Noise reduction system
US4162462A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 23, 1977 |
| Grant date | Jul 24, 1979 |
| Priority date | — |
| Expiry date | May 23, 1997 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03G9/025
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A noise reduction system is provided with an encoder for compressing the dynamic range of an audio input signal in accordance with the amplitude of the input signal and recording the compressed one into a tape recorder, and a decoder for expanding the dynamic range of a reproduced audio signal from the tape recorder to the original one in accordance with the amplitude of the reproduced audio signal. 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 second controlled amplifier circuit having a transfer function related to the character of the first controlled amplifier circuit substantially in inverse-function manner.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.