| 摘要 |
PROBLEM TO BE SOLVED: To accomplish an electret capacitor microphone without deteriorating its function and performance under the environment containing moisture, steam and the like. SOLUTION: Water-repellent coating mainly consisting of PTFE is applied to front protecting cloth of a microphone, a part of a housing is formed of a hydrogen ion conductive solid-state electrolytic film, porous electrodes are provided on both sides thereof, and a voltage obtained from a power source side of a pre-amplifier for electret microphone through a low-pass filter comprised of a resistor and a capacitor is connected to the porous electrodes. COPYRIGHT: (C)2007,JPO&INPIT
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