CN1195461A - Display screen with speakers - Google Patents

Abstract

The display screen 32 (e.g., a projection screen) includes a panel with a light-reflecting surface, characterized in that the screen is a distributed sound radiator loudspeaker, on which a transducer 9 is integrally and independently mounted to vibrate the radiator to resonate and provide sound output.

Description

Display screen with speakers

technical field

This invention relates to display screens and more particularly, but not exclusively, to projection screens.

Background technique

A panel loudspeaker is proposed in GB-A-2262861 comprising:

A resonant multimode radiator element consisting of a cell sandwich screen of two skin materials with a spaced core of transverse porosity, wherein the screen is such that its bending strength (B) in all directions relative to The ratio of the cube (μ) of the screen mass per unit surface area is at least 10;

a mounting device which supports the screen or connects a supporting body frame to the screen in a free and undamped manner;

and an electromechanical drive connected to the screen for exciting multimode resonances in the radiating screen in response to electrical input in the frequency band of operation of the loudspeaker.

Disclosure of the Invention

Embodiments of the present invention use components whose properties, structure and configuration are obtainable generally and/or specifically by fulfilling the teachings of our co-pending International Application contemporaneously herewith (My Application No. P.5711). Members of this class have the ability to retain and propagate input vibrational energy by bending waves in the operating region where the thickness extends laterally, usually (but not necessarily) to the member edges; with or without anisotropy in bending strength, such that The resonant vibrating components are distributed in said area to facilitate the coupling of sound with the surrounding air; and have a predetermined preferred position or location in said area for the transducer device, especially its Active active or moving parts that are active for acoustic vibration activity in the area in question and for signals, usually electrical, of the sound content corresponding to such vibration activity. The use of such components as or in "passive" acoustic devices without transducer devices, such as for reverberation or with Acoustic devices for acoustic filtering or for "voicing" a spatial sound; and as or in "active" acoustic devices with transducer means, such as for use when providing converted In a relatively wide range of sound sources or loudspeakers when an input signal into said sound is used, or in a microphone such as when exposed to sound to be converted into another signal.

The invention then particularly relates to display screens with acoustic means such as speakers.

The above described components are referred to herein as distributed acoustic radiators and are intended to be featured in the aforementioned PCT applications and/or specifically provided herein.

The present invention is a display screen comprising a panel with a light reflective or light emitting surface, characterized in that the screen itself is a distributed sound radiating loudspeaker with an integrally and individually mounted transducer transducer to vibrate the radiator and cause it to resonate to produce an acoustic output. The radiator consists of a rigid lightweight panel with a porous core sandwiched between a pair of high modulus skins; a surrounding frame; and a resilient suspension to which the screen is mounted. The porous core layer may have a honeycomb structure of aluminum foil. The skin can consist of fiber-reinforced plastic.

Projection screens include panel speakers attached to the sides of the screen to provide left and right channel information. The left and right speakers can be hinged on the radiator so that they can be folded relative to the radiator when stored.

The left and right speakers also preferably use distributed acoustic radiators, each radiator having a transducer integrally and individually mounted thereon to vibrate and resonate the radiator. The display screen may be a projection screen or an electronic display screen such as a thin film self-luminous screen.

From another perspective, the present invention is also an audio-visual device, which is characterized in that it is the above-mentioned projection screen. The audio-visual device includes at least one rear channel loudspeaker, also in the form of a distributed acoustic radiator having an integral and separately mounted transducer for vibrating the radiator into resonance.

Brief introduction to the drawings

The invention is illustrated by way of example and in conjunction with the accompanying drawings, in which:

Fig. 1 is a schematic diagram of the distributed loudspeaker described and claimed in the international application pending for examination (our scheme number is P.5711);

Fig. 2 a is a partial sectional view according to line A-A in Fig. 1;

Figure 2b is an enlarged view in partial section of a distributed radiator of the type shown in Figure 2a, showing two alternative configurations;

Figure 3 is a perspective view of an embodiment of a projection screen according to the present invention;

Fig. 4 is a partial detailed view of the screen in Fig. 3;

FIG. 5 is a top view of the room with the projection screen of FIG. 3. FIG.

