Variable directivity electret condenser microphone

摘要

Provided is a variable directivity electret condenser microphone that can simplify a circuit configuration, and outputs an audio signal in an unbalanced manner. Included are electrically independent first and second electret condenser microphone units in which first and second fixed electrodes are arranged back to back and facing each other in a mutually non-conductive state, and first and second diaphragms are arranged facing the first and second fixed electrodes with fixed intervals from the first and second fixed electrodes, respectively, a first impedance converter having an input terminal connected to the first fixed electrode, a DC cut capacitor selectively connected between an output terminal of the first impedance converter and an input terminal of the second impedance converter, and a directivity variable switche that can alternatively select a mode from at least a first directivity mode to a third directivity mode.

主权项

1. A variable directivity electret condenser microphone comprising:
electrically independent first and second electret condenser microphone units in which first and second fixed electrodes are arranged back to back and facing each other in a mutually non-conductive state, and first and second diaphragms are arranged facing the first and second fixed electrodes with fixed intervals from the first and second fixed electrodes, respectively; a first impedance converter having an input terminal connected to the first fixed electrode; a second impedance converter; a DC cut capacitor selectively connected between an output terminal of the first impedance converter and an input terminal of the second impedance converter; and a directivity variable switch that is able to alternatively select a mode from at least a first directivity mode to a third directivity mode, wherein, when the directivity variable switch selects the first directivity mode, the DC cut capacitor is connected in series between the output terminal of the first impedance converter and the input terminal of the second impedance converter, when the directivity variable switch selects the second directivity mode, the second fixed electrode is connected to the output terminal of the first impedance converter, and the second diaphragm is connected to the input terminal of the second impedance converter, when the directivity variable switch selects the third directivity mode, the second diaphragm is connected to the output terminal of the first impedance converter, and the second fixed electrode is connected to the input terminal of the second impedance converter, and the first diaphragm is connected to a ground at all times, and an unbalanced output of an audio signal is derived from an output terminal of the second impedance converter.