Abstract: A crystal sound producer has a piezoelectric crystal plate diaphragm which produces sound waves when applied with a voltage thereacross. A waveform transform plate has slits or linear grooves through which the sound waves from the diaphragm are radiated in semicylindrical waves. As these semicylindrical waves propagate in the air, they superpose one another to form generally plane waves which sound natural to the human hearing. The crystal sound producer can be used in portable articles such as badges.

Abstract: A plane speaker comprises a frame having an opening; a diaphragm facing said opening and having secured its peripheral edge portion to the frame; an actuating plate attached perpendicularly to the back of said diaphragm; a coil mounted on the surface of said actuating plate; and magnets attached to the frame opposite to each other in relation to said coil.

Abstract: A thin film member formed of a synthetic resin material, a paper material or a non-magnetic metal foil material is provided on its both surfaces with conductors. The thin film member is then corrugated, as by folding, to form a number of elongate, arcuate corrugations which serve as a diaphragm. Rod-like permanent magnets extending perpendicularly to the conductors on each trough in the corrugations and generating magnetic flux in the same direction are retained over substantially the entire length between adjacent trough portions. The diaphragm is supported on both surfaces of each side edge thereof by support members which are expandable and contractable only in the direction extending perpendicularly to the diaphragm.

Abstract: An electromagnetic type acoustic transducer comprises a vibratable diaphragm including a conductor and disposed within a magnetic field defined by a permanent magnet. Support members which are expandable and contractible in the direction at right angles with the diaphragm are fixed to both surfaces of the diaphragm. A frame is provided for fixing the support members such that the expansion and contraction thereof is not prevented. The support members may be folded and formed to a bellows-like state. Use is also made of a conductor forming spiral convolutions. The permanent magnet is disposed and retained at a vibration gap with respect to the diaphragm.