| 摘要 |
PROBLEM TO BE SOLVED: To increase a drive amplitude of a diaphragm and to improve the sound volume without losing the sound quality even under an environment with a high humidity. SOLUTION: A diaphragm 52 of a plane polygonal shape (including a circle) with an electrode film 52 formed to the surface thereof and an electrode plate 56 of a plane polygonal shape (including a circle) are stacked with a ring spacer member 58 inbetween and a bias power supply 60 (bias voltage E) using the diaphragm 54 to be a positive pole and generating source (sound signal source) 62 of a sound signal (e) are connected between the electrode film 52 formed to the surface the diaphragm 54 and the electrode plate 56. Then the diaphragm 54 is made of a ceramic foil whose thickness is 1μm or over and 30μm or below (zirconia, silicon nitride, silicon carbide, alumina or the like).
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