Abstract: A process for preparation of a polymeric piezo-electric material and material prepared by said process are described, wherein said process comprises polarizing a polymeric piezo-electric material by a polarization treatment which comprisescooling a vinylidene fluoride-trifluoroethylene copolymer from a temperature higher than the phase transition temperature of said copolymer which exists between room temperature and the melting point of said copolymer, and either maintaining the temperature range at which said copolymer possesses a maximum in dielectric constant occurs, or cooling gradually through said temperature range, while applying an electric field at least within said temperature range.

Abstract: An electro-acoustic transducer comprising a flexible film of piezoelectric material, at least one electrode provided on one side of said film amd a plurality of electrodes provided on the other side of said film to form a piezoelectric diaphragm and said piezoelectric diaphragm is imparted with a locally differing resiliency and/or tension, is provided. By using this piezoelectric electro-acoustic transducer in a loudspeaker, it is possible to improve acoustic characteristics thereof particularly in a high frequency range, to obtain a variety of acoustic characteristics and to effect motional feed back to minimize distortion of reproduced sound without involving any difficulty in manufacturing or affecting proper performance of the transducer.

Abstract: An electro-acoustic transducer comprising a flexible film of piezoelectric material, at least one electrode provided on one side of said film and a plurality of electrodes provided on the other side of said film to form a piezoelectric diaphragm and said piezoelectric diaphragm is imparted with a locally differing resiliency and/or tension, is provided. By using this piezoelectric electro-acoustic transducer in a loudspeaker, it is possible to improve acoustic characteristics thereof particularly in a high frequency range, to obtain a variety of acoustic characteristics and to effect motional feed back to minimize distortion of reproduced sound without involving any difficulty in manufacturing or affecting proper performance of the transducer.

Abstract: An electro-acoustic transducer with a piezoelectric diaphragm which is backed with a plurality of different resilient members for imparting a suitable resiliency and/or tension to said diaphragm to highly improve its acoustic characteristics with a simple construction.

Abstract: A piezoelectric electro-acoustic transducer employing as a diaphragm a uniaxially stretched film of a shape having the major axis and the minor axis, wherein the expansion-contraction direction of the diaphragm, in which a piezoelectric constant is at a maximum, is substantially in parallel with the minor axis thereof, whereby the piezoelectric electro-acoustic transducer can provide a high converting efficiency, especially in the low frequency range.