Microphone assembly for speech recording using noise-adaptive output level control
US4287391A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 21, 1979 |
| Grant date | Sep 1, 1981 |
| Priority date | — |
| Expiry date | Jun 21, 1999 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG10L2021/02161
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A microphone which uses noise-adaptive automatic output level control in speech recording. An input amplifier cooperates with a voltage doubler to form an automatic gain control. A diode and capacitor circuit provides for envelope detection of the signal which is then differentiated, amplified and detected to result in a DC control signal. This control signal is applied to an output amplifier which functions as a three pole Chebyshev filter in which a reduction of gain dampens one pole of the filter causing the response to drop off, so that the signal appearing at the output of the microphone has a substantially high speech-to-noise ratio. The output signal appears at a constant level where it may then be acted upon by the automatic gain control of an associated tape recorder connected to the microphone.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.