Classifications

• • 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
  • H04R1/025—Arrangements for fixing loudspeaker transducers, e.g. in a box, furniture
• • 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
  • H04R2201/00—Details of transducers, loudspeakers or microphones covered by H04R1/00 but not provided for in any of its subgroups
  • H04R2201/02—Details casings, cabinets or mounting therein for transducers covered by H04R1/02 but not provided for in any of its subgroups
  • H04R2201/021—Transducers or their casings adapted for mounting in or to a wall or ceiling

Definitions

• the invention relates to loudspeakers and more particularly to loudspeakers comprising panel-form acoustic radiating elements.
• 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 a ceiling tile for a suspended ceiling and incorporating a loudspeaker, characterised in that the tile is in the form of a distributed mode acoustic radiator, and by a transducer mounted wholly and exclusively on the radiator to vibrate the radiator to cause it to resonate.
• a resilient suspension may be disposed at the periphery of the radiator and by which the radiator is supported in the suspended ceiling.
• the radiator may be a stiff lightweight panel comprising a cellular core sandwiched by high modulus skins.
• Figure 1 is a diagram showing a distributed-mode loudspeaker as described and claimed in our co-pending International application No... (our case P.5711);
• 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 3a is a perspective diagram of a room incorporating a suspended ceiling
• Figure 3b is a cross-sectioned side view of an embodiment of distributed-mode loudspeaker according to the present invention in the form of a ceiling tile.
• the transducer (9) is driven by a signal amplifier
• 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
• thermoplastics allow 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.
• piezo and electro dynamic transducers have negligible electromagnetic radiation or stray magnet fields.
• Conventional speakers have a large magnetic field, up to 1 metre distant unless specific compensation counter measures are taken.
• electrical connection can be made to the conductive parts of an appropriate DML panel or an electrically conductive foam or similar interface may be used for the edge mounting.
• 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 raid- 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 radiation from the acoustic panel is largely non-directional, the percentage of phase related information increases off axis. For improved focus for the phantom stereo image, placement of the speakers, like pictures, at the usual standing person height, confers the benefit of a moderate off-axis placement for the normally seated listener optimising the stereo effect.
• Figure 3 illustrates a ceiling tile (36) of the kind adapted to be supported in a grid-like suspended frame (99) to form a suspended ceiling, and which is formed as a loudspeaker (81) of the kind shown in Figures 1 and 2, that is to say comprising a stiff, lightweight multi-mode resonating panel (2) having a core (22) enclosed by skins (21) on both sides.
• the panel (2) is mounted at its periphery on a resilient suspension (3) of foam rubber which is supported on the frame (99) .
• the suspension (3) may be attached to either the panel (2) or to the frame (99) by means of an adhesive, but the connection may be by gravity alone.
• the panel (2) carries a transducer (9), e.g.
• the transducer (9) may be positioned on the panel as described in our co-pending International No. (our file P.5711).
• the acoustic panel is made as an expanded polystyrene foam core of typically l ⁇ g/ro.3 density, 8mra thick, skinned with hardened aluminium alloy skins of 0.1mm.
• a soft foam or felt strip, some 3mm thick is fixed to the perimeter to provide a partially compliant mounting when placed in the ceiling frames and also helps to suppress any possible vibration in the ceiling framing sections.
• a preferred form of excitations is a unitary moving coil inertial transducer with a 25mm or 38mm voice coil, 6 ohms impedance, 40 watt power handling, with the coil bonded directly to the panel surface.
• a compact cup type magnet system enclosed and self sealing may also be bonded directly to the panel via a resilient decoupling ring chosen for its vibro-mechanical properties and dimensional stability.
• a low cost form ceiling tile can be made with a plastics foam cored paper faced board material, which may have a light alloy foil layer for fire retardancy, driven by low cost piezo vibration exciters. Reduced maximum sound levels are obtained, still more than sufficient for personnel announcements, voice overs and background music distribution. The wide area coverage is maintained.
• metallic or carbon conductive skins or cores are employed the speaker may be earth bonded or grounded to maintain EMC screening of an installed structure.
• a ceiling tile loudspeaker does not require a frame, chassis, or acoustic baffle.
• the entire speaker panel is unitary and may be placed in position just like a passive decorative ceiling tile.
• the acoustic panel is relatively lightweight, reducing ceiling loadings and aiding installation. It may readily be made fire resistant. It can be decorated, painted or papered to render it invisible in a ceiling installation without significant acoustic impairment.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Multimedia (AREA)
• Diaphragms For Electromechanical Transducers (AREA)
• Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)
• Details Of Audible-Bandwidth Transducers (AREA)

Priority Applications (20)

Applications Claiming Priority (7)

Publications (1)

Family

ID=34865242

Family Applications (1)

Country Status (19)

Cited By (34)

Families Citing this family (2)

Citations (4)

Family Cites Families (1)

• 1996
  • 1996-09-02 CA CA002230053A patent/CA2230053A1/en not_active Abandoned
  • 1996-09-02 IL IL12348496A patent/IL123484A/xx not_active IP Right Cessation
  • 1996-09-02 ES ES96929395T patent/ES2131407T3/es not_active Expired - Lifetime
  • 1996-09-02 BR BR9610450A patent/BR9610450A/pt not_active IP Right Cessation
  • 1996-09-02 SK SK257-98A patent/SK25798A3/sk unknown
  • 1996-09-02 TR TR1998/00358T patent/TR199800358T1/xx unknown
  • 1996-09-02 RO RO98-00633A patent/RO119040B1/ro unknown
  • 1996-09-02 JP JP9510954A patent/JPH11514509A/ja not_active Ceased
  • 1996-09-02 DE DE69601725T patent/DE69601725T2/de not_active Expired - Lifetime
  • 1996-09-02 AT AT96929395T patent/ATE177576T1/de not_active IP Right Cessation
  • 1996-09-02 EA EA199800253A patent/EA002109B1/ru not_active IP Right Cessation
  • 1996-09-02 WO PCT/GB1996/002153 patent/WO1997009843A1/en not_active Application Discontinuation
  • 1996-09-02 EP EP96929395A patent/EP0847662B1/en not_active Expired - Lifetime
  • 1996-09-02 NZ NZ316552A patent/NZ316552A/en unknown
  • 1996-09-02 PL PL96325272A patent/PL182618B1/pl unknown
  • 1996-09-02 HU HU9900181A patent/HUP9900181A3/hu unknown
  • 1996-09-02 AU AU68810/96A patent/AU703071B2/en not_active Ceased
  • 1996-09-02 DK DK96929395T patent/DK0847662T3/da active
• 1998
  • 1998-07-28 HK HK98109442A patent/HK1008640A1/xx not_active IP Right Cessation

Patent Citations (5)

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