| 摘要 |
PURPOSE:To obtain stable sound pressure mean at 0.8-3kHz sound level which is in practical sound frequency band by holding the peripheral part of a diaphragm in the vertically middle part of a resonator and without making a sound hole either on the upper wall or lid of the resonator. CONSTITUTION:A step part is formed in the middle part on the inner peripheral wall of a resonator 1, and the peripheral part of a diaphragm 5 is held on the step part. The diaphragm 5 is composed of a metallic sheet, and a piezoelectric element 6, composed of a piezoelectric ceramic film and electrode film, is formed on the under face of the diaphragm 5. Further, the bottom of the resonator 1 is closed by a lid body 7. When closing the bottom of the resonator 1 by the lid 7, connection pins 8 and 9 are bent upward, and the tips of them come into contact with the surfaces of the diaphragm 5 and the piezoelectric element 6. Terminals 2 and 3 are connected with the diaphragm 5 and the piezoelectric element 6 respectively. At the center of the lid 7, a circular sound hole 4 is provided. |
