Abstract
A miniature variable-reluctance microphone-reproducer is described which has wide application in military emergency communication radio and the like. The device is less than 13 in.3 in size. The magnetic mechanism utilizes a U-shape folded armature having one end fixed to a pole structure. The latter has a U-shape and retains a pair of thin magnets adjacent to one end of the armature. The acoustical diaphragm is thin aluminum with a corrugated rim. This diaphragm is protected by a metal cover having a small hole, which is covered with a damping pad. Suspended on a frame over this cover is a rubberized fabric water barrier. Ambient pressure is relieved by a capillary tube partially filled by a fine wire. Used as a microphone, the response is fairly flat from 200 to 1000 Hz and rises to an optimum around 3000 Hz. The sensitivity is −75 dB re 1 V/μbar, at 1000 Hz. When used as a reproducer it is normally held close to the ear, and the response with 5-mW drive is of the order of 76 dB above 0.0002 μbar around 3000 Hz, falling off below this frequency. The water barrier arrangement permits short-term immersion to 18-in. depth.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