The best way to carry out the invention

Referring to Figure 1 of the accompanying drawings, there is shown a panel speaker 81 described and claimed in our co-pending International Application contemporaneously with our Application No. P.5711, which includes a A rectangular frame 1 of frame 3, said suspension supporting a distributed acoustic radiation screen 2 around its inner periphery. Transducer 9, such as that detailed in our co-pending International Application (My Application No. P.5683/4/5) contemporaneously, is mounted entirely and solely on or within panel 2 by x and On the predetermined orientation defined by y, the position of its orientation is calculated according to the calculation described in our pending international application (my program number P.5711) at the same time, so as to launch bending waves into the screen to make the screen resonate. Fires a single output.

The transducer 9 is driven by a signal amplifier 10, such as an audio amplifier, connected to the transducer by conductor 28. The loading and power requirements of the amplifier can be quite standard, similar to the usual cone speakers, with a sensitivity level of 86-88dB/watt under room loading conditions. The amplifier load impedance is roughly 6ohms and the power handling is 20-80watts. Where the screen core and/or skins are made of metal, they may act as heat sinks for the transducer, removing heat from the transducer's motor coils and thus improving power handling.

2a and 2b are partial representative cross-sectional views of the loudspeaker 81 of FIG. 1 . Figure 2a shows that the frame 1, surround 3 and screen 2 are connected together by respective adhesive joints 20. Suitable frame materials include lightweight frames such as image frames made of extruded metal such as aluminum alloy or plastic. Suitable surround materials include resilient materials such as foam rubber and foam plastic. Suitable adhesives for joint 20 include epoxy, polypropylene, and cyanoacrylate adhesives.

Figure 2b illustrates on an enlarged scale that the screen 2 is a rigid lightweight screen with a core 22 made of, for example, rigid plastic foam 97, such as cross-linked polyvinyl chloride or metal foil, plastic or the like, with pores extending transversely to the plane of the screen and surrounded by an opposing skin 21, such as paper, card, plastic or metal foil or sheet. Where the skins are made of plastic, they may be reinforced in a well known manner with fibers such as carbon, glass, kevlar (RTM) or similar to increase their modulus.

Discloseable cover materials and reinforcements include paper, bonded paper layers, melamine and other materials such as mylar, kapton, polyvinyl chloride, phenol, polyester or related plastics, fiber reinforced plastics, etc., and sheet metal Or foil, including carbon, glass, kevlar (RTM), Nomex (RTM) that is, aramid, and various twisted (lays) and fabric-like fibers. Investigations of Vectra grades of liquid crystal polymer thermoplastics have shown that they are useful for injection molding ultra-thin skins such as those below 30 cm in diameter or skins of smaller dimensions. The material itself forms a crystalline structure in the direction of the jet which is the preferred orientation for good propagation of high frequency energy from the drive point to the periphery of the screen.

Additional injection molding of this and other thermoplastics provides injection molds with positioning and registration features such as grooves or rings to precisely position transducer components such as motor coils and magnet suspensions. Also for some weaker core materials, it has been calculated that increasing the skin thickness in areas such as up to 150% of the transducer diameter or locally in the annulus is beneficial in enhancing that area and the coupled vibrational energy into the screen. For softer foam materials the high frequency response will be improved by this method.

Disclosed core materials include expanded or foamed plastic or pulp materials, or even suitable low-density aerosol metals, fabricated porous or corrugated aluminum alloy sheets or foils, or Kevlar (RTM), Nomex (RTM), regular or bonded paper, and various synthetic plastic films. Some suitable core materials effectively exhibit self-generating skins that are useful in their manufacture and/or have inherently sufficient strength for lamination-free skin interlayers. A high performance porous core material is known under the trade name 'Rohacell' which is useful as a radiant screen and has no skin. From a practical point of view, the aim is to obtain an overall finish and strength suitable for a particular application, including in particular the optimum composition of the core and skin layers and the conduction between them.

