Patent ID: 8103038
Filing Date: 2012-01-24
Classification: H04R

Abstract:
1. A boundary microphone comprising: a flat microphone case having a metallic base part in which an upper surface side is open, and a metallic microphone cover having a plurality of sound wave introduction holes and attached to the base part to cover the upper surface side of the base part; a condenser microphone unit, including a field effect transistor serving as an impedance converter, disposed in the microphone case; a microphone cord having a two-core shield covered wire, a shielding wire covering the two-core shield covered wire, and an electrical insulating cover covering said shielding wire, said microphone cord inserted through a cord insertion hole arranged in the base part and connected electrically to the condenser microphone unit; a binding band fixed on the cord for securing the cord in the microphone case; and an electrical connecting device disposed adjacent the cord insertion hole in the microphone case; wherein the microphone cord includes a shielding wire exposed part formed in the microphone case where the shielding wire substantially entirely covering the two-core shield in the case is directly exposed in the case; said shielding wire exposed part extends from the binding band to the condenser microphone unit; and the electrical connecting device electrically connects said shielding wire exposed part to the base part so that a high-frequency current caused by electromagnetic waves is not detected by the field effect transistor, which prevents the generation of noise.