Patent ID: 7903829

Claim:
A microphone comprising: a first bidirectional microphone unit formed by connecting a first set of two unidirectional microphone units, each of which has a cylindrical case assembly and a vibrating section, the cylindrical case assembly including a cylindrical inner case and a cylindrical outer case connected to and surrounding the cylindrical inner case, the cylindrical case assembly having a front side and a rear side, the cylindrical inner case including a rear plate having a plurality of through holes formed therethough and connected at the rear side thereof and the vibrating section connected to the front side thereof with bias voltages of opposite polarities being applied to the vibrating sections of the first set of two unidirectional microphone units; a second bidirectional microphone unit formed by connecting a second set of two unidirectional microphone units, each of which has a cylindrical case assembly and a vibrating section, the cylindrical case assembly including a cylindrical inner case and a cylindrical outer case connected to and surrounding the cylindrical inner case, the cylindrical case assembly having a front side and a rear side, the cylindrical inner case including a rear plate having a plurality of through holes formed therethough and connected at the rear side thereof and the vibrating section connected to the front side thereof with bias voltages of opposite polarities being applied to the vibrating sections of the second set of two unidirectional microphone units; and a metal connection ring for each one of the first and second bidirectional microphone units, wherein respective ones of each of the two unidirectional microphone units are axially aligned relative to each other with the rear plates being spaced apart from and facially opposed to each other, wherein a respective one of the metal connection rings is connected to the respective cylindrical outer cases and surrounds a rear portion of the respective cylindrical inner cases and the cylindrical outer cases of each axially-aligned two unidirectional microphone units in a manner to form a gap between the respective ones of the facially-opposing rear plates, respective ones of the metal connection rings extending axially in contact with the respective rear portions of the cylindrical outer cases and surrounding only a rearward portion of the respective ones of the facially-opposing rear plates while enclosing the gap and wherein a directional axis of the second bidirectional microphone unit is arranged to be shifted by 90 degrees with respect to a directional axis of the first bidirectional microphone unit.