JPS6436195A - Piezoelectric speaker - Google Patents

Abstract

PURPOSE:To improve the low frequency sound pressure and to obtain a flat sound pressure frequency characteristic by forming a composite sounding body being the combination of two bimorph piezoelectric sounding bodies and a flat diaphragm and providing a box type case to both faces. CONSTITUTION:Two bimorph piezoelectric sounding bodies 2a, 2b are arranged respectively to both faces of the flat diaphragm 4 having sounding holes at the center and a larger area than the area of the end face of the piezoelectric sounding bodies. The piezoelectric sounding bodies 2a, 3b and the flat diaphragm 4 are bonded incorporatedly at each end to provide electric connection and to form a composite sounding body and insulating box cases 10a, 10b having sounding holes are in close contact with both faces of the circumferential ridge of the flat diaphragm 4 respectively. The flange of each piezoelectric sounding body becomes a vibration node, the fixed border condition is confirmed, the high frequency distortion is decreased and the sound pressure versus frequency characteristic is made smooth. Thus, in designing properly the acoustic characteristic of the cavities 14-16 to attain a large low frequency sound pressure and to widen the band having a flat frequency characteristic.