining the acoustically active area by slotting the panel structure. A slot is a structure that may only partly pass through the plate.

When the suspension is intended to support a vibratory oscillator, the method further includes locating a desired plate location, such as an anti-wave node, for mounting the vibratory oscillator to drive the plate, and locating one or more adjacent The nodal region configuring the drive position of the oscillator suspension.

The method may include cutting material of the plate to define a cantilever to form the suspension. The suspension is a suspension with at least three cantilevers.

The invention is illustrated by way of example in the accompanying drawings. in,

Figure 1 is a cross-sectional view taken through a partially resonant panel loudspeaker and showing a suspension arrangement for a vibrating oscillator;

Figure 2 is a small scale bottom plan view of the resonant speaker panel shown in Figure 1;

Figure 3 is a bottom plan view of a resonant speaker board illustrating an example of three vibratory oscillator suspensions;

Figure 4 is a plan view of a board with a resonant board speaker;

Figure 5 is an enlarged fragmentary plan view of detail "A" in Figure 4; and

6 and 7 are another partial cross-sectional views at the line A-A in FIG. 5 .

In the drawings, with particular reference to Figures 1 and 2, there is shown a resonant panel loudspeaker 14 of the general type described in International Patent Application WO97/09842. The loudspeaker comprises a generally rectangular resonant panel 1 made of a rigid but lightweight material forming an acoustic radiator; and an inertial vibrating oscillator 4 mounted on the panel 1 to induce flexures in the panel wave, causing it to resonate and produce a sound output. The system of panels may be of monolithic construction but as shown comprises a honeycomb core 2 sandwiched between two opposing skins 3 .

The inertial vibration oscillator 4 comprises a voice coil/tubular bobbin assembly 13 mounted in the circular hole 12 of the plate 1 by, for example, bonding such that the assembly 13 is formed from one surface of the plate (the upper surface shown in FIG. 1 ). ) extends and extends into the annular gap 15 of the magnet assembly 5, 6, 7, and is defined between the disc-shaped pole piece 7 and the pole cap 6, and the pole piece 7 and the pole cap 6 clamp a disc-shaped magnet 5 together.

The assembly comprising the magnet 5, the poles 6 and 7 is mounted on the plate 1 for it to be attached to the annular flange 8 protruding from the cup 6 after the coil is energized by a signal and comprises three equal The flexible suspension of spacer rubber pads 9 is used for axial movement relative to the coil/bobbin assembly 13, only one of which pads can be seen in FIG. 1 . Whereas the pads 9 are mounted on finger suspensions 10 formed by cutting U-shaped slots 11 in the plate region of low average velocity and at equal intervals around and concentrically with the holes 12, as shown in Fig. 2, the inner end 16 of the cantilever then becomes free for vertical movement relative to the plane of the plate 1.

The pad 9 is attached close to the free end 16 of the cantilever 10 . It should be understood that, if necessary, the pad 9 can be omitted, and the magnet assembly 5, 6, 7 can be directly installed on the cantilever 10.

FIG. 3 shows various examples of suspensions for suspending a vibration oscillator on the plate 1 . These examples include: a single straight finger cantilever 10 bounded by a U-shaped slot or cutout 11 as shown in Figures 1 and 2; a cantilever 17 defined by a helical slot 18; and a resilient cantilever Bearing, including a cantilever member 19 defined between a pair of opposing arc-shaped slots 20 and having a circular central portion 21 and a pair of opposing protruding portions 22, the ends of which are connected to the plate, the magnet system is connected to the portion 21 Central location 23.

Figures 4 to 7 disclose an example of a resonant panel loudspeaker 14 of the general type previously described, having a resonant panel 1 forming part of a larger panel 24, which may be, for example, a trim panel of a motor vehicle such as a car. In this example, loudspeaker 14 has a rectangular resonant plate 1 bounded by grooves or slots 25 in a larger plate 24, which plate 1 is suspended in plate 24 by means of suspension arms 27, which are formed by The relatively parallel arrangement of slots 26 delimits, across the slot 25 surrounding the area of the low mean velocity plate 1 . Each side of the plate 1 is provided with a cantilever. The vibration oscillator 4 can be suspended as described above or in a desired manner. As shown in FIG. 6 , the slot 25 passes only partly through the plate 1 . As shown, the slot 25 passes through the upper skin 3 and the core 2 of the panel 1, leaving the lower skin to cover the slot. Alternatively, as shown in FIG. 7 , the slot 25 can go completely through the plate 1 .