Some preferred formulations for screens use metal and metal alloy skins, or alternatively carbon fiber reinforcement. All of these, as well as alloy aerosol or metal porous core designs, will have practical radio frequency shielding characteristics which are important in some EMC applications. Common panel or cone speakers have no inherent EMC shielding capability.

In addition, preferred piezoelectric dynamic transducers have negligible electromagnetic radiation or leakage fields. Ordinary loudspeakers have a large magnetic field, which will reach a distance of 1 meter if special compensation measures are not adopted.

Where shielding is to be maintained in the application, an electrical connector may be fabricated for the conductive portion of the appropriate DML screen or an electrically conductive foam or similar connector may be used when mounting the edge.

The suspension 3 dampens the edge of the screen 2 to prevent excessive edge movement of the screen. Additionally or alternatively, other dampers, such as wires, may be attached to selected locations in the screen to dampen excess motion to allow an even distribution of resonances across the screen. The wiring may be of pitch-based material, as is used in typical loudspeaker housings, or may be of elastic or rigid polymeric sheet material. Some materials, especially paper and card, and some cores can be self-damping. If desired, damping can be added in the mechanism of the screen by using an elastic fit glue instead of a rigid fit glue.

Effective said selective damping involves specific application of the sheet material of the screen and of the device permanently attached thereto. Edges and corners are of particular interest for the dominant and slightly scattered low-frequency vibration modes of their panels. Edge fixation of the damping means facilitates the creation of a panel that is fully framed by said thin sheet material, although the corners may often be relatively free, such as stretched for low frequency operation. The connector can be glue or self-adhesive material. Another useful form of damping, especially in finer effects and/or mid and high frequencies, may be by means of suitable substances or substances fixed to the sheet material at predetermined effective central local locations in said area.

The sound screen panels as described above are bi-directional. The sound energy emanating from the rear is not in strong phase with respect to the sound energy emanating from the front. The result is favorable overall accumulation of sound power in the room, distribution of sound energy of equal frequency, reduction of reflection and standing wave effects and good quality reproduction of natural spaces and environments in playback sound recordings.

Although the radiation emanating from the acoustic panel is largely non-directional, the percentage of information-related phase increases off-axis. Because of the improved focus of the pseudo-stereoscopic image, the orientation of the loudspeakers, like the picture, is at the height of an ordinary person standing upright, thus providing an advantageous moderate off-axis orientation for optimum stereoscopic effect for a normally seated listener . Also, the triangular left/right geometry relative to the listener provides another angular component. This is how good stereo sound is obtained.

The invention also has the advantage of targeting a group of listeners compared to conventional loudspeaker reproduction. The intrinsic propagation properties of sound radiation from a sound screen give it a sound volume that does not obey the inverse square law of distance from the same point source. Because the decrease in intensity with distance is much smaller than that predicted by the inverse square law, the result is that for off-centre and poorly positioned listeners, the intensity field of screen loudspeakers enhances a better stereophonic sound than conventional loudspeakers. Effect. This is because off-center listeners do not suffer from the double problem of being close to nearby speakers: first the loudness of nearby speakers is greatly increased, and then the loudness of further speakers is correspondingly reduced.

A flat, lightweight panel speaker also has the advantage of being visually appealing, having good sound quality and requiring only one transducer and no overlap of full-range sound from each panel membrane.

FIG. 3 shows a multimedia audiovisual system comprising a moving image projector 31 for projecting an image onto a projection screen formed by a loudspeaker panel 32 of the type shown in FIGS. 1 and 2 .

