Abstract: An electro-acoustic transducer has a piezo-electric film polymer diaphragm which is stressed to a part spherical surface and the periphery of which is clamped. Electrodes placed over the surface of the diaphragm apply an electric field transverse the plane thereof which causes elongation parallel to the plane of the diaphragm. The rim of the diaphragm is mounted in a supporting framework which forms part of an enclosure isolating one side of the diaphragm from the atmosphere. The enclosure may be evacuated to improve the performance of the transducer by avoiding problems due to the formation of standing waves within the enclosure.

Abstract: An electro-acoustic transducer having a sound-generating diaphragm and means for driving the diaphragm in which the diaphragm is provided with perforations filled with damping material to oppose the formation of standing waves in the diaphragm. The perforations are arranged in between three and eight generally radially extending curved bands, each band being formed of a plurality of parallel rows of perforations extending along the length of the band.