Electret condenser microphone
An electret condenser microphone includes a microphone capsule having a diaphragm, a fixed electrode and an extraction electrode. The extraction electrode includes a closed-bottomed cylinder composed of a conductive material. The fixed electrode has holes extending from an air chamber between the diaphragm and the fixed electrode to an air chamber within the extraction electrode, and is fixed to a shoulder of the extraction electrode to form the air chamber that serves as acoustic capacitor within the extraction electrode.
1. An electret condenser microphone comprising, a microphone capsule comprising:
a diaphragm that vibrates in response to sound waves;
a fixed electrode that faces the diaphragm and configures a capacitor with the diaphragm; and
an extraction electrode for electrically connecting electric circuit members to the surface of the fixed electrode remote from the surface that faces the diaphragm, wherein
the extraction electrode comprises a closed-bottomed cylinder composed of a conductive material, the fixed electrode has holes extending from an air chamber between the diaphragm and the fixed electrode to an air chamber defined by the extraction electrode, and the fixed electrode is fixed to a shoulder of the extraction electrode to define the air chamber that serves as an acoustic capacitor within the extraction electrode.
2. The electret condenser microphone according to claim 1 , wherein
the extraction electrode is disposed in the microphone capsule; and
the fixed electrode and the electric circuit members are electrically connected via the extraction electrode by assembling the microphone capsule into a microphone case.
3. The electret condenser microphone according to claim 1 , wherein
the microphone capsule includes a capsule case accommodating the diaphragm, the fixed electrode and the extraction electrode therein.
4. The electret condenser microphone according to claim 1 , wherein
the extraction electrode comprises large- and small-diameter column segments that are integrally molded; and
an insulating sleeve is interposed between an outer peripheral surface of the large-diameter column segment and an inner peripheral surface of the capsule case.
5. The electret condenser microphone according to claim 4 , wherein
the fixed electrode is fixed to a shoulder provided on an inner side at the open end of the large-diameter column segment.
6. The electret condenser microphone according to claim 4 , wherein
the cylindrical insulating sleeve has a convex portion on its fringe of the end adjacent the diaphragm, and the convex portion supports a fringe of the diaphragm.
7. The electret condenser microphone according to claim 1 , wherein
an outer peripheral surface of the large-diameter column segment and an inner peripheral surface of the insulating sleeve are attached firmly by insert molding.