| 摘要 |
1,011,871. Microphones. SHINE BROTHERS Inc. May 24, 1962 [May 25, 1961], No. 20010/62. Heading H4J. In a moving coil microphone an acoustic resistance 30 (Fig. 1) defines a communication path between a chamber 31 and the diaphragm 21 and a second acoustic resistance 32 defines a communication path between the chamber 31 and a chamber 44, whereby the chamber 44 is in communication with the diaphragm 21 through the chamber 31 and the resistances 30, 32. As described, the chamber 31 is one of a number of apertures in a yoke 19 all of which are covered by the acoustic resistance 32. The resistance 32 is a felt or cloth washer, the compression on which is controlled by a nut 34. A cardioid response is obtained by appropriate phase shift. The voice coil is provided in an air gap 16 provided between an inner pole piece 14 and an outer pole piece 15. A magnet 13 is sandwiched between the pole piece 14 and a yoke 19. The pole piece 15 is carried on a ring 18 mounted on the yoke 19 and the magnetic circuit is closed except for the air gap 16. The voice coil consists of turns of fine wire cemented together to form a tube and then cemented to the diaphragm 21. The diaphragm 21 is carried on a resistance ring 22 secured on the outer pole piece 15. The spacing between the pole pieces 14, 15 is maintained by a brass bushing 17. Between the front of the diaphragm 21 and a front perforated screen 12 is an apertured resonator plate 23. Sounds reach the diaphragm 21 through the perforated screen 12 and plate 23. A second acoustic path is provided by an avenue progressing through a protective screen 39, through recesses 40 in the outer surface of pole piece 15, and through circularly arranged apertures 41 in the resistance ring 22 to the rear of the diaphragm 21. Sound waves from the rear of the diaphragm 21 progress through the air gap 16, through apertures 29 in the brass backing 17 to the acoustic resistance 30, of felt. A cloth screen 28 is also provided. The acoustic path is continued to chamber 44 which is in acoustic communication with a chamber 45 through apertures 46 in a shock mount 26. The chamber 45 houses a transformer 3. Connections to a cable jack 4 are provided through a sealed grommet 5. Specification 529,233 is referred to. |
