Abstract: A flat panel rectangular or elliptical loudspeaker has one or more anisotropic diaphragms 14, 15, made of double skinned fluted polypropylene copolymer (core flute) or corrugated cardboards having a longitudinal bending strength greater than the transverse bending strength. The diaphragm is vibrated by a driver unit 16 which comprises a magnet 17 and voice coil 18. In this version the magnet 17 is mounted on the rear diaphragm 15 and the voice coil 18 is mounted on the front diaphragm 14. The two diaphragms 14, 15 are mounted at their edges to a frame 11 with the driver unit 16 mounted in the space enclosed by the frame and the diaphragms.

Abstract: A loudspeaker system is disclosed for active noise reduction. The loudspeaker has a substantially flat or planar diaphragm which is vibrated by an appropriate driver to generate a cancelling signal to cancel noise in the vicinity of the loudspeaker. The loudspeaker includes an input transducer such as a microphone which detects the ambient noise. The microphone is preferably incorporated in the panel structure of the loudspeaker in such a way that the ambient noise information can be captured and presented to active noise cancelling circuitry. The circuitry then provides an appropriate signal to the loudspeaker driver so that the cancelling sound source is provided by the loudspeaker. The use of flat panel loudspeaker technology has been found to provide effective noise reduction and is very appropriate for circumstances in which noise reduction is desirable, for example in aircraft, bus or vehicle seats or telephone kiosks.