Abstract: A shielded case includes a plurality of walls. At least one of the walls is formed by at least first and second separate sections which abut one another along an interface. A depression is formed in at least one of the first and second sections so as to cause at least one of said sections to expand toward the other of section thereby pressure-welding said first and second sections to one another along at least part of said interface.

Abstract: A shielded case includes a plurality of walls. At least one of the walls is formed by at least first and second separate sections which abut one another along an interface. A depression is formed in at least one of the first and second sections so as to cause at least one of said sections to expand toward the other of section thereby pressure-welding said first and second sections to one another along at least part of said interface.

Abstract: A piezoelectric speaker which generates sound by vibrating a plane diaphragm using a plurality of piezoelectric drivers is disclosed. The diaphragm is formed of resin foam plates and the piezoelectric drivers are contained therein while being interposed and supported at the centers thereof. The piezoelectric drivers are divided into at least two groups which have different primary resonance frequencies.

Abstract: A piezoelectric speaker in which a diaphragm containing a piezoelectric driver is fixed on a frame through an elastic supporting member. The diaphragm is an assembly of two resin foam plates facing each other. Each resin foam plate has a recess and a projecting member at the substantial center of the recess bottom. The piezoelectric driver is accommodated in the space made of the two recesses while being interposed and supported by the projecting members at the substantial center thereof.

Abstract: A piezoelectric loudspeaker using a thin plate of piezoelectric ceramics of a high dielectric constant, and fixing a piezoelectric transducer including a thin plate of piezoelectric ceramic of a high dielectric constant onto a diaphragm stretched on a frame, thereby forming a sound generator.The piezoelectric loudspeaker is so constructed that the resonance frequency of the sound generator is set at the low frequency band side of an audio frequency region and that of a cavity by the frame is set at the high frequency band side, the thin plate piezoelectric ceramic of high dielectric constant being used, so that the piezoelectric loudspeaker is of an ultrathin type and can cover the whole audio frequency region.

Abstract: A piezoelectric loudspeaker thin plate-like shaped and using a piezoelectric ceramic plate for a sound-generating portion, which comprises a disc-shaped diaphragm formed of a metallic plate, a disc-shaped film using a material of a smaller Q-factor and formed about equal in diameter to the disc-shaped diaphragm, and a disc-shaped piezoelectric ceramic plate smaller in diameter than the disc-shaped diaphragm, these three members being stuck concentrically with each other, so that the integral-stuck member is supported at its outer peripheral portion to a frame.

Abstract: A piezoelectric buzzer comprises: a piezoelectric transducer; a casing comprising a hollow body having one end closed by a perforated end wall, a lid adapted to close the other end of the hollow body, and an annular groove defined on the inner peripheral surface of the open end of the hollow body for loosely receiving the peripheral portion of the lid. The annular groove and the lid are so dimensioned and so shaped as to avoid any undesired suppression of the frequency of resonance of the casing which takes place during vibration of the transducer.