| 摘要 |
PROBLEM TO BE SOLVED: To make a reproduction frequency band of voice wide by energizing an electrode provided by forming a ceramics piezoelectric element into a dome shape. SOLUTION: Expansion and contraction of a ceramics piezoelectric element 1 is converted into vertical vibration of the entire piezoelectric element, and a sound wave is obtained by holding a peripheral end part of the ceramics piezoelectric element 1 on a frame 2. In addition, the cross-sectional shape of the ceramics piezoelectric element 1 in the vertical direction is defined as a structure, on which plural circular arcs with different radius are piled. Thus, since resonance frequency is inversely proportional to the radius, a curved surface of the dome-shaped piezoelectric element is constituted by continuing curved surfaces with respective different radii and the resonance frequency becomes hard to appear. Namely, a peak due to primary resonance or a peak due to higher-order resonance are not generated, therefore, a frequency characteristic becomes flatter and making the band become wide. In addition, influences of the resonance frequency due to a metal plate and inconvenient vibration in the shape of a diaphragm are not generated.
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