Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R7/00—Diaphragms for electromechanical transducers; Cones
  • H04R7/02—Diaphragms for electromechanical transducers; Cones characterised by the construction
  • H04R7/04—Plane diaphragms
  • H04R7/06—Plane diaphragms comprising a plurality of sections or layers
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R1/00—Details of transducers, loudspeakers or microphones
  • H04R1/02—Casings; Cabinets ; Supports therefor; Mountings therein
  • H04R1/028—Casings; Cabinets ; Supports therefor; Mountings therein associated with devices performing functions other than acoustics, e.g. electric candles
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R7/00—Diaphragms for electromechanical transducers; Cones
  • H04R7/02—Diaphragms for electromechanical transducers; Cones characterised by the construction
  • H04R7/04—Plane diaphragms
  • H04R7/045—Plane diaphragms using the distributed mode principle, i.e. whereby the acoustic radiation is emanated from uniformly distributed free bending wave vibration induced in a stiff panel and not from pistonic motion
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R2307/00—Details of diaphragms or cones for electromechanical transducers, their suspension or their manufacture covered by H04R7/00 or H04R31/003, not provided for in any of its subgroups
  • H04R2307/029—Diaphragms comprising fibres
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R2499/00—Aspects covered by H04R or H04S not otherwise provided for in their subgroups
  • H04R2499/10—General applications
  • H04R2499/15—Transducers incorporated in visual displaying devices, e.g. televisions, computer displays, laptops