With regard to the application of the present invention to automotive trim panels and similar decorative structures, the slot can be formed at an early stage of manufacture, such as by laser or water jet cutting, and the slot only needs to be wide enough to provide a stable clearance for the vibrating assembly. In practice, a width of 1 mm or 2 mm is usually sufficient. The width of the suspension assembly depends on the effective length of the suspension required to reasonably maintain the overall assembly, the strength and linear stiffness of the plate in this area, and the acceleration forces. A value of 4 to 25 mm proves to be an effective width of the cantilever.

Another advantage concerns its durability under lateral acceleration forces. A relatively narrow slot width allows the plate to be more securely grounded than surface features that are adhesively bonded to the flexible suspension assembly. In the latter, the suspension is able to withstand damage during disassembly.

In cases where radiation separation between the front and rear panel surfaces is required for acoustic configurations, larger panels may serve as buffer panels and are usually reinforced by local structures such as door frames or some frame or support. In a construction application, the structural panel is reinforced by the design of the house or building. Between the front and rear panels, sound leakage through narrow gaps is negligible. This slow leakage facilitates stray noise isolation from the back of the board to the front of the board, which is important in some applications.

As for the car trim board, it is considered to laminate a light-weight soft trim cloth on a thin layer of soft porous polyurethane sponge in the later stage of manufacture. The structure can be applied over the slot without significantly disrupting the principle of operation. The slot is invisible to the user. A further subtle improvement in sound isolation can be obtained from the finite acoustic resistance of the sponge and cloth-covered slots.

The advantages of the configuration shown in the figure are as follows: 1. The suspension can be made of the same material as the plate, so the cost is low; 2. The suspension can be located within the thickness of the plate or the thickness increase is only small; 3. Multiple such suspensions can be found position to suspend the plate from a relatively fixed portion of the vibrating oscillator, and/or suspend the plate from a frame or other support; and 4. Simple cantilever/beam calculations immediately provide the required flexibility magnitude.

Claims (19)

1. A resonant panel-form loudspeaker characterised by suspension means arranged in at least one panel region of low average velocity.

2. A resonant panel-form loudspeaker according to claim 1, characterised in that the suspension means is formed by cutting the panel structure to form at least one suspension member integral with the panel.

3. A resonant panel-form loudspeaker according to claim 2, characterised in that the cut-out comprises a pair of parallel slots through the panel structure.

4. A resonant panel-form loudspeaker according to claim 2 or claim 3, wherein the suspension means comprises an array of cantilever members.

5. A resonant panel-form loudspeaker according to any one of claims 2 to 4, characterised in that the cantilever member maintains stiffness in the panel face to produce compliance in a plane perpendicular to the panel.

6. A resonant panel-form loudspeaker according to any preceding claim, characterised by a flexible suspension fixed to the panel.

7. A resonant panel-form loudspeaker according to claim 6, when dependent on any one of claims 2 to 5, characterised in that the flexible suspension means is secured to the suspension member.

8. A resonant panel-form loudspeaker according to any preceding claim, characterised by a distributed mode acoustic radiator.

9. A resonant plate loudspeaker according to any preceding claim, characterised in that the plate includes an acoustically active region and a region of low average velocity surrounding the acoustically active region, the slot or groove in the plate defining the acoustically active region.

10. A resonant panel-form loudspeaker according to claim 9, characterised in that the slot or groove passes only partially through the panel structure.

11. A decorative panel characterized by having a resonant plate-type speaker according to claim 9 or 10.

12. A motor vehicle characterized by having a decorative panel according to claim 11.

13. A method of manufacturing a resonant panel-form acoustic device, characterised by locating at least one panel region of low average velocity and locating suspension means in that region.

14. A method according to claim 13, characterised in that the acoustically active area of the panel is defined by surrounding the acoustically active area with an area of the panel of low average velocity, and then cutting the panel structure in that area to form the suspension means.

15. A method according to claim 13 or 14 as dependent on claim 11, characterized in that the acoustically active area of the plate is defined by means of a slotted plate structure.

16. The method of claim 15, wherein the slot is formed only partially through the plate structure.

17. A method according to any one of claims 13 to 16, wherein the suspension means is formed by defining the cantilevered members by cutting the material.

18. A method according to any one of claims 13 to 17, wherein forming a vibration oscillator suspension means comprises finding a desired plate drive location for coupling the vibration oscillator to the plate to drive the plate and finding one or more regions of low average velocity adjacent the drive location at which the oscillator suspension means is arranged.

19. The method of any of claims 11 to 16, wherein a suspension device is formed having at least three cantilevered members.

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