Abstract: Active acoustic device comprises a panel member (11) having distribution of resonant modes of bending wave action determining acoustic performance in conjunction with transducer means (31-34). The transducer means (31-34) is coupled to the panel member (11) at a marginal position. The arrangement is such as to result in acoustically acceptable action dependent on said distribution of active said resonant modes. Methods of selecting the transducer location, or improvement by location of localised marginal clamping, rely on assessing best or better operative interaction of said transducer means (31-34) and the panel members (11) according to parameters of acoustic output for the device as an acoustic radiator.

Abstract: A mobile telephone (10) comprising a body (12) and a bending wave loudspeaker which comprises a panel-form member (14) capable of supporting bending waves and a transducer (24) mounted to the panel-form member to excite bending wave vibration in the panel-form member to produce an acoustic output. The body (12) defines an open-faced cavity (16) and the panel-form member is movable between first and second positions with the panel-form member covering the open face of the cavity (16) when in the first position, and spaced away from the cavity when in the second position.

Abstract: A bending wave panel-form acoustic radiator formed from sheet material to define an acoustically active area and having at least one integral stiffening member in the form of a corrugation extending out of the plane of the sheet and at least partially across the acoustically active area of the radiator, which stiffening member is of substantially U-shaped cross section. Also disclosed is a method of making a bending wave panel-form acoustic radiator, comprising forming a sheet into a panel having at least one integral corrugation member extending out of the plane of the sheet and at least partly across the sheet and of substantially U-shape cross-section, to stiffen the sheet to have a desired ability to support and propagate bending waves.

Abstract: An acoustic device has a plurality of resonant bending wave modes along the length of a member. The fundamental frequency of resonant bending wave modes in directions perpendicular to the length is much higher, so that the lower frequency resonant bending wave modes are substantially one directional. A plurality of transducers may be spaced across the width of the member at a preferred position along the length of the panel.

Abstract: Electronic apparatus having a support structure or casing and a loudspeaker attached thereto, the loudspeaker comprising a resonant panel-form member and a vibration exciter mounted to the panel-form member to apply bending wave energy thereto to cause the member to resonate to produce an acoustic output. The vibration exciter is grounded on the support structure or casing and is adapted to support the panel-form member on the support structure or casing, thus forming a mount for the panel-form member.

Abstract: A loudspeaker comprising a resonant panel-form member adapted to produce an acoustic output and a vibration exciting system on the panel-form member and adapted to apply bending wave energy thereto, characterised in that the vibration exciting system is adapted to apply a bending couple to the panel-form member.

Abstract: A loudspeaker comprising a bending wave panel, an enclosure in which the bending wave panel is mounted to enclose one face of the panel, a compliant suspension between the panel and the enclosure by which the panel is supported in the enclosure, a vibration exciter attached to the panel to apply bending wave energy thereto, and an acoustic absorber in the enclosure to reduce standing waves in the enclosure, wherein the compliant suspension and the acoustic absorber are integral. A method of making such a loudspeaker is also disclosed.

Abstract: A loudspeaker comprising a bending wave panel, an enclosure in which the bending wave panel is mounted to enclose one face of the panel, a compliant suspension between the panel and the enclosure by which the panel is supported in the enclosure, a vibration exciter attached to the panel to apply bending wave energy thereto, and an acoustic absorber in the enclosure to reduce standing waves in the enclosure, wherein the compliant suspension and the acoustic absorber are integral. A method of making such a loudspeaker is also disclosed.

Abstract: A loudspeaker comprising a panel capable of supporting bending waves and at least two exciters mounted to the panel for exciting bending waves in the panel to produce an acoustic output, each of the exciters being adapted for connection to respective independent sources of drive signals. A loudspeaker system and a method for operating it also are disclosed. The loudspeaker and system are useful, e.g., as a sound-generating ceiling tile.

