PURPOSE: To improve output sound pressure at frequency bands of the first resonance and the second resonance by combining a resonance body with the one-side face of a piezo-electric vibrator through an annular combined body, by connecting a diaphragm at the almost center of the other-side face, and by holding the peripheral part of the diaphragm by a frame.

CONSTITUTION: Piezo-electric ceramic boards 3 and 4 to which a silver electrode is baked are adhered at the upper and lower surfaces of an intermediate electrode board 2 which is formed by an annular piezo-electric vibrator 1. For the combined diameter which is combined with each resonance body 8 on the one-side face of the vibrator 1, an annular combined body 7 whose ratio to outer diameter is 0.5∼1.0 is combined for each outer diameter, and the peripheral part of the resonance body 8 is supported and fixed by the inside face of a frame 6, and a supporting body 9, which positions the resonance body 8, is installed. At the almost center of the other-side face of the vibrator 1, the center top part of a diaphragm 5 is connected, and in addition, the peripheral part of the diaphragm 5 is connected to the peripheral part of the frame 6. In this way, an output sound-pressure characteristic improves at a frequency band of the first resonance and the second resonance, and a superior output sound-pressure frequency characteristic can be obtained.