Definitions

• the invention relates to noticeboards and the like visual display apparatus.
• a panel-form loudspeaker comprising:- a resonant multi-mode radiator element being a unitary sandwich panel formed of two skins of material with a spacing core of transverse cellular construction, wherein the panel is such as to have ratio of bending stiffness (B) , in all orientations, to the cube power of panel mass per unit surface area ( ⁇ ) of at least 10; a mounting means which supports the panel or attaches to it a supporting body, in a free undamped manner; and an electro-mechanical drive means coupled to the panel which serves to excite a multi-modal resonance in the radiator panel in response to an electrical input within a working frequency band for the loudspeaker.
• B bending stiffness
• ⁇ cube power of panel mass per unit surface area
• Embodiments of the present invention use members of nature, structure and configuration achievable generally and/or specifically by implementing teachings of our co ⁇ pending PCT application no. (our case P.5711) of even date herewith.
• Such members thus have capability to sustain and propagate input vibrational energy by bending waves in operative area(s) extending transversely of thickness often but not necessarily to edges of the member(s); are configured with or without anisotropy of bending stiffness to have resonant mode vibration components distributed over said area(s) beneficially for acoustic coupling with ambient air; and have predetermined preferential locations or sites within said area for transducer means, particularly operationally active or moving part(s) thereof effective in relation to acoustic vibrational activity in said area(s) and signals, usually electrical, corresponding to acoustic content of such vibrational activity.
• the invention is visual display apparatus comprising a notice or the like board, characterised in that the notice or the like board is a distributed mode acoustic radiator having a transducer mounted wholly and exclusively thereon to vibrate the radiator to cause it to resonate.
• the display apparatus is thus a loudspeaker which can be used to reinforce the visual information displayed thereon.
• the radiator may comprise a stiff lightweight panel having a cellular core sandwiched between skin layers, a surrounding frame and a resilient suspension mounting the panel in the frame.
• the frame may have a return lip concealing the suspension.
• the skins may be of or may comprise paper and the core may comprise paper honeycomb.
• the transducer may be a piezo electric bender.
• Figure 2a is a partial section on the line A-A of Figure 1;
• Figure 2b is an enlarged cross-section through a distributed mode radiator of the kind shown in Figure 2a_ and showing two alternative constructions;
• Figure 3 is a perspective diagram of a first embodiment of noticeboard according to the present invention.
• Figure 4 is a perspective view of a second embodiment of noticeboard according to the present invention.
• Figure 5 is a partial cross-sectional view of the noticeboard shown in Figures 3 and 4, and
• Figure 6 illustrates one form of transducer.
• a panel-form loudspeaker (81) of the kind described and claimed in our co-pending International application No. (our case P.5711) of even date herewith comprising a rectangular frame (1) carrying a resilient suspension (3) round its inner periphery which supports a distributed mode sound radiating panel (2) .
• a transducer (9) e.g as described in detail with reference to our co-pending International applications Nos. (our cases P.5683/4/5) of even date herewith, is mounted wholly and exclusively on or in the panel (2) at a predetermined location defined by dimensions x and _, the position of which location is calculated as described in our co-pending International application No. (our case P.5711) of even date herewith, to launch bending waves into the panel to cause the panel to resonate to radiate an acoustic output.
• the transducer (9) is driven by a signal amplifier (10), e.g. an audio amplifier, connected to the transducer by conductors (28) .
• a signal amplifier (10) e.g. an audio amplifier
• Amplifier loading and power requirements can be entirely normal, similar to conventional cone type speakers, sensitivity being of the order of 86 - 88dB/watt under room loaded conditions.
• Amplifier load impedance is largely resistive at 6 ohms, power handling 20-80 watts. Where the panel core and/or skins are of metal, they may be made to act as a heat sink for the transducer to remove heat from the motor coil of the transducer and thus improve power handling.
• Figures 2a_ and 2b are partial typical cross-sections through the loudspeaker (81) of Figure 1.
• Figure 2a shows that the frame (1), surround (3) and panel (2) are connected together by respective adhesive-bonded joints (20) .
• Suitable materials for the frame include lightweight framing, e.g. picture framing of extruded metal e.g. aluminium alloy or plastics.
• Suitable surround materials include resilient materials such as foam rubber and foam plastics.
• Suitable adhesives for the joints (20) include epoxy, acrylic and cyano-acrylate etc. adhesives.
• Figure 2b illustrates, to an enlarged scale, that the panel (2) is a rigid lightweight panel having a core (22) e.g. of a rigid plastics foam (97) e.g. cross linked polyvinylchloride or a cellular matrix (98) i.e. a honeycomb matrix of metal foil, plastics or the like, with the cells extending transversely to the plane of the panel, and enclosed by opposed skins (21) e.g. of paper, card, plastics or metal foil or sheet.
• the skins are of plastics, they may be reinforced with fibres e.g. of carbon, glass, Kevlar (RTM) or the like in a manner known per se to increase their modulus.
• RTM Kevlar
• Envisaged skin layer materials and reinforcements thus include carbon, glass, Kevlar (RTM), Nomex (RTM) i.e. aramid etc. fibres in various lays and weaves, as well as paper, bonded paper laminates, melamine, and various synthetic plastics films of high modulus, such as Mylar (RTM) , Kaptan (RTM) , polycarbonate, phenolic, polyester or related plastics, and fibre reinforced plastics, etc. and metal sheet or foil. Investigation of the Vectra grade of liquid crystal polymer thermoplastics shows that they may be useful for the injection moulding of ultra thin skins or shells of smaller size, say up to around 30cm diameter.
• This material self forms an orientated crystal structure in the direction of injection, a preferred orientation for the good propagation of treble energy from the driving point to the panel perimeter.
• Additional such moulding for this and other thermoplastics allows for the mould tooling to carry location and registration features such as grooves or rings for the accurate location of transducer parts e.g. the motor coil, and the magnet suspension.