The loudspeaker/projection screen 32 comprises a screen 2 having aluminum or carbon fiber reinforced skins 21 sandwiching a honeycomb core 22 of aluminum foil. These composites can be firmly joined together with any epoxy adhesive. For a screen panel with dimensions of 1.22 x 1.38 meters, the thickness of the aluminum skin is 300 microns. The thickness of the core layer is 11 mm and the cell size of the honeycomb is 9.5 mm. This screen is very rigid, low density, high modulus and isotropic.

A pair of smaller auxiliary speakers 114 of the kind introduced in Fig. 1 and Fig. 2 can also be hinged by hinges 34 on the left and right sides of the center channel speaker panel 32, therefore, the auxiliary panel can be relative to the main panel when not in use. 32 rotation, then open to the position as shown in the figure when in use. The auxiliary panel 114 is used to receive and radiate respective left and right channel information, eg for stereo operation.

The auxiliary loudspeaker 114 also comprises a screen 2 with a skin 21 of aluminum foil, or carbon fiber or glass fiber reinforced plastic. A decorative film such as polyester can also be added on one or both of the surface layers. The core layer 22 of the screen panel 114 can be aluminum foil with a honeycomb porous shape, or a porous paper body. If paper material is used, it can also be impregnated with plastics such as phenolic compounds to increase the stiffness of the paper. The size of the holes may be in the range of 3 to 6 mm and the thickness of the core layer may be in the range of 3 to 10 mm. If the surface layer is made of aluminum foil, its thickness is 25 to 100 microns. Use epoxy adhesive to assemble the screen.

Stereo sound is the reproduction of two-channel sound, which includes the generation of the illusion of sound levels. The generation of illusion includes the location of the sound source, the far and near configuration of the original recording, and its atmosphere. The stereo sound of traditional loudspeakers is relatively strong in the position of the phantom sound source and the sound far and near configuration in some aspects, but it is insufficient in the expression of natural space and atmosphere. This is because the near-point sound source characteristics of commonly used piston speakers make it easy to distinguish their physical positions by hearing, which is contradictory to the needs of the overall stereo image position.

It is often said that loudspeakers as reproduction devices should disappear into the illusion of sound hierarchy. Part of the problem is that commonly used loudspeakers have a relatively narrow directivity of forward radiation. In addition, the sound on the outside and rear of the cabinet is balanced, and the sound that strongly drives the reverberant sound field in the room loses its original sound and balance as the frequency response changes significantly. These are detrimental to the feeling of natural sound space and atmosphere.

In the embodiment of Fig. 3, a pair of sound screen board speakers of the left and right channels are used, which can set composite vibrations in a specific wide frequency range of 100 Hz to 20 kHz on the entire screen.

The main loudspeaker panel 32 is suspended on the suspension device 33 as shown in the figure, and of course the panel can be replaced by supporting the panel on a floor stand.

FIG. 5 shows how the projection apparatus of the present invention is arranged in a room 145 together with seats 146 . The device includes a projector 31 for projecting an image onto a screen 32; it also includes a pair of auxiliary woofers 35 of conventional construction arranged on both sides of the room to improve bass intensity; and a pair of rear effect speakers 117 are also called surround speakers. Speakers are listed on the back wall of the room. Judging from their wide and uniform volume dispersion characteristics, the type shown in Figure 1 and Figure 2 is also suitable for rear speakers. The aftereffect speaker may have the same structure as the auxiliary speaker 114 .

The panel loudspeaker shown in Fig. 1 and Fig. 2 has a significant non-directional characteristic. For sound reproduction of the surround channels of a sound system, the energy must be widely distributed, ideally from non-directional sources. It is important that the sound source is not well positioned, otherwise the feeling of a large surround space (simulated sound field behind the listener) is not satisfactory.

Commonly used directional and dynamic low-volume loudspeakers can be used for surround reproduction. Due to the intensity phenomenon of hearing. Listeners sitting near surround speakers will find that their perception is strongly influenced by the orientation of the speakers, greatly compromising the effect of the surround and their overall appreciation of the multi-channel soundstage. Directionality is so powerful that it works with the Haas effect which increases directivity close to light sources to draw the hearing away from the main foreground audio channel.