Abstract: A method of and apparatus for producing acoustic output employs a bending wave member to which a number of exciters are coupled over at least part of the area. The exciters are individually addressable to generate impulses in response to digital input that has been suitably shaped and delayed, the impulses being integrated in the panel so that a form of synchronous summation takes place by bending action making use of the dispersive properties of the device. The resulting acoustic output has a reinforced fundamental frequency and reduced harmonics.

Abstract: A vibration exciter adapted for location in a cavity in a member to be vibrated. A motor coil assembly (6) has a coil rigidly fixed to a tubular member, the motor coil assembly having an outer peripheral face, and a magnet assembly (3-5) is disposed concentrically of the motor coil assembly and arranged for axial movement relative thereto. The magnet assembly has opposed generally disc-like pole pieces (4, 5), the periphery of one of which is disposed within and adjacent to the motor coil assembly, and the periphery of the other (5) of which pole pieces is formed with a flange (8) arranged to lie adjacent to and to surround the motor coil assembly. The flange has aperture portions (11) through which the outer peripheral face of motor coil assembly is adapted to be fixed directly to the cavity wall in the member to be vibrated.

Abstract: A transducer (14) for producing a force which excites an acoustic radiator, e.g. a panel (12) to produce an acoustic output. The transducer (14) has an intended operative frequency range and comprises a resonant element which has a distribution of modes and which is modal in the operative frequency range. Parameters of the transducer (14) may be adjusted to improve the modality of the resonant element. A loudspeaker (10) or a microphone may incorporate the transducer.

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: A formulation e.g., a pesticidal formulation in the form of a dispersion comprising a continuous aqueous phase, and a discontinuous phase comprising a non-aaueous material capable of transport through the aqueous phase to cause Ostwald ripening of the dispersion, wherein there is contained within the discontinuous phase a pesticidal material, which may or may not be the said non-aqueous material,wherein the discontinuous phase comprises a stabiliser in an amount sufficient to depress migration of the non-aqueous material through the aqueous phase, and thereby diminish or prevent Ostwald ripening of the dispersion, characterised in that the stabiliser has a molecular weight of not more than 10,000, and is soluble in the discontinuous phase, but insoluble in and not transportable through the aqueous phase. The production of the formulation can be carried out in a metered in-line mixing plant, since the thermodynamics of the mixing process is such that the particle size tends to a predictable value.

Abstract: Agricultural formulations of fluroxypyr that contain an ester of fluroxypyr that is liquid at ambient temperatures, such as the 1-butoxy-2-propyl ester or the 2-ethylhexyl ester, and that contain a reduced amount of organic solvent or no organic solvent are disclosed. The formulations have good physical properties and are highly effective herbicides.

Abstract: Agricultural formulations of fluroxypyr that contain an ester of fluroxypyr that is liquid at ambient temperatures, such as the 1-butoxy-2-propyl ester or the 2-ethylhexyl ester, and that contain a reduced amount of organic solvent or no organic solvent are disclosed. The formulations have good physical properties and are highly effective herbicides.

Abstract: A ribbon transducer has the ends of its ribbon held by end fixings which incorporate damping member. The end fixing may include a resilient support member fixed to the ribbon, with the ribbon overlying a pad of damping material and having its outer end held clamped, or alternatively left free.

Abstract: A ribbon transducer has its ribbon which is held at each end made capable of lateral movement for adjustment puroses by providing a plurality of traverse cross-suspension elements to which the ribbon is secured, with each of these cross-suspension elements being capable of transverse displacement, for example by rotation of mounting pillars.

Abstract: The moving coil loudspeaker drive-unit comprises a voice coil (4) wound on a former (3) and having fixed thereto a diaphragm (6) and a rear suspension spider (5). The drive unit of the invention comprises a component part build-ring (7) incorporated with the voice coil former (3) and adapted to interconnect the rear suspension spider (5) with the coil former (3) and to accurately locate it with respect to the voice coil (4). The build-ring (7) is also adapted to connect the diaphragm (6) to the coil former (3) together with the dust dome (8). The build-ring (7) also includes projections (9) to accommodate the electrical voice coil termination arrangements (10).