EA000612B1

EA000612B1 - Noticeboards incorporating loudspeakers

Info

Publication number: EA000612B1
Application number: EA199800264A
Authority: EA
Inventors: Генри Азима; Мартин Колломз; Нейл Харрис
Original assignee: Нью Трэнсдьюсерз Лимитед
Priority date: 1995-09-02
Filing date: 1996-09-02
Publication date: 1999-12-29
Also published as: HUP9904010A2; CZ58398A3; CA2230234A1; EA199800264A1; DE69601648T2; SK26498A3; DE69601648D1; DK0847667T3; ATE177282T1; BR9610426A; IL123438A; AU6882196A; EP0847667A1; ES2131410T3; PL325244A1; NZ316563A; CN1195456A; RO119042B1; HK1008645A1; EP0847667B1

Abstract

1. Visual display apparatus comprising a notice or the like board (48), characterized in that the notice the like board (48) is a distributed mode acoustic radiator (2) having a transducer (9) mounted wholly andexclusively thereon having capability to sustain and propagate input vibrational energy to vibrate the radiator to resonate. 2. Visual display apparatus according to Claim 1, characterised in that the radiator (2) has a cellular core (22) sandwiched between skin layers (21). 3. Visual display apparatus according to Claim 2, characterised by a frame (1) surrounding the radiator. 4. Visual display apparatus according to Claim 3, characterised by a resilient suspension (3) mounting the radiator in the frame. 5. Visual display apparatus according to Claim 4, characterised in that the frame (1) has a return lip (4) concealing the suspension (3). 6. Visual display apparatus according to any one of Claims 2 to 5 characterised in that the skins (21) comprise paper. 7. Visual display apparatus according to any one of Claims 2 to 6 characterised in that the core (22) is of paper honeycomb. 8. Visual display apparatus according to any preceding Claim characterised in that the transducer (9) is a piezo electric bender.

Description

The present invention relates to bulletin boards and similar devices for the visual presentation of information.

Prior art

From GB-A-2262861, a panel-made loudspeaker is known, comprising:

a resonant multi-mode radiating element made in the form of a single multi-layered panel formed from two outer layers with an intermediate core having a transverse cellular structure, where the panel has a bending stiffness ratio (B) in all directions to the power in cube panel mass per unit surface area (μ ) equal to at least 10;

fastening means supporting the panel or allowing to fasten it to the support freely and without damping;

and electromechanical driving means connected to the panel and used to excite a multi-mode resonance in the radiating panel in response to an electrical input signal within the operating frequency range of the loudspeaker.

In US-A-3,247,925 in the name of Varnak, a device is disclosed that is a low-frequency resonant panel loudspeaker mounted on a chassis and driven by electromechanical transducers mounted on a chassis.

DISCLOSURE OF INVENTION

In various embodiments of the present invention, elements having the nature, structure and configuration as a whole and / or specifically the PCT publication No. WG 97/09842 of the simultaneously considered application are used. These elements are thus made with the ability to withstand and propagate vibration energy through bending waves in the working area (work areas), passing across the thickness often, but not necessarily, to the edges of the element (s); they have or do not have bending stiffness anisotropy in order to distribute the components of the vibration of the resonant mode in the specified zone (s), mainly for acoustic connection with the ambient air; they also have predetermined preferred positions or points within this zone for the transducer means, in particular, for an operationally active or moving part (s) with respect to acoustic vibration activity in this zone (s) and signals (usually electrical) corresponding to acoustic the contents of such vibrational activity. The international publication No. WG 97/09842 at the same time considering the application from the same date describes the use of such elements in “passive” acoustic devices without transducer means, for example, for reverberation or for acoustic filtering or for acoustic “sounding” of space or space and in “active "Acoustic devices containing transducer means, for example, in a wide range of sound sources or loudspeakers that receive an input signal to convert to sound or microphones that convert sound into other signals.