• Additional with some weaker core materials it is calculated that it would be advantageous to increase the skin thickness locally e.g. in an area or annulus up to 150% of the transducer diameter, to reinforce that area and beneficially couple vibration energy into the panel. High frequency response will be improved with the softer foam materials by this means.
• Envisaged core layer materials include fabricated honeycombs or corrugations of aluminium alloy sheet or foil, or Kevlar (RTM), Nomex (RTM), plain or bonded papers, and various synthetic plastics films, as well as expanded or foamed plastics or pulp materials, even aerogel metals if of suitably low density.
• Some suitable core layer materials effectively exhibit usable self-skinning in their manufacture and/or otherwise have enough inherent stiffness for use without lamination between skin layers.
• a high performance cellular core material is known under the trade name 'Rohacell' which may be suitable as a radiator panel and which is without skins. In practical terms, the aim is for an overall lightness and stiffness suited to a particular purpose, specifically including optimising contributions from core and skin layers and transitions between them.
• the suspension (3) may damp the edges of the panel (2) to prevent excessive edge movement of the panel. Additionally or alternatively, further damping may be applied, e.g. as patches, bonded to the panel in selected positions to damp excessive movement to distribute resonance equally over the panel.
• the patches may be of bitumen-based material, as commonly used in conventional loudspeaker enclosures or may be of a resilient or rigid polymeric sheet material. Some materials, notably paper and card, and some cores may be self-damping. Where desired, the damping may be increased in the construction of the panels by employing resiliently setting, rather than rigid setting adhesives.
• Effective said selective damping includes specific application to the panel including its sheet material of means permanently associated therewith. Edges and corners can be particularly significant for dominant and less dispersed low frequency vibration modes of panels hereof. Edge-wise fixing of damping means can usefully lead to a panel with its said sheet material fully framed, though their corners can often be relatively free, say for desired extension to lower frequency operation. Attachment can be by adhesive or self-adhesive materials. Other forms of useful damping, particularly in terms of more subtle effects and/or mid- and higher frequencies can be by way of suitable mass or masses affixed to the sheet material at predetermined effective medial localised positions of said area.
• An acoustic panel as described above is bi ⁇ directional. The sound energy from the back is not strongly phase related to that from the front. Consequently there is the benefit of overall summation of acoustic power in the room, sound energy of uniform frequency distribution, reduced reflective and standing wave effects and with the advantage of superior reproduction of the natural space and ambience in the reproduced sound recordings.
• the board itself may thus be specified, dimensioned and electrodynamically driven to operate as a wide coverage acoustic radiating panel a flat loudspeaker.
• a moderate audience of up to 10 persons for a small 0.56m square metre panel or 30-50 persons for a 0.7 to 1.2 square metre size may be served at natural volume levels with highly articulate reproduction of speech and also background music or relevant sound effects, as required. Due to the naturally dispersed acoustic radiation properties of the panel, the distorting effects of local boundary reflections are minimised. A substantial physical obstruction of a proportion of the acoustic panel does not significantly impair the sound distribution. Lower sound levels and lower levels of electrical input power are required for a given level of articulation/intelligibility.
• the acoustic panel would comprise low cost structure of paper honeycomb or foam core 3 to 6mm thick bonded to reinforcing paper, plastic film or plastic film coated paper skins of 0.08 to 0.3mm thickness.
• the preferred drive for an inexpensive design using a flat surface or even embedded transducer is piezo electric, operated in bending or mass loaded, vibration coupled forms.
• transducers have a naturally rising acoustic output with frequency which is predictably and optimally adjusted to a flat response by a combination of series resistive drive to the capacitance load of the transducer, and also by mass loading of the piezo element (for a given mass the acceleration is inversely proportional to frequency) and via the detailed specification of the mechanical properties of the board.
• the fibrous loss factor in the skins By control of the fibrous loss factor in the skins, the visco elastic properties of the adhesive bonding the skin to core, and the piezo element to the skin by applied surface laminates, including the backing for the displayed image or text, and the bulk properties of the core in shear and compression, the desired frequency response may be achieved.
• alloy or part alloy skins will provide good energy coverage over the panel, with a proportionally lower loss factor which appropriately matched to a higher power moving coil type of transducer.
• the latter has a flat region of frequency response.
• the transducer may be of the embedded type concealed within. If magnetic screening is required for the latter, thin
• 0.5mm mild steel foils may be included under the skin surface over the transducer area. A small gain in efficiency will also result due to improved flux linkage.
• Figures 3 to 5 illustrate a noticeboard, advertising display board or the like (48) incorporating the loudspeaker technology of Figures 1 and 2.
• a loudspeaker (81) incorporating a rigid lightweight distributed mode acoustic radiator panel (2) of the kind shown in Figures 1 and 2 has graphic information, e.g. text and/or pictures of any desired kind printed on the panel (2) .
• the graphic information can then be supplemented by an audio message via the loudspeaker to reinforce the message.
• the loudspeaker/display board (48) is mounted on a stand (23) in the form of an easel.
• the loudspeaker/display board may be suspended on wire (33) as shown in Figure 4.
• the noticeboard may be supported in any other desired manner.
• the frame (1) may incorporate a return lip (41) to conceal the resilient suspension (3) which is attached between the rear face thereof and the peripheral margin of the panel (2) .
• FIG. 6 shows a transducer (9) for a distributed mode panel (2) in the form of a crystalline disc-like piezo bender (27) mounted on a disc (118), e.g. of brass, which is bonded to a face of the panel (2), e.g. by an adhesive bond (20) .
• a transducer (9) for a distributed mode panel (2) in the form of a crystalline disc-like piezo bender (27) mounted on a disc (118), e.g. of brass, which is bonded to a face of the panel (2), e.g. by an adhesive bond (20) .
• a transducer (9) via leads (28) will cause the piezo disc

