| 摘要 |
PROBLEM TO BE SOLVED: To increase the 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) and an electrode plate 54 of a plane polygonal shape (including a circle) are stacked with a ring spacer member 56 inbetween and a bias powder supply 58 (bias voltage E) using the diaphragm 52 to be a positive pole and a generating source (sound signal source) of a sound signal (e) are connected between the diaphragm 52 and the electrode plate 54. Then the diaphragm 52 is made of a metallic foil whose thickness is 0.5μm or over and 30μm or below (beryllium copper, titanium, stainless steel, aluminum, nickel or the like).
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