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Browse Prior Art Database

Microphone Suspension and Noise Shield

IP.com Disclosure Number: IPCOM000075770D
Original Publication Date: 1971-Nov-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Linton, R: AUTHOR [+3]

Abstract

In the early days of radio, broadcasting microphones, Fig. 1, were suspended from a set of springs that attenuated shocks reaching the microphone. These springs acted in tension, not shear or bending.

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Microphone Suspension and Noise Shield

In the early days of radio, broadcasting microphones, Fig. 1, were suspended from a set of springs that attenuated shocks reaching the microphone. These springs acted in tension, not shear or bending.

When a microphone is mounted in a dictation unit, such as the IBM Model 224 portable unit, noise can reach the microphone from the unit's motor and gear train by being transmitted mechanically to the microphone housing, and by transmission through the air. This mounting system effectively attenuates either type of noise.

The microphone is a dynamic microphone mounted to the machine's end plate. When a dynamic microphone is vibrated in a direction along its axis, an output is noted from the microphone leads. This output is indistinguishable from output created by acoustical noise. The end plate to which the microphone is mounted vibrates in a direction along the axis of the microphone. The microphone is isolated from the end plate in such a manner that the vibration amplitude of the microphone would be much less (by 20 db at 300 Hz) than that of the end plate. A bezel attached to the front of the microphone, Fig. 2, has holes pointing axially outward so that sound from the machine cover, as an example, is prevented from entering the microphone from the sides.

Airborne noises generated by the drive motor and gear train are blocked by a flexible washer-like rubber noise shield located at the microphone-housing gap, Fig. 3. The sus...