Noise reduction system
US4187477A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 21, 1977 |
| Grant date | Feb 5, 1980 |
| Priority date | — |
| Expiry date | Oct 21, 1997 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03G9/025
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A noise reduction system including an encoder for compressing the dynamic range of an audio input signal in accordance with the amplitude thereof, a transmission medium coupled to the encoder, and a decoder having a transfer function inverse to that of the decoder. The encoder includes a first controlled amplifier circuit in which, when the input audio signal is in low- and middle- levels, sufficient emphasis is made to the signal at high frequencies, and when it is in high-level, the emphasis quantity at high frequencies is restrictive. The decoder includes a voltage-current converting circuit for converting voltage of the reproduced audio signal into current and a second controlled amplifier circuit amplifying the converted current and having a transfer function inverse to that of the first controlled amplifier circuit. The second controlled amplifier includes a variable response amplifier having a capacitor and a resistor in series circuit between the output of the voltage-current converting circuit and the output terminal of the second voltage controlled amplifier, a variable gain current amplifier connected at the input thereof to the output of the voltage-current converting c…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.