Landscapes

• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Physics & Mathematics (AREA)
• Multimedia (AREA)
• Diaphragms For Electromechanical Transducers (AREA)
• Piezo-Electric Transducers For Audible Bands (AREA)
• Fittings On The Vehicle Exterior For Carrying Loads, And Devices For Holding Or Mounting Articles (AREA)
• Cookers (AREA)
• Road Signs Or Road Markings (AREA)
• Graft Or Block Polymers (AREA)
• Devices For Indicating Variable Information By Combining Individual Elements (AREA)
• Audible And Visible Signals (AREA)
• Pinball Game Machines (AREA)
• Illuminated Signs And Luminous Advertising (AREA)
• Acyclic And Carbocyclic Compounds In Medicinal Compositions (AREA)

Priority Applications (22)

Applications Claiming Priority (7)

Publications (1)

Family

ID=34865251

Family Applications (1)

Country Status (21)

Cited By (26)

Families Citing this family (4)

Citations (6)

• 1996
  • 1996-09-02 HU HU9904010A patent/HUP9904010A2/hu unknown
  • 1996-09-02 IL IL12343896A patent/IL123438A/xx not_active IP Right Cessation
  • 1996-09-02 TR TR1998/00368T patent/TR199800368T1/xx unknown
  • 1996-09-02 DE DE69601648T patent/DE69601648T2/de not_active Expired - Lifetime
  • 1996-09-02 PL PL96325244A patent/PL182243B1/pl unknown
  • 1996-09-02 NZ NZ316563A patent/NZ316563A/en unknown
  • 1996-09-02 EP EP96929406A patent/EP0847667B1/en not_active Expired - Lifetime
  • 1996-09-02 WO PCT/GB1996/002165 patent/WO1997009848A1/en not_active Application Discontinuation
  • 1996-09-02 SK SK264-98A patent/SK26498A3/sk unknown
  • 1996-09-02 JP JP9510966A patent/JPH11512260A/ja active Pending
  • 1996-09-02 DK DK96929406T patent/DK0847667T3/da active
  • 1996-09-02 CN CN96196701A patent/CN1195456A/zh active Pending
  • 1996-09-02 AU AU68821/96A patent/AU704227B2/en not_active Ceased
  • 1996-09-02 AT AT96929406T patent/ATE177282T1/de not_active IP Right Cessation
  • 1996-09-02 CA CA002230234A patent/CA2230234A1/en not_active Abandoned
  • 1996-09-02 BR BR9610426-0A patent/BR9610426A/pt not_active Application Discontinuation
  • 1996-09-02 EA EA199800264A patent/EA000612B1/ru not_active IP Right Cessation
  • 1996-09-02 ES ES96929406T patent/ES2131410T3/es not_active Expired - Lifetime
  • 1996-09-02 RO RO98-00636A patent/RO119042B1/ro unknown
  • 1996-09-02 CZ CZ98583A patent/CZ58398A3/cs unknown
• 1998
  • 1998-07-28 HK HK98109449A patent/HK1008645A1/xx not_active IP Right Cessation

Patent Citations (7)

Non-Patent Citations (1)

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