| 摘要 |
961,369. Microphones. AKUSTISCHE U. KINO-GERATE G.m.b.H. May 15, 1962 [Feb. 3, 1962], No. 18588/62. Heading H4J. An electrodynamic transducer is mounted in the centre of a circular disc 8, Fig. 3, which serves as a mounting panel or a circuit panel for a transistor amplifier, 9, associated with the transducer. The transducer is provided with coupling volumes 3 on each side of the diaphragm 1 which communicate with the open air by ducts 4 and 6 of such length that sound paths from the entrances 5 and 7 are substantially equal, and of such cross-section that the impedance of the ducts extending from the front of the diaphragm is substantially equal to the impedance of the ducts from the rear of the diaphragm. The arrangement is such that the microphone is sensitive to spherical wave fronts such as result from a speaker whose mouth is close to the transducer, and insensitive to plane wave fronts such as would result from interfering signals from sources at distances from the transducer.
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