| 摘要 |
PROBLEM TO BE SOLVED: To enable measuring the surface voltage of an electret in a state where a diaphragm and a fixed electrode, either of them is subjected to electret processing, are assembled. SOLUTION: Either the diaphragm 11 or the fixed electrode 13 included in a condenser microphone unit is subjected to electret processing. In measuring the surface voltage of the electret, an oscillator 30 oscillates the diaphragm 11 at a predetermined frequency, in a state where the diaphragm 11 and the fixed electrode 13 are arranged oppositely to each other via a spacer ring 15; and change in electrostatic between the diaphragm 11 and the fixed electrode 13 generated by the oscillation is taken out as a measured signal of the electret surface voltage via an impedance transformer 50. COPYRIGHT: (C)2006,JPO&NCIPI
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