A surround reproduction system with one or more loudspeakers constructed according to FIGS. 1 and 2 emits a strong sound field or approximately equalized intensity with rather weak directivity. For a large number of listeners, even some listeners close to the panel speakers (as close as 0.5 meters) will not perceive any apparent directionality of the instant reproduction channel without compromising the hearing of the important front channel. A significant improvement in multi-channel sound reproduction systems is achieved overall as a result of the desirable radiation characteristics of the acoustic panel loudspeakers.

The surround speaker can also be hung on the rope if desired, or be camouflaged by adding a suitable image on the screen panel 2 to form a picture.

Figure 4 shows how the frame 1 of the projection/speaker panel is constructed with folded edges 36 to conceal the suspension 3. The frames of the auxiliary speaker 114 and the surround speaker 117 can also be configured in the same way.

industrial application

Acoustic panels of a certain size that can be used as projection screens for stills, movies and video images are also speakers that can be used as a home theater center channel or dialogue channel. The preferred size (up to 0.6 meter wide) acoustic screen panel of the present invention uniquely provides very good acoustical audience coverage. Performance description High sound intelligibility throughout the listener area, the main advantage is that even listeners close to the screen will not feel the impact of excessively close to the sound level, an unaltered wind flow of traditional direct radiating cone speakers Voice.

There is a second and unique feature of the projection screen of the present invention. For traditional center channel speakers, the human ear is easily positioned at the center of the speaker's sound, and all sounds seem to come from this concentrated small sound source, which damages the sense of reality. But for sound screen panels, its unique non-directional radiation properties mean that sound comes from the screen's broad acoustic area rather than from a single point. When the image is combined with the sound on the screen, it adds a powerful synchronous effect. The absence of specific sound source localization required here allows the ear/brain to perceive the combined effect of a free combination of phantom, actual or approximate sound positions that will be synchronized with where the visual image on the surface of the sound screen appears.

For well-recorded parts of dialogue, not only can the sound image follow the visual image, but it can also convey the information needed for the perception of depth and distance. For example, the auditory quality of the audience in the theater has also been greatly enhanced.

Claims (12)

1. A display screen comprising a panel with a light-reflecting or light-emitting surface, characterized in that the screen is a loudspeaker of a distributed acoustic radiator with transducers integrally and individually mounted thereon to vibrate radiators, causing them to resonate to provide acoustic output. 2. The display screen of claim 1 wherein the radiator comprises a rigid lightweight screen having a porous core sandwiched between a pair of high modulus skins. 3. The display screen of claim 2, wherein a frame surrounds the panel. 4. A display screen as claimed in claim 3, characterized by a resilient suspension for mounting the screen in the frame. 5. The display screen according to any one of claims 2 to 4, characterized in that the porous core layer is made of honeycomb aluminum foil. 6. A display screen as claimed in any one of claims 2 to 5, characterized in that the skin consists of fibre-reinforced plastic. 7. The display screen according to any one of the preceding claims, characterized in that panel speakers are attached to both sides of the display screen to provide left and right channel information. 8. The display screen of claim 7, wherein the left and right side speakers are hinged to the frame and are foldable relative to the radiator for storage. 9. The display screen according to claim 7 or 8, wherein the left and right side speakers are distributed acoustic radiators, all having a transducer integrally and individually mounted thereon, to vibrate the radiator to induce its resonance. 10. A display screen as claimed in any preceding claim, wherein the screen is a projection screen. 11. An audio-visual device, characterized in that it is a projection screen as claimed in any one of the preceding claims. 12. The audio-visual device according to claim 11, characterized in that at least one rear channel speaker of the distributed acoustic radiator has a transducer integrally and individually mounted thereon to vibrate the radiator And make it resonate.

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