The present invention more specifically relates to devices for the visual presentation of information, equipped with built-in acoustic devices, for example, loudspeakers.

The above elements are referred to below as distributed-mode acoustic emitters and have the distinguishing features given in the above PCT application, as well as others, as specifically indicated below.

The present invention is a device for the visual presentation of information containing a bulletin board or similar board to which announcements can be attached, for example, with buttons, characterized in that the bulletin board or similar board is an element adapted to withstand and propagate the input vibrational energy using curving waves in at least one working zone, passing across the thickness to distribute the vibration components of the resonant mode, is less than one zone and having predetermined preferred positions or points in this zone for the transducer means, and the transducer is installed completely and exclusively on the specified element in one of the specified positions or points for transmitting vibrations to the element to create resonance in it to form acoustic emitter, which when resonance creates an acoustic output signal. The emitter may have a cellular core enclosed between the outer layers. Outer layers may be paper. The core may contain a paper honeycomb panel. A device for the visual presentation of information may contain a frame surrounding the emitter. Elastic edging can be used to attach the radiator to the frame. The frame may have a shoulder, closing the border. The transducer may include a piezoelectric flexural transducer.

Brief Description of the Drawings

The following is a more detailed description of the present invention with reference to the accompanying drawings, where FIG. 1 is a diagram illustrating the loudspeaker of the distributed mode of the international publication W097 / 09842 of the simultaneously considered application;

FIG. 2a is a partial section along the line A-A in FIG. one ;

FIG. 2b is an enlarged cross-section of a distributed mode emitter of the type shown in FIG. 2a and illustrating two alternative constructions;

FIG. 3 is a perspective view of the first embodiment of the billboard of the present invention;

FIG. 4 is a perspective view of a second embodiment of the notice board of the present invention;

FIG. 5 is a partial section of the notice board of FIG. 3 and 4 and FIG. 6 illustrates one form of transducer.

Variants of the best embodiment of the invention

FIG. 1 shows a loudspeaker (81) having a panel shape and belonging to the type described and declared in international publication No. WO 97/09842, simultaneously considered application from the same number and the same applicant, containing a rectangular frame (1) for installing an elastic bordering ( 3) along the inner perimeter, which holds the sound-emitting panel (2) of the distributed mode. The converter (9), for example, described in detail with reference to international publications No. WO 97/09859, WO 97/09861, WO 97/09858, of the same number and same applicant, is installed completely and exclusively on or the sound-emitting panel (2) in the predetermined position described by the x and y coordinates, whereby the position is calculated by the method given in international publication No. WO 97/09842 from the same number and the same applicant, to the direction of the bending waves into the panel, which causes the panel to resonate and emit an acoustic output signal.

The converter (9) is driven by a signal amplifier (10), for example, an audio amplifier connected to the converter by conductors (28). The requirements for the load and the power of the amplifier can be quite normal, like amplifiers for loudspeakers of the conical type, the sensitivity is about 86-88 dB / W under room load conditions. The impedance of the load of the amplifier is active at 6 ohms, the processed power is 20 - 80 watts. If the core and / or outer layers of the panel are made of metal, they can serve as a heat sink for the converter to remove heat from the working winding of the converter, which improves the processing power.

FIG. 2a and 2b show typical partial sections of the loudspeaker (81) of FIG.

1. In FIG. 2a shows that the frame (1) bordering (3) and the sound-emitting panel (2) are connected to each other by corresponding adhesive joints (20). Suitable materials for the frame include light shaped profiles, for example, profiles for picture frames made from extruded metal, for example aluminum, or from plastics. Suitable bordering materials include resilient materials such as foamed rubber and foamed plastics. Suitable adhesives for the compound (20) include epoxy, acrylic and cyano-acrylate and other adhesives.

