Noise reducing apparatus
US4281295A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 30, 1978 |
| Grant date | Jul 28, 1981 |
| Priority date | — |
| Expiry date | Aug 30, 1998 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B1/64
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A frequency region split type noise reducing apparatus, comprising a compressor and an expander; the compressor (or the expander) including a plurality of frequency region splitting filters for splitting the frequency range of the signal into a plurality of frequency regions, a plurality of level sensors for detecting the levels of the signals in the respective frequency regions split by the plurality of filters, a plurality of voltage controlled amlifiers responsive to the level detected outputs of the corresponding level sensors for linearly compressing (or expanding) in terms of a logarithmic scale the dynamic range of the signal, and an adder for adding the outputs as compressed by the voltage controlled amplifiers for providing a composite signal, and the expander (or the compressor) including an amplifier and a switch circuit for connecting the compressor (or expander) to the amplifier to form a negative feedback circuit, whereby the expander (or the compressor) is implemented by a negative feedback amplifier including the amplifier and the negative feedback circuit.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.