Abstract: A loudspeaker drive unit comprising a visual display screen, a resonant panel-form member positioned adjacent to the display screen and at least a portion of which is transparent and through which the display screen is visible, and vibration exciting means to cause the panel-form member to resonate to act as an acoustic radiator.

Abstract: A method of making an acoustic device in the form of a loudspeaker drive unit having a resonant panel-form member adapted to provide an acoustic output when excited with bending wave energy, comprising forming a resilient suspension for the panel-form member by moulding and simultaneously fixing the resilient suspension to the panel-form member.

Abstract: Visual display apparatus comprising a notice board in the form of a distributed mode acoustic radiator having a transducer (9) mounted thereon at a preferential location or site for coupling to resonant bending wave modes to vibrate the radiator to cause it to resonate.

Abstract: A loudspeaker (81) comprising an enclosure, an acoustic radiator (2) in the enclosure, a compliant suspension (3) mounting the radiator in the enclosure for pistonic movement relative thereto, and transducer means (9) for driving the radiator pistonically, characterized in that the radiator is a panel-form distributed mode acoustic radiator, by a first transducer mounted wholly and exclusively on the radiator to vibrate the radiator to cause it to resonate, and by means (11) for varying the air pressure in the enclosure to cause the radiator to move pistonically.

Abstract: Acoustic devices have members extending transversely of thickness and capable of sustaining bending waves causing consequential acoustic action by reason of areal distribution of resonant modes of natural bending wave vibration consonant with required achievable acoustic action of said member over a desired operative acoustic frequency range. Areal distribution of stiffness including variation(s) therein is used to get desired locations for bending wave transducers and/or good resonant mode acoustic action from inherently unfavorable shapes of members. Members with combined pistonic action drive and bending wave excitement at centers of mass and geometry are featured.

Abstract: A mid/high frequency loudspeaker drive unit comprising a stiff lightweight resonant panel form member, a housing to which the panel fog member is mounted, a resilient suspension connected between the edges of the panel form member and the housing, the arrangement being such that the housing and the panel for member together define a closed cavity, and an electrodynamic exciter for applying bending wave energy to the panel form member to cause it to resonate to produce an acoustic output, the exciter comprising a magnet assembly rigidly fixed to the housing and defining an annular gap, and a voice coil and coil former assembly disposed in the annular gap and rigidly fixed to the panel form member near to the geometric center thereof, wherein only the resilient suspension centers the voice coil and coil former assembly in the annular gap.

Abstract: A visual display unit having a display screen, a housing in which the display screen is mounted, and a loudspeaker in the housing comprising a member capable of sustaining and propagating input vibrational energy by a plurality of resonant bending wave modes in an operative area, the frequencies of the resonant bending wave modes being interleaved so that resonant bending wave modes are evenly distributed. A transducer is mounted wholly and exclusively on the operative area of the member at a preferential location which substantially maximizes acoustic coupling to the resonant bending wave modes in the member, the resonant bending wave modes in turn producing an acoustic output.

Abstract: A lap-top computer (128) comprising a combined keyboard (137) and display screen (129), characterised by an opposed pair of loudspeakers (39, 40) attached to the computer, and in that each loudspeaker comprises a distributed mode acoustic radiator having a transducer (9) wholly and exclusively mounted thereon to vibrate the radiator to cause it to resonate.

Abstract: A ceiling tile adapted to be supported in an overhead opening and function as a loudspeaker. The tile is in the form of a distributed mode acoustic radiator with a transducer mounted wholly and exclusively on the radiator at a location for coupling to resonant bending wave modes so as to vibrate the radiator and cause it to resonate.

Abstract: A portable compact-disc player (41), characterized by an opposed pair of loudspeakers (81) attached to the player, and in that each loudspeaker comprises a distributed mode acoustic radiator having a transducer (9) wholly and exclusively mounted thereon to vibrate the radiator to cause it to resonate.

Abstract: A panel form loudspeaker/microphone combination has a distributed resonant bending wave member and two transducers mounred on the member at sites where the number of vibrationally active resonance anti-nodes is relatively high. One transducer is capable of vibrating the member to couple to and excite resonant bending wave modes in the member and cause the member to produce an acoustic output. The other transducer also is capable of coupling to he resonant bending wave modes in the member, but it produces an output signal in response to resonance of the member due to incident acoustic energy. The combination may be part of a loudspeaker system including an amplifier for the source signal coupled to the first transducer, and a signal receiver coupled to the second transducer for treating the output signal.

Abstract: An inertial vibration transducer (9) characterised by a motor coil assembly comprising a tubular member (18) and a coil (13) rigidly fixed to the tubular member, and by a magnet assembly (15) disposed concentrically within the motor coil, and resilient means (19) supporting the magnet assembly for axial movement relative to the motor coil, the motor coil and tubular member being adapted to be rigidly mounted to a distributed mode radiator (2).

Abstract: A panel-form loudspeaker has two distributed mode acoustic radiators coupled by a resilient suspension. Each radiator has its own transducer.

Abstract: A greetings or the like card (144), characterized by a board (2) forming at least part of the card and in that the board is a distributed mode acoustic radiator having a transducer (9) mounted wholly and exclusively on the radiator to vibrate the radiator to cause it to resonate.

Abstract: A visual display unit having a display screen, a housing in which the display screen is mounted, and a loudspeaker in the housing comprising a member capable of sustaining and propagating input vibrational energy by a plurality of resonant bending wave modes in an operative area, the frequencies of the resonant bending wave modes being interleaved so that resonant bending wave modes are evenly distributed. A transducer is mounted wholly and exclusively on the operative area of the member at a preferential location which substantially maximizes acoustic coupling to the resonant bending wave modes in the member, the resonant bending wave modes in turn producing an acoustic output.

Abstract: A vibration transducer adapted to be mounted on and launch bending waves into a member having opposed faces by applying a localized couple to the member. Also disclosed is a loudspeaker having such a transducer mounted on a member which acts as an acoustic resonator by sustaining resonant mode bending wave vibrations. The transducer comprises a motor coil assembly having a coil rigidly fixed to a tubular member, and a magnet assembly comprising opposed pole pieces, the periphery of one pole piece being disposed within and adjacent to the motor coil assembly, and the periphery of the other pole piece being disposed outside of and adjacent to the outside of the motor coil assembly. The magnet assembly has a central attachment portion adapted to be rigidly attached to the member to be vibrated.

Abstract: A panel-form loudspeaker (81) comprising a resonant distributed mode acoustic radiator having a periphery, a transducer (9) mounted to the radiator to excite distributed mode resonance in the radiator, and a frame (1) supporting the radiator, the transducer being coupled between the radiator and the frame to vibrate the panel to cause it to resonate to produce an acoustic output, characterized in that frame supports the radiator round its periphery and by resilient suspension means coupled between the frame and the radiator periphery.

Abstract: A panel-form loudspeaker has two distributed mode acoustic radiators coupled by a resilient suspension. Each radiator has its own transducer.

Abstract: A vending machine (108) of the kind comprising a store of articles or products to be dispensed, user operated means (137) for selecting the article or product to be dispensed, means, e.g. a coin freed mechanism authorising dispensing, and a dispensing outlet (142), characterised by a distributed mode acoustic radiator (2) and a transducer (9) mounted wholly and exclusively on the radiator to vibrate the radiator to cause it to resonate.