| 摘要 |
PURPOSE:To improve sensitivity between a basic resonnce point, second and third resonance points and to obtain stable characteristics over a wide range frequency band by giving to a resonator a shape overlapping a trapezoid of a larger profile over that of a smaller profile. CONSTITUTION:A piezo-electric ceramic vibrator 1 constitutes a bimorph vibrator by sticking it together with a metallic diaphragm 10. A resonator 11 has an amplifying function for mechanical acoustic conversion and is constituted of metal or resin. This resonator 11 has a shape whose profile has a large trapezoidal part 11a and a small trapezoidal part 11b. The resonator 11 is constituted by firmly fixing a smaller diameter surface of a sectional trapezoidal shape of the resonator 11 at the center of the bimorph vibrator. Thus large and small trapezoidal shape consisting of the resonator enhance an acoustic conversion efficiency at a basic resonance point, and second and third high-order resonance point, obtaining a stable sensitivity over a wide frequency band by using an in- case air resonance. |
