| 摘要 |
PURPOSE:To improve various characteristics such as sensitivity and to improve mass-productivity as well as miniaturization, by attaining conversion by using a change in capacity corresponding to the vibration of an electret film arranged on both flanks of a frame body. CONSTITUTION:A frame body, etc., are installed in cylindrical container 7 and cover 8 is fixed in to form one enclosure; and on both flanks of cylindrical electrode 9 to be installed in container 7, electret films 10 and 11 are formed in electric contact. Therefore, the frame body is constituted which has electrode 9 corresponding to the body of a large drum and films 10 and 11 corresponding to films of the large drum. Cover 8 as a back electrode and film 10, and container 7 and films 10 and 11 are held at fixed intervals by insulating materials 12 and 13 inserted between cover 8 and film 10, and container 7 and film 11. Through pipe 14 for sound pressure leading-in provided penetrating the flank of container 7, sound pressure is led into container 7 to cause films 10 and 11 to vibrate and consequently the capacities between film 10 and cover 8, and film 11 and container 7 vary, so that an electric signal obtained from an acoustic signal by converting will be led out via lead wire 16. |