FIG. 2b is shown on an enlarged scale that the sound-emitting panel (2) is a rigid light panel having a core (22) made, for example, of rigid foamed plastic (97), for example, cross-linked polyvinyl chloride, or a cellular matrix (98), those. from a cellular matrix of metal foil, plastic, etc., while the cells cross the plane of the panel and are covered by opposite layers of the shell (21), for example, paper, cardboard, plastic, metal foil or sheet. If the outer layers of the shell are made of plastic, they can be reinforced with fibers, for example, carbon, glass, Kevlar (registered trademark (TM)) or other material in a known manner to increase their module.

Thus, the applicable materials of the outer layers of the shell and the amplifier include carbon, glass, Kevlar (TM), Nomex (TM), aramid and other fibers of various styling and weaving options, as well as paper, multilayer bonded paper, melamine and various films of synthetic high modulus plastics such as mylar (TM), captan (TM), polycarbonate, phenolic, polyester or similar fiber-reinforced plastics and the like, as well as metal foils and sheets. Studies of the Vectra-type liquid crystal polymer thermoplastics have shown that they can be used for injection molding of ultra-thin films or smaller casings, say up to 30 cm in diameter. This material independently forms a crystalline structure oriented in the direction of injection, which is the preferred orientation for the propagation of higher acoustic frequencies from the point of excitation to the perimeter of the panel.

In addition, such a casting for this and other thermoplastics allows the use of molds for applying labels for positioning and alignment, such as a groove or ring, for precise installation of converter components, i.e., winding and hanging the magnet. In addition, for some less durable materials, a positive result is calculated by a local increase in the film thickness, for example, in a zone or in a ring, up to 150% of the diameter of the transducer to enhance this zone and transfer the vibration energy to the sound-emitting panel. Due to this, the use of softer foamed materials improves the high-frequency characteristics.

The core materials can serve as ready-made cellular or corrugated aluminum alloy structures in the form of a sheet or foil or from Kevlar (TM), Nomex (TM), plain or multi-layer paper and various films of synthetic plastic, as well as porous plastics or cellulose materials, and even metallic aerogels, if they have a sufficiently low specific gravity. Some suitable core materials have the useful property to independently form a surface film during manufacture and / or otherwise have sufficient intrinsic stiffness that allows them to be used without lamination between the outer layers of the shell. Highly effective cellular core material is known under the trade name "Rohacell", which can be used as a radiating panel and which does not have external layers of the shell. In practice, the main task underlying the invention is to achieve maximum lightness and rigidity, especially including the optimization of the core and outer layers of the shell and transitions between them.

In some preferred embodiments of sound-emitting panels, outer layers of the sheath of metal and metal alloys or, alternatively, carbon fiber reinforcement are used. Both of these options, as well as designs with an “airgel” alloy or with a metal honeycomb core, have significant radiofrequency radiation shielding properties, which should be considered when designing various applications associated with electromagnetic radiation. Conventional panels or speakers of the conic type do not have the ability to shield electromagnetic radiation.

In addition, preferred forms of piezo and electrodynamic transducers have negligible electromagnetic radiation or residual magnetic fields. Conventional loudspeakers create a strong magnetic field at a distance of up to 1 m, unless specific measures are taken to compensate for them.

If it is important in practice to preserve the shielding function, electrical connections can be made with conductive parts of the corresponding loudspeaker panel with a distributed mode (DML panel) or electrically conductive foam material or similar material can be used at the interface to attach the edges.

Edging (3) can dampen the edges of the sound-emitting panel (2) to avoid excessive movements of the edges of the panel. Additionally or alternatively, auxiliary damping may be used, for example, in the form of overlays connected to the panel in selected positions to dampen excessive displacements and to evenly distribute the resonance over the panel. Pads can be made of bitumen-based material widely used in conventional loudspeaker cabinets, or they can be made of elastic or rigid polymeric sheet material. Some types of materials, especially paper and cardboard, as well as frame materials can be self-damping. If desired, the damping in the construction of the panels can be enhanced by the use of adhesives that retain elasticity during curing.

Effective selective damping includes the specific use of the panel, including sheet materials of the tools that make up the panel. Edges and corners may be especially important for the dominant and less dissipated low-frequency vibration modes of the sound-emitting panel of the present invention. Attaching damping means to the edges allows you to get a panel with fully framed parts made of sheet material, although their corners can remain relatively free, say for the required low-frequency gain. Fastening can be done with adhesive or self-adhesive material. Other forms of useful damping, especially for finer effects and / or for mids and highs, can be accomplished with a load or weights attached to the sheet material at predetermined, effectively averaged localized positions in the specified zone.

The sound-emitting panel described above is bidirectional. The sound energy emitted from the rear is not strictly phase aligned with that emitted from the front. Thus, a positive effect is achieved of the total summation of acoustic energy in the room, obtaining sound energy with a uniform distribution of frequencies, reducing the effects of the reflected and standing waves, as well as improving the reproduction of natural space and the atmosphere of reproducible sound recordings.

Despite the fact that the radiation of the sound-emitting panel is largely non-directional, the percentage of information associated with the phase increases with distance from the axis. For improved focusing for a phantom stereo effect, placing the loudspeakers, like pictures, at the height of a normal person’s height gives a positive effect of moderate displacement from the axis for a normally sitting listener, which optimizes the stereo effect. Similarly, the left / right triangular geometry relative to the listener adds an angular component. Thus, it is possible to get good stereo sound.

For a group of listeners, there is an additional advantage over sound reproduction through conventional loudspeakers. The inherent, distributed nature of the sound emitted by the sound-emitting panel gives it a volume that does not obey the law of inverse proportionality to the square of the distance for an equivalent point source. Due to the fact that the intensity decreases significantly less with the distance than the law of inverse proportionality to the square of the distance, then for the out-of-center and incorrectly placed listeners, the intensity field of the panel loudspeaker gives an improved stereo effect compared to conventional loudspeakers. This is because the out-of-center listener is not affected by the double problem of positioning the nearest loudspeaker, first an excessive increase in the volume of the nearest loudspeaker, and then a corresponding decrease in the volume of the remote loudspeaker.

In addition, the positive effect of the invention is to create a flat, lightweight, visually attractive panel loudspeaker with good sound quality and requires only one transducer, without a crossover to get full-range sound from each aperture of the panel.

The sound-emitting panel technology of FIG. 1 and 2 can be used for ordinary material boards, widely used for ads and advertising, without affecting the usual methods of processing these boards, ie, lamination, screen printing or spray painting.

Thus, the board can be specified, set its dimensions and electrodynamically excited to work as a non-directional sound-emitting panel or a flat loudspeaker. Thus, a sound-emitting panel with an area of 0.56 m ² can serve a group of up to 10 people, and a sound-emitting panel with an area of 0.7-1.2 m ² can serve a group of 30-50 people with a natural volume level and with a clear reproduction of speech and even background music or the corresponding sound effects. Due to the property of the sound-emitting panel, it is natural to distribute acoustic radiation, the distortions caused by reflections from local boundaries are minimized. Significant physical obstacles to the part of the sound-emitting panel only slightly degrade the distribution of sound.

To obtain this level of clarity / recognition, lower levels of sound and input electrical power are required.

In a preferred embodiment, the sound-emitting panel contains an inexpensive structure of a paper cellular or foamed core with a thickness of 3 to 6 mm, associated with reinforcing layers of paper, plastic film or paper laminated with plastic film with a thickness of 0.08 to 0.3 mm. The preferred drive for an inexpensive design is a flat-surface piezoelectric transducer, or even built-in, and operating in a bending mode or with its own weight to transmit vibrations.

Such transducers have a naturally increasing acoustic output signal with a frequency, predictably and optimally adjustable to a flat amplitude-frequency characteristic, a combination of a resistive exciter with a series-connected capacitive load of the transducer, while through the detailed specifications of the mechanical properties of the board. The required frequency response can be obtained by adjusting the loss factor in the fibers of the outer layers, the elastic characteristics and the viscosity of the adhesive binder between the outer layers of the shell and the core and between the piezoelectric element and the outer layer due to the applied surface layer, including the substrate for the text or image to be hung out, as well as the general properties core shear and compression.

For higher sound levels and for sound-emitting panels of a larger area, the outer layers of the cladding, made entirely or partially of alloy, giving a proportionally lower loss coefficient, are well suited, which is consistent with more powerful transducers with a moving winding. The latter have a flat frequency response. If a flat continuous surface is required on both sides of the sound-emitting panel, the transducer can be embedded in the panel and hidden in it. If it is necessary to obtain the effect of magnetic shielding of the transducer, then thin strips of mild steel with a thickness of 0.5 mm can be placed under the external sides of the transducer. Thanks to improved magnetic flux coupling, a slight increase in efficiency is achieved.

A small, inexpensive bulletin board does not require special frames or special damping. In the table form of such a board, sufficient damping is ensured by simply contacting the lower edge of the sound-emitting panel with the surface on which it is installed. The device will have a folding support, which is equipped with frames for photographs and which are effective even if made from light cardboard.

Some classes of rigid foamed plastics, for example, unplasticized PVC, have sufficient properties throughout the volume to work in the theoretical range of the sound-emitting panel. They can be used directly as sound-emitting panels of this type without additional reinforcing external panels.

FIG. 3-5 shows the sign-on board, billboard or similar device (48) in which the loudspeaker technology of FIG. 1 and 2. Thus, the loudspeaker (81) containing a rigid and light sound-emitting panel (2) of the distributed mode shown in FIG. 1 and 2, has graphic information, such as text and / or an image of any desired type, printed on the sound-emitting panel (2). Graphic information can be supplemented by an audio message through the loudspeaker, which enhances the impact.

As shown in FIG. 3, a loudspeaker / bulletin board (48) is mounted on a stand (23), made in the form of an easel. Alternatively, the speaker / bulletin board can be suspended on a wire (33), as shown in FIG. 4. Alternatively, the bulletin board may be installed in any other appropriate manner.

As shown in FIG. 5, the frame (1) may comprise a shoulder (4) for masking the elastic bordering (3), which is fastened between the rear surface and the perimeter of the sound-emitting panel (2).

FIG. 6 shows a converter (9) for a sound-emitting panel (2) of a distributed mode in the form of a crystalline discoid piezo element (27) mounted on a disk (11 8) made, for example, of brass, which is connected to the surface of the sound-emitting panel (2), for example, adhesive by compound

FIG. 1 (20). During operation, the acoustic signal applied to the transducer (9) via conductors (28) causes the disc-shaped piezo element to bend and, thereby, elastically deform the sound-emitting panel (2) to direct the bending waves to the panel.

Claims

1. A device for the visual presentation of information containing a message board (48) or a similar board to which ads or similar materials can be attached, for example, with buttons, characterized in that the message board (48) or similar board is a sound-emitting panel (2 ) a distributed mode, on which a transducer (9) is installed, exciting in the said panel bending vibrations that cause resonance in the panel to produce sound.

2. The device according to claim 1, characterized in that the panel (2) has a honeycomb core (22), enclosed between two outer layers (21) of the shell.

3. The device according to claim 2, characterized in that it contains a frame (1) surrounding the panel.

4. The device according to claim 3, characterized in that it contains an elastic suspension (3) securing the panel in the frame.

5. The device according to claim 4, characterized in that the frame (1) has a reverse protrusion (4) hiding the suspension (3).

6. Device according to any one of paragraphs.2-5, characterized in that the outer layers of the shell contain paper.

7. The device according to any one of claims 2 to 6, characterized in that the core (22) is made of a paper honeycomb structure.

8. A device according to any one of claims 1 to 7, characterized in that the transducer (9) is a piezoelectric bending element.