Audio compressor, expander, and noise reduction circuits for consumer and semi-professional use
US5185806A · kind A · utility
Inventors
Key dates
| Filing date | Dec 11, 1990 |
| Grant date | Feb 9, 1993 |
| Priority date | — |
| Expiry date | Dec 11, 2010 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03G9/18
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
Three related embodiments of audio signal dynamic range circuits for consumer and semi-professional audio signal compressors, expanders, and compressor/expander noise reduction systems incorporate certain basic features of professional Spectral Recording (SR) while adapting SR for use with consumer recording media (particularly audio cassette tape) and reducing the cost and complexity of the SR circuitry. In addition, the three embodiments, and particularly the preferred embodiment, provide substantial compatibility with the existing B-type and C-type consumer and semi-professional noise reduction systems. Subjective performance substantially equivalent to 16-bit PCM audio systems is achieved with analog audio cassette tape media. In all three embodiments there are two cascaded stages: (1) a high-level stage having a high-frequency fixed-band/sliding band action-substitution sub-state and a low-frequency fixed-band sub-stage and (2) a low-level stage having only a high-frequency fixed-band/sliding band action-substitution sub-stage. The dynamic action regions of the high-frequency action-substitution sub-stages are staggered. Each of the high-frequency sub-stages provides up to 12